The Effect of Implant Constraint and Ligament Repair on Compartment Balancing After Medial Collateral Ligament Injury in TKA.

BACKGROUND An intraoperative midsubstance injury to the medial collateral ligament (MCL) is a devastating complication of total knee arthroplasty (TKA). No single treatment method has been shown to yield optimal stability. This cadaveric study compared primary MCL repair, increasing prosthetic constraint, and a combination of both techniques on tibiofemoral compartment gapping after an iatrogenic MCL injury. METHODS We performed 16 cadaveric, robotic-assisted TKAs (CORI; Smith+Nephew) and recorded tibiofemoral gap measurements at 10°, 30°, 60°, and 90° of flexion with a posterior-stabilized (PS) prosthesis as the control group. The experimental groups had no MCL repair and a PS component, no MCL repair and a varus-valgus constrained (VVC) component, MCL repair with a PS component, and MCL repair with a VVC component. The MCL was repaired with 2 figure-8 nonabsorbable sutures. Gap measurements were manually tensioned by the same surgeon for all specimens. The mean medial tibiofemoral gap with the 3 different methods of interest (the no MCL repair with VVC component group, the MCL repair with PS component group, and the MCL repair with VVC component group) was compared with the control group for the rate of deficit (RD) and was compared with the no MCL repair and PS component group for the rate of improvement (RI). Simple statistics were used to calculate the mean medial balance for the groups, and analysis of variance (ANOVA) modeling was used to determine the mean changes in RD and RI, with significance set at p < 0.05. RESULTS The mean RD was highest for the no MCL repair with PS component group at 621.13%, demonstrating an approximately 6-fold increase in medial tibiofemoral gapping compared with the control group. This was followed by the no MCL repair with VVC component group at 93.02%, the MCL repair with PS component group at 65.66%, and the MCL repair with VVC component group at 20.01% (p < 0.001). The mean RI for the MCL repair with VVC component group was highest at 83.08%, meaning that the combination of VVC component and MCL repair resulted in an 83% improvement in medial tibiofemoral gapping from no MCL repair with PS component. This was followed by the MCL repair with PS component group at 76.62% and the no MCL repair with VVC component group at 72.95% (p < 0.001). CONCLUSIONS This cadaveric study demonstrates that primary MCL repair with VVC component was the best for minimizing the deficit after an MCL injury and provided the highest RI. MCL repair with PS component and no MCL repair with VVC component were less effective reconstructive choices. This study supports the combination of a simple MCL repair with VVC component as the most stable reconstructive option following an intraoperative MCL injury.