Femoral Tunnel Malposition, Increased Lateral Tibial Slope, and Decreased Notch Width Index Are Risk Factors for Non-Traumatic Anterior Cruciate Ligament Reconstruction Failure

Large variability in minimal clinically important difference, substantial clinical benefit and patient acceptable symptom state values among literature investigating patellar stabilization surgery: A systematic review

PURPOSE

To investigate minimal clinically important difference (MCID), substantial clinical benefit (SCB), patient acceptable symptom state (PASS) values for patient-reported outcome measures (PROMs) after patellar stabilization surgery for patellar instability. Secondary outcomes included to describe methods to calculate clinically significant outcomes (CSOs), and to report on the achievement of these metrics.

METHODS

On 31 July 2024, three databases were searched. Information on whether studies calculated MCID, SCB or PASS values or used previously established values was recorded. Data on study characteristics, CSO values, and the method of MCID quantification (e.g., distribution vs. anchor) were extracted.

RESULTS

A total of 17 articles with 1447 patients (1462 knees) were included. A total of 18 unique outcome measures were reported. Six out of 15 (40%), 2 out of 5 (40%), and zero studies used prior established values for MCID, SCB and PASS, respectively. MCID ranged widely (e.g., International Knee Documentation Committee [IKDC]: 5.6-20.5; Kujala Anterior Knee Pain Scale: 5.38-11.9 and Lysholm: 5.6-11.1). Fourteen out of 15 utilized a distribution-based method to calculate MCID, with only one study using an anchor-based method. SCB values ranged widely as well (e.g.

, IKDC

14.5-23.6; Knee Osteoarthritis and Outcome Score [KOOS] symptoms: 4.2-14.2 and KOOS activities of daily living [ADLs]: 6.5-25.7). Large variability was found among percentages of patients that achieved MCID values (e.g.

, IKDC

28%-98.6%, Kujala: 38%-100%, Lysholm: 44%-98.4% and Tegner: 84%-95%).

CONCLUSION

The significant heterogeneity in reported thresholds for MCID, SCB and PASS across studies highlights critical challenges in interpreting results after patellar stabilization surgery, specifically regarding what constitutes a clinically relevant outcome. MCID was the most commonly reported metric and calculated predominantly with distribution-based methods, with over half of the studies using previously established thresholds. PASS and SCB were widely underreported as well, suggesting a need for studies investigating patellar stabilization to prioritize the calculation of all three metrics, using anchor-based techniques.

LEVEL OF EVIDENCE

Level IV.

Increased anterior tibial subluxation and differences between anterior tibial subluxation in the lateral and medial compartments are associated with failure of primary anterior cruciate ligament reconstruction: A systematic review and meta-analysis

PURPOSE

The purpose of this study is to investigate whether increased anterior tibial subluxation (ATS) and differences between ATS in the lateral and medial compartments (ATSL-M) are associated with primary anterior cruciate ligament (ACL) reconstruction (ACLR) failure.

METHODS

PubMed, Scopus, Embase and Web of Science were systematically searched from their inception through 21 November 2023. The focus was on comparative studies reporting ATS in patients who experienced primary ACLR failure, in contrast to patients after primary ACLR with no evidence of graft failure. A random-effects model was employed to calculate the overall standardized mean difference between the two groups.

RESULTS

A total of eight studies involving 963 patients were included in the final review. Three studies (64 cases and 171 controls) measured ATS on radiographs. The failed ACLR group exhibited a significantly increased ATS on radiographs compared to the control group (p < 0.001). Six studies (324 cases and 488 controls) measured lateral ATS on magnetic resonance imaging and five of them (285 cases and 374 controls) also measured medial ATS. The average values of lateral and medial ATS, as well as ATSL-M, were calculated and compared between the two groups. The failed ACLR group demonstrated significantly increased lateral (p < 0.001) and medial ATS (p < 0.001), the average value of lateral and medial ATS (p < 0.001) and ATSL-M (p = 0.039) compared to the control group.

CONCLUSION

Increased ATS and ATSL-M are associated with primary ACLR failure. The measurement of tibiofemoral position shows promise for its application in preoperative planning and postoperative management of ACLR.

LEVEL OF EVIDENCE

Level III.

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.

Machine learning models predicting risk of revision or secondary knee injury after anterior cruciate ligament reconstruction demonstrate variable discriminatory and accuracy performance: a systematic review

BACKGROUND

To summarize the statistical performance of machine learning in predicting revision, secondary knee injury, or reoperations following anterior cruciate ligament reconstruction (ACLR), and to provide a general overview of the statistical performance of these models.

