Poster 341: Nonoperative Treatment of MCL Tears in ACL/MCL Injuries Does Not Increase ACL Retear Rates
Authors: Bauman Scot , Benner Rodney , Shelbourne K. Donald 
Published: August 2024

Objectives: There continues to be controversy regarding the treatment of medial collateral ligament (MCL) tears when torn in conjunction with the anterior cruciate ligament (ACL). There is a push to acutely repair or reconstruct the MCL in this setting due to lower revision rates following the ACL reconstruction (ACLR). However, most nonoperative treatment philosophies are focused on immobilization through bracing instead of the more rigid casting approach. The purpose of this study was to determine if there was a difference in ACL retear rates or postoperative stability between those with ACL/MCL injuries and isolated ACL injuries when the MCL was treated nonoperatively, including rigid casting prior to the ACLR. Methods: Between 1982 and 2022, 6047 patients planning to have an ACLR were enrolled into the study. The population was determined with inclusion criteria of a primary ACLR using a patellar tendon graft with minimum 1-year follow up. Patients were excluded with revision ACLR, lateral side or posterior cruciate ligament involvement, or lacking postoperative KT data. Patients were divided into two groups, isolated ACLR (N = 5670) and ACL/MCL (N = 377). All MCL tears were treated nonoperatively and when indicated, they were casted in 30° of flexion and changed weekly until a solid end point was achieved and patients had the ability to bear full weight on the involved side. Once medial side stability was attained, preoperative rehabilitation commenced and range of motion was normalized before the ACLR. Postoperatively, all patients followed the same accelerated rehabilitation program. The KT manual maximum (MM) difference between knees, in millimeters, was used for analysis. Graft retear rate was determined through subjective surveys sent yearly to each patient after surgery. To reduce confounding bias in the analysis, the ACL/MCL patients were control matched 1:1 to the isolated ACL injury patients based on sex, age, postoperative activity rating, and surgery timing, which led to 304 patients in each group. Results: Prior to matching, both groups had similar mean ages and rates of having postoperative activity levels ≥7, however, the ACL/MCL group showed higher rates of males (69.0%) and subacute surgery (71.9%) compared to the isolated ACLR group (59.7% males and 56.6% subacute surgery). After matching, the mean age for both groups was similar (ACL/MCL: 24.6 years, isolated ACLR: 24.9 years) and they showed identical rates of males, postoperative activity rating ≥7, and subacute surgery at 66.4%, 90.4%, and 73.0%, respectively. The KT MM difference for the ACL/MCL group was not statistically significantly different when compared to the isolated ACLR group (1.8mm vs 1.6mm; p=0.196). The ACL retear rate for the ACL/MCL group was 7.9% compared to 6.6% for the isolated ACLR group, which was not statistically significantly different, p = 0.531. Conclusions: When the MCL is treated nonoperatively, including the use of a cast, before an ACLR, postoperative stability and rates of ACL retears are similar to those with an isolated ACL tear. Due to similar outcomes for both groups, surgeries to the MCL, and thus potential complications that can come with it, can be avoided. We postulate that the lack of differences in laxity and retear rates for the ACL/MCL group may be due to more rigid cast immobilization for the MCL, as opposed to bracing. Further study is needed to evaluate this hypothesis.