Novel measurement technique of the tibial slope on conventional MRI

Association between anatomical risk factors and medial meniscus posterior root tears: a retrospective study

BACKGROUND

The purpose of this study was (a) to investigate the association between the potential anatomical risk factors and medial meniscus posterior root tears (MMPRTs), and (b) to determine the optimal cutoff values of risk factors for discriminating MMPRTs.

METHODS

A retrospective study was conducted, from January 2018 to January 2020, 86 patients with MMPRTs identified by an experienced musculoskeletal radiologist using 3-T magnetic resonance imaging (MRI), and also confirmed during arthroscopic surgery were included in this study. Moreover, MMPRTs patients were matched with 128 patients with other types of medial meniscal tear knees at the same period according to patients' demographics. We categorized the two patient groups into subgroups based on the causes of meniscus root tears. A subgroup analysis was performed to evaluate the parameter differences between traumatic and degenerative MMPRT in these groups. The associations between clinical and anatomic factors and MMPRTs were analyzed. Additionally, a logistic regression analysis was performed to detect risk factors correlated with MMPRTs.

RESULTS

Based on the analysis, binary logistic regression models analysis indicated that medial posterior tibial slope (MTS) (odds ratio (OR) = 1.212, P = 0.005), hip knee ankle (HKA) (OR = 1.657, P < 0.001) and medial femoral condyle length/medial tibial plateau length (MFCL/MTPL) (OR = 16.597, P = 0.019) were the risk factors correlated with MMPRTs. A subgroup analysis revealed that the MTS, HKA, and MFCL/MTPL were risk factors associated with traumatic MMPRTs. Additionally, age, MTS, HKA, and MFCL/MTPL were identified as risk factors linked to degenerative MMPRTs. Additionally, the receiver operating characteristic (ROC) curves demonstrated these factors had comparable accuracy at predicting MMPRTs (under the curve were 0.635, 0.700 and 0.627, respectively). The cutoff values of those factors were 7.4º, 2.4º, and 1.2, respectively.

CONCLUSIONS

Based on results from the current study, we identified MTS > 7.4º, HKA > 2.4º and MFCL/MTPL > 1.2 were the risk factors correlated with MMPRTs.

Identifying Risk Factors from Preoperative MRI Measurements for Failure of Primary ACL Reconstruction: A Nested Case-Control Study with 5-Year Follow-up

BACKGROUND

Identifying patients at high risk for failure of primary anterior cruciate ligament reconstruction (ACLR) on the basis of preoperative magnetic resonance imaging (MRI) measurements has received considerable attention. In this study, we aimed to identify potential risk factors for primary ACLR failure from preoperative MRI measurements and to determine optimal cutoff values for clinical relevance.

METHODS

Retrospective review and follow-up were conducted in this nested case-control study of patients who underwent primary single-bundle ACLR using hamstring tendon autograft at our institution from August 2016 to January 2018. The failed ACLR group included 72 patients with graft failure within 5 years after primary ACLR, while the control group included 144 propensity score-matched patients without failure during the 5-year follow-up period. Preoperative MRI measurements were compared between the 2 groups. Receiver operating characteristic (ROC) curve analyses were conducted to determine the optimal cutoff values for the significant risk factors. Odds ratios (ORs) were calculated, and survival analyses were performed to evaluate the clinical relevance of the determined thresholds.

RESULTS

A greater lateral femoral condyle ratio (LFCR) (p = 0.0076), greater posterior tibial slope in the lateral compartment (LPTS) (p = 0.0002), and greater internal rotational tibial subluxation (IRTS) (p < 0.0001) were identified in the failed ACLR group compared with the control group. ROC analyses showed that the optimal cutoff values for IRTS and LPTS were 5.8 mm (area under the curve [AUC], 0.708; specificity, 89.6%; sensitivity, 41.7%) and 8.5° (AUC, 0.655; specificity, 71.5%; sensitivity, 62.5%), respectively. Patients who met the IRTS (OR, 6.14; hazard ratio [HR], 3.87) or LPTS threshold (OR, 4.19; HR, 3.07) demonstrated a higher risk of primary ACLR failure and were significantly more likely to experience ACLR failure in a shorter time period.

CONCLUSIONS

Preoperative MRI measurements of increased IRTS, LPTS, and LFCR were identified as risk factors for primary ACLR failure. The optimal cutoff value of 5.8 mm for IRTS and 8.5° for LPTS could be valuable in the perioperative management of primary ACLR.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Steeper tibial and meniscal slopes as predictive factors for ramp lesions in anterior cruciate ligament injuries

The relationship between ramp lesion (RL), tibial slope (TS), and meniscal slope (MS) remains inadequately explored. This study aims to investigate whether TS and MS are predictive factors for anterior cruciate ligament (ACL) injuries associated with RL, and to evaluate the performance of TS and MS in predicting RL, including determining optimal cut-off values. A retrospective cohort study was conducted on 253 patients who underwent ACL reconstruction. Magnetic resonance imaging was used to measure TS and MS on tibial plateaus. Logistic regression analyses determined associations between TS, MS, and RL. Receiver operating characteristic (ROC) curves evaluated predictive performance and cut-off values. A total of 65 cases (25.7%) were found to have RL. Significant differences in causes of injury, medial TS (MTS), medial MS (MMS), and bone bruises were observed between groups. In the unadjusted model and adjusted models, they showed significant (P < 0.001) associations for MTS (1.73-1.75) and MMS (OR range = 2.14-2.24). The AUC for MTS was 0.72 (95% CI 0.65-0.79, P < 0.001) with a cut-off value of 6.73°, for MMS was 0.80 (95% CI 0.74-0.86, P < 0.001) with a cut-off value of 4.03°, indicating good predictive performance. Larger MTS and MMS are significant predictive factors for RL in patients with ACL injury. Clinicians should closely monitor ACL injury patients with elevated MTS or MMS. Utilizing MTS or MMS as a predictive parameter shows promise for the identification of RL.

Modifiers of the Posterior Tibial Slope as a Predisposing Factor for Anterior Cruciate Ligament Ruptures

Background

An increased posterior tibial slope (PTS) has been shown to be a risk factor for anterior cruciate ligament (ACL) ruptures, but the difference in the mean PTS between patients with ACL ruptures and patients with intact ACLs is only approximately 1°, and the PTS has a wide range between 1° and 22°. Therefore, an ACL rupture may be associated with other morphological differences along with the PTS.

Purpose

To evaluate whether the predictive value of the PTS can be increased with new parameters associated with the proximal tibia, distal femur, and extensor mechanism.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

This study included 81 patients who underwent surgical treatment for isolated ACL ruptures and 81 patients with intact ACLs as the control group.Lateral PTS (LPTS), medial PTS (MPTS), lateral femoral condylar offset, anterior patellar offset (APO), lateral tibial plateau offset, and tibial tubercle offset were measured on magnetic resonance imaging. The patella-lateral tibial plateau ratio (P-LTPR) was obtained by dividing the APO by the lateral tibial plateau offset, and the patella-tibial tubercle ratio (P-TTR) was obtained by dividing the APO by the tibial tubercle offset. Patients with ACL ruptures and intact ACLs were subdivided according to an LPTS ≥8° and an LPTS <8° and compared.

Results

The parameters independently associated with ACL ruptures were P-LTPR (P = .001), P-TTR (P = .006), LPTS (P = .016), and MPTS (P = .047). In patients with intact ACLs and an LPTS ≥8°, P-LTPR was negatively correlated with LPTS and MPTS (P = .015 and P < .001, respectively; r = -0.736 and r = -0.758, respectively). In patients with an LPTS ≥8°, P-LTPR was associated with ACL ruptures, with 77.8% sensitivity and 73.7% specificity, at values >1.38, while P-TTR was associated with ACL ruptures, with 68.3% sensitivity and 67.7% specificity, at values >1.77. In patients with an LPTS <8°, P-TTR was associated with ACL ruptures, with 68.7% sensitivity and 77.2% specificity, at values >1.86.

Conclusion

An evaluation of the P-LTPR and P-TTR parameters when assessing anatomic risk factors for an ACL rupture may increase the predictive information provided by the PTS. P-LTPR may be especially useful in re-evaluating the risk of ACL ruptures in patients who are considered to have a high risk because of a high PTS but an intact ACL, and P-TTR may be useful in re-evaluating the risk of ACL ruptures in patients who are considered to have a low risk because of a low PTS.

A Novel Assessment of Sagittal Proximal Tibial Morphology and Relationship to Proximal Posterior Tibial Slope: Lateral Supratubercle Angle

BACKGROUND

Multiple techniques have been utilized to measure posterior tibial slope (PTS) without consensus on which imaging modality, view, and axis combination is most consistent for risk assessment and preoperative planning in primary and revision anterior cruciate ligament (ACL) surgery. An exclusively proximal-based measurement of PTS has yet to be defined.

PURPOSE/HYPOTHESIS

The purpose of this study was to establish normal values for novel measurements of sagittal proximal tibial morphology, the lateral supratubercle angle (LSTA) and the lateral supratubercle distance (LSTD), in normative and primary ACL tear cohorts. The secondary aim was to establish cutoff values and determine if these tibial measurement values are predictive of the presence of an ACL tear. It was hypothesized that LSTA will be significantly different between cohorts.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

The medical records of patients with a knee complaint between August 2016 and June 2024 were retrospectively reviewed, and the patients were placed into either the normative or primary ACL tear cohort. Three independent observers measured LSTA, LSTD, and PTS along both the lateral (L) and medial (M) tibial plateaus on standard lateral knee radiographs. Means were calculated for each measurement and compared between groups. The receiver operating characteristic curve was used to determine the sensitivity and specificity of significant measurements.

RESULTS

Significant differences were found between normative (n = 150) and primary ACL tear (n = 150) groups in LSTA-L (normative: 9.9°± 4.4° vs primary ACL tear: 11.1°± 4.4°; P = .02), LSTA-M (normative: 10.3°± 4.4° vs ACL tear: 11.4°± 4.6°; P = .03), and PTS-M (normative: 9.2°± 3.2° vs primary ACL tear: 10.0°± 3.1°; P = .03).

CONCLUSION

Mean values and ranges for LSTA and LSTD have been established in normative and primary ACL tear cohorts. LSTA-L, LSTA-M, and PTS-M significantly differed between the cohorts. Future studies with LSTA will evaluate the utilization of these proximal tibial deformity-based measurements in ACL surgery, retear risk assessment, and slope-reducing osteotomy planning.

Sagittal Slope-Reducing High Tibial Osteotomy Decreases Anterior Cruciate Ligament Force and Coupled Internal Tibial Rotation Under Pivoting Loads: A Computational Modeling Study

BACKGROUND

Sagittal-plane slope-reducing high tibial osteotomy (HTO) can reduce the risk of anterior cruciate ligament (ACL) injury in knees with a high posterior tibial slope. The biomechanical effect of slope-reducing HTO on tibiofemoral kinematics and force carried by the ACL remains less well understood.

HYPOTHESIS

Decreased tibial slope will be associated with decreased ACL force, coupled internal tibial rotation (ITR), and anterior tibial translation (ATT) under both compressive and combined compressive and valgus loads.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Computational models of 10 cadaveric knees were created using magnetic resonance imaging- and computed tomography-based 3-dimensional renderings of the bones, articular cartilage, and menisci. Virtual slope-reducing HTO was performed on each tibial geometry in 1° increments, creating tibial slopes spanning -5° to 15°. All knees were flexed to 15°, and loads consisting of (1) axial compression (100 N) and (2) combined axial compression (100 N) and valgus torque (8 N·m) were then applied to each knee at each tibial slope. The outcome measures were ACL force, coupled ITR, and ATT. Relationships between tibial slope and each outcome measure were assessed via linear regression (α = .05), and the effects of 10° slope-reducing HTO, from 15° to 5°, on each outcome measure were reported.

RESULTS

A 10° slope-reducing HTO decreased ACL force by 53% under compression (1.7 N of ACL force per degree decrease in tibial slope; P < .001) and 47% under combined compression and valgus (4.7 N of ACL force per degree decrease in tibial slope; P < .001). Regarding kinematics, a 10° slope-reducing HTO decreased coupled ITR by 64% under combined compression and valgus (0.99° of coupled ITR per degree decrease in tibial slope; P < .001). Finally, a 10° slope-reducing HTO decreased ATT by 54% under compression (0.14 mm of ATT per degree decrease in tibial slope; P < .001).

