Higher Meniscal Slope Is a Risk Factor for Anterior Cruciate Ligament Injury in Skeletally Immature Patients

Malrotation Strongly Influences Posterior Tibial Slope Measurement on Lateral Radiographs of the Knee

Background

Posterior tibial slope (PTS) is commonly measured on lateral radiographs, but there is an ongoing discussion on which criteria are essential as quality standards.

Purpose/Hypothesis

The purpose of this study was to evaluate the effect of malrotation of the tibia on lateral radiographs for PTS measurement. It was hypothesized that malrotation alters the measured PTS.

Study Design

Descriptive laboratory study.

Methods

An infratuberositary osteotomy was performed on a tibial saw bone model, and 3 conditions-2 with increased PTS-were tested with the same experimental setup (series 1, closed osteotomy; series 2, 5-mm anterior opening; series 3, 10-mm anterior opening). Long lateral radiographs were taken from +12.5° of external tibial rotation (ETR) to -20° of internal tibial rotation (ITR), in steps of 2.5°. PTS was measured with the mechanical axis (MA) and the proximal anatomic axis (PAA). In addition, the distance between the medial and lateral posterior tibial condyles was measured (in mm).

Results

In test series 1, between +12.5° to 0° of ETR and 0° to-20° of ITR, a change in PTS of 2.8°± 1.0 (ETR) and 3.7°±1.3 (ITR) for the MA and 3.7°± 1.4 (ETR) and 4.1°±1.5 (ITR) for the PAA was detected. In test series 2, changes of 1.5°± 0.5 (ETR) and 3.7±1.3 (ITR) for the MA and 1.6°± 0.6 (ETR) and 4.3°±1.4 (ITR) for the PAA were observed; likewise, in test series 3, changes of 1.8°± 0.7 (ETR) and 3.7°±1.3 (ITR) for the MA and 2.2°± 0.9 (ETR) and 4.2°±1.3 (ITR) for the PAA were observed. ETR of +12.5° resulted in a distance of 5 mm, and ITR of -20° resulted in a distance of 10 mm between the posterior tibial condyles in all testing conditions. There was no significant difference among the 3 testing conditions (P > .05). A change of 1 mm in distance was equivalent to 2° (ITR) or 2.5° (ETR) of change in rotational alignment and 0.4° of change in PTS measurement, irrespective of whether MA or PAA was used.

Conclusion

Tibial malrotation strongly influences PTS measurement on lateral radiographs. ETR leads to an underestimation, and ITR to an overestimation, of PTS. Every 1° of change in rotational alignment was equivalent to 0.2° of change in PTS measurement. For a reliable PTS measurement on lateral radiographs, the posterior tibial condyles should be superimposed exactly.

Clinical Relevance

Dependent on PTS values, surgical correction of the PTS can be indicated. For a correct indication, it is of utmost importance to be able to determine the posterior slope exactly. This investigation demonstrates the effect of tibial rotation on PTS measurement and defines quality criteria, as well as a simple grading system for lateral radiographs for the measurement of the PTS. This helps surgeons to interpret radiographs correctly, allowing a better decision-making process, if and when a corrective osteotomy for PTS correction is indicated.

Morphological Risk Factors for Pediatric Anterior Cruciate Ligament Tears and Tibial Spine Fractures

BACKGROUND

Both tibial spine fractures (TSFs) and anterior cruciate ligament (ACL) tears result in functional loss of knee stability. Nonetheless, it remains unclear why some patients sustain ACL tears, whereas others have TSFs.

PURPOSE

To identify the common morphological risk factors for pediatric ACL tears and TSFs and to determine the morphological differences between them using multiplanar reconstruction of magnetic resonance imaging (MRI).

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Age- and sex-matched participants (159 total [53 ACL tears, 53 TSFs, and 53 controls]) aged <18 years who visited a pediatric tertiary-care center for ACL tears, TSFs, or anterior knee pain from March 2009 to April 2023 were included. Each group comprised 41 male and 12 female participants. Data on demographic characteristics and estimated bone age based on the knee MRI atlas were retrospectively collected, and various knee morphological parameters were evaluated using multiplanar reconstruction of MRI. Parameters showing significant differences among the 3 groups were selected as independent variables for multivariable multinomial logistic regression analysis, with the groups as dependent variables.