METHODS

Three online databases (PubMed, MEDLINE, EMBASE) were searched from database inception to February 6, 2024, to identify literature on the use of machine learning to predict revision, secondary knee injury (e.g. anterior cruciate ligament (ACL) or meniscus), or reoperation in ACLR. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Demographic data and machine learning specifics were recorded. Model performance was recorded using discrimination, area under the curve (AUC), concordance, calibration, and Brier score. Factors deemed predictive for revision, secondary injury or reoperation were also extracted. The MINORS criteria were used for methodological quality assessment.

RESULTS

Nine studies comprising 125,427 patients with a mean follow-up of 5.82 (0.08-12.3) years were included in this review. Two of nine (22.2%) studies served as external validation analyses. Five (55.6%) studies reported on mean AUC (strongest model range 0.77-0.997). Four (44.4%) studies reported mean concordance (strongest model range: 0.67-0.713). Two studies reported on Brier score, calibration intercept, and calibration slope, with values ranging from 0.10 to 0.18, 0.0051-0.006, and 0.96-0.97 amongst highest performing models, respectively. Four studies reported calibration error, with all four studies demonstrating significant miscalibration at either two or five-year follow-ups amongst 10 of 14 models assessed.

CONCLUSION

Machine learning models designed to predict the risk of revision or secondary knee injury demonstrate variable discriminatory performance when evaluated with AUC or concordance metrics. Furthermore, there is variable calibration, with several models demonstrating evidence of miscalibration at two or five-year marks. The lack of external validation of existing models limits the generalizability of these findings. Future research should focus on validating current models in addition to developing new multimodal neural networks to improve accuracy and reliability.

Revision Anterior Cruciate Ligament Reconstruction in Combination With Meniscal and Osteochondral Allograft Transplantation for Complex Knee Injury

Revision anterior cruciate ligament reconstruction (ACLR) may present a challenge as a result of several factors, including malpositioned bone tunnels, tunnel osteolysis, and the presence of previous hardware. In addition, concomitant pathology, specifically meniscal and cartilaginous injuries, may be present and should be addressed to minimize the risk of re-rupture. Revision ACLR and treatment of accompanying injuries can be performed either as a 1-stage or 2-stage procedure, yet the latter may increase surgical risk for the patient and extend recovery time. The over-the-top technique serves as a good option for revision ACLR and can be performed with careful consideration of patient-specific anatomy and with proper surgical planning. Therefore, this Technical Note aims to present our 1-stage surgical technique for revision ACLR using over-the-top technique with an Achilles tendon allograft, along with concomitant treatment for meniscal deficiency and a medial femoral condyle chondral defect using meniscal and osteochondral allografts, respectively.

Modifiable and non-modifiable risk factors affecting surgical failure after revision ACL reconstruction: a cohort study

BACKGROUND

Research on factors influencing the outcomes of revision anterior cruciate ligament (ACL) reconstruction is relatively scarce and mostly relies even on reports from a single group. Understanding the factors contributing to the failure of revision ACL reconstruction can provide valuable information for achieving better clinical outcomes and assist in patient counseling before surgery. Therefore, this study aimed to analyze the factors contributing to surgical failure after revision ACL reconstruction.

METHODS

The medical records of consecutive patients who underwent single-bundle revision ACL reconstruction using the transportal technique between 2010 and 2020 and had a minimum follow-up of 2 years were retrospectively reviewed. Eligible patients were classified into two groups on the basis of the presence of surgical failure during the follow-up period (group NF, patients who did not experience surgical failure; group F, patients who experienced surgical failure). In this study, surgical failure after revision ACL reconstruction was defined as meeting any of the following conditions during follow-up: the presence of graft re-tear confirmed by magnetic resonance imaging (MRI), anterior-posterior laxity graded ≥ 2, or rotational laxity graded ≥ 2. A comparative analysis was conducted on demographic data, as well as peri-, intra-, and postoperative data between the groups. Additionally, a regression analysis was performed to investigate factors influencing surgical failure after revision ACL reconstruction.

