Stiffness After Total Knee Arthroplasty: Is It a Result of Spinal Deformity?

Background: There are no studies to date analyzing the effect of spinal malalignment on outcomes of total knee arthroplasty (TKA). Knee flexion is a well-described lower extremity compensatory mechanism for maintaining sagittal balance with increasing spinal deformity. The purpose of this study was to determine whether a subset of patients with poor range of motion (ROM) after TKA have unrecognized spinal deformity, predisposing them to knee flexion contractures and stiffness. Methods: We retrospectively evaluated a consecutive series of patients who underwent manipulation under anesthesia (MUA) for poor ROM after TKA. Using standing full-length biplanar images, knee alignment and spinopelvic parameters were measured. Patients were stratified by pelvic incidence minus lumbar lordosis as a measure of spinal sagittal alignment with a mismatch of >= 10 degrees defined as abnormal, and we calculated the incidence of sagittal spinal deformity. Results: Average ROM before MUA was extension 3 degrees and flexion 83 degrees. About 62% of patients had a pelvic incidence minus lumbar lordosis mismatch of >= 10 degrees. In the spinal deformity group, post-MUA ROM was improved for flexion only, whereas both flexion and extension were improved in the nondeformity group. Conclusion: Compensatory knee flexion because of sagittal spinal deformity may predispose to poor ROM after TKA. Patients with clinical suspicion should be worked up preoperatively and counseled accordingly. (C) 2020 Elsevier Inc. All rights reserved.