RESULTS

The mean chronological age at the time of MRI was 13.2 ± 2.3 years. Height, weight, body mass index, bone age, articular medial tibial slope, and bony medial tibial slope did not differ among the groups. Articular lateral tibial slope was independently associated with the occurrence of both ACL tears (relative risk ratio [RRR], 1.42 [95% confidence interval (CI), 1.16-1.74]; P = .001) and TSFs (RRR, 1.33 [95% CI, 1.10-1.62]; P = .004). A high notch width index was a protective factor against ACL tears (RRR, 0.86 [95% CI, 0.77-0.96]; P = .006) but not against TSFs (RRR, 1.01 [95% CI, 0.91-1.12]; P = .848).

CONCLUSION

A high articular lateral tibial slope was a common risk factor for ACL tears and TSFs. Patients with ACL tears had a narrower intercondylar notch than those with TSFs and controls.

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.

Medial meniscal and bony slopes are higher in knees with failed ACL reconstruction than in patients with successful ACL reconstruction

BACKGROUND

We aimed to compare tibial soft tissue and bony slopes in patients with failed and non-failed ACL reconstructions (ACLR). We hypothesized that patients with failed ACLR have increased slopes compared to non-failed ACLR, and unexplained failures have higher slopes than failures with clear technical errors and failed synthetic ligaments.

METHODS

Between 2015 and 2022, 130 patients with failed ACLR were retrospectively identified; 79 knees with adequate MRI scans were analyzed. These were compared to 57 non-failed ACLRs. MRI measurements included lateral and medial tibial bony slope (LBS, MBS) and lateral and medial meniscal slope (LMS, MMS). Subgroup analysis assessed for failures with technical errors and failed synthetic ligaments.

RESULTS

In all patients, the LMS and MMS reduced the bony slope towards the horizontal without reaching statistical significance. Failed ACLR had significantly higher MBS (7.1° ± 2.9 vs. 4.6° ± 2.5, p < 0.001) and MMS (5.6° ± 3.5 vs. 3.4° ± 2.8, p < 0.001). The area under the curve for MBS was 0.721 (CI: 0.628-0.813). The Youden optimal threshold value of MBS ≥ 5.1° (sensitivity 80 %, specificity 56.1 %) yielded an odd's ratio for failure of 5.1 (CI:2.3-11.6; p < 0.001). Revisions with technical errors had slopes that were not significantly different to non-failed ACLR. Revisions with synthetic grafts had MBS (7.3° ± 3.2 vs. 4.6° ± 2.5; p = 0.007) and MMS (6° ± 3.8 vs. 3.4° ± 2.8; p = 0.021) that were significantly higher to non-failed ACLR.

CONCLUSION

Medial bony and meniscal slopes are higher in patients with unexplained failed ACLRs and revisions with synthetic grafts, but ACLR with technical errors failed with slopes similar to non-failed ACLRs. Increased medial slope values are a risk factor for surgical failure.

LEVEL OF EVIDENCE

III.

Association Between Posterior Tibial Slope and ACL Injury in Pediatric Patients: A Systematic Review and Meta-analysis

BACKGROUND

The posterior tibial slope (PTS) has been proposed to be a radiographic risk factor for anterior cruciate ligament (ACL) injury in adults. However, this has not been well established in pediatric patients.

PURPOSE

This systematic review and meta-analysis was performed to investigate any association between PTS and ACL tears in the pediatric population.

STUDY DESIGN

Systematic review and meta-analysis; Level of evidence, 4.

METHODS

A systematic review was performed to identify studies that examined the relationship between PTS, medial tibial slope (MTS), and lateral tibial slope (LTS) and ACL tears in children and adolescents aged ≤18 years. Full-text observational studies comparing PTS, MTS, and/or LTS values between pediatric (≤18 years of age) patients with and without ACL injury were included in this analysis. Review articles and case series were excluded. The authors calculated the mean difference (MD) via a restricted maximum-likelihood estimator for tau square and a Hartung-Knapp adjustment for random-effects model.