CONCLUSION

Slope-reducing HTO decreased ACL force linearly by reducing ATT with compression and also by decreasing coupled ITR with combined compression and valgus.

CLINICAL RELEVANCE

Slope-reducing HTO decreased ATT and coupled ITR, dampening movements known to load the ACL. These findings may provide a further biomechanical basis for the ability of slope-reducing HTO to decrease the risk of ACL injury.

Medial and lateral posterior tibial slope in the skeletally immature: Variability across pediatric ages without a consistent trend

INTRODUCTION

Increased knee posterior tibial slope (PTS) angle elevates anterior cruciate ligament (ACL) strain and ACL injury risk. Adult biomechanical research indicates that decreasing the PTS may reduce ACL injuries. Younger patients have much higher risk of ACL injury than adults, with limited anatomic research on tibial slope. The purpose of this study is to evaluate the pediatric medial and lateral PTS in a larger cohort group than prior research.

METHODS

Eighty-three computed tomography (CT) scans of the knee from children aged <2 to 11 years were evaluated using OsiriX imaging software. The PTS was evaluated at two distinct points on sagittal CT sections: (1) At the medial and 2) lateral tibial plateaus, both aligned with the central part of the coronal view of the femoral condyles.

RESULTS

The medial and lateral PTS demonstrated variability across ages <2 to 11 years, with mean values ranging from 3.6° ​± ​1.8°-8.7° ​± ​5.3° for medial slopes and 5.1° ​± ​3.3°-12.4° ​± ​3.6° for lateral slopes. The proportion of patients with at least one slope >10° peaked at age 8 (100 ​%) and age 6 (67 ​%). Simple linear regression revealed no statistically significant relationship between age and tibial slope for medial (coefficient of -0.07, p ​= ​0.574, R2 ​= ​0.004) or lateral slopes (coefficient of -0.08, p ​= ​0.459, R2 ​= ​0.007).

CONCLUSION

Corrective osteotomy of increased PTS to lower the risk of ACL injury may be performed in high injury risk adult patients. However, such invasive procedures are not recommended for the skeletally immature because osteotomy in the growth plates in the proximal tibia could induce growth disturbance. In a unique skeletally immature patient with high risk of recurrent ACL injury, guided growth might be an option in high risk for lowering PTS in a controlled manner. As younger patients have some of the higher risks of primary and recurrent ACL injury, future research in this area may offer another approach to lower the risk of these injuries.

LEVEL OF EVIDENCE

Level III.

Patient-Reported Outcomes Measurement Information System Captures Clinically Meaningful Improvement After Transtibial Pull-Out Repair of Medial Meniscal Posterior Root Tears: Two-Year Outcomes

PURPOSE

To (1) establish cohort-specific minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) thresholds for Patient-Reported Outcomes Measurement Information System (PROMIS) values and legacy knee-specific patient-reported outcome measures (PROMs) after isolated medial meniscal posterior root tear (MMPRT) repair using the transtibial pull-out repair technique; (2) determine achievement rates; and (3) analyze correlations among scores.

METHODS

Patients undergoing primary isolated MMPRT transtibial pull-out repair with preoperative and minimum 2-year postoperative data were analyzed. PROMs included the PROMIS-Pain Interference (PI) score, PROMIS-Physical Function (PF) score, PROMIS-Depression (D) score, Knee Injury and Osteoarthritis Outcome Score Jr (KOOS Jr), and International Knee Documentation Committee (IKDC) score. Paired 2-tailed Student t tests evaluated PROM changes from preoperatively to postoperatively, with the level of significance at P < .05. MCID thresholds were determined using the distribution-based method, whereas PASS thresholds were anchor based. Pearson correlation coefficients were used to compare PROM scores.

RESULTS

Sixty-eight patients (mean age, 57.2 ± 9.7 years; 75.0% female sex; mean body mass index, 32.2 ± 6.1) were included and followed up for 32.9 ± 10.6 months. From preoperatively to final follow-up, all PROMs significantly improved (P < .05). The MCID thresholds and achievement rates were 6.5 and 63%, respectively, for the PROMIS-PF score; -5.7 and 69%, respectively, for the PROMIS-PI score; -4.8 and 50%, respectively, for the PROMIS-D score; 10.5 and 87%, respectively, for the IKDC score; and 10.3 and 75%, respectively, for the KOOS Jr. The PASS thresholds and rates were 47.8 and 59%, respectively, for the PROMIS-PF score; 53.6 and 54%, respectively, for the PROMIS-PI score; 40.5 and 49%, respectively, for the PROMIS-D score; 67.7 and 66%, respectively, for the IKDC score; and 72.3 and 66%, respectively, for the KOOS Jr. The strongest correlations were observed between the PROMIS-PI score and the KOOS Jr (r = -0.687) and IKDC score (r = -0.660). The PROMIS-D score showed the weakest correlations with the KOOS Jr and IKDC score (r = 0.395 and r = -0.399, respectively). Knee-specific PROMs showed a strong correlation with each other (r = 0.710).

CONCLUSIONS

This study establishes cohort-specific MCID and PASS thresholds for the PROMIS subscale scores, IKDC score, and KOOS Jr at a minimum 2-year follow-up after isolated transtibial pull-out MMPRT repair. At 2 years, the MCID and PASS were achieved by 63% and 59% of patients, respectively, for the PROMIS-PF score; 69% and 54%, respectively, for the PROMIS-PI score; and 50% and 49%, respectively, for the PROMIS-D score. For the IKDC score and KOOS Jr, the MCID rates were 87% and 75%, respectively, and the PASS rates were 66% and 66%, respectively.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

The posterior cruciate ligament angle in the setting of anterior cruciate ligament deficient knees: the effect of gender, age, time from injury and tibial slope

PURPOSE

This study aimed to assess the posterior cruciate ligament (PCL) angle in anterior cruciate ligament (ACL) deficient knees and correlate it with anatomical and demographic factors such as tibial slope, anterior tibial translation, age, gender, and time of injury.

MATERIAL AND METHODS

Patients were eligible for inclusion if they were clinically diagnosed with an ACL tear confirmed by MRI. For each patient, the following parameters were evaluated: PCL angle (PCLA), medial tibial slope (MTS), lateral tibial slope (LTS), medial anterior tibial translation (MATT), and lateral anterior tibial translation (LATT).

RESULTS

A total of 193 patients were included in the study, comprising 91 (47.2%) females and 102 (52.8%) males, with a mean age of 30.27 ± 12.54 years. The mean time from injury to MRI was 14.18 ± 55.77 days. In the overall population, the mean PCL angle was 128.72 ± 10.33°, the mean medial tibial slope was 3.57 ± 2.33°, and the mean lateral tibial slope was 6.07 ± 3.52°. The mean medial and lateral anterior tibial translations were 4.76 ± 2.02 mm and 7.01 ± 2.48 mm, respectively. In 190 cases (98.4%), the PCL angle was ≥ 105°. The PCL angle negatively correlated with medial and lateral anterior tibial translation (p < 0.05). Females exhibited a higher PCL angle compared to males (p = 0.019).

CONCLUSION

In the context of ACL lesions, the PCL angle has a normal value in acute injuries (> 105°) and decreases over time. The PCL angle is negatively correlated with anterior tibial translation, and females have a higher PCL angle compared to males.

LEVEL OF EVIDENCE IV

Retrospective Cohort.

Changes in the position of the medial meniscus owing to degenerative meniscus tears

Background

While meniscal extrusion has been recognized as a key factor in meniscal dysfunction and osteoarthritis (OA) development, the specific movement of the posterior horn of the medial meniscus (MM) during extrusion, particularly in early-stage OA, remains unexplored. Therefore, in this study, we investigated the position of the MM in patients with medial knee pain and a Kellgren-Lawrence grade ≤1, investigating the relationship between meniscal extrusion and degenerative tears. We hypothesized that the MM extrusion (MME) would be larger when degenerative tears are present; the anterior horn would move posteriorly, and the posterior horn would move anteriorly, accordingly.

Methods

A total of 181 knees (mean age 61.7 ± 12.1 years; 97 men and 84 women) were included. Simple radiographs were used to measure the weight-bearing line ratio and medial proximal tibia angle. Magnetic resonance imaging was used to measure the medial proximal tibia slope, medial meniscus extrusion, anterior and posterior horn position, and degenerative tears on the posterior segment of the medial meniscus. Those with degenerative tears were designated as group T and those without were designated as group C. Student's t-test and Pearson's χ2 test were performed to compare groups T and C. Statistical significance was set at p < 0.05.

Results

Group T had a significantly larger medial posterior tibial slope (group T: 7.4 ± 2.3°; group C: 6.6 ± 2.2°, p = 0.010) and medial meniscus extrusion (group T: 2.7 ± 1.4 mm; group C: 1.9 ± 1.2 mm, p < 0.001) scores compared with group C. Furthermore, the posterior point of the anterior horn (group T: 16.3 ± 5.0 %; group C: 14.3 ± 3.8 %, p = 0.004) and anterior point of the posterior horn (group T: 36.4 ± 7.1 %; group C:26.9 ± 5.9 %, p < 0.001) were significantly larger in group T than in group C.

Conclusion

Degenerative MM tears cause not only MME but also an anteroposterior shift.

Relationship of Medial Meniscus Posterior Root Tears with Proximal Tibial Morphology and Knee Osteoarthritis

The meniscus is vital to knee function. Medial meniscus posterior root tear (MMPRT) causes a loss of hoop tension. This, in turn, reduces the meniscus's ability to transmit load. Thus, the higher pressure on the weight-bearing surface speeds up joint degeneration. proximal tibial morphology (PTM) describes the geometric structure of tibia near the knee joint and tibial plateau. Medial posterior tibial slope angle (MPTSA) has the most significant impact on knee biomechanics among PTM measurements. This study aims to investigate the relationship between PTM and MMPRT, and evaluate the association between medial meniscal extrusion amount (MMEA) and osteoarthritis (OA) in patients with MMPRT.This retrospective study analyzed knee magnetic resonance imaging (MRI) of 100 patients with MMPRT and 100 age, gender, side-matched controls. MPTSA, mediolateral length (MLL), medial anteroposterior width (MAW), and lateral anteroposterior width (LAW) were used to evaluate PTM. MMEA and tear gap (TG) correlation and their relationship with knee OA severity was assessed.MPTSA was significantly higher in MMPRT group compared with controls (p < 0.001). Moderate positive correlation was found between MMEA and OA severity (R 2 = 0.445, p < 0.001). Cartilage loss was observed when MMEA exceeded 4 mm (sensitivity: 80.68%; specificity: 83.33%). MMEA increased by 1.10 mm for each 1 mm increase in TG.This groundbreaking study reveals that steeper medial tibial plateau is a significant risk factor for MMPRT. Strikingly, MMEA exceeding 4 mm serves as a critical threshold for cartilage loss which is the first finding of OA, potentially revolutionizing treatment decisions. These findings not only enhance our understanding of MMPRT pathomechanics but also provide crucial insights for early intervention strategies, potentially altering the course of OA progression in patients with MMPRT.

Patient Age and Activity Level, Posterior Tibial Slope, and Use of Allograft Are Significant Risk Factors for Anterior Cruciate Ligament Reconstruction Failure: A Systematic Review

Purpose

To assess the consistency of risk factor reporting for anterior cruciate ligament reconstruction (ACLR) failure after primary reconstruction, identify risk factors more frequently associated with ACLR failure, and help clinicians prevent reinjury in patients with risk factors for ACLR failure.

Methods

Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used to conduct a systematic review. Initial title and abstract screening yielded 561 studies, from which 76 studies were assessed for eligibility. Thirty-two full-text studies met the following inclusion criteria: (1) clinical studies of anterior cruciate ligament injuries; (2) patients undergoing ACLR; (3) clinical outcome data, including failure rate; (4) studies assessing preoperative risk factors for failure; and (5) manuscripts published within the past 6 years. These studies were subdivided into those that defined ACLR failure as revision surgery or graft failure.

Results

Ten risk factors were included in the review for 22 studies defining ACLR failure as revision surgery. Eight risk factors were included in the review for 10 studies defining ACLR failure as graft failure. Posterior tibial slope (PTS) (80%, 4/5 studies), age (79%, 11/14 studies), and graft characteristics (71%, 5/7 studies) such as allograft versus bone-patellar tendon-bone autograft, high-dose radiation, and BioCleanse preparation technique were the most significant risk factors for revision ACLR. PTS (100%, 2/2 studies) and activity level (67%, 2/3 studies) were the most significant risk factors for graft failure.

