Kinematic analysis of spinopelvic balance in total knee arthroplasty

Purpose: This study aims to evaluate the effects of robotic total knee arthroplasty (rTKA) on spinopelvic motion parameters dynamically and statically in patients with advanced-stage knee osteoarthritis who underwent rTKA. Methods: Patients who underwent unilateral robotic total knee arthroplasty for primary knee osteoarthritis by a same surgical team at Koç University Hospital between July 2022 and November 2023 were included in this study. Dynamic analyses of pelvic and lumbar spine movements were conducted during walking and sit-to-stand transitions, both preoperatively and at minimum one year follow-up, using gait analysis. Additionally, static measurements of spinopelvic parameters, including sacral slope, pelvic tilt, and pelvic incidence, were assessed using lateral lumbosacral radiographs. Functional outcomes of the patients were compared preoperatively and postoperatively using the WOMAC and OKS questionnaires. Results: A total of 28 patients (23 women, 5 men) were included in this study, with an average age of 69.9 ± 6.86 years, an average body mass index (BMI) of 29.5 kg/m² ± 5.18, and an average follow-up period of 13.8 months. According to the Kellgren-Lawrence classification, 13 patients (46.42%) were classified as stage 3 and 15 patients (53.58%) as stage 4. Postoperative dynamic measurements revealed significant changes in pelvic tilt values during both walking and sit-to-stand transitions. These changes in pelvic tilt were observed throughout the movement and in momentary angular measurements during sit-to-stand transitions. In the dynamic measurements, significant improvements in the movement of both knees compared to preoperative results were also observed. In the radiological measurements, a significant difference was found only in the sacral slope values in the standing radiographs compared to preoperative measurements. Both WOMAC and OKS functional scores showed marked improvements postoperatively. Conclusion: This study provides a dynamic perspective on the effects of robotic total knee arthroplasty (rTKA) on spinopelvic parameters. It demonstrates that rTKA not only restores knee joint function but also has the potential to improve postural dynamics by correcting compensatory spinopelvic movements. Furthermore, the findings emphasize the importance of preoperative dynamic evaluation of the pelvis and spine to enhance surgical efficacy and support functional recovery.