RESULTS

A total of 348 articles were identified in the initial database search, yielding 10 for final inclusion and analysis. There was no statistically significant association between PTS (MD, 1.13°; 95% CI, -0.55° to 2.80°; P = .10), MTS (MD, 0.36°; 95% CI, -0.37° to 1.10°; P = .27), or LTS (MD, 1.41°; 95% CI, -0.20° to 3.02°; P = .075) and risk for ACL injury in this population.

CONCLUSION

The current study found that unlike what has been shown in adult populations, increased PTS may not be a significant risk factor for ACL tears in pediatric and adolescent patents. LTS was the only measured parameter that neared statistical significance, perhaps suggesting a potential role for this measurement in determining ACL risk if further research is done in this population.

Evaluation of Tibial Slope on Radiographs in Pediatric Patients With Tibial Spine Fractures: An Age- and Sex-Matched Study

Background

A recent study has reported that the radiographic measurement of posterior tibial slope (PTS) is larger in male pediatric patients with tibial spine fractures (TSF) than in controls. However, they found no difference in PTS between female patients and controls.

Purpose

(1) To identify whether PTS is larger in female pediatric patients with TSF than in female controls and (2) to validate the relationship between PTS and pediatric TSF in male patients.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

After an a priori power analysis, 84 pediatric patients with TSF (50 female patients and 34 male patients) and 84 age- and sex-matched controls were enrolled in this study. Demographic information, including sex, age, and race, was recorded. Skeletal maturity was determined based on the stage of epiphyseal union on knee radiographs. PTS was defined as the angle between a line perpendicular to the longitudinal axis of the tibia and the posterior inclination of the medial tibial plateau on standard knee lateral radiographs.

Results

The mean age when the TSF occurred was 11.2 ± 2.7 years for female patients and 12.9 ± 2.5 years for male patients. There was no significant difference in skeletal maturity between female patients and female controls or between male patients and male controls. The mean PTS was not significantly different between female patients (8.8°± 2.8°) and female controls (8.3°± 3.1°) (P = .366) or between male patients (9.0°± 2.8°) and male controls (9.3°± 2.6°) (P = .675). Those with a PTS >1 SD (2.9°) above the mean (8.8°) had no greater odds (1.0 [95% CI, 0.4-2.5]; P≥ .999) of having a TSF than others.

Conclusion

PTS was not found to be a risk factor for pediatric TSF in female or male patients in this study.

Physeal-Sparing Anterior Cruciate Ligament Reconstruction with Iliotibial Band Autograft in the Skeletally Immature Knee

Conventional adult anterior cruciate ligament reconstruction techniques are controversial in skeletally immature patients due to the risk of iatrogenic physeal damage and potential growth disturbance. The physeal-sparing, combined intra- and extra-articular anterior cruciate ligament reconstruction using an autogenous iliotibial band was developed to mitigate this risk in prepubescent, skeletally immature patients, with excellent functional outcomes and a low revision rate. This article describes the surgical details of this reproducible reconstruction technique.

Assessment of Anatomic Restoration and Clinical Outcomes Between Medial and Lateral Meniscal Allograft Transplantation

Background:

Proper anatomic restoration is an important consideration for meniscal allograft transplantation (MAT), even with the different anatomica characteristics between the medial meniscus and lateral meniscus.

Purpose/Hypothesis:

The purpose of this study was to assess the accuracy of anatomic restoration in medial and lateral MAT (MMAT and LMAT) procedures and to compare their outcomes. We hypothesized that (1) the anatomic differences between the medial and lateral menisci will mean a less accurate anatomic restoration for MMAT and (2) clinical outcomes after MMAT will be inferior compared with LMAT.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

We retrospectively evaluated 20 patients who underwent MMAT using the bone plug technique and 21 patients who underwent LMAT using the keyhole technique at a single institution from July 2014 to June 2019. Demographic data, previous surgeries, and concomitant procedures were recorded, as were lower limb alignment and osteoarthritis grade on radiographs. Using preoperative and follow-up magnetic resonance imaging, the meniscal position, rotation, extrusion, and intrameniscal signal intensity were evaluated. Clinical outcomes were evaluated using the International Knee Documentation Committee and Lysholm scores.

