Summary

The present study found variation in ACL-injured patients, with females having significantly more valgus alignment than males and the tibia having a larger impact on varus or valgus malalignment than the femur.

Abstract

Background

The specific influence of native coronal alignment on concomitant knee pathology in primary ACL-injured patients remains unclear. Further, our understanding of whether the specific cause of the coronal malalignment is based in the tibia, femur, or both, is relatively underappreciated.

Purpose

The purpose of this study was to investigate the primary cause of varus and valgus malalignment in patients with ACL tears, specifically identifying whether pathologic alignment lies within the tibia or femur and to determine if secondary concomitant injuries with an ACL tear are related to coronal alignment.

Methods

An IRB-approved retrospective assessment of consecutive patients from one surgeon who underwent primary ACL reconstructions between June 2019 and July 2024 was performed. Demographics and radiographic measurements were assessed prior to ACL reconstruction. Patients were separated into three cohorts: neutral, varus, and valgus alignment based on long-leg coronal mechanical axis. Concomitant injuries were documented during surgery. Comparisons across subgroups used one-way ANOVA and Tukey’s HSD to determine differences among cohorts. Comparisons between the cohorts was made for mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), tibial slope, sex, and concomitant injuries.

Results

The study consisted of 250 patients (116 females) who underwent primary ACL reconstruction. For the entire cohort, the mean mLDFA was 86.3±1.7° and the mean mMPTA was 87.3±2.2°. Based on the mechanical axis, 113 patients were classified as neutral with an average mLDFA of 86.2±1.4° and a mMPTA of 87.5±1.7°, 77 patients were classified as varus with an average mLDFA of 87.3±1.6° and a mMPTA of 85.5±1.6°, and 60 patients were classified as valgus with an average mLDFA of 85.1±1.6° and a mMPTA of 89.5±1.8°.

In the coronal plane, the varus cohort revealed deformities from the tibia in 33 patients (42.9%), from the femur in 25 patients (32.5%), from both in 9 patients (11.7%), and from neither in 10 patients (13.0%). In the valgus cohort, deformity was from the tibia in 30 patients (50.0%), from the femur in 16 patients (26.7%), from both in 9 patients (15.0%), and from neither in 5 patients (8.3%).

Females had a significantly higher mMPTA than the males, 88.1° vs. 86.7°, respectively (p<<0.001). There was no difference in sex for mLDFA (p=0.202). There were significantly more females in the valgus cohort compared to the neutral and varus cohorts (P<0.001). Concomitant meniscal, chondral, and ligament injuries displayed no significant associations between each cohort. The mean posterior tibial slope was 11.1°, with 102 patients (40.8%) surpassing a slope ≥ 12°.

Conclusion

The present study found variation in ACL-injured patients, delineating distinctions in coronal alignment profiles. Concomitant meniscus, chondral, and ligament, injuries had a limited association with coronal plane alignment within the studied cohorts. Females had significantly more valgus alignment than males, with most of their deformity originating from the tibia. Comparing the varus and valgus cohorts to the neutral cohort, more patients exhibited tibial based deformity rather than femoral based deformity with the tibia contributing nearly two times as much to the deformity.