Conclusions

Age, PTS, use of allograft, and activity level are significant preoperative risk factors that should be considered when attempting to prevent reinjury in ACLR candidates. Studies investigating risk factors for ACLR failure often fail to control for confounding variables that can influence outcomes.

Level of Evidence

Level IV, systematic review of Level II to IV studies.

Increased posterior tibial slope is a risk factor for anterior cruciate ligament injury and graft failure after reconstruction: A systematic review

IMPORTANCE

Anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) graft failure are important clinical concerns that result in long recovery periods, potential long-term knee instability, and poor patient outcomes. Identifying risk factors such as posterior tibial slope (PTS), meniscal slope (MS), and meniscal bone angle (MBA) is important for improving risk stratification, guiding management decisions, and reducing the incidence of both ACL injury and ACLR graft failure.

OBJECTIVE

This systematic review and meta-analysis aim to determine whether increased PTS, increased MS, and decreased MBA serve as independent predictors of both ACL injury and ACLR graft failure.

EVIDENCE REVIEW

A comprehensive search of the literature was conducted following Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. For evaluating ACL injury, the review included comparative studies measuring PTS, MS, or MBA between ACL injury patients and ACL-intact controls. For ACLR graft failure, studies comparing these measurements between patients with ACLR graft failures and those with successful ACLR outcomes were included. Data were pooled using a random-effects model to calculate the overall mean difference (MD) between groups.

FINDINGS

Out of 1,683 initially identified studies, 75 studies were selected for detailed analysis, 53 analyzing ACL injury and 24 studies analyzing ACLR graft failure. The meta-analysis revealed that increased PTS significantly increases the risk of both ACL injury (MD 1.64°; 95% CI: 1.08-2.20, p ​< ​0.01) and ACLR graft failure (MD 1.76°; 95% CI: 1.03-2.48, p ​< ​0.01). This is statistically significant for both lateral and medial PTS, and across both radiograph and magnetic resonance imaging. A higher lateral MS (MD 3.25°; 95% CI: 1.70-4.80, p ​< ​0.01) and a lower lateral MBA (MD -3.85°; 95% CI: -6.38-1.32, p ​< ​0.01) were also significantly associated with an increased risk of ACL injury. However, no statistically significant differences were observed for MS or MBA between ACLR graft failure and successful ACLR groups.

CONCLUSION AND RELEVANCE

The findings indicate that increased PTS, whether measured medially or laterally, is a statistically significant risk factor for both ACL injury and ACLR graft failure. Additionally, increased lateral MS and decreased lateral MBA are associated with ACL injury. This evidence supports the consideration of tibial slope in risk assessment, preoperative planning, and surgical decision-making for both prevention of ACL injury and ACLR procedures. Further research is necessary to fully understand the role of MS and MBA in ACL injury.

LEVEL OF EVIDENCE

Level IV; systematic review of level III-IV studies.

Increased Lateral Posterior Tibial Slope Is Associated With a Greater Rate of Lateral Meniscal Injury in Acute Noncontact Anterior Cruciate Ligament Ruptures

PURPOSE

To determine whether there is an association between increasing posterior tibial slope and meniscal tears in a group of patients with isolated, noncontact and acute anterior cruciate ligament (ACL) ruptures from a large ACL registry.

METHODS

Our institution's ACL Registry was consulted to identify patients between the age of 18 and 45 years who underwent primary ACL reconstruction between January 2019 and July 2022 for acute, noncontact ACL rupture. Patients with pre-existing meniscal pathology, chronic ACL reconstructions, revisions, and multiligament knee injuries were excluded. Preoperative magnetic resonance imaging scans were used to measure lateral and medial posterior tibial slope. Meniscal injuries seen during arthroscopy were recorded on the basis of operative reports. Independent cohorts were created on the basis of the presence or absence of a meniscal tear. Two-tailed Student t tests were used to compare average medial and lateral posterior tibial slopes between groups. Separate analyses were performed for the presence of isolated lateral meniscal tears, isolated medial meniscal tears, and both medial and lateral meniscal tears. Multivariable logistic regression models were generated to evaluate other potential risk factors for each tear outcome, including age, sex, and body mass index (BMI). Receiver operating characteristic curve analysis was conducted to explore the potential of identifying an optimal threshold for predicting the presence of a meniscal tear based on lateral posterior tibial slope.

RESULTS

In total, 1,056 patients ultimately met inclusion criteria. There were 498 (47%) patients with any meniscal tear, 346 (33%) patients with lateral meniscus tears, 245 (23%) patients with medial meniscus tears, and 93 (9%) patients with both medial and lateral tears. The average lateral and medial posterior tibial slopes were 5.5° (-4.2° to 13.4°) and 5.7° (0° to 15.7°), respectively. Increased lateral tibial slope was associated with a statistically significant increase in rate of any meniscal tear (adjusted odds ratio 1.10, 95% confidence interval 1.04-1.16, P < .001) and lateral meniscal tear, specifically (adjusted odds ratio 1.11, 95% confidence interval 1.04-1.18, P < .001). In regression analysis, male sex and body mass index ≥35 were found to increase the risk of all meniscal tear types. With a receiver operating characteristic curve analysis identifying lateral posterior tibial slope threshold values that resulted area under the curve ranges from 0.55 to 0.57, we were unable to identify an optimal threshold for posterior tibial slope in predicting meniscal tears.

CONCLUSIONS

In this single-institution, registry-based study, increasing lateral posterior tibial slope was associated with a greater rate of meniscus injury in acute ACL ruptures, whereas medial tibial slope demonstrated no correlation. No optimal threshold of posterior slope could be identified above which the odds of a meniscal tear were significantly elevated. Regression analysis identified BMI ≥35 and male sex as independent risk factors for meniscal tear in this select population.

LEVEL OF EVIDENCE

Level III, comparative retrospective case series.

Anterior Cruciate Ligament-Injured Knees With Meniscal Ramp Lesions Manifest Greater Anteroposterior and Rotatory Instability Compared With Isolated Anterior Cruciate Ligament-Injured Knees

PURPOSE

To investigate the effects of ramp lesion (RL) and its repair on knee instability in patients with anterior cruciate ligament (ACL) injury by quantitatively assessing anteroposterior and rotational knee instability before and after ACL reconstruction.

METHODS

All primary double-bundle ACL reconstructions using hamstring autografts between 2016 and 2021 were evaluated retrospectively. Patients with RLs without other meniscal injuries were included in group R, whereas those with isolated ACL injuries constituted group C. RL was repaired using all-inside devices in all patients in group R. Knee instability, including the amount of anterior tibial translation (ATT), and the acceleration and external rotational angular velocity of the knee joint (ERAV) during the pivot-shift test were assessed at the time of surgery. The pivot-shift test grade was recorded.

RESULTS

A total of 73 patients were included in this study. Preoperatively, group R (n = 23) had significantly greater pivot-shift grades (P = .039), ATT (6.0 mm, group R; 4.5 mm, group C, P < .001), acceleration (6.8, 2.8; P = .037), and ERAV (3.9, 2.8; P = .001) than group C (n = 50). Intraoperatively, ATT (-1.0 mm, -1.0 mm; P < .001), acceleration (1.2, 1.1; P < .001), and ERAV (1.4, 1.2; P < .001) were significantly decreased compared with the preoperative values in both groups. No significant differences in these values were observed between groups R and C.

CONCLUSIONS

ACL-injured knees accompanied by RLs exhibited significantly greater anteroposterior and rotatory instability than knees with isolated ACL injuries; increased knee instability can be effectively addressed by performing RL repair in conjunction with ACL reconstruction. The quantitative assessments employed-specifically measuring ATT, acceleration, and ERAV during the pivot-shift test-have allowed us to delineate these aspects of knee instability with greater precision.

LEVEL OF EVIDENCE

Level Ⅲ, retrospective comparative study.

The Association Between Concomitant Meniscal Tear, Tibial Slope, Static Knee Position, and Anterior Knee Laxity in ACL-Deficient Patients

Background

Whether the tibial slope or the concomitant meniscal tear is related to static knee position or anterior knee laxity remains controversial.

Purpose

To investigate the association between medial and lateral posterior tibial slope, concomitant meniscal tear, static knee position using magnetic resonance imaging (MRI), and anterior knee laxity measured with the GNRB arthrometer.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 60 patients who underwent anterior cruciate ligament (ACL) reconstructions were retrospectively enrolled from May 2020 to October 2022. All patients underwent both MRI and GNRB arthrometry after the injury. The static knee position and medial and lateral tibial slopes were measured using MRI. The meniscal tear type was confirmed during arthroscopic surgery. Descriptive data were retrospectively reviewed from the medical records.

Results

The side-to-side differences of anterior tibial translation at 134 N in the intact meniscus, isolated lateral meniscal tear, isolated medial meniscal tear, and both meniscal tear groups were 3.63 ± 1.4 mm, 4.61 ± 1.5 mm, 2.85 ± 1.5 mm, and 4.85 ± 1.6 mm, respectively (P = .003). The slopes of the force-displacement curve in the GNRB arthrometer were 6.55 ± 4.8 mm/N, 16.99 ± 5.6 mm/N, 9.69 ± 10.8 mm/N, and 10.89 ± 7.4 mm/N in the intact meniscus, lateral meniscal tear, medial meniscal tear, and both meniscal tear groups, respectively (P = .001). Subgroup analysis showed that patients with lateral meniscal tears tended to have greater anterior knee laxity based on the GNRB arthrometer tests. The medial and lateral tibial slopes were not correlated with static knee position or anterior knee laxity.

Conclusion

Patients with ACL deficiency and concomitant lateral meniscal tears are more likely to exhibit greater anterior knee laxity, as measured using the GNRB. Clinicians should consider the concomitant lateral meniscal tear when planning surgery and arranging postoperative care. Tibial slopes were not found to be correlated with static knee position or anterior knee laxity.

A small notch width index, steeper medial and lateral tibial slope and higher lateral/medial tibial slope ratio are relevant knee morphological factors for ACL injuries in skeletally immature patients-A systematic review

Purpose

The incidence of anterior cruciate ligament (ACL) injuries in skeletally immature patients has drastically increased over the last decades. Morphology of the knee might play an important role. This literature review provides a systematic overview of knee morphological factors relevant to ACL injury in skeletally immature patients. The hypothesis of the present study is that multiple knee morphological parameters-such as a steep medial and lateral tibial slope (MTS and LTS) and a narrow intercondylar notch-can be identified as potentially relevant factors for ACL injury in this population.

Methods

Systematic review according to PRISMA guidelines. MEDLINE, Embase and Cochrane were searched in December 2023 for studies reporting on knee morphology and ACL injury in skeletally immatures. The following inclusion criteria were used: English/Dutch studies, full-text available, human studies and skeletally immature patients. Parameters with clinical homogeneity and presented in two or more studies as means with standard deviation were included in a meta-analysis using RevMan. Parameters that could not be included in the meta-analyses were presented in a descriptive manner.

Results

After screening 1825 studies, a total of 18 studies were included, of which 16 studies had parameters included in the meta-analyses. These studies investigated 31 knee morphological factors for ACL injury in skeletally immatures. Meta-analyses identified a smaller notch width index (NWI) (0.25 vs. 0.26, mean difference: -0.02 95% confidence interval [CI]: -0.03 to -0.01, p ≤ 0.00001) steeper MTS and LTS (4.8° vs. 3.6° (mean difference: 0.55° 95% CI: 0.09-1.01, p = 0.02) and 4.3° vs 2.8° (mean difference: 2.04° 95% CI: 0.75-3.32, p = 0.0003), respectively) and higher LTS/MTS ratio as risk factors for ACL injury in skeletally immature patients.

Conclusions

A small NWI, steeper MTS and LTS and higher LTS/MTS ratios were identified as relevant knee morphological factors for ACL injuries in skeletally immature patients.

Level of Evidence

Level III.

Enhanced reliability and time efficiency of deep learning-based posterior tibial slope measurement over manual techniques

PURPOSE

Multifaceted factors contribute to inferior outcomes following anterior cruciate ligament (ACL) reconstruction surgery. A particular focus is placed on the posterior tibial slope (PTS). This study introduces the integration of machine learning and artificial intelligence (AI) for efficient measurements of tibial slopes on magnetic resonance imaging images as a promising solution. This advancement aims to enhance risk stratification, diagnostic insights, intervention prognosis and surgical planning for ACL injuries.