Results:

The mean follow-up was 41.15 ± 18.86 and 45.43 ± 21.32 months for the MMAT and LMAT patients, respectively. Concomitant procedures were performed in 90% of MMATs and 15% of LMATs. There was no significant difference between the native and postoperative root positions after LMAT; however, for MMAT, the position of the anterior root was located significantly posteriorly (P = .002) and medially (P = .007) compared with preoperatively. In addition, the allograft medial meniscus was restored in a more internally rotated position (P = .029). MMATs also exhibited significantly increased meniscal extrusion compared with LMATs (posterior horn, P < .001; midbody, P = .027; anterior horn, P = .006). However, there was no significant difference between the 2 groups at final follow-up in intrameniscal signal intensity or clinical scores.

Conclusion:

LMAT showed higher accuracy than MMAT in restoring meniscal position and rotation, and there was less meniscal extrusion. However, clinical scores improved after both LMAT and MMAT compared with preoperative values, and midterm clinical outcomes were similar. The small anatomical errors seen in the MMAT technique were not clinically relevant at midterm follow-up.

Posterior Tibial Slope in Patients With Torn ACL Reconstruction Grafts Compared With Primary Tear or Native ACL: A Systematic Review and Meta-analysis

Background:

Increased posterior tibial slope (PTS) is a risk factor for anterior cruciate ligament (ACL) rupture and failure of ACL reconstruction (ACLR) grafts.

Purpose:

The purpose was to conduct a systematic review of literature on PTS measurements and to conduct a meta-analysis of comparable PTS measurements based on a patient’s ACL status. It was hypothesized that patients with torn ACLR grafts would have significantly larger medial and lateral PTS compared with patients with native ACLs or those who underwent primary ACLR.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic review was performed using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Included were studies that reported medial and/or lateral PTS measurements, those that reported PTS measurements based on ACL status (ie, intact ACL, primary ACL tear, failed ipsilateral ACLR, or revision ACLR), and those that reported their specific PTS measurement technique. Average PTS measurements, measurement location (medial or lateral tibial plateau) and technique, imaging modality used, and ACL status were extracted from each study. Data were pooled using DerSimonian and Laird random-effects models, and results were compared using the Altman interaction test.

Results:

The literature search identified 1705 studies, of which 82 (N = 12,971 patients) were included. There were 4028 patients in the intact ACL group (31%), 7405 in the primary ACLR group (57%), and 1538 in the failed ACLR group (12%). Measurements were obtained from lateral radiographs in 31 studies (38%), from magnetic resonance imaging in 47 studies (57%), and from computed tomography in 4 studies (5%). The failed ACLR group had a significantly larger lateral PTS (9.55°; 95% CI, 8.47°-10.63°) than either the primary ACL tear (7.13°; 95% CI, 6.58°-7.67°) or intact ACL (5.57°; 95% CI, 5.03°-6.11°) groups (P < .001 for both). The failed ACLR group also had a significantly larger medial PTS (9.05°; 95% CI, 7.80°-10.30°) than the primary (6.24°; 95% CI, 5.71°-6.78°) or intact ACL (6.28°; 95% CI, 5.21°-7.35°) groups (P < .001 for both).

Conclusion:

Both lateral and medial PTS measurements were greater in patients who had failed previous ACLR than those with a primary ACL tear or an intact native ACL. The lateral PTS of patients with primary ACL tears was greater than those with an intact native ACL.

Editorial Commentary: Increased Tibial Slope Is Associated With Anterior Cruciate Ligament Injury Risk, and Tibial Slope Increases in the Skeletally Immature, Anterior Cruciate Ligament-Deficient Knee: A Chicken or Egg Causality Dilemma?

Increased tibial slope is associated with increased risk of anterior cruciate ligament (ACL) injury in the skeletally immature. Recent studies, however, emphasize a mutual influence, as tibial slope has been shown to increase over time in the ACL-deficient skeletally immature knee. It is hypothesized that altered biomechanics with enhanced posterior force transmission in the ACL-deficient knee may influence the developing physis, leading to altered longitudinal growth and increased tibial slope. In addition to tibial slope, the meniscal geometry, including meniscal bone angle and meniscal slope, have been shown to influence the risk of ACL injury. In the skeletally immature knee, especially, the soft tissue geometry is thought to have significant impact on ACL injury risk. However, it remains unknown whether alteration of the meniscal slope may represent a causality of ACL deficiency.