RESULTS

A total of 58 patients were included (group NF, 40 patients; group F, 18 patients). In between-group comparisons of demographic, peri-, and intra-operative data, group F exhibited a higher frequency of multiple revision surgeries (P = 0.001), increased preoperative osteoarthritis grade (P = 0.001), and shallower femoral tunnel depth (P = 0.002) compared with group NF. At the final follow-up, group F demonstrated relatively poor clinical outcomes, both subjectively and objectively. Multivariate regression analysis revealed that all variables that showed differences in the preceding comparisons were independent factors affecting surgical failure after revision ACL reconstruction.

CONCLUSIONS

Surgical failure after revision ACL reconstruction can occur in a substantial number of patients, influenced by non-modifiable factors, such as cases corresponding to multiple revision surgery and preoperative osteoarthritis grade, and modifiable factors, such as femoral tunnel depth.

Editorial Commentary: Increased Tibial Slope and Decreased Medial Proximal Tibial Angle Negatively Affect Anterior Cruciate Ligament Graft Maturation: Objective Evidence on When to Add a Lateral Extra-Articular Augmentation Procedure to a Soft-Tissue Anterior Cruciate Ligament Reconstruction

Recent anterior cruciate ligament (ACL) research focuses on risk factors for ACL graft failure and techniques and augmentations to limit failure. One of the most recognized risk factors is sagittal malalignment in the form of high posterior tibial slope (PTS), especially PTS ≥12°, which leads to increased force through the ACL and ACL graft. To reduce the risk associated with increased PTS, lateral augmentation techniques, typically either a lateral extra-articular tenodesis or an anterolateral ligament reconstruction, improve clinical outcomes, and the authors preferred graft choice, particularly in such cases, is bone-patellar tendon-bone autograft. Furthermore, in revision cases, there exists a strong argument to perform a slope reducing osteotomy to correct bony malalignment which, if left untreated, could lead to ACL graft failure. Slope-reducing osteotomies are reported to significantly decrease anterior tibial translation and forces on the ACL graft. Coronal malalignment is also a risk factor for ACL failure (although not as extensively studied as sagittal alignment). Both varus and valgus alignment of the knee can lead to increased forces through the ACL or ACL graft compared with knees in neutral alignment, and workup requires proper lateral and long-leg anteroposterior radiographs to determine sagittal and coronal alignment and guide treatment algorithms. Recent research shows that decreased medial proximal tibial angle of the knee (increasing varus alignment of the tibia) may delay graft maturation. However, there is yet to be a consensus about what exactly contributes to ACL graft failure in the coronal plane and what is the best treatment option, especially in the primary setting when an osteotomy is not indicated. Again, we recommend bone-patellar tendon-bone autograft as our preferred graft choice unless contraindicated by skeletal immaturity.

The 45° and 60° of sagittal femoral tunnel placement in anterior cruciate ligament reconstruction provide similar knee stability

PURPOSE

The aim of the present study was to compare 45° and 60° of sagittal femoral tunnel angles in terms of anterior tibial translation (ATT), valgus angle and graft in situ force following anterior cruciate ligament reconstruction (ACLR).

METHODS

Ten porcine knees were subjected to the following loading conditions: (1) 89 N anterior tibial load at 35° (full extension), 60° and 90° of knee flexion and (2) 5 N m valgus tibial moment at 35° and 45° of knee flexion. ATT and graft in situ force of the intact anterior cruciate ligament (ACL) and ACLR were collected using a robotic universal force/moment sensor (UFS) testing system for (1) ACL intact, (2) ACL-deficient (ACLD) and (3) two different ACLR using different sagittal femoral tunnel angles (coronal 45°/sagittal 45° and coronal 45°/sagittal 60°).

RESULTS

During the anterior tibial load, the femoral tunnel angle of ACLR knees at coronal 45°/sagittal 45° and 60° had significantly higher ATT than that of the ACL-intact knees at 60° of knee flexion (p < 0.05). The femoral tunnel angle of ACLR knees at coronal 45°/sagittal 60° had significantly lower graft in situ force than that of the ACL-intact knees at 60° and 90° of knee flexion (p < 0.05). During the valgus tibial moment, the femoral tunnel angle of ACLR knees at coronal 45°/sagittal 45° and 60° had significantly lower graft in situ force than that of the ACL-intact knees at all knee flexions (p < 0.05).

CONCLUSIONS

The femoral tunnel angle of ACLR knees at coronal 45°/sagittal 45° provided similar ATT, valgus angle and graft in situ force to that of ACLR knees at coronal 45°/sagittal 60°. Therefore, both femoral tunnel angles could be used in ACLR, as the sagittal femoral tunnel angle does not appear to be relevant in post-operative knee stability.

