Subsidence of All-Polyethylene Tibial Components Used in Unicondylar Knee Arthroplasty: A Cohort Study

Introduction: Unicompartmental designs and techniques have been developed to preserve bone stock and minimize soft tissue trauma. Early modern designs and techniques have been introduced with little support in the peer-reviewed literature. Material and methods: From October 2002 to May 2004, 64 consecutive DePuy Preservation unicondylar knee arthroplasties (UKAs) were performed in 56 patients. Two patients died of unrelated consequences, leaving 62 UKAs for review (55 medial, 7 lateral). All procedures were performed through a quadriceps-sparing approach. All components were cemented, including an all polyethylene tibial component. Clinical and radiographic follow-up data were reviewed and analyzed. Results: At an average follow-up of 2.5 years, six (11%) of the medial tibial components have subsided. Of these, four had moderate-to-severe pain, one did require a revision to a total knee arthroplasty (TKA), and another did stabilize. An additional two patients continued to have knee pain (one requiring conversion to TKA), leaving a total of 55 UKAs (89%) functioning well at early follow-up. Additional complications have included four deep vein thromboses, three cardiac issues following the index procedure, one surgical site infection, one intraoperative medial femoral condyle fracture, and one reoperation for loose cement fragments. Conclusion: This study demonstrates a high rate of subsidence for all-polyethylene tibial components used in UKA, resulting in pain and failure of the arthroplasty. Despite the less invasive approach, we found complications that are usually associated with TKA surgery as well as those unique to UKA.