OPTIMIZATION OF EXTENSION BALANCE IN PRIMARY TOTAL KNEE ARTHROPLASTY: A STEPWISE APPROACH TO THE CORRECTION OF FLEXION CONTRACTURE

Introduction. Residual extension deficit after total knee arthroplasty (TKA) adversely affects gait, increases energy expenditure during walking, and reduces patient satisfaction. The choice of optimal surgical strategy—bal­ancing soft-tissue release against additional resection of the distal femur—remains a subject of debate, as each additional amount of bone removal may result in elevation of the joint line and increase the risk of mid-flexion instability. Materials and Methods. This single-center prospective study included 104 patients who underwent primary TKA at the Multidisciplinary Clinic of Tashkent State Medical University between 2022 and 2024 and had a preoper­ative extension deficit of ≥10°. A stepwise intraoperative algorithm was applied: (1) removal of posterior osteophytes; (2) posterior capsular release; (3) release of the posterior cruciate ligament (PCL) in cases of a PCL-retaining technique or conversion to a posterior-stabilized (PS) implant; and (4) additional resection of the distal femur of up to 4 mm. The extension deficit was assessed intraoperatively after each step. Patients were stratified according to the Lombardi classification into mild (10–14°), moderate (15–30°), and severe (>30°) extension deficits. Results. The mean preoper­ative fixed flexion deformity (FFD) was 17.3° ± 8.4°, decreasing to 2.1° ± 2.6° at 12 months postoperatively. Removal of posterior osteophytes corrected the deficit by an average of 3.8°, posterior capsular release provided an additional correction of 4.1°, PCL release corrected a further 2.9°, and additional distal femoral resection resulted in 2.2° of correction per each millimeter of bone resection. Complete correction (≤5° of residual deficit) was achieved in 91.3% of patients. Additional resection of >4 mm was required only in the severe-deficit group (8 of 14 patients). In these patients, mid-flexion instability was more frequently observed at 12 months postoperatively (3 of 8 versus 0 of 96; p = 0.001). The KSS at 12 months was higher in patients who underwent ≤4 mm of additional resection (87.2 vs. 75.4; p = 0.002). Conclusion. A stepwise algorithm prioritizing soft-tissue release over additional bone resection enables acceptable functional extension to be achieved in 91% of cases while preserving the joint-line level. Additional distal femoral resection of >4 mm should be considered a last-resort measure, as it substantially increases the risk of mid-flexion instability.