Acquired Idiopathic Stiffness After Contemporary Total Knee Arthroplasty: Incidence, Risk Factors, and Results Over 25 Years

Background: Acquired idiopathic stiffness (AIS) remains a common failure mode of contemporary total knee arthroplasties (TKA5). The present study investigated the incidence of AIS and manipulation under anesthesia (MUA) at a single institution over time, determined outcomes of MUAs, and identified risk factors associated with AIS and MUA. Methods: We identified 9771 patients (12,735 knees) who underwent primary TKA5 with cemented, modular metal-backed, posterior-stabilized implants from 2000 to 2016 using our institutional total joint registry. Mean age was 68 years, 57% were female, and mean body mass index was 33 kg/m(2). Demographic, surgical, and comorbidity data were investigated via univariate Cox proportional hazard models and fit to an adjusted multivariate model to access risk for AIS and MUA. Mean follow-up was 7 years. Results: During the study period, 456 knees (3.6%) developed AIS and 336 knees (2.6%) underwent MUA. Range of motion (ROM) increased a mean of 34 degrees after the MUA; however, ROM for patients treated with MUA was inferior to patients without AIS at final follow-up (102 degrees vs 116 degrees, P < .0001). Significant risk factors included younger age (HR 2.3, P < .001), increased tourniquet time (HR 1.01, P < .001), general anesthesia (HR 1.3, P = .007), and diabetes (HR 1.5, P = .001). Conclusion: Acquired idiopathic stiffness has continued to have an important adverse impact on the outcomes of a subset of patients undergoing primary TKA5. When utilized, MUA improved mean ROM by 34 degrees, but patients treated with MUA still had decreased ROM compared to patients without AIS. Importantly, we identified several significant risk factors associated with AIS and subsequent MUA. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

The study found that acquired idiopathic stiffness (AIS) and manipulation under anesthesia (MUA) have a certain incidence among patients undergoing total knee arthroplasties (TKA). MUA can improve range of motion, but patients treated with MUA have lower range of motion compared to those without AIS.