Intraoperative management of pre-operative flexion contractures using robotic-assisted total knee arthroplasty.

Abstract

To determine how the severity of preoperative flexion contracture influences intraoperative resection strategy, final balance, postoperative range of motion and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR) outcomes in robotic-assisted total knee arthroplasty (RA-TKA). This retrospective cohort study included primary imageless RA-TKAs performed using the RObotic Surgical Assistant (ROSA) Knee System. Knees with preoperative flexion contracture were categorized as >0° to 5°, >5° to 10° and >10°. Preoperative standing full-length radiographs were used to measure hip-knee-ankle angle. Intraoperative resection, gap and balance data were collected. Preoperative and 6-week postoperative range-of-motion data were obtained from medical records, and KOOS-JR scores were collected preoperatively and at 1 year. In total, 263 knees with preoperative flexion contracture were included, with final intraoperative outcomes available for 227 knees. Distal medial femoral resection increased with contracture severity (9.0 ± 1.3, 9.3 ± 1.2 and 9.8 ± 0.8 mm in the >0°-5°, >5°-10° and >10° groups; <i>p</i> < 0.001), whereas tibial construct thickness remained similar (<i>p</i> = 0.908). Final gaps, gap imbalances and coronal laxity were comparable across groups. At 6 weeks, extension differed across groups (<i>p</i> = 0.030), whereas flexion did not (<i>p</i> = 0.138); residual flexion contracture >5° was observed in 2.5%, 0.0% and 10.3% of knees (<i>p</i> = 0.024). Among knees with paired 1-year KOOS-JR data (<i>n</i> = 137), preoperative, postoperative and change scores did not differ across groups (<i>p</i> = 0.336, <i>p</i> = 0.696 and <i>p</i> = 0.231). Each additional degree of flexion contracture was associated with greater distal medial femoral resection (<i>β </i>= 0.06 mm per degree, <i>p</i> = 0.009). Preoperative flexion contracture was associated with minor differences in intraoperative resection strategy, particularly distal medial femoral resection. Final intraoperative balance and early outcomes were similar across flexion contracture groups. Level III, retrospective cohort study.