The Ratio of Tibial Slope and Meniscal Bone Angle for the Prediction of ACL Reconstruction Failure Risk

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.

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.

Menta S, Ranawat AS. Systematic Review of Clinical Outcomes After Proximal Tibia Anterior Closing-Wedge Osteotomy With ACL Reconstruction

Background

While increased posterior tibial slope (PTS) is an important risk factor for failure after anterior cruciate ligament (ACL) reconstruction, controversy exists regarding indications and outcomes of proximal tibia anterior closing-wedge osteotomy (ACWO) with concomitant ACL reconstruction in patients with ACL tears.

Purpose

To assess clinical outcomes after combined ACL reconstruction and proximal tibia ACWO.

Study Design

Systematic review; Level of evidence, 4.

Methods

In accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines, we performed a systematic review of the existing literature on ACWO and ACL reconstruction using PubMed (MEDLINE), Cochrane Library, Scopus, and Embase. The search phrases included "anterior closing wedge osteotomy,""anterior closing wedge tibial osteotomy,""anterior closing wedge proximal tibial osteotomy,""anterior cruciate ligament," and "revision anterior cruciate ligament." Non-English publications and single-patient case reports were excluded. Extracted data included study details, patient demographics, patient-reported outcomes (PROs), clinical outcomes, radiographic outcomes, complications, and return-to-sport (RTS) rates.

Results

A total of 6 studies with 110 patients (110 knees) were included. Two-stage ACWO and ACL reconstruction was reported in 2 studies of 78 patients (71%), while a single-stage technique was reported in 4 studies of 32 patients (29%). ACWO was performed in the setting of primary ACL tear in 23 patients (21%) and in recurrent ACL tear in 87 patients (79%). Patients demonstrated postoperative improvements in Lysholm, pivot-shift test, and side-to-side difference in anterior tibial translation. After ACWO, all studies reported mean postoperative PTS of <10° (range, 4.4°-9.2°). Of patients with available RTS data (n = 43), the same-level RTS rate ranged from 65% to 100%. A two-stage procedure reported in 1 study had a lower RTS rate (n = 13 of 20 [65%]) than that of 2 studies with single-stage procedure (n = 4 of 5 [80%] and n = 18 of 18 [100%]). The overall complication rate was 0.9% to 1.3%, and there were no reported ACL retears.

Conclusion

The current evidence, which is constrained by the quantity and quality of studies, showed that ACWO with single- or two-stage ACL reconstruction in patients with ACL insufficiency and increased PTS was associated with significant improvements in PROs and high RTS rates.

Various Definitions of Failure Are Used in Studies of Patients Who Underwent Anterior Cruciate Ligament Reconstruction

Purpose

To conduct a literature review to assess the definitions of anterior cruciate ligament reconstruction (ACLR) failure used throughout the orthopaedic literature.

Methods

A systematic search of Embase, Ovid Medline, SPORTDiscus, and Web of Science was conducted by a university librarian to identity level I-IV clinical studies on ACLR failure. Inclusion criteria consisted of patients who underwent ACLR and included a definition of failure of ACLR. Patients who underwent anterior cruciate ligament (ACL) repairs, animal/cadaver studies, review studies, non-English language articles, and non-full text articles were excluded. Failure data were extracted from each study and categorized. Other data that were extracted included follow-up time after ACLR, failure reoperation rate, and failure reoperation procedure. Descriptive statistics was used to analyze the data.

Results

Out of 2,775 studies, 104 (3.75%) met inclusion criteria and were analyzed in this review. The most common definition of ACLR failure included the use of a physical examination, specifically Lachman's test (21/104 [20.2%]), anterior laxity assessment, or a Pivot-Shift test (24/104 [35.2%]) or undergoing or requiring revision ACLR (39/104 [37.5%]). Although some studies used quantitative tests or imaging to help define "failure," others simply defined it as graft rerupture that was otherwise not defined (22/104 [22.5%]). Other common definitions included: the use of imaging (magnetic resonance imaging/radiographs) to confirm graft re-rupture (37/104 [35.6%]), patient-reported outcomes (recurrent instability)/patient reported outcomes measures (International Knee Documentation Committee [IKDC], Knee injury and Osteoarthritis Outcome Score [KOOS], Tegner) (18/104 [17.3%]), and the use of an arthrometer (KT-1000/2000, Rollimeter, or Kneelax) (17/104 [16.3%]). The least common definitions included graft failure or rerupture confirmed by arthroscopy (13/104 [12.5%]) and nonrevision surgery (2/104 [1.0%]). The failure rate of this procedure ranged from 0% to 100% depending on the definition of "failure."

