Preoperative radiographic valgus alignment predicts the extent of lateral soft tissue release and need for constraint in valgus total knee arthroplasty.

Background: In total knee arthroplasty (TKA) for valgus knees, the decision to use a constrained implant is often made intraoperatively depending on the extent of soft tissue releases performed and residual soft tissue imbalance. The purpose of this study is to determine if preoperative radiographic criteria of valgus knees can predict the extent of soft tissue releases required and the level of constraint needed to balance the knee during TKA.

Methods: A single surgeon's 807 consecutive TKA standing hip-knee-ankle radiographs from 2007-2012 were analyzed. One hundred eighty-seven valgus knees were identified and annotated. Statistical univariate and multivariate analyses were performed for both outcomes, lateral release and articulation, to assess the association with risk factors of gender, age, and preoperative radiographic markers of valgus deformity. A P -value <.05 represented a significant difference between groups.

Results: Use of a constrained articulation was associated with increased valgus deformity (mechanical hip-knee-ankle angle, P < .0001) and extent of lateral soft tissue release ( P < .0001). No relationship existed between the use of a constrained articulation and age or gender ( P > .05). A preoperative anatomic tibiofemoral valgus angle of >16.8° was associated with the use of a constrained articulation during surgery.

Conclusions: Our data demonstrate that preoperative radiographic characteristics of the valgus knee can be utilized to predict the extent of lateral soft tissue release and whether a constrained articulation will be required in TKA. This will provide surgeons with useful information to offer accurate preoperative counseling to patients and to ensure that the appropriate prosthetic parts are available during surgery.