METHODS

Images and demographic information from 120 patients who underwent ACL reconstruction surgery were used for this study. An AI-driven model was developed to measure the posterior lateral tibial slope using the YOLOv8 algorithm. The accuracy of the lateral tibial slope, medial tibial slope and tibial longitudinal axis measurements was assessed, and the results reached high levels of reliability. This study employed machine learning and AI techniques to provide objective, consistent and efficient measurements of tibial slopes on MR images.

RESULTS

Three distinct models were developed to derive AI-based measurements. The study results revealed a substantial correlation between the measurements obtained from the AI models and those obtained by the orthopaedic surgeon across three parameters: lateral tibial slope, medial tibial slope and tibial longitudinal axis. Specifically, the Pearson correlation coefficients were 0.673, 0.850 and 0.839, respectively. The Spearman rank correlation coefficients were 0.736, 0.861 and 0.738, respectively. Additionally, the interclass correlation coefficients were 0.63, 0.84 and 0.84, respectively.

CONCLUSION

This study establishes that the deep learning-based method for measuring posterior tibial slopes strongly correlates with the evaluations of expert orthopaedic surgeons. The time efficiency and consistency of this technique suggest its utility in clinical practice, promising to enhance workflow, risk assessment and the customization of patient treatment plans.

LEVEL OF EVIDENCE

Level III, cross-sectional diagnostic study.

Cut-off value for the posterior tibial slope indicating the risk for retear of the anterior cruciate ligament

PURPOSE

The significance of the posterior tibial slope (PTS) has increasingly come into focus in anterior cruciate ligament (ACL) reconstruction being a risk factor for ACL graft failure. Nevertheless, inconsistent data on the critical value of the PTS exist. The purpose of this study was to define a cut-off value for the PTS in ACL surgery.

METHODS

In a retrospective cohort study, 350 revision ACL reconstructions (ACL-RR) with a failed ACL hamstring graft and 350 primary ACL reconstructions (ACL-R) were matched according to age, gender, concomitant injuries and graft characteristics and compared to a healthy control group. Using the proximal anatomic axis, lateral knee radiographs were evaluated for the PTS, interrater reliability was defined, ROC curves, Fischer's exact test and Baptista-Pike method were applied to define specificity and the odds ratio for a critical PTS value.

RESULTS

Radiographic evaluation proved excellent interrater reliability (intraclass correlation coefficient 0.969). Evaluation of the PTS revealed 10.0 ± 2.2 (5-15) degrees in the ACL-RR group, 7.8 ± 1.8 (4.2-13) degrees in the ACL-R group and 6.6 ± 1.9 (3.6-12) degrees in the control group with significant differences between the groups (p < 0.001). A PTS value of 10.1 degrees proved a specificity of 98% for the prediction of an ACL graft failure and indicated an 11-fold risk for a retear of the ACL.

CONCLUSION

A PTS exceeding 10.1 degrees carries an 11-fold risk for ACL graft failure and, therefore, should be considered in ACL reconstruction. These findings might serve as a cut-off value for the indication of a slope-reducing high tibial osteotomy in ACL surgery.

LEVEL OF EVIDENCE

Level III.

The presence of a Segond fracture in ACL-injured patients is associated with increased internal tibial rotation on preoperative MRIs

BACKGROUND

Segond fracture is considered a component of the anterolateral complex (ALC) injury, yet the underlying cause and clinical outcomes of this bony avulsion remain subjects of debate. Additionally, MRI measurements of altered tibiofemoral position in anterior cruciate ligament (ACL)-injured patients with a Segond fracture have not been reported. The purpose of this study is to measure the rotational tibiofemoral position on MRI in ACL-injured patients with a Segond fracture.

METHODS

A total of 44 patients with a primary ACL injury and a concomitant Segond fracture were included in the Segond fracture group, with the time from injury to MRI within 3 months. Avulsion was confirmed via preoperative computed tomography (CT) scans. The control group comprised 44 matched patients with primary ACL injury and an MRI-determined ALC injury but without a Segond fracture, also with the time from injury to MRI within 3 months. The MRI-determined ALC injury included injuries to the anterolateral ligament, Kaplan fibers, and anterolateral joint capsule, as identified based on previous studies. Sex, age, and BMI were matched between the two groups using propensity score matching (PSM). Arthroscopic findings, concomitant collateral ligament injuries, and preoperative MRI measurements were compared between the two groups.

RESULTS

The Segond fracture group demonstrated a higher frequency of concomitant patellar and femoral trochlear injuries (p = 0.0110) and lateral collateral ligament injuries (p = 0.0121) compared to the control group. Additionally, significantly increased internal rotational tibial subluxation (IRTS) (p = 0.0095) and axial internal tibial rotation (ITRa) (p = 0.0306) were observed in the Segond fracture group. A strong positive correlation was found between IRTS and ITRa (rp = 0.8201), indicating that these two tibial rotation measurement methods were correlated. No significant differences were observed in the measurements of anteroposterior tibiofemoral position and posterior tibial slope (PTS) between the two groups.

CONCLUSION

The presence of a Segond fracture was associated with significantly increased internal tibial rotation measured on MRIs, suggesting that this bony avulsion may represent a more severe form of ALC injury in ACL-injured patients and should be managed with caution.

Posterior tibial slope angle in contact versus non-contact anterior cruciate ligament injuries

BACKGROUND

Increased Posterior Tibial Slope (PTS) angle has been reported to be a risk factor for primary anterior cruciate ligament (ACL) tears. However, it is unknown whether increased PTS has an associated increased risk for non-contact versus contact ACL injury.

PURPOSE

The purpose of this study is to determine whether patients with non-contact ACL injury have a higher PTS angle than those with contact ACL injury.

METHODS

A total of 1700 patients who underwent primary ACL reconstruction between January 2011 and June 2023 at a single academic institution were initially included. Electronic medical records were reviewed for demographic information as well as evidence that the patient sustained a contact or non-contact ACL injury. Patients in the contact cohort were propensity score matched to patients in the non-contact cohort by age, sex and BMI. Additionally, patients in the contact cohort were then propensity score matched to a control group of patients with intact ACLs also by age, sex and BMI.

RESULTS

One hundred and two patients with contact injury were initially identified and 1598 patients with non-contact injuries were identified. Of the 102, 67 had knee X-rays that were suitable for measurement. These 67 contact injury patients were propensity score matched to 67 noncontact patient and 67 patients with intact ACLs based on age, sex and BMI. There were no significant differences between contact and non-contact cohorts in age (28.7±6.3 vs. 27.1±6.5, p = 0.147), sex (Female: 36.0% vs. 34.3%, p = 0.858), or BMI (26.7±5.6 vs 26.1±3.4, p = 0.475). There was no significant difference in PTS angle between contact versus non-contact ACL injury patients (11.6±3.0 vs.11.6±2.8, p = 0.894). There was a significant difference in PTS between the contact ACL injury and the intact cohort (11.6±3.0 vs. 10.0±3.9, p = 0.010) and the non-contact ACL injury and the intact cohort (11.6±2.8 vs. 10.0±3.9, p = 0.010).

CONCLUSION

There was no significant difference in the degree of PTS between patients who sustained contact versus non-contact ACL injuries. Additionally, there was a significantly increased PTS in both the contact and non-contact ACL injury cohorts compared to patients with intact ACLs.

Does Tibial Plateau Slope and Depth Influence ACL Strain In Vivo?

Background

The anterior cruciate ligament (ACL) is loaded under tension when the tibia translates anteriorly relative to the femur. The shape of the articular surfaces of the tibiofemoral joint may influence the amount of anterior tibial translation under compressive loading. Thus, a steep lateral tibial plateau and a shallow medial plateau are thought to be risk factors for ACL injury.

Purpose/Hypothesis

The purpose of this study was to evaluate whether tibial plateau slope and depth influence peak ACL strain during a single-leg jump. We hypothesized that there would be a significant correlation between tibial plateau slope and depth with ACL strain.

Study Design

Descriptive laboratory study.

Methods

A total of 17 healthy participants (8 male, 9 female) were assessed using magnetic resonance imaging (MRI) and high-speed biplanar radiography to obtain peak ACL strain during a single-leg jump. Two orthopaedic surgeons used the sagittal plane MRI scans to measure the medial and lateral tibial plateau slopes and the medial tibial plateau depth. The intraclass correlation coefficient was used to assess measurement reliability, and the Spearman rank correlation was used to evaluate the relationship between measurements of tibial morphology and peak ACL strain during the single-leg jump.

Results

The overall range of intraclass correlation coefficients for intra- and interrater reliability of the medial and lateral tibial plateau slopes and medial plateau depth was 0.59 to 0.97. No significant correlations were found between peak ACL strain and any of the slope or depth measurements.

Conclusion

In this cohort of healthy participants, correlations between any of the tibial plateau measurements with peak ACL strain during a single-leg jump were not detected. These findings are consistent with prior work, suggesting that tibial plateau slope and depth may not be linked to risk for ACL rupture. However, it is possible that tibial plateau morphology may interact with other factors to increase ACL injury risk or that individuals with extreme slope angles may produce differing results.

Clinical Relevance

This study enhances the knowledge of the loading mechanisms for the ACL and thus improves the understanding of risk factors for ACL injury.

Increased global posterior tibial slope is significantly associated with higher ACL graft signal intensity on 2-Year postoperative MRI after primary ACL reconstruction using hamstring tendon autografts

BACKGROUND

The healing and remodeling process of tendon grafts after anterior cruciate ligament (ACL) reconstruction (ACLR) has received significant attention. This study aims to identify preoperative factors associated with postoperative signal intensity of the ACL graft after primary ACLR.

METHODS

A total of 90 patients underwent primary ACLR using hamstring tendon autografts by the same senior surgeon between January 2013 and December 2020 were included. Patients were followed up and scheduled for a 2-year postoperative magnetic resonance imaging (MRI) scan at our institute. Concomitant injuries were confirmed by arthroscopy. Posterior tibial slope (PTS) and anterior tibial subluxation (ATS) were measured on preoperative MRI, whereas the normalized signal intensity of the ACL graft was evaluated on postoperative MRI and calculated as the ratio of the graft signal intensity to that of the patellar tendon. Multivariable linear regression models were performed to identify preoperative factors associated with the postoperative signal intensity of the ACL graft.

RESULTS

Multivariable analyses showed that increased global PTS (GPTS) (P = 0.008) and concomitant articular cartilage injuries (P = 0.005) were associated with higher average signal intensity of the ACL graft on two-year postoperative MRI, while preoperative internal rotational tibial subluxation (IRTS) calculated as the difference between lateral ATS and medial ATS did not show a significant association. Specifically, an increased GPTS was significantly associated with higher signal intensity in the proximal section of the ACL graft (P = 0.005), whereas no significant associations were observed in the middle and distal sections.

CONCLUSIONS

Increased preoperative GPTS was significantly associated with higher signal intensity of the ACL graft on 2-year postoperative MRI after primary ACLR, suggesting that a steep preoperative tibial slope may contribute to a suboptimal ligamentization process in hamstring tendon autografts.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Steeper Slope of the Medial Tibial Plateau, Greater Varus Alignment, and Narrower Intercondylar Distance and Notch Width Increase Risk for Medial Meniscus Posterior Root Tears: A Systematic Review

PURPOSE

To evaluate the available literature on the relationship between knee bony morphology and medial meniscus posterior root tears (MMPRTs) to determine which tibiofemoral morphologic risk factors may predispose the development of MMPRTs.

METHODS

Embase, MEDLINE, and PubMed databases were searched to identify all relevant human clinical studies investigating knee morphologic features and MMPRTs. Shape features were compared between control groups and patients with MMPRTs. The methodological index for nonrandomized studies (MINORS) instrument was utilized to assess the methodological quality of included studies.

RESULTS

Thirteen level III evidence studies and 1 level IV evidence study were included in this review (n = 2,181), with 895 patients in the MMPRT group and 1,286 in the control group. Tibial morphology features associated with an increased risk for MMPRTs included an increased medial tibial slope (6 studies), increased tibial torsion (1 study), increased medial meniscal slope (1 study), and shallower medial tibial plateau concavity (1 study). Varus mechanical alignment was found to increase the risk for MMPRTs (4 studies). Femoral morphology features associated with an increased risk for MMPRTs included an A-type intercondylar notch (1 study), increased medial femoral condyle (MFC) angle (1 study), narrower intercondylar distance (1 study), narrower intercondylar notch width (1 study), shorter MFC distal offset distance (1 study), increased MFC width (1 study), increased MFC to medial tibial condyle width ratio (1 study), greater distance between the medial tibial eminence and MFC (1 study), and smaller femoral offset ratios of both the medial and lateral condyles (1 study).