Conclusion

In this study, we found that a variety of definitions of failure are used among studies published in the orthopaedic literature. The most common criteria for failure of ACLR were the results of physical examination tests (35%), the need for undergoing a revision ACLR (36%), and the use of imaging to diagnose the failure (34%). About 17% of studies included in this review used patient-reported outcomes, specifically recurrent instability, or PROMs (IKDC, KOOS, Tegner) in their assessment of failure of ACLR. The least used definitions of "failure" of ACLR included nonrevision ACLR surgery (2%). Although some studies used similar tests or categories in their definition of failure, there were a variety of score and grade cutoff points between them.

Level of Evidence

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

Effect of demographic features on morphometric variables of the knee joint: Sample of a 20 to 40-year-old Turkish population

This study aimed to investigate the relationship between body mass index (BMI), age, and sex and morphological risk factors that may cause internal knee injuries. The magnetic resonance images of 728 participants who met the inclusion criteria and had a mean age of 34.4 ± 6.8 years were analyzed retrospectively. Demographic differences were analyzed by measuring 17 morphological parameters known to be associated with internal knee injuries. Men had a higher anterior cruciate ligament length (ACLL), anterior cruciate ligament width, (ACLW) lateral femoral condylar width (LFCW), medial femoral condylar width (MFCW), lateral femoral condylar depth (LFCD), distal femoral width (DFW), and intercondylar femoral width (IFW) than women (P < .05). By contrast, the medial meniscus bone angle (MMBA) was lower in men than in women (P < .05). Women aged 31 to 40 years had a lower Insall-Salvati index (ISI) and lateral tibial posterior slope (LTPS) than those aged 21 to 30 years (P < .05), whereas men aged 31 to 40 years had a lower ISI than those aged 21 to 30 years (P < .05). Women with BMI ≥ 30 had a higher LFCW and MFCW but a lower ISI than those with BMI < 30 (P < .05). Men with BMI ≥ 30 had a higher LFCW, MFCW, DFW, and MMBA than those with BMI < 30 (P < .05). The use of value ranges structured according to demographic characteristics, rather than a single value range for all patient groups, may contribute to the evaluation and treatment of the morphological features that are thought to be effective in the development of internal knee injuries. These values may also shed light on future radiological risk scoring systems and artificial intelligence applications in medicine.

Morphometric risk factors effects on anterior cruciate ligament injury

OBJECTIVES

This study aims to compare the morphometric differences between patients with and without an anterior cruciate ligament (ACL) injury and to investigate the anatomical risk factors associated with ACL injury.

PATIENTS AND METHODS

Between February 2020 and February 2022, a total of 100 patients (57 males, 43 females; mean age: 36.2±6.8 years; range, 18 to 45 years) who were operated for isolated non-contact ACL tear as the patient group and a total of 100 healthy individuals (58 males, 42 females; mean age: 35.0±6.9 years; range, 18 to 45 years) without an ACL tear as the control group were included. Magnetic resonance imaging scans of the knee joint were included in the study. Morphological variables of the ACL, distal femur, proximal tibia, and menisci were measured.

RESULTS

The mean ACL inclination angle and medial meniscus bone angle were 37.7±3.8 and 20.2±2.9 in the patient group and 48.1±3.3 and 25.0±2.9 in the control group. According to the results of multivariate analysis, those with small ACL inclination angle and medial meniscus bone angle were more likely to have ACL tear (odds ratio: 0.128, intraclass correlation coefficient: 0.038-0.430, p=0.001).

CONCLUSION

Small ACL inclination angle and medial meniscus bone angle can be a risk factor for ACL tear.

Ipsilateral ACL injured patients with Segond fractures demonstrate increased posterior tibial slope

BACKGROUND

The anterolateral complex has been demonstrated to assist with rotational stability and prevention of anterior tibial translation during the pivot shift. In this study the Segond fracture is used as a surrogate for an anterolateral complex injury to determine if there is an association between Segond fracture and increased posterior tibial slope.

