A Restricted Functional Balancing Technique for Total Knee Arthroplasty with a Varus Deformity: Does a Medial Soft-Tissue Release Result in a Worse Outcome?

BACKGROUND: A functional alignment technique for total knee arthroplasty (TKA) utilizes implant position modifications to balance the soft tissues. There is concern that, in some cases, extreme coronal and tibial component alignment could facilitate early implant failure. To be cautious, a restricted functional alignment may be used. The purpose of our study was to evaluate the results of TKA in patients who have varus deformities using a restricted functional alignment technique. We hypothesized that adding a medial soft-tissue release within restricted boundaries would not result in inferior outcomes.

METHODS: A retrospective review was performed on robotic arm-assisted TKA patients with varus deformities utilizing a functional balancing strategy with a three-degree varus coronal limb and tibial component alignment restriction. Outcome scores of those patients still requiring a medial- soft tissue release were compared to those without for inferior outcomes.

RESULTS: A total of 202 of 259 (78.0%) knees were able to be balanced without any medial soft- tissue release with an average final hip-knee-ankle (HKA) alignment of 1.9° varus. The remaining 57 knees required a medial soft-tissue release. They had an average final HKA of 2.8° varus and an average medial proximal tibial angle of 2.5° varus. Comparing the cohorts without and with a release, at final follow-up averaging two years, there was not a statistically significant difference in Knee Society-Knee Score (97.7 and 98.4, P = 0.525), Functional Score (86.7 and 88.7, P = 0.514), Forgotten Joint Score (59.8 and 66.6, P = 0.136), and Knee Injury Osteoarthritis Outcome Survey for Joint Replacement Junior Score (79.5 and 84.8, P = 0.066).

CONCLUSION: Utilizing a restrictive functional balancing strategy for TKA minimizes the need for soft-tissue releases and provides for excellent overall outcomes. An additional medial soft-tissue release can still be utilized without an inferior average two-year outcome.