Mobile-bearing Dislocation of Unicompartmental Knee Arthroplasty after Stroke Successfully Treated with Total Knee Arthroplasty: A Case Report

Abstract

Background: Unicompartmental knee arthroplasty (UKA) is an established treatment for isolated compartment osteoarthritis, offering rapid recovery and preserved kinematics. Bearing dislocation is a recognised mode of failure of mobile-bearing designs, and neuromuscular compromise, such as that associated with stroke, is a particularly important risk factor for recurrent failure. Presentation of Case: A 51-year-old man underwent medial UKA of the right knee for medial-compartment osteoarthritis. In the early postoperative period, he sustained an acute ischaemic (non-haemorrhagic) stroke. Approximately one month after the index procedure, he developed bearing dislodgement with loosening, managed with polyethylene insert exchange using a thicker bearing. One month after revision, he again presented with morning-onset pain, and radiographs demonstrated recurrent dislodgement of the insert. Given the recurrent failure on a background of post-stroke neuromuscular dysfunction, conversion to total knee replacement (TKR) was undertaken, with radiographs confirming a well-positioned arthroplasty construct. Discussion: Recurrent mobile-bearing dislodgement after UKA in a patient with new-onset hemiparesis reflects the impact of altered muscle tone, proprioception, and gait on a ligament-dependent implant. Conclusion: Early conversion to a more constrained TKR construct should be considered in preference to repeated isolated insert exchange when neuromuscular compromise drives recurrent bearing failure.