METHODS

Patients' charts and radiographs were analyzed retrospectively for the presence of Segond fractures on injury radiographs. These patients, the Segond cohort, were then age and gender matched to a control cohort. Demographic as well MRI measurements of medial and lateral posterior tibial slope and lateral-to-medial slope asymmetry were collected for each cohort. Secondary outcome of anterior cruciate ligament reconstruction failure data was also collected.

RESULTS

The Segond group demonstrated a statistically significantly greater lateral posterior tibial slope (8.42° versus 6.55°, P = 0.003) as well as medial posterior tibial slope (6.57° versus 5.34° degrees, P = 0.045). There was no significant differences between lateral-to-medial asymmetry (2.18°versus 1.83°, P = 0.246).

CONCLUSION

Patients with Segond fractures at the time of anterior cruciate ligament injury have increased medial and lateral posterior tibial slope. This may relate to increased rotational and translational instability associated with anterolateral complex injuries. Surgeons treating these patient may use this information to counsel their patients on the risks of associated pathology at the time of arthroscopy such as lateral meniscal posterior root tears.

Meniscal Bone Angle Is a Strong Predictor of Anterior Cruciate Ligament Injury

Purpose

To evaluate the influence of lateral posterior tibial slope (LPTS) and meniscal bone angle (MBA) on primary anterior cruciate ligament (ACL) tear risk in an adult population through the LPTS-MBA ratio.

Methods

A retrospective case-control study was performed with patients from a tertiary hospital who underwent primary ACL surgery and had preoperative magnetic resonance imaging (MRI). These subjects were matched by age and sex in a 1:1 ratio to patients who had an MRI without ACL tear. LPTS and MBA were measured on MRI scan. Quantitative data are presented in the median ± interquartile range (IQR). Identification of independent risk factors for primary ACL tear was performed using multivariable logistic regression. Receiver operating characteristics curves detected any variable with strong discriminative capacity.

Results

In total, 95 patients with primary ACL tear confirmed on MRI were matched with 95 controls (N = 190). Nearly 80% were male subjects, with a median age of 26 years. In the ACL tear group, the median value of LPTS-MBA ratio was 0.20 (IQR 0.11-0.37) versus 0.12 (IQR 0.08-0.19) in the control group (P = .001). LPTS had a median value of 4.20° in the ACL tear group (IQR 2.05-7.35°) and 2.90° in the control group (IQR, 2.05-5.00°) (P = .026), whereas MBA was 19° (IQR, 16-24°) versus 26° (IQR, 24-30°) (P = .001), respectively. Logistic regression showed that LPTS (odds ratio 1.20, 95% confidence interval 1.03-1.42, P = .021) and MBA (odds ratio 0.78, 95% confidence interval 0.71-0.85, P = .001) were independent predictors. The area under the curve (AUC) of LPTS-MBA ratio was 0.69, greater than that of LPTS alone (AUC = 0.61) but lower than that for MBA (AUC = 0.82).

Conclusions

In this study, a reduced MBA was the strongest predictive variable associated with a primary ACL tear. A threshold of 22.35° of MBA was associated with an increased risk of ACL tear, with a sensitivity of 70% and specificity of 84%. A cut-off of 0.22 of LPTS-MBA was associated with an increased risk of ACL tear, with a sensitivity of 55% and specificity of 87%.

Level of Evidence

Level III, case-control study.

An increased posterior tibial slope is associated with a higher risk of graft failure following ACL reconstruction: a systematic review

PURPOSE

The posterior tibial slope (PTS) is considered a risk factor for anterior cruciate ligament (ACL) injury. However, the influence of PTS on graft failure following ACL reconstruction remains relatively unknown. Therefore, this systematic review was conducted to investigate whether PTS could be a potential risk factor for graft failure after ACL reconstruction.

METHODS

PubMed, EMBASE, Cochrane Library, Web of Science, China National Knowledge Infrastructure Database, and Wanfang Database were comprehensively searched from inception to March 31, 2021. Observational studies reporting the associations of medial tibial plateau slope (MTPS) or lateral tibial plateau slope (LTPS) with graft failure after ACL reconstruction were evaluated.