LEVEL OF EVIDENCE

Not applicable.

App-based analysis of the femoral tunnel position in ACL reconstruction using the quadrant method

PURPOSE

The purpose of this study was to examine the intra- and interobserver variability of an app-based analysis of the femoral tunnel position using the quadrant method in primary anterior cruciate ligament reconstruction.

MATERIALS AND METHODS

Between 12/2020 und 12/2021 50 patients who underwent primary anterior cruciate ligament reconstruction were included in this retrospective study. Intraoperative strictly lateral fluoroscopic images of the knee with marked femoral tunnel were analyzed by four observers using the quadrant method. For retest reliability analysis, measurements were repeated once by 2 observers after 4 weeks.

RESULTS

The femoral tunnel position of all included patients averaged 27.86% in the depth relation and 15.61% in the height relation. Statistical analysis showed an almost perfect intra- and interobserver reliability in the depth and height relation. The ICC was 0.92 in the depth relation and 0.84 in the height relation. The Pearson's correlation coefficient in the depth and height relation of observer 1 (0.94/0.81) was only slightly different from the Pearson's correlation coefficient of observer 2 (0.92/0.85). The app-based tunnel analysis took on average 59 ± 16 s per measurement.

CONCLUSION

The femoral tunnel analysis with the app-based quadrant method has an almost perfect intra- and interobserver reliability. By smartphone camera, a fast and highly accurate, if necessary also intraoperative, control of the tunnel position can be performed.

LEVEL OF EVIDENCE

Level 3-diagnostic retrospective cohort study.

Editorial Commentary: Increased Lateral Femoral Condyle Ratio, Increased Posterior Tibial Slope, and Narrow Notch Width Are all Risk Factors for Anterior Cruciate Ligament Tear, and Anterior Cruciate Ligament Graft Tear

Bony risk factors for anterior cruciate ligament (ACL) injuries have been investigated during past 2 decades. Deep posterior femoral condylar depth, measured by the lateral femoral condyle ratio, influences anterolateral instability and the graft survival following ACL reconstructions. Before planning of revision ACL reconstruction, other bony risk factors, including the posterior tibial slope and intercondylar notch width, should be carefully evaluated to protect the ACL graft.

The relationship between lateral femoral condyle ratio measured by MRI and anterior cruciate ligament injury

Background

Previous studies have shown that the lateral femoral condyle ratio (LFCR) measured by X-ray has a significant relationship with the anterior cruciate ligament (ACL) injury. However, few relevant studies have been performed on LFCR measured by magnetic resonance imaging (MRI).

Purpose

(1) To evaluate the relationship between LFCR measured by MRI and ACL injury or rerupture. (2) To compare the LFCR measured by MRI with existing bony morphological risk factors and screen out the most predictive risk factors for primary ACL injury or rerupture.

Study Design

Cohort study; Level of evidence, 3.

Methods

Totally 147 patients who underwent knee arthroscopic surgery from 2015 to 2019 with minimum follow-up of 48 months were retrospectively evaluated. Patients were placed into three groups: 1) the control group of patients with simple meniscus tears without ligament injury; 2) the primary noncontact ACL injury group; 3) ACL rerupture group (ACL reconstruction failure). The LFCR measured by MRI and other previous known risk factors associated with MRI (notch width index, medial tibial slope, lateral tibial slope, medial tibial depth, lateral tibial height) were performed to evaluate their predictive value for ACL injury and rerupture. All the risk factors with p < 0.01 according to univariate analysis were included in the logistic regression models. Receiver operating characteristic (ROC) curves were analyzed for sensitivity, specificity, cut-off, and area under the curve (AUC). Z tests were used to compare the AUC values.

Results

The LFCR measured by MRI was obviously higher in primary ACL injury group (0.628 ± 0.020) and in ACL rerupture group (0.625 ± 0.021) than that in the control group (0.593 ± 0.030). The best risk factor was the LFCR with a cut-off of 0.602 (AUC, 0.818; 95% CI, 0.748-0.878; sensitivity, 90%; specificity, 66%). When combined with lateral tibial slope (cutoff, 7°) and lateral tibial height (cutoff, 3.6 mm), the diagnostic performance was improved significantly (AUC, 0.896; 95% CI, 0.890-0.950; sensitivity, 87%; specificity, 80%).

