Radiologic changes affecting ankle joint after total knee arthroplasty: retrospective study aimed at comparing in frontal ankle alignment in patients undergoing total knee arthroplasty using navigation-assisted functional alignment versus conventional jig-based mechanical alignment techniques.

Abstract

Objectives: This doctoral thesis evaluates the impact of mechanical alignment (MA) and functional alignment (FA) in total knee arthroplasty (TKA) on frontal ankle alignment. Through a retrospective comparative design, radiographic parameters, clinical findings, and patient-reported outcome measures (PROMs) were analyzed to identify distal biomechanical adaptations and assess their clinical relevance. The aim was to inform more individualized surgical planning and optimize biomechanical and functional outcomes. Materials and Methods: Patients undergoing primary TKA for osteoarthritis were divided according to alignment strategy (MA or FA). Preoperative evaluation included clinical assessment of knee and ankle range of motion, stability, and functional status, together with standardized long-leg weight-bearing radiographs. Measurements comprised(HKA),ground–plafond angle, ground–talus angle, plafond–talus angle, mechanical plafond axis, mechanical talus axis, and lateral distal tibial angle. All procedures were performed at the Rizzoli Orthopaedic Institute using conventional instrumentation for MA and computer-assisted navigation (ExatechGPS) for FA. At a minimum 12-month follow-up, patients underwent repeat clinical and radiographic assessment, including PROMs (KSS, Oxford Knee Score, WOMAC, SF-36, EuroQoL-5D). Pre- and postoperative findings were compared to evaluate changes in ankle and hindfoot alignment and their relationship with symptoms and functional outcomes. Results: A total of 105 patients (52 FA, 53 MA) were included. Both groups showed significant improvement in clinical outcomes and PROMs at one year. HKA correction was significant in both cohorts, while ankle and hindfoot modifications were modest. MA demonstrated a tendency toward lateral talar displacement, whereas FA showed medial plafond adaptation, though differences were not statistically significant. Preoperative ankle pain was the main predictor of persistent postoperative symptoms. Conclusions: MA and FA provide comparable short-term outcomes, with subtle distal biomechanical differences. Preoperative ankle status plays a pivotal role in postoperative symptom persistence, emphasizing thorough ankle–hindfoot evaluation in TKA planning.