CONCLUSION

Multiple tibiofemoral shape features, including a steeper slope of the medial tibial plateau, greater varus alignment, and a narrower intercondylar distance and notch width, were found to be predictive factors for MMPRTs.

LEVEL OF EVIDENCE

Level IV (Systematic review of Level III and IV studies).

Increased Posterior Tibial Slope Is Associated With Increased Risk of Meniscal Root Tears: A Systematic Review

BACKGROUND

While increased posterior tibial slope (PTS) is an established risk factor for anterior cruciate ligament tears, the association between tibial slope and meniscal posterior root tears is not well-defined.

PURPOSE

To summarize the available literature evaluating the association between PTS and meniscus root injuries compared with patients without root tears.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A literature search was performed using the Scopus, PubMed, and Embase databases. Human clinical studies evaluating the associations between the medial tibial slope (MTS), lateral tibial slope (LTS), lateral-to-medial (L-to-M) slope asymmetry, and the risk of meniscus root tears were included. Patients with medial meniscus posterior root tears (MMPRTs) and lateral meniscus posterior root tears (LMPRTs) were compared with a control group without root injury. Study quality was assessed using the methodological index for non-randomized studies criteria.

RESULTS

Ten studies with 1313 patients were included (884 patients with root tears; 429 controls). The LMPRT subgroup (n = 284) had a significantly greater LTS (mean ± SD, 7.3°± 1.5° vs 5.7°± 3.91°; P < .001), MTS (5.26°± 1.2° vs 4.8°± 1.25°; P < .001), and increased L-to-M asymmetry (2.3°± 1.3° vs 0.65°± 0.5°; P < .001) compared with controls. The MMPRT group (n = 600) had significantly increased MTS relative to controls (8.1°± 2.5° vs 4.3°± 0.7°; P < .001). Furthermore, there was a higher incidence of noncontact injuries (79.3%) and concomitant ramp lesions (56%) reported in patients with LMPRT.

CONCLUSION

Increased MTS, LTS, and L-to-M slope asymmetry are associated with an increased risk of LMPRTs, while increased MTS is associated with MMPRTs. Surgeons should consider how proximal tibial anatomy increases the risk of meniscus root injury.

Evaluation of posterior tibial slope relationship with common knee pathologies in pediatric and adolescent age groups in the Turkish population

Anterior cruciate ligament rupture (ACLR), tibial eminence fracture (TEF), and Osgood-Schlatter disease (OSD) have been linked to a steep posterior tibial slope (PTS) in children and adolescents. This study aims to examine and compare these associations. 418 patients aged 8-18, 237 males and 181 females with knee pain between 2010 and 2019 were included and the patients belonged to the Turkish population. They consisted of ACLR (n = 47), TEF (n = 22), OSD (n = 51), and a control group (n = 298). The study and control groups were compared for PTS, sex, and age, with ACLR, TEF, OSD, retrospectively. The ACLR, OSD, and TEF groups had higher PTS values than the control group ( P < 0.001). There was no significant difference in ACLR-OSD, ACLR-TEF, and OSD-TEF comparisons ( P = 0.22, P = 0.99, and P = 0.99, respectively). PTS increase was linked to ACLR, TEF, and OSD in the multinomial regression analysis, ( P < 0.001). Increase in PTS was associated with ACLR, TEF, and OSD for both males and females (independently of other factors; ACLR: P < 0.001, P < 0.001, OR: 1.59, OR: 2.63, TEF: P = 0.001, P < 0.001, OR: 1.98, OR: 1.44; OSD: P = 0.001, P < 0.001, OR: 1.49, OR: 1.28 for males and females respectively). ACLR, TEF, and OSD are associated with increased PTS in the pediatric and adolescent age groups, and there are differences between these pathologies in terms of the amount of PTS increase, age, and sex. Consideration of age and gender in pediatric and adolescent patients with increased PTS may be useful in predicting pathologies associated with increased PTS. Level of evidence: III retrospective comparative study.

Is an excessively high posterior tibial slope a predisposition to knee injuries in children? Systematic review of the literature

BACKGROUND

The literature agrees that an increased posterior tibial slope (PTS) increases the risk of anterior cruciate ligament (ACL) rupture in adults. However, there is no consensus on the average normal value and it varies with growth. We carried out a systematic review of the literature to answer 4 questions faced with an increase in PTS in children: METHOD: We conducted a systematic review of the literature in accordance with PRISMA criteria. The inclusion criteria were all studies analyzing the association between increased PTS and the occurrence of knee disease in patients, the majority of whom were under 18 years of age or had immature skeletons. For each study, we recorded the demographic characteristics of the patients, the type of measurements performed, the PTS values and the association between the PTS value and the occurrence of pathology.

RESULTS

A total of 294 studies were identified. After analysis, 11 studies were included (n = 1173 patients). Six studies examined the association between PTS and anterior cruciate ligament (ACL) rupture (n = 5) or recurrence of rupture (n = 1). Two studies investigated the association between tibial slope and proximal tibial fracture and 3 studies investigated the association between tibial slope and growth disease (Osgood Schlatter (OSD) or osteochondritis dissecans of the knee). Of the 5 ACL studies, all studies found a significant increase in PTS in patients with ACL rupture (range min 2.1 ° max 4.3 °) compared with healthy subjects. Concerning growth lesions, 3 studies found an increased PTS in patients with OSD or osteochondritis. The studies concerning fractures of the proximal end of the tibia also found an increase in PTS.

CONCLUSIONS

This review highlighted the potential link between an abnormally high PTS value and the occurrence of knee pathologies in children, in particular ACL rupture. Children with a high PTS and an ACL rupture will require longer-term follow-up and should be warned of the greater risk of re-rupture.

LEVEL OF EVIDENCE

IV; systematic review.

Increased medial tibial slope is a possible risk factor for patellar cartilage lesions

Introduction

Axial malalignment in the coronal plane has been identified as a significant risk factor for knee cartilage damage, leading to osteoarthritis progression. However, the impact of sagittal axial deviation on cartilage damage remains underexplored. Biomechanical studies have suggested that an increased tibial slope leads to altered pressure distribution in the articular cartilage, potentially contributing to cartilage damage. Despite these biomechanical insights, clinical evidence linking increased tibial slope to cartilage damage is lacking.

Methods

This retrospective study focuses on patients who underwent surgical cartilage transplantation between January 2016 and July 2023. A total of 108 patients were divided into two groups based on the presence or absence of other pathologies contributing to cartilage damage. Clinical data, including tibial slope measurements from lateral radiographs, were collected. A further subgroup-matched pair analysis was conducted comparing cases with patellar lesions and healthy knees. Statistical analysis compared tibial slope values between groups and assessed correlations between tibial slope and cartilage lesion grade.

Results

Patients without other identifiable pathologies exhibited a significantly higher medial tibial slope compared to those with known causative factors for cartilage damage (p < 0.05). Cartilage damage, particularly in the patellar region, was more prevalent in patients with an increased tibial slope. Patients with patellar lesions had a significant increased slope than healthy controls (p < 0.05). However, there was no significant correlation between cartilage lesion grade and tibial slope.

Conclusion

The study identified increased medial tibial slope as a possible independent risk factor for cartilage damage in the knee, especially in the patellar region.

Level of Evidence

Level IV.

Tibiofemoral bone configuration is not associated with hamstring muscle strength in male and female patients with ACL reconstruction

PURPOSE

Previous evidence indicated that the tibiofemoral bone configuration might elevate the risk of an anterior cruciate ligament (ACL) injury. Furthermore, a low hamstring-to-quadriceps muscle ratio predisposes especially females to unfavourable knee kinematics. The primary objective of the present study was to investigate sex-specific associations between tibiofemoral bone geometry and isokinetic knee flexion torque in patients with primary ACL injury followed by ACL reconstruction.

METHODS

N = 100 patients (72 = male, 28 = female, age = 31.3 ± 10.2, body mass index = 25.3 ± 3.6) with primary ACL rupture with isokinetic knee flexion torque assessments before and 6 months after ACL reconstruction surgery were analysed. Magnetic resonance imaging scans were analysed for medial posterior tibial slope (MPTS) and lateral posterior tibial slope, notch width index (NWI) and lateral femoral condyle index (LFCI). Additionally, isokinetic knee flexion torque (60°/s) and hamstring-quadriceps ratios were evaluated. Subsequently, functional parameters were correlated with imaging data for gender subgroups.

RESULTS

The findings showed that presurgical isokinetic knee flexion torque was not associated with any marker of femoral or tibial bone geometry. Further, while significant differences were observed between female (0.883 ± 0.31 Nm/kg) and male (1.18 ± 0.35 Nm/kg) patients regarding preoperative normalized knee flexion torque (p < 0.001), no significant sex differences were found for percentage increases in normalized knee flexion torque from presurgery to postsurgery. Generally, female patients demonstrated significantly higher MPTS magnitudes (p < 0.05) and lower LFCI values (p < 0.05) compared to men.

CONCLUSION

The present results demonstrated no association between tibial or femoral bone geometry and muscle strength of the hamstrings in patients with ACL reconstruction, indicating an important mismatch of muscular compensation to deviations in bone geometry. There were no sex-specific differences in tibiofemoral bone parameters.

LEVEL OF EVIDENCE

Level III.

Medial posterior tibial slope measurements are overestimated on long radiographs and 3D CT compared to measurements on short lateral radiographs

Purpose

This study assessed the measurements of the medial posterior tibial slope (MPTS) using long radiographs and three-dimensional (3D) computed tomography (CT) scans and compared them to measurements taken on short lateral knee radiographs. The study aimed to identify whether the at-risk slope measurements previously defined on the short radiographs would be similar to long radiographs and 3D CT scans.

Methods

A retrospective radiological review of 52 cases, who underwent planning for a slope-changing high tibial osteotomy and had short and long lateral radiographs and 3D CT scans of the tibia. Two independent observers measured the MPTS on the three modalities. The MPTS was defined as the angle between a tangent to the medial tibial plateau and the referenced tibia anatomical axis. The MPTS measurements from the short and long radiographs were compared to each other and then were compared to the measurements performed on the CT scan. False positives were defined as those cases with MPTS measurements of >78° on CT scans or long radiographs while having measurements ≤78° on short radiographs. These false positive cases are the ones which would be falsely labelled as having an abnormal slope based on the previously validated short radiograph slope threshold ≥12°.

Results

A total of 52 cases were analysed (67.9% males and 32.1% females). The mean age was 27 ± 5.4 years. The mean weight was 71.5 ± 7.7 kg, and the mean height was 1.8 ± 0.1 m. The mean MPTS measured on the short radiographs was 77.3 ± 2.3°; on the long radiographs, it was 75.8 ± 2.0°; and on the CT scan, it was 75.3 ± 2.1°. There was a positive correlation between the measurements taken on both the short and long radiographs (r = 0.9) (p < 0.001). Additionally, there was a positive correlation between CT tibial slope measurements and both short and long radiographs tibial slope measurements (r = 0.86, r = 0.87), respectively (both p < 0.001). False positives were 13 (25%) patients on long radiographs, and 12 (23.1%) patients on CT scans, who had their MPTS measurements ≤78° (equivalent of PTS ≥ 12°) while their measurements were >78° on the short radiographs.

Conclusion

Measurements of the MPTS can be overestimated by 1.5-2° on long lateral knee radiographs or 3D CT scans compared to measurements taken on short lateral radiographs. Different thresholds for the abnormal PTS measurements on long radiographs and CT scans, should be defined, considering the overestimated measurements in these modalities.

Level of Evidence

Level IV case series.

Posterior Tibial Slope Measured on Plain Radiograph Versus MRI and Its Association With Revision Anterior Cruciate Ligament Reconstruction: A Matched Case-Control Study

BACKGROUND

Posterior tibial slope (PTS) has been identified as a possible modifiable risk factor for anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) failure. However, the findings in the literature are inconsistent. This may be explained by several different reasons, including different measurement methods, differing definitions of ACLR failure, and possible inclusion of suboptimal films.

