Outcomes of Medial Pivot Total Knee Arthroplasty (MP-TKA) Based on Preoperative Coronal Deformity.

Introduction: The medial pivot total knee arthroplasty (MP-TKA) was developed to better replicate the kinematics of the healthy knee. Although outcomes of MP-TKA have been investigated, previous studies involved primarily varus preoperative deformities. The objective of this study was to determine patient outcomes using the Knee Injury and Osteoarthritis Outcome Score Jr (KOOS Jr) following MP-TKA in relation to the type (varus/neutral/valgus) and severity (moderate/severe) of preoperative coronal deformity.

Methods: This was a single-center retrospective cohort study of 311 knees receiving MP-TKA between April 25, 2017, and May 27, 2022, with a pre-operative long-leg hip-knee-ankle (HKA) angle measured by biplanar EOS. Patients were assigned to one of five varus/valgus alignment groups: neutral (0 ± 3 degrees), moderate (3 to 15 degrees), or severe (15+ degrees) pre-operative coronal deformity.

Results: Differences in sex were noted, while all other demographic and comorbid conditions were similar. The mean post-operative period between the date of surgery and KOOS Jr. collection was 17.6 months across all groups. Severe valgus knees (n = 5) had an average (mean ± SD) postoperative KOOS Jr of 71.7 ± 10.6, while moderate valgus knees (n = 49) demonstrated a postoperative average KOOS Jr. of 72.5 ± 19.6. Neutral knees (n = 53) had an average postoperative KOOS Jr of 65.2 ± 22.3, while moderate varus (n = 180) and severe varus (n = 24) had an average KOOS Jr of 69.9 ±19.1 and 73.2 ± 16.1, respectively. There was no difference noted in postoperative scores between the five deformity groups.

Discussion: The utilization of MP-TKA in patients who have moderate and severe valgus deformity showed similarly favorable outcomes when compared to neutral as well as moderate and severe varus knees. Further studies are needed to determine long-term outcomes with widespread MP-TKA use for all preoperative coronal deformities.