RESULTS

Twenty studies involving 12 case-control studies, 4 retrospective studies and 4 cross-sectional studies including 5326 patients met the final inclusion criteria. The high heterogeneity and the characteristics of nonrandomized controlled trials limited data synthesis. Fifteen of the 20 included studies detected a significant association between increased PTS and ACL graft failure, while 5 studies concluded that increased PTS was not associated with ACL graft failure. Ten studies suggested that MTPS is associated with ACL graft failure, and six studies suggested that LTPS is associated with ACL graft failure. The mean MTPS values for nonfailure group ranged from 3.5° ± 2.5° to 14.4° ± 2.8°. For the graft failure group, MTPS ranged from 4.71° ± 2.41° to 17.2° ± 2.2°. The mean LTPS values for nonfailure group ranged from 2.9° ± 2.1° to 11.9° ± 3.0°. For the graft failure group, LTPS ranged from 5.5° ± 3.0° to 13.3° ± 3.0°. The reported PTS values that caused ACL graft failure was greater than 7.4° to 17°.

CONCLUSION

Based on the current clinical evidence, increased PTS is associated with a higher risk of ACL graft failure after ACL reconstruction. Despite various methods of measuring PTS have high reliability, there is still vast disagreement in the actual value of PTS.

LEVEL OF EVIDENCE

IV.

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.

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

PURPOSE

To evaluate the relation between the femoral intercondylar index, tibial slope, and meniscal slope between 3 different groups of skeletally immature patients: primary anterior cruciate ligament (ACL) injury (group 1), ACL reconstruction failure (group 2), and control group, without an ACL injury history (group 3).

METHODS

This retrospective study evaluated magnetic resonance imaging scans of the knees of 605 skeletally immature patients obtained between 2015 and 2020. The inclusion criteria were as follows: patients younger than 16 years who were skeletally immature and underwent knee magnetic resonance imaging for any reason.

RESULTS

A total of 605 skeletally immature patients were included in the study. The ratio of patients with ACL injury (cases) to those without ACL injury (controls) was 1:2.5. Patients with ACL injury had significantly greater medial meniscal slope and lateral meniscal slope values than the control group without ACL injury (P < .001). There was no statistically significant difference between patients with primary ACL injury and those with ACL reconstruction failure for all measured variables.

CONCLUSIONS

The medial and lateral meniscal slope values were significantly higher in skeletally immature patients with ACL injury than in the control group of patients without ACL injury. There was no statistically significant difference in measurements of the femoral intercondylar index, lateral meniscal slope, medial meniscal slope, lateral tibial slope, or medial tibial slope between patients with primary injury and those with ACL reconstruction failure.

LEVEL OF EVIDENCE

Level III, retrospective comparative trial.

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.

Editorial Commentary: The Ratio of Tibial Slope and Meniscal Bone Angle is a Strong Predictor for Anterior Cruciate Ligament Injury: A Steep Hill and a Shallow Speed Bump are a Hazardous Combination

The lateral tibial posterior slope (LTPS) and the lateral meniscal bone angle (MBA) are important geometrical features of the knee joint and have therefore been of interest in the setting of anterior cruciate ligament injury (ACL) and ACL reconstruction. An emerging body of evidence suggests that LTPS is an independent risk factor for primary and recurrent ACL injury. Furthermore, biomechanical and clinical evidence is emphasizing the crucial contribution of the lateral meniscus to rotatory knee stability. Thus, not surprisingly, the MBA has also been shown to be an independent risk factor regarding ACL injury. The ratio of LTPS and MBA is a relatively new idea but has shown to be highly predictive for primary and recurrent ACL injury and may be used to identify patients at high risk of ACL reconstruction failure.

Predictors of Pediatric Anterior Cruciate Ligament Injury: The Influence of Steep Lateral Posterior Tibial Slope and Its Relationship to the Lateral Meniscus

PURPOSE

To examine the relationship between posterior tibial slope and lateral meniscal bone angle (LMBA) on anterior cruciate ligament (ACL) tear risk in a pediatric population.

METHODS

In this case-control study, non-contact ACL-injured pediatric patients with no significant lateral meniscal lesions were matched by age and sex in a 1:1 ratio to a group of radiologically normal controls. Knee magnetic resonance imaging (MRI) studies were analyzed by 3 independent, blinded observers measuring the medial posterior tibial slope (MTS), lateral posterior tibial slope (LTS), and LMBA. Sagittal slope asymmetry was calculated as the absolute difference in degrees between slopes, and the relationship between LMBA and LTS was calculated as a ratio. Binary logistic regressions identified independent predictors of ACL injury. Receiver operator characteristics were performed to determine predictive accuracy.