PURPOSE

To compare PTS values obtained using plain radiographs (XR-PTS) in a young (≤21 years of age), skeletally mature patient population with those obtained using magnetic resonance imaging (MRI), as well as to quantify the number of suboptimal lateral knee radiographs obtained across an integrated health care system and determine the potential effect of including these radiographs on summary statistics of XR-PTS.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Skeletally mature adolescent and young adult patients ≤21 years of age were identified from the ACLR registry of Kaiser Permanente. The cases of concern were patients requiring revision ACLR. The controls were patients who had an ACLR and did not require a revision procedure. The XR-PTS measurements were made on plain radiographs by a single blinded reviewer. These results were compared with measurements obtained using MRI. The quality of each plain radiograph was evaluated by measuring posterior/distal femoral condylar overlap and length of tibial diaphysis captured on the radiograph. Summary statistics with and without inclusion of measurements made on suboptimal radiographs were calculated.

RESULTS

Of the initial 634 patients with ACLR (317 case-control pairs), 561 (88.5%) had radiographs available and were included for the analysis comparing radiograph to MRI slope measurements. For the evaluation of slope between case and control pairs with radiograph information available, there were 257 case-control pairs; there were 124 pairs when those with suboptimal radiographs were excluded. There was no difference in MRI-measured lateral tibial posterior slope or medial tibial posterior slope for the 257 case-control pairs with XR-PTS information and for the 124 pairs with optimal radiographs. XR-PTS in the revision cohort was significantly steeper than in the control group when suboptimal radiographs were included in the analysis. There was no difference when patients with suboptimal radiographs were excluded. PTS measurements made on plain radiographs were larger than those made on MRI. There was a poor correlation between measurements made using these 2 modalities (r = 0.22 for radiograph and medial PTS).

CONCLUSION

This study did not find a significantly steeper XR-PTS in patients who had to undergo revision ACLR when suboptimal radiographs were not included in the analysis. The present study's results confirmed the findings from a previous study of the same patient population that used MRI. However, there was poor correlation between PTS measurements made using plain radiograph and MRI.

Proximal tibial anatomical axis and anterior tibial cortex-based measurements of posterior tibial slope on lateral radiographs differ least from actual posterior tibial slope-A biomechanical study

Purpose

To compare different measurement techniques of the posterior tibial slope (PTS) on lateral radiographs with the actual in situ PTS and evaluate the effect of tibial malrotation and image section length.

Methods

Actual PTS was measured on eight fresh-frozen tibiae using a portable 6-axis measuring arm with an accuracy of ±0.01°. True lateral radiographs were taken in the neutral position and after applying 10/20/30° internal/external rotation (IR/ER) and 5/10/15° varus/valgus rotation. The PTS was measured radiographically using five different reference axes: anterior tibial cortex (ATC), anatomical tibial axis, proximal tibial anatomical axis (PTAA), posterior tibial cortex (PTC) and fibular shaft axis (FSA).

Results

The ATC and PTAA methods showed the lowest deviation from the actual PTS, while the PTC method showed the highest difference of 5.5 ± 1.5° (medial) and 7.1 ± 1.8° (lateral) among all tested methods (p < .001). The PTAA technique showed a 1.9 ± 1.4° (medial) and 2.9 ± 1.8° (lateral) difference from the actual slope (n.s.). ER caused the PTS to increase 0.7 ± 2.0° (10° ER, n.s.) to 3.4 ± 2.1° (30° ER, p < .05), whereas IR caused the PTS to decrease 1.6 ± 1.3° (n.s) to 4.1 ± 1.7° (p < .05) when comparing to the PTAA method for the neutral position. Varus and valgus rotation showed the highest deviation from the neutral rotation at 15° valgus (3.1 ± 2.1°, n.s.).

Conclusion

Tibial slope measurements have a high degree of variability between different measurement methods, while the ATC and PTAA methods showed the least deviation from the actual PTS measured in this in vitro model. Malrotation resulted in a severe distortion of the PTS values, which may alter preoperative planning and intraoperative results. Therefore, radiographic PTS measurements may be contrasted with more objective, reproducible and reliable measuring methods.

Level of Evidence

There is no level of evidence as this study was an experimental laboratory study.

Mid-term patient-reported outcomes are inferior in opening-wedge high tibial osteotomy patients with untreated medial meniscus posterior root tear

Purpose

The impact of untreated medial meniscus posterior root (MMPR) tear (MMPRT) during opening-wedge high tibial osteotomy (OWHTO) on patient-reported outcomes (PROs) remains poorly understood. This retrospective cohort study aimed to investigate the association between the presence of MMPRT and post-operative PROs in patients who underwent OWHTO.

Methods

A total of 83 knees that underwent OWHTO that were followed up for 6.6 years were included. Post-operative PROs were assessed using the knee injury and osteoarthritis outcome score (KOOS) subscales. Medial meniscus extrusion (MME) was measured by magnetic resonance imaging (MRI). MMPRT was diagnosed based on preoperative MRI and intraoperative arthroscopy findings. The participants were categorized into the MMPRT and MMPR intact (MMPRI) groups, and their KOOS subscales were compared. Additionally, logistic regression analysis was conducted to explore the correlation between KOOS and MMPRT presence.

Results

In total, 29 out of 80 (36.3%) knees were classified into the MMPRT group, while three knees underwent total knee arthroplasty. Preoperative MME was 3.5 ± 1.9 (range 0-8.9) mm, showing correlation with the presence of MMPRT (p = 0.004) by regression analysis. The post-operative KOOS subscales of the MMPRT group were lower than the MMPRI group for pain (p = 0.017), activities of daily living (ADLs) (p = 0.001), sports (p < 0.001) and quality of life (QOL) (p < 0.001). Additionally, regression analysis showed the presence of MMPRT was correlated with lower KOOS subscale scores for pain (p = 0.041), ADLs (p = 0.011), sports (p < 0.001) and QOL (p = 0.002).

Conclusion

Preoperative MMPRT correlated with a reduction in mid-term post-operative PROs, as assessed using the KOOS, among patients who underwent OWHTO. Surgeons should consider addressing an MMPRT at the time of OWHTO.

Level of Evidence

Level IV.

Slope Osteotomies in the Setting of Anterior Cruciate Ligament Deficiency

➤ Posterior tibial slope (PTS) of ≥12° represents an important risk factor for both anterior cruciate ligament (ACL) injury and ACL reconstruction failure.➤ PTS measurements can significantly differ on the basis of the imaging modality and the measurement technique used. PTS should be measured on strictly lateral radiographs, with a recommended proximal tibial length of 15 cm in the image. The PTS measurement can be made by placing 2 circles to define the proximal tibial axis, 1 just below the tibial tubercle and another 10 cm below it. PTS measurements are underestimated when made on magnetic resonance imaging and computed tomography.➤ Slope-reducing osteotomies can be performed using a (1) supratuberosity, (2) tubercle-reflecting transtuberosity, or (3) infratuberosity method. The correction target remains a topic of debate. Although it is controversial, some authors recommend overcorrecting the tibial slope slightly to a range of 4° to 6°. For instance, if the initial slope is 12°, a correction of 6° to 8° should be performed, given the target tibial slope of 4° to 6°.➤ Clinical outcomes following slope-reducing osteotomies have been favorable. However, potential complications, limited data with regard to the impact of slope-reducing osteotomies on osteoarthritis, and uncertainty with regard to the effects on the patellofemoral joint are notable concerns.➤ Patients with complex deformities may need biplanar osteotomies to comprehensively address the condition.

Risk-factor analysis of the proximal tibia morphology for secondary ipsilateral injury after anterior cruciate ligament reconstruction: A retrospective cross-sectional study

Many studies have reported the risk factors associated with primary anterior cruciate ligament (ACL) injury. However, few studies have focused on the bony morphology of secondary ipsilateral injury after ACL reconstruction. This study aimed to investigate the morphological risk factors of the proximal tibia contributing to secondary ipsilateral injury after ACL reconstruction. Twenty patients who were selected from secondary ipsilateral injury after ACL reconstruction between January 2015 and May 2020 were included in the secondary injury group. They were matched in a 1:2 ratio to the control group, which underwent primary ACL reconstruction during the same period and did not experience reinjury at the minimum 2-year follow-up, based on age, gender, and body mass index. All parameters, including medial tibial posterior slope, lateral tibial posterior slope (LTPS), medial tibial plateau depth, and lateral tibial plateau height, were recorded by using magnetic resonance imaging. Binary logistic regression analysis and receiver operator characteristic curves were conducted to explore the risk factors for reinjury and determine the cutoff value for the significant parameter. The LTPS was significantly larger in the secondary injury group than in the control group (9.6 ± 1.5° to 7.0 ± 1.4°, P < .001), and there was no significant difference in the medial tibial posterior slope, medial tibial posterior slope, and lateral tibial plateau height between the 2 groups (P > .05). The LTPS was found to be an independent risk factor for secondary ipsilateral injury after ACL reconstruction (odds ratio = 3.220, 95% confidence interval = 1.904-5.446, P < .001). The cutoff value of the LTPS was 8.8°, with a sensitivity of 91.7% and a specificity of 81.2%. The LTPS could be a unique predictor of secondary ipsilateral injury after ACL reconstruction. Orthopedists should implement effective measurements during primary reconstruction when the LTPS is >8.8°.

Posterior Tibial Slope Measurements of the Medial and Lateral Plateaus Vary Widely Between Magnetic Resonance Imaging and Computed Tomography

PURPOSE

To compare posterior tibial slope (PTS) measurements of the medial tibial plateau (MTP) and lateral tibial plateau (LTP) on magnetic resonance imaging (MRI) versus computed tomography (CT) to determine the agreement of measurement between imaging modalities.

METHODS

Patients aged 15 to 65 years with concurrent MRI and CT imaging were initially included. Knees with significant arthrosis (Kellgren-Lawrence grade >2), proximal tibia fracture, or artifact obscuring visualization were excluded. Two independent raters measured PTS of the MTP and LTP on paired MRI and CT. Inter- and intrarater reliability were assessed using the intraclass correlation coefficient (ICC). Intermethod agreement was assessed using ICC and Bland-Altman analyses. An acceptable Bland-Altman limit of agreement (LOA) was set at ±2°, requiring 95% of measurement differences between imaging modalities to fall between ±2° for an acceptable level of agreement.

RESULTS

Forty-six knees in 45 patients met final inclusion criteria. Inter-rater reliability was good for MRI (ICC 0.78-0.83) and moderate to good for CT (ICC 0.64-0.80) studies. Intrarater reliability was moderate to excellent (ICC 0.64-0.94). Intermethod agreement between MRI and CT was poor at the MTP (ICC 0.34-0.42) and moderate at the LTP (ICC 0.59-0.70). Bland-Altman analysis demonstrated high variability of PTS measurements between MRI and CT: 0.16° (95% LOA -6.10° to 6.41°) for MTP for Rater 1; 0.22° (95% LOA -5.01° to 5.45°) for LTP for rater 1; -0.95° (95% LOA -7.22° to 5.33°) for MTP for Rater 2; -0.99° (95% LOA -6.48° to 4.85°) for LTP for rater 2, with only 47.83% to 60.87% of measurement differences falling within the predetermined acceptable LOA of ±2°.

CONCLUSIONS

Although the inter- and intrarater reliability was moderate to excellent, the degree of agreement between PTS measurements on MRI and CT was highly variable at both medial and lateral plateaus. Although some variability may have been due to the study's limitations, PTS measurements at individual plateaus may not be interchangeable between MRI and CT.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Correlation of medial tibial slope and lateral tibial slope measured on radiographs and magnetic resonance imaging in patients with anterior cruciate ligament injury

OBJECTIVES

The study aimed to investigate the correlation between medial tibial slope (MTS) and lateral tibial slope (LTS) on magnetic resonance imaging (MRI), MTS measured by different imaging, and the intra- and interobserver reliability of measurements between reviewers with gaps of experience over 10 years.

PATIENTS AND METHODS

This retrospective study included 97 patients (93 males, 4 females; mean age: 30.8±8.3 years; range, 17 to 49 years) with anterior cruciate ligament (ACL) injuries who subsequently underwent double-bundle ACL reconstruction by a single surgeon between January 2005 and December 2014. The MTS was measured on lateral knee radiographs, and MTS and LTS were measured on MRIs. Three different reviewers, including a postgraduate year doctor, an orthopedic resident, and an attending orthopedic surgeon, performed the measurements. Each reviewer measured the slope of the same image three times. The correlations of MTS on radiographs and MTS/LTS on MRIs were calculated. Intra- and interobserver reliability were evaluated.

