Summary

High-grade medial-sided knee injuries have a high healing potential, despite being in the setting of high energy mechanism or multiligamentous knee injuries. Concomitant PCL tears, severe valgus gapping at physical exam or extensive posteromedial corner injury in the MRI, showed to be negative predictors for healing of HGMI.

Abstract

Purpose

High-grade medial-sided knee injuries (HGMI) have a high healing potential. However, a subgroup of patients will evolve with residual medial instability despite conservative treatment. To date, there is no clarity on the predictors of healing in HGMI. The objective of this study is to identify those risk factors for failure of conservative treatment in HGMI.

Materials And Methods

Prospective analytical study of consecutive patients between 2018-2021 who met the following inclusion criteria: (1) acute LMAG (<2 weeks) confirmed by magnetic resonance imaging (MRI), (2) physical examination by trained knee surgeon <2 weeks after injury, (3) conservative treatment =8 weeks (KNT, splint 0-30, partial weight-bearing). Exclusion criteria: bilateral injuries, distal avulsions with Stener effect, previous surgeries. The following variables were recorded: age, smoking, high energy mechanism (HEM) and valgus gapping according to IKDC. A blinded MSK Radiologist evaluated the MRIs reporting concomitant ACL tear, PCL, maximum coronal distance from medial femoral condyle to MCLs, and absence of the posterior oblique ligament (POL) in axial views. The control group was defined as those patients in whom conservative treatment re-established medial stability, and the group of cases as those with residual pathological medial instability at physical examination and stress x-rays. Chi2 and Wilcoxon Mann-Whitney tests were used to find significant associations with failure of conservative treatment, and a bivariate relative risk was estimated, adjusted for age and sex (p<0.05). Sample size calculation of 80 patients (power 80%).

Results

86 HGMI met the selection criteria, 71 men (82.5%), mean age 43 years (21-72). 51.2% were HEM, and 75.6% were multiligament injuries (43 ACL, 22 PCL, 12 ACL+PCL). In 68 patients (79%) conservative treatment was successful in restoring medial stability and 18 patients (21%) evolved with pathological residual instability. After statistical analysis, the following variables were identified as risk factors for conservative treatment failure: concomitant PCL (RR 3.3), valgus gapping 0° and 30° IKDC D <2 weeks (RR 13.2 and 13.6 respectively), absence of POL in axial slice of MRI (RR 3.4) and femoral condyle-sLCM distance >10mm (RR 1.4). None of the variables studied was exclusive to either of the two groups, since these variables were negative predictors for healing, but not pathognomonic for failure of non-operative treatment.

Conclusions

HGMI have a high healing potential, despite being in the setting of HEM or multiligamentous knee injuries. Concomitant PCL tears, severe valgus gapping at physical exam or extensive posteromedial corner injury in the MRI, showed to be negative predictors for healing of HGMI.