Challenges in Residual Bearing Removal: A Rare Case of Mobile Bearing Fracture in Unicompartmental Knee Arthroplasty with Literature Review.

Background: Mobile bearing fracture is a rare long-term complication of unicompartmental knee arthroplasty (UKA), and relevant reports are sparse. Hence, its treatment options need further exploration.

Case Presentation: This study presents the case of fracture of a polyethylene insert that occurred 12 years after mobile bearing medial UKA in a 75-year-old overweight woman who then underwent surgical intervention at our institution. However, we encountered significant challenges in removing the fragments from the broken bearing, resulting in retention of the remaining one-third of the fragment. We solved this problem by replacing the fractured insert with thicker mobile bearing. During the 1-month postoperative follow-up, the patient achieved good range of motion and excellent satisfaction, with no reported complications and a Knee Society Score of 90. Additionally, we reviewed the literature on the treatment for mobile bearing fractures after UKA.

Conclusions: Bearing fracture is a rare cause of failure of mobile bearing UKA. This case highlights the challenges of UKA fracture bearing retrieval and underscores that mobile bearing replacement can be an effective intervention. The case we report shows that when removal of a residual meniscal bearing in a posterior dislocation is difficult to achieve, compromise may be an appropriate option because it does not cause additional complaints to the patient. This case emphasizes the importance of the surgeon having a thorough preoperative understanding of the location and potential pitfalls of fracture fragments in such situations.