Influence of Kinematic Alignment on Soft Tissue Releasing and Manipulation Under Anesthesia Rates in Primary Total Knee Arthroplasty

I ntroduction: Total knee arthroplasty (TKA) is typically performed to restore a neutral mechanical alignment. Recently, there has been increased interest in kinematic alignment to restore the patient's individual alignment. The purpose of this study is to determine if kinematic balancing reduces the need for intraoperative soft tissue releases and rates of manipulation under anesthesia compared to mechanical alignment. Materials and Methods: A query was performed between January 2021 and July 2022 to identify all patients who underwent a primary TKA that was performed with kinematic alignment (KA), which revealed 97 patients (107 TKAs). A cohort of consecutive patients from the preceding six months was gathered of patients who underwent primary TKA with mechanical alignment (MA). This cohort consisted of 199 patients (223 TKAs), yielding a total study cohort of 296 patients (330 knees). Mean age was 64.7 years, mean body mass index (BMI) was 33.1 kg/m(2), and 57.1% of patients were female. Rates of manipulation under anesthesia and intraoperative release status were analyzed. Results: Average range of motion preoperatively improved from 108.9 degrees to 114.4 degrees in the KA group but decreased from 112.3 degrees to 109.9 degrees in the MA group at six weeks (p<0.0001). Three of 107 knees (2.8%) required an additional pie-crusting of the superficial MCL in the KA group, whereas 58 of 223 knees (26.0%) did in the MA group (p<0.0001). Three of 107 knees (2.8%) in the KA group and 24 of 223 knees (10.8%) in the MA group required MUA (p<0.0001). Conclusion: Kinematic alignment significantly reduced the need for intraoperative soft tissue releases and postoperative manipulation under anesthesia. Further studies of the influence of kinematic alignment on these outcomes across multiple surgeons should be performed and/ or compared to mechanical alignment.