RESULTS

20 study patients were compared with 20 sex- and age-matched controls (age 14.8 ± 2.42, mean ± standard deviation). LTS was significantly higher in the ACL-injured group (11.30° ± 3.52° versus 7.00° ± 2.63°, P = .0001), as were the absolute slope difference (7.10 ± 2.92° versus 3.14 ± 3.25°, P = .0002) and LTS:LMBA ratio (0.46 ± 0.17 versus 0.26 ± 0.12, P = .0001). No significant differences were observed for MTS or LMBA. Independent predictors were LTS (odds ratio [OR] 1.58, 95% confidence interval [CI] 1.18 to 2.13, P = .002), LTS:LMBA ratio (OR 3.13, 95% CI 1.48 to 6.62, P = .003), and absolute slope difference (OR 1.65, 95% CI 1.17 to 2.32, P = .005). LTS:LMBA ratio was the strongest predictor variable (area under the curve 0.86).

CONCLUSION

This study suggests that LTS, absolute slope difference, and LTS:LMBA ratio are significant pediatric ACL-injury risk factors. All 3 demonstrate good predictive accuracy; however, the relationship between steep LTS and shallow LMBA was the strongest predictor.

LEVEL OF EVIDENCE

III, case-control study.

Enlarged tibial eminence may be a protective factor of anterior cruciate ligament

Anterior cruciate ligament (ACL) is a primary stabilizer of the knee and constrains joint motion, and its injury is very common in clinic. There are many studies on the risk factors of ACL injury such as the ACL diameter, intercondylar notch width index (NWI), sagittal condylar shape, tibial posterior slope, tibia eminence size and so on. Large amount of research data has confirmed that all above are closely related to ACL injury. Among them the morphological characteristics of femoral condyle and tibial plateau are closely related to ACL injury. For example the tibial eminence, which is the hot topic of recent research. Whether or how does it relate to ACL injury has draw much interest of researchers. Since the tibial eminence and the ACL are both located in the intercondylar notch and adjacent to each other, we hypothesize the size of the tibial eminence may relate to the rupture of ACL. For there is report have found that reduced medial tibial eminence was associated with ACL injury, we suggest a hypothesis that enlarged tibia eminence may be a protective factor of ACL.

The Association Between Tibial Slope and Revision Anterior Cruciate Ligament Reconstruction in Patients ≤21 Years Old: A Matched Case-Control Study Including 317 Revisions

BACKGROUND

There is evidence that tibial slope may play a role in revision risk after anterior cruciate ligament reconstruction (ACLR); however, prior studies are inconsistent.

PURPOSE

To determine (1) whether there is a difference in lateral tibial posterior slope (LTPS) or medial tibial posterior slope (MTPS) between patients undergoing revised ACLR and those not requiring revision and (2) whether the medial-to-lateral slope difference is different between these 2 groups.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

We conducted a matched case-control study (2006-2015). Cases were patients aged ≤21 years who underwent revision surgery after primary unilateral ACLR; controls were patients aged ≤21 years without revision who were identified from the same source population. Controls were matched to cases by age, sex, body mass index, race, graft type, femoral fixation device, and post-ACLR follow-up time. Tibial slope measurements were made by a single blinded reviewer using magnetic resonance imaging. The Wilcoxon signed rank test and McNemar test were used for continuous and categorical variables, respectively.

RESULTS

No difference was observed between revised and nonrevised ACLR groups for LTPS (median: 6° vs 6°, P = .973) or MTPS (median: 4° vs 5°, P = .281). Furthermore, no difference was found for medial-to-lateral slope difference (median: -1 vs -1, P = .289). A greater proportion of patients with revised ACLR had an LTPS ≥12° (7.6% vs 3.8%) and ≥13° (4.7% vs 1.3%); however, this was not statistically significant after accounting for multiple testing.

CONCLUSION

We failed to observe an association between revision ACLR surgery and LTPS, MTPS, or medial-to-lateral slope difference. However, there was a greater proportion of patients in the revision ACLR group with an LTPS ≥12°, suggesting that a minority of patients who have more extreme values of LTPS have a higher revision risk after primary ACLR. A future cohort study evaluating the angle that best differentiates patients at highest risk for revision is needed.