RESULTS

The average MTS and LTS measured on MRI were not significantly different (6.4° and 6.9°, respectively; p=0.268) and exhibited a moderate positive correlation (r=0.544, p<0.001). The average MTS on radiographs was significantly greater than that on MRI (10.5° and 6.4°, respectively; p<0.001) with a low positive correlation (r=0.480, p<0.001). The intraobserver reliability of the postgraduate year doctor, the orthopedic resident, and the attending orthopedic surgeon were moderate to excellent. The interobserver reliability of MTS on radiographs was excellent (intraclass correlation coefficient [ICC]=0.925; p<0.001). The interobserver reliability of MTS on MRI as well as LTS on MRI was good (ICC=0.755 and 820, respectively; all p values <0.001).

CONCLUSION

Average MTS and LTS measured on MRI in patients with ACL injury exhibited a moderate positive correlation. The average MTS measured on radiographs was significantly greater than that on MRI with a low positive correlation.

The presence of a deep lateral femoral notch sign in ACL-injured patients is associated with a 2.7° steeper posterior tibial slope and a 19% higher frequency of lateral meniscal injuries

PURPOSE

The purpose of this study was to study the relationship between the presence of a deep lateral femoral notch sign (DLFNS) in anterior cruciate ligament (ACL)-injured patients and a higher posterior lateral tibial slope (LPTS), a reduced meniscal bone angle (MBA), a higher LPTS/MBA ratio and a higher incidence of concomitant injuries in primary ACL tears.

METHODS

A retrospective case-control study was performed in patients submitted to primary ACL reconstruction with an available preoperative magnetic resonance imaging (MRI) scan. Patients with ACL tears and a femoral impactation with a depth ≥2 mm were assorted to the DLFNS group and patients with ACL tear and without a DLFNS to the control group. LPTS and MBA were measured in MRI. The presence of concomitant injuries (meniscal, posterior cruciate ligament, medial collateral ligament, lateral collateral ligament and bone injuries) was assessed in MRI. Quantitative data are presented in the median ± interquartile range (IQR).

RESULTS

There were 206 patients included in the study, with 46 patients assorted to the DLFNS group and 160 patients to the control group. In the DLFNS group, the median LPTS was 6.7° (IQR: 4.0-8.2) versus 4.0° in the control group (IQR: 2.2-6.5) (p = 0.003). The LPTS/MBA ratio was significantly higher in the DLFNS group, with a median of 0.32 (IQR: 0.19-0.44), in comparison to the control group, with a median of 0.19 (IQR: 0.11-0.31) (p < 0.001). The multivariable logistic regression analysis showed that the LPTS is an independent risk factor to having a DLFNS (odds ratio [OR] = 1.161; 95% confidence interval [CI]: 1.042-1.293, p = 0.007). There was a higher incidence of concomitant lateral meniscal injuries in the DLFNS group (67% vs. 48%, p = 0.017).

CONCLUSIONS

In patients with ACL tears, the presence of a DLFNS is associated with a steeper lateral posterior tibial slope, as well as a higher incidence of concomitant lateral meniscal injuries.

LEVEL OF EVIDENCE

Level III.

The influence of tibial length on radiographic posterior tibial slope measurement: How much tibia do we need?

PURPOSE

The purpose of this study was to determine whether significant differences exist when comparing posterior tibial slope (PTS) measured using increasing lengths of the tibia to determine the anatomical axis.

METHODS

Patients with full-length weight-bearing tibial radiographs were retrospectively identified from 2014 to 2022 at a single institution. Patients were excluded if there was any previous history of lower extremity fracture or osteotomy. The anatomical axis of the tibia was determined using the full length of tibial radiographs, and the "reference PTS" was measured using this axis. Using the same radiograph, the PTS was measured using four different anatomical axes at standardized tibial lengths. While the center of the proximal circle remained constant at 5-cm below the tibial plateau, the center of the distal circle was drawn at four points: a) overlapping circles; b) 10-cm distal to the tibial plateau; c) 15-cm distal to the tibial plateau; d) half the length of the tibia, measured from the tibial plateau to the tibial plafond. Bivariate correlation and frequency distribution analysis (measurements >2-degrees from reference PTS) were performed between the reference PTS and PTS measured at each of the four other lengths.

RESULTS

A total of 154 patients (39.8 ± 17.4 years old, 44.2% male) were included in the final analysis. Measurements at each of the four tibial lengths were all significantly different from the reference PTS (p < 0.001). The correlation strength improved with increasing tibial length (overlapping: R = 0.681, 10-cm: R = 0.821, 15-cm: R = 0.937, and half-tibia: R = 0.963). The number of PTS measurements >2-degree absolute difference from the reference PTS decreased with increasing tibial length (overlapping: 40.3%, 10-cm: 24.0%, 15-cm: 26.0%, and half-tibia: 18.8%).

CONCLUSION

Assessment of PTS is dependent on the length of the tibia utilized to obtain the anatomical axis. Accuracy and precision of PTS measurements improved with increasing length of tibia used to determine the anatomical axis.

STUDY DESIGN

Case series.

A larger radius of the medial femoral posterior condyle is a risk factor for medial meniscus posterior root tears

BACKGROUND

Studies have shown an association between medial meniscus posterior root tears (MMPRT) and morphologic characteristics of the bone. However, the association between distal femoral bone morphology and MMPRT, particularly the medial femoral posterior condyle, is poorly understood. Our study aimed to determine the association between the morphologic characteristics of the medial posterior femoral condyle and MMPRT.

METHODS

A retrospective case-control study was performed from January 2021 to January 2022. After screening based on the inclusion and exclusion criteria, two matched groups were analyzed: the MMPRT group and the isolated lateral meniscus tears group. The hip-knee-ankle angle (HKA) and Kellgren-Lawrence grade (KLG) were measured on radiographs; the medial tibial slope angle (MTSA), medial tibial plateau depth (MTPD), and radius of the medial femoral posterior condyle (RMFPC) were measured on magnetic resonance imaging (MRI) in both groups. The area under the curve (AUC) and the best cutoff value for predicting MMPRT were calculated by using receiver operating characteristic (ROC) curve analysis.

RESULTS

The final analysis included a total of 174 patients (87 MMPRT patients and 87 controls). Significant differences were shown in the RMFPC (17.6 ± 1.0 vs. 16.2 ± 1.0, p < 0.01) and MTSA (6.4 ± 2.0 vs. 4.0 ± 1.3, p < 0.01), which were larger than those of the control group. The MTPD (1.8 ± 0.6 vs. 2.9 ± 0.7, p < 0.01) and HKA (175.4 ± 2.2 vs. 179.0 ± 2.7, p < 0.01) of the injury group were significantly different from the control group, and both were lower than the control group. However, between the MMPRT and control groups on the KLG (2.3 ± 0.6 vs. 2.2 ± 0.6, p = 0.209), there was no statistically significant difference. Among them, the RMFPC cutoff value was calculated to be 16.8 mm by ROC curve analysis, and the sensitivity and specificity were both 81.61%.

CONCLUSIONS

This study demonstrated that larger RMFPC, MTSA, smaller MTPD, and HKA were all associated with MMPRT, and RMFPC ≥ 16.8 mm was considered as a significant risk factor for MMPRT.

Precise and efficient measurement of tibial slope on magnetic resonance imaging (MRI): two novel autonomous pipelines by traditional and deep learning algorithms

Background

The measurement of posterior tibial slopes (PTS) can aid in the screening and prevention of anterior cruciate ligament (ACL) injuries and improve the success rate of some other knee surgeries. However, the circle method for measuring PTS on magnetic resonance imaging (MRI) scans is challenging and time-consuming for most clinicians to implement in practice, despite being highly repeatable. Currently, there is no automated measurement scheme based on this method. To enhance measurement efficiency, consistency, and reduce errors resulting from manual measurements by physicians, this study proposes two novel, precise, and computationally efficient pipelines for autonomous measurement of PTS.

Methods

The first pipeline employs traditional algorithms with experimental parameters to extract the tibial contour, detect adhesions, and then remove these adhesions from the extracted contour. A cyclic process is employed to adjust the parameters adaptively and generate a better binary image for the following tibial contour extraction step. The second pipeline utilizes deep learning models for classifying MRI slice images and segmenting tibial contours. The incorporation of deep learning models greatly simplifies the corresponding steps in pipeline 1.

Results

To evaluate the practical performance of the proposed pipelines, doctors utilized MRI images from 20 patients. The success rates of pipeline 1 for central, medial, and lateral slices were 85%, 100%, and 90%, respectively, while pipeline 2 achieved success rates of 100%, 100%, and 95%. Compared to the 10 minutes required for manual measurement, our automated methods enable doctors to measure PTS within 10 seconds.

Conclusions

These evaluation results validate that the proposed pipelines are highly reliable and effective. Employing these tools can effectively prevent medical practitioners from being burdened by monotonous and repetitive manual measurement procedures, thereby enhancing both the precision and efficiency. Additionally, this tool holds the potential to contribute to the researches regarding the significance of PTS, particularly those demanding extensive and precise PTS measurement outcomes.

Steep medial posterior tibial slope angle and ramp lesion are independent risk factors for an increase in quantitatively measured pivot shift in patients with ACL-deficient knees

Background

Delayed anterior cruciate ligament (ACL) reconstruction often causes residual anterolateral rotatory instability (ALRI) and consequent knee osteoarthritis, warranting the recommendation of early ACL reconstruction within 6 months after injury. Nonetheless, some cases show notable instability, even shortly after injury. The purpose of this study was to identify risk factors for an increase in quantitatively measured pivot shift in patients with ACL-deficient knees within 6 months after injury.

Methods

Patients with primary ACL reconstruction within 6 months after injury and quantitative triaxial accelerometer measurements of preoperative pivot shift were included. Descriptive statistics were calculated for 11 independent variables (age, gender, time from injury to surgery, KT-1000, knee extension angle, lateral and medial posterior tibial slope angle, medial and lateral meniscus tears, ramp lesion and Tegner active scale). A single regression analysis was performed on the 11 items and acceleration during the pivot shift, and a multiple regression analysis was performed for items with p value less than 0.1.

Results

Overall, 111 patients met the inclusion criteria. Single regression analysis showed that medial posterior tibial slope angle, medial meniscus tear and ramp lesion were significantly correlated with acceleration during the pivot shift (p < 0.001, p = 0.04 and p = 0.001). Multiple regression analysis identified medial posterior tibial slope angles and ramp lesions as independent factors for increased preoperative pivot shift (p = 0.005 and 0.01).

Conclusion

A steep medial posterior tibial slope angle and ramp lesion were independent risk factors for increased quantitatively measured pivot shift in patients with ACL-deficient knees.

Level of Evidence

Level IV, case series study.

[The correct tibial slope? Comparison of measuring methods]

INTRODUCTION

From a biomechanical point of view, the tibial slope plays a significant role in relation to the loading of the ligament structures in the knee joint. Currently, there are various methods of measurement for the tibial slope, which makes it difficult to compare the measurement results obtained. These differences can be decisive factors for the indication and the extent respectively of the correction of the tibial slope. The aim of this work is to present the differences in results between the measurement methods, and to compare these with the posterior tibial slope (PTS).

METHODS

By means of a comparative analysis, six measurement techniques for the tibial slope were examined. Using six parameters (correlation coefficient, range, deviation of the average slope value, correction coefficient, difference in the corrected measurements, range of the corrected measurements), these results were compared with the PTS. In this prospective study, the PTS was measured in 107 (49 male, 58 female, age 42.6 ± 23.4 years) strictly lateral plain radiological projections of the tibia with the talocrural joint in comparison with the measurement methods according to Han, Brazier, Moore and Harvey, Pietrini and LaPrade and a supratuberosity measurement.

RESULTS

The posterior slope was observed at a mean value of 6.9° (± 8.6°). Compared with the PTS, tibial slope values were increased in 55.5 % of all measurements examined and decreased in 42.4 %. In 2 % the values were identical to those of PTS. The deviations observed were significant at up to +2.9° (± 1.7°) and -2.3° (± 1.5°) respectively in comparison with the measured PTS (p < 0.001). 25.9 % of the results showed a slope value more than 2°too high and 17.6 % one less than -2° too low. Thus, in 43 % of the results clinically relevant results that were too high or too low were observed for the tibial slope compared with the PTS (p < 0.001). The correlation analyses showed very high linear connections with PTS (p < 0.001) for all methods, from r2 = 0.88 (in Moore and Harvey) up to r2 = 0.98 (in Han). The ranges varied between 13.90° (Moore and Harvey) and 18.30° (Han).

