Rotating Hinge Revision Total Knee Arthroplasty Provides Greater Arc of Motion Gains for Patients Who Have Severe Arthrofibrosis

Background: Arthrofibrosis is a common postoperative total knee arthroplasty (TKA) complication that results in limited range of motion (ROM). There is limited literature on outcomes after revision TKA (rTKA) for arthrofibrosis based on preoperative ROM restriction. The aims of this study were to: (1) examine ROM trajectory after rTKA for arthrofibrosis patients who have severe versus nonsevere limitations; (2) compare ROM gains and final arc of motion (AOM) between severe and nonsevere cohorts; (2a) compare ROM gain in a severe cohort treated with a rotating hinge (RH) versus a non-RH (NRH) construct; and (3) assess the impact of arthrofibrosis severity on patient-reported outcome measures. Methods: Patients were divided into 2 groups: group A had preoperative ROM < 70^° (severe), and group B had preoperative ROM > 70^° (non-severe). Patients were assessed clinically using AOM gain, absolute ROM, Knee injury and Osteoarthritis Outcomes Score for Joint Replacement, lower extremity activity scale, and pain scores. Postoperative gains in AOM were compared between both groups. Results: A total of 56 rTKAs (group A (severe): n = 36, group B (non-severe): n = 20) were performed for patients who have postoperative fibrosis. Group B had better ROM at the 1-year time point (group B: 95.9 ± 22.5 degrees versus group A: 83.2 ± 25.7 degrees). Group A had significantly better improvement in absolute AOM than group B (31.1 ± 20.9 versus 11.4 ± 25.0 degrees, P < 0.01). The RH group demonstrated significantly better absolute AOM gain than the NRH group (41.3 ± 19.4 versus 18.3 ± 15.2 degrees, P < 0.001). However, there were no significant differences in patient-reported outcome measures between groups A and B or between RH and NRH groups at the final follow-up. Conclusions: Final ROM achieved between severe and nonsevere arthrofibrosis groups was similar, and patients who have severe arthrofibrosis can expect greater absolute ROM gains and similar functional outcomes than nonsevere arthrofibrosis patients. The RH rTKAs provided greater AOM gains for patients who have severe arthrofibrosis, with equivalent functional outcomes to non-RH implants. For severe arthrofibrosis patients, RH designs provided twice the overall ROM gain; however, longer follow-up is necessary to determine whether RH designs have inferior overall implant survivorship.