Restricted Kinematic Alignment Total Knee Arthroplasty Using CT-Based Patient-Specific Jigs: An Observational...

Restricted kinematic alignment (rKA) aims to restore patient-specific knee anatomy within defined safety boundaries during total knee arthroplasty (TKA). Evidence regarding the feasibility of rKA using indigenously developed patient-specific instrumentation (PSI) in the Indian population remains limited.

This single-center, single-surgeon prospective observational study included consecutive patients aged ≥ 50 years with primary osteoarthritis undergoing rKA-TKA using an indigenously developed CT-based patient-specific jig system (PERFIT-R) between January 2022 and January 2024. Valgus knees were excluded as the system was initially developed for varus morphology, limiting generalizability. CT-based preoperative planning was used to guide component positioning within restricted kinematic alignment boundaries. Functional outcomes were assessed preoperatively and at 6, 12, and 18 months postoperatively using WOMAC, Oxford Knee Score (OKS), Knee Society Score (KSS), SF-12, EQ-5D, and Forgotten Joint Score (FJS). Agreement between planned and achieved bone resections was assessed intraoperatively using caliper measurements as an indicator of execution consistency. Complications were recorded prospectively.

A total of 246 patients were included in the study cohort, with follow-up ranging from 6 to 18 months. The mean age was 64 ± 8.9 years, and 13.8% were male. Statistically significant improvements were observed in WOMAC, OKS, KSS, SF-12 Physical Component Score, and EQ-5D across follow-up (p < 0.05). The magnitude of improvement exceeded commonly reported minimal clinically important difference (MCID) thresholds; however, these findings should be interpreted cautiously as MCID values were derived from external populations and were not validated in this cohort. The Forgotten Joint Score remained relatively stable during follow-up. Planned bone resections were generally within ± 1 mm of intended values, suggesting intraoperative execution consistency rather than radiographic alignment accuracy. The overall complication rate was 2.0%, with no revision procedures during the follow-up period.

CT-based patient-specific instrumentation-guided restricted kinematic alignment TKA appears feasible in a selected cohort, with consistent intraoperative execution and favorable early functional outcome trends. However, in the absence of a control group, standardized radiographic validation, and long-term follow-up, these findings should be interpreted as preliminary and hypothesis-generating. Further comparative studies with objective alignment assessment and extended follow-up are required before definitive conclusions regarding clinical effectiveness and generalizability can be established.