Conclusion

The increased LFCR measured by MRI was associated with a significantly higher risk for ACL injury or rerupture. The combination of LFCR, lateral tibial slope and lateral tibial height were the most predictive risk factors. This may help clinicians identify susceptible individuals and allow precision approaches for better prevention, treatment and management of this disease.

Editorial Commentary: The Number One Cause of Anterior Cruciate Ligament Reconstruction Graft Failure Is a Misplaced Femoral Tunnel: Over-the-Top Technique Plus Lateral Extra-Articular Tenodesis Is Recommended

Patient factors (notably high tibial slope and narrow femoral intercondylar notch width) and surgical factors (including meniscus treatment and anterior cruciate ligament [ACL] tunnel position) contribute to ACL reconstruction failure. The number one cause of failure is a misplaced ACL femoral tunnel. Tunnel malposition leads to a higher incidence of postoperative meniscal lesions, inferior clinical outcomes, and higher revision rates.

Decreased posterior tibial slope is a risk factor for primary posterior cruciate ligament rupture and posterior cruciate ligament reconstruction failure: A systematic review

PURPOSE

To determine bony knee morphological factors associated with primary posterior cruciate ligament (PCL) rupture or PCL graft failure after PCL reconstruction.

METHODS

Three databases, namely MEDLINE, PubMed and EMBASE, were searched on 30th May 2023. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Data such as receiver operating characteristic curve parameters, as well as p-values for comparisons of values between patients with PCL pathology and control patients, were recorded.

RESULTS

Nine studies comprising 1054 patients were included. Four studies reported that patients with PCL injury had flatter medial posterior tibial slopes (MTS) than controls, with mean values of 4.3 (range: 3.0-7.0) and 6.5 (range: 5.0-9.2) degrees, respectively. Two studies reported an MTS cutoff value ranging below 3.90-3.93° being a significant risk factor for primary PCL rupture or PCL graft failure. Two studies reported that shallow medial tibial depths were associated with primary PCL rupture, with mean values of 2.1 (range: 2.0-2.2) and 2.6 (range: 2.4-2.7) mm in PCL injury and control groups, respectively. Stenotic intercondylar notches and femoral condylar width were not consistently associated with PCL injuries.

CONCLUSION

Decreased MTS is associated with primary PCL rupture and graft failure after PCL reconstruction with values below 3.93° being considered as a significant risk factor. Less common risk factors include shallow medial tibial depth, while femoral condylar width and parameters with regards to the intercondylar notch, such as notch width, notch width index and intercondylar notch volume, demonstrated conflicting associations with primary or secondary PCL injuries.

LEVEL OF EVIDENCE

Level III.

Satisfactory outcomes after one-stage revision anterior cruciate ligament reconstruction using rectangular tunnel technique

PURPOSE

One-stage revision anterior cruciate ligament reconstruction (ACLR) with the anatomic rectangular tunnel (RT) technique using bone-patellar tendon-bone (BTB) grafts results in anatomically precise tunnel placement and secure graft fixation. This study evaluated knee joint laxity and clinical outcomes in terms of femoral tunnel overlap. It was hypothesised that there would be no significant differences in knee joint laxity or clinical outcomes regardless of femoral tunnel overlap.

METHODS

Between 2012 and 2021, a single surgeon conducted 196 one-stage revision ACLRs with the RT technique using BTB grafts. Patients were divided based on the presence of femoral tunnel overlap. Knee joint laxity was evaluated using the Lachman test, pivot shift test, and side-to-side difference measured with a KT-1000 arthrometer. Clinical outcomes were assessed using the Lysholm score, Knee Injury and Osteoarthritis Outcome Score (KOOS), and International Knee Documentation Committee (IKDC) Knee Examination Form 2000. Knee joint laxity and clinical outcomes were compared between groups after a median follow-up of 2.5 years (range 2.0-8.0).

RESULTS

The study included 30 and 73 patients in the overlap and non-overlap groups, respectively. No significant differences were observed in the results of the Lachman test, pivot shift test, or KT-1000 arthrometer as well as in the Lysholm, KOOS, or IKDC scores between the two groups. Based on the IKDC scores, all patients were graded as normal or nearly normal.

CONCLUSION

One-stage revision ACLR with the RT technique using BTB grafts improved knee joint laxity and had favourable clinical outcomes regardless of femoral tunnel overlap. To achieve optimal results in one-stage revision ACLR, it is crucial to create a tunnel within the anatomical attachment area and ensure proper graft fixation and tensioning.

LEVEL OF EVIDENCE

III.