Summary

An increased posterior femoral condylar depth and the bone tunnel posterior margin length are associated with a higher risk of ACLR graft failure in teenagers, suggesting that LFCR, AMR, and PLR are valuable predictors.

Abstract

Purpose

This study examines the relationship between lateral femoral condyle depth and the risk of graft failure after anatomic double-bundle anterior cruciate ligament reconstruction (ACLR) in teenagers. Additionally, it explores the association between bone tunnel posterior margin length and ACLR graft failure.

Methods

We conducted a retrospective review of teenage patients who underwent anatomic double-bundle ACLR at our institution between 2016 and 2022, with a minimum follow-up period of 24 months. Teenagers were included as individuals aged 15 to 19 years. Patients were divided into two groups: those who showed no evidence of graft failure after primary ACLR (control group) and those who experienced graft failure after the procedure (failed group). The lateral femoral condyle ratio (LFCR) was calculated using preoperative MRI as the ratio of posterior femoral condylar depth to total condylar length. We selected a postoperative CT slice to correspond to the preoperative MRI slice used for LFCR measurement, and defined the anterior medial bundle ratio (AMR) and posterior lateral bundle ratio (PLR) as the ratio of posterior margin length of each bone tunnel to the total condylar length. We used the Mann-Whitney U test to compare groups, with statistical significance set at p < 0.05. Receiver operating characteristic (ROC) curve analysis was conducted to determine the optimal cutoff for identifying an increased risk of ACLR graft failure.

Results

Among the 127 patients (46 male, 81 female) who met the inclusion criteria, 113 patients (39 male, 74 female) were placed in the control group, while 14 patients (7 male, 7 female) were placed in the failed group. The failed group exhibited significantly higher LFCR, AMR, and PLR values compared to the control group (p<.001 for all), indicating a strong association with ACLR graft failure. The median LFCR was significantly higher in the failed group, at 61% [range: 54% to 67%], compared to 56% [range: 50% to 65%] in the control group. Similarly, the median AMR was 19% [range: 14% to 31%] in the failed group, and 14% [range: 4% to 30%] in the control group, while the median PLR was 12% [range: 7% to 19%] in the failed group, and 9% [range: 3% to 21%] in the control group. ROC curve analysis identified an increased risk of ACLR graft failure with an LFCR greater than 63%, with a sensitivity of 77% and specificity of 72%, an AMR greater than 15%, with a sensitivity of 60% and specificity of 92%, and a PLR greater than 12%, with a sensitivity of 87% and specificity of 71%.

Conclusions

This study demonstrates that an increased posterior femoral condylar depth and the bone tunnel posterior margin length are associated with a higher risk of ACLR graft failure in teenagers, suggesting that LFCR, AMR, and PLR are valuable predictors. These findings could suggest the need for further research to explore its potential role in preoperative assessment and surgical planning. Level of Evidence: Level III retrospective prognostic trial.