CONCLUSION

Depending on the measurement method, the slope values obtained should be individually evaluated, in order to draw the correct clinical conclusions. In principle, the radiological assessment of the whole lower leg is essential, so that concomitant pathologies in the area of the entire tibia can be detected. In everyday clinical practice, the measurement according to Han et al., and thus a shorter X‑ray projection, makes it possible to draw optimal conclusions about the PTS. LOE: Prospective diagnostic study, Level II.

Variability Between Full-Length Lateral Radiographs and Standard Short Knee Radiographs When Evaluating Posterior Tibial Slope in Revision ACL Patients

Background

Increased posterior tibial slope (PTS) has been identified as a risk factor for failure after anterior cruciate ligament (ACL) reconstruction. Correction of PTS may improve outcomes after revision ACL reconstruction. There are conflicting reports demonstrating the measurement of the PTS on standard short knee (SSK) radiographs versus full-length lateral (FLL) radiographs including the entire tibia.

Purpose/Hypothesis

To compare PTS measurements between SSK and FLL radiographs in patients who failed primary ACL reconstruction. It was hypothesized that there would be high variability between the SSK and FLL radiographic measurements.

Study Design

Cohort study (diagnosis); Level of evidence, 2.

Methods

The medial and lateral PTS were measured on the SSK and FLL radiographs of 33 patients with failed primary ACL reconstructions. All measurements were performed by 2 trained independent observers (A.A.M., J.S.), and inter- and intraobserver reliability were calculated using the intraclass correlation coefficient (ICC). Measurements recorded by the observer with the higher intraobserver ICC were used for comparison of the PTS on SSK versus FLL radiographs.

Results

Both the inter- and the intraobserver reliability values of the PTS measurements were excellent. There was a significant difference in mean PTS on the medial plateau as measured on the SSK and FLL radiographs (11.2°± 5.3° vs 12.5°± 4.6°; P = .03), with the FLL radiographs demonstrating higher PTS. There was also a significant difference in the mean PTS on the lateral plateau as measured on SSK versus FLL radiographs (10.7°± 4.3° vs 12.2°± 4°, respectively; P = .01), with the FLL radiographs demonstrating higher PTS. Notably, 66.67% of the absolute measurements for PTS on the medial plateau differed by ≥2°, with variability as high as 8.5°.

Conclusion

Results indicated that FLL and SSK radiographs are not interchangeable measurements for PTS associated with failed ACL reconstruction. Because FLL radiographs demonstrate less variability than SSK radiographs, we recommend obtaining them to evaluate these complex patients.

Measurement of tibial slope using biplanar stereoradiography (EOS®)

OBJECTIVES

Posterior tibial slope (PTS) is an important anatomic parameter of the knee related to anteroposterior instability. Biplanar stereoradiography allows for simultaneous low-dose acquisition of anteroposterior and lateral views with 3D capability, enabling separate lateral and medial plateau analyses. We aimed to evaluate the possibility and compare the reproducibility of measuring medial and lateral PTS on EOS® images with two different patient positionings and compare it with CT of the knees as the gold standard.

METHODS

This is a retrospective study including volunteers who underwent lower limb stereoradiography and knee CT from 01/08/2016 to 07/31/2019. Sixty legs from 30 patients were studied. PTS were measured using stereoradiography and CT by two radiologists. Intraclass correlation was used to calculate intrarater and interrater reproducibilities. Pearson's correlation coefficients were used to calculate the correlation between stereoradiography and CT. We also compared the reproducibility of the stereoradiography of volunteers with 2 different positionings.

RESULTS

The mean stereoradiography PTS values for right and left knees were as follows: lateral, 12.2° (SD: 4.1) and 10.1° (SD: 3.5); medial,12.2° (SD: 4.4) and 11.6° (SD: 3.9). CT PTS mean values for right and left knee are as follows: lateral, 10.3° (SD:2.5) and 10.6° (SD: 2.8); medial: 8.7° (SD: 3.7) and 10.4° (SD: 3.5). Agreement between CT and EOS for angles between lateral and medial PTS was good (right, 0.874; left, 0.871). Regarding patient positioning on stereoradiography, interrater and intrarater reproducibilities were greater for patients with nonparallel feet (0.738-0.883 and 0.870-0.975).

CONCLUSIONS

Stereoradiography allows for appropriate delineation of tibial plateaus, especially in patients with nonparallel feet, for the purpose of measuring PTS. The main advantage is lower radiation doses compared to radiography and CT.

Bone-patellar tendon-bone autograft is associated with a higher rate of return to preinjury levels of performance in high-level athletes than anterior cruciate ligament reconstruction using hamstring autograft

PURPOSE

Return to preinjury levels of performance (RTP) is the main goal after anterior cruciate ligament reconstruction (ACL-R) for athletes when ACL graft rupture is a career-threatening event. The purpose of this study was to elucidate the associated factors for RTP and subsequent ACL injury after ACL-R using bone-patellar tendon-bone (BPTB) or hamstring (HT) autograft in high-level athletes with a minimum postoperative follow-up of 24 months.

METHODS

This retrospective study included 157 patients who had preinjury Tegner activity level of 9 and underwent primary ACL-R using BPTB (average age, 16.9 years; 35 males and 36 females) or HT (average age, 17.2 years; 49 males and 37 females). The mean follow-ups were 33.6 months in BPTB and 44.5 months in HT, respectively. The data were obtained based on routine clinical follow-ups and telephone interviews performed by the surgeon. Multivariate logistic regression analysis was conducted to determine the association of patient variables with RTP and subsequent ACL injury.

RESULTS

Ninety-nine patients (63.1%) were able to RTP. The rate of RTP in BPTB (74.6%) was significantly higher than that of HT (53.5%) (p < 0.05). The overall average timing of RTP after ACL-R was 10.0 months while that was significantly earlier in BPTB (9.7 months) than in HT (10.5 months) (p < 0.05). Twenty-three (14.6%) and 21 patients (13.4%) had ACL graft ruptures and ACL injuries in the contralateral knees, respectively. Multivariate analyses showed that BPTB (odds ratio [OR], 2.590; 95% confidence interval [CI], 1.300-5.160; p = 0.007) was associated with a higher potential for RTP after ACL-R. The incidence of ACL graft rupture after ACL-R decreased with BPTB (OR, 0.861; 95% CI, 0.770-0.962; p = 0.009).

CONCLUSIONS

The use of BPTB autograft was associated with a higher rate of RTP and a lower incidence of ACL graft rupture compared to ACL-R using HT autograft.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Factors influencing the posterior cruciate ligament buckling phenomenon-a multiple linear regression analysis of bony and soft tissue structures of the knee joint

PURPOSE

To determine whether posterior cruciate ligament (PCL) buckling (angular change) is associated with anterior cruciate ligament (ACL) status (intact or ruptured), meniscal bone angle (MBA), anterior tibial translation (ATT), body weight, femoral-tibial rotation (FTR), posterior tibial slope (PTS), PCL length and femoral-tibial distance (FTD) and to identify the factors that have the greatest influence.

METHODS

All enrolled participants were scanned with a 3.0 T, 8-channel coil MRI system (Magnetom Verio; Siemens). Bone and soft tissue parameters were measured by MIMICS software for each subject and each measured parameter was correlated with PCL buckling phenomena. The correlated and statistically significant parameters were then analyzed by multiple linear regression to determine the magnitude of the effect of the different parameters on the PCL buckling phenomenon.

RESULTS

A total of 116 subjects (50 ACL ruptured and 66 age, weight and height matched volunteers with uninjured knees) were enrolled. Among all measured parameters, there were 8 parameters that correlated with PCL angle (PCLA), of which ACL status had the strongest correlation with PCLA (r = - 0.67, p =  < 0.001); and 7 parameters that correlated with PCL-posterior femoral cortex angle (PCL-PCA), of which ATT had the strongest correlation with PCL-PCA (r = 0.69, p =  < 0.001). PCLIA was not significantly correlated with any of the measured parameters. Multiple linear regression analyses revealed four parameters can explain PCLA, of which ACL status had the strongest effect on PCLA (absolute value of standardized coefficient Beta was 0.508). Three parameters can explain PCL-PCA, of which ATT had the strongest effect on PCLIA (r = 0.69, p = < 0.001), ATT has the greatest effect on PCL-PCA (absolute value of normalized coefficient Beta is 0.523).

CONCLUSIONS

PCLA may be a simple and easily reproducible and important supplement for the diagnosis of ACL injury; PCL-PCA is a simple and easily reproducible and important complementary tool for the detection of ATT. The use of PCLA is more recommended to aid in the diagnosis of ACL injury.

Three Morphological Risk Factors for Predicting Isolated Meniscal Bucket-handle Tear

Purpose

The study aimed to investigate whether morphometric variables of the knee can predict isolated meniscal bucket-handle tears and identify the risk factors.

Methods

The study included 146 participants with a mean age of 36.547 ± 12.279 years. They included two groups of 73 patients each: one group with isolated meniscal bucket-handle tears and another with no knee injury (control group). Magnetic resonance imaging findings of the participants were retrospectively assessed. A few morphometric variables associated with distal femur, proximal tibia, and cruciate ligaments were measured.

Results

Cruciate ligament tensity (CLT), medial femoral condylar height (MFCH), and lateral meniscal bone angle (LMBA) were found to be 12.7 ± 0.3, 30.1 ± 2.5 mm, and 21.2° ± 3.4°, respectively, in patients with meniscal bucket-handle tear, compared with 11.9 ± 0.2, 28.3 ± 2.7 mm, and 26.5° ± 3.7° in the control group, respectively. Based on multivariate Firth's logistic regression analysis, CLT (Odds ratio [OR]: 456.533; 95% confidence interval [CI]: 27.582 to > 999.999), MFCH (OR: 1.603; 95% CI: 1.023-2.513), and LMBA (OR: 0.780; 95% CI: 0.624-0.975) could distinguish between meniscal bucket-handle tears and knees without meniscus tears (p < 0.05). Based on the multicategorical multinominal regression model, CLT (OR: > 999.999; 95% CI: 49.937 to > 999.999) and MFCH (OR: 1.903; 95% CI: 1.005-3.606) were the determinant variables in differentiating medial meniscal bucket-handle tears from knees without meniscus tears (p < 0.05).

Conclusion

Large CLT, high medial condyle, and small LMBA were revealed as the morphometric risk factors for meniscal bucket-handle tear.

The potential of posterior cruciate ligament buckling phenomenon as a sign for partial anterior cruciate ligament tears

INTRODUCTION

Diagnosis of a partial tear of the anterior cruciate ligament (ACL) can be challenging with physical examination and imaging techniques. Although magnetic resonance imaging (MRI) has high sensitivity and specificity for diagnosing complete ACL tears, its effectiveness may be limited when it is used to diagnose for partial tears. The hypothesis of the present study is that the posterior cruciate ligament (PCL) buckling phenomenon, which is a secondary sign of complete ACL tears on MRI, may be a useful method for diagnosing partial ACL tears.

MATERIALS AND METHODS

The data of 239 patients who underwent knee arthroscopy in a single institution between 2016 and 2022 were analyzed retrospectively. Patients were divided into three groups based on the condition of their ligaments: partial tears, complete tears and intact ligaments. To evaluate the buckling phenomenon on sagittal T2-weighted MRI, measurements of the posterior cruciate ligament angle (PCLA) and the posterior cruciate ligament-posterior cortex angle (PCL-PCA) were conducted in each group. Subsequently, the ability of these two measurement methods to distinguish partial tears from the other groups was assessed.

RESULTS

Both methods provided significantly different results in all three groups. Partial tears could be distinguished from intact ligaments with 86.8% sensitivity, 89.9% specificity when PCLA < 123.13° and 94.5% sensitivity, 93.2% specificity when PCL-PCA < 23.77°. Partial tears could be distinguished from complete tears with 79.5% sensitivity, 78.4% specificity when PCLA > 113.88° and with 86.1% sensitivity, 85.3% specificity when PCL-PCA > 16.39°.

CONCLUSION

The main finding of the present study is that the PCLA and PCL-PCA methods are useful on MRI for diagnosing partial ACL tears. PCLA value between 113°-123° and PCL-PCA value between 16°-24° could indicate a partial ACL tear. With these methods, it is possible to distinguish partial tears from healthy knees and reduce missed diagnoses. In addition, the differentiation of partial and complete tears by these methods may prevent unnecessary surgical interventions.

LEVEL OF EVIDENCE

Level III.