Revision of Failed Unicompartmental Knee Arthroplasty
James P. McAuley, MD, Gerard A. Engh, M.D., Deborah J. Ammeen, BS
Little information is published on the salvage of failed unicompartmental knee arthroplasties (UKAs). This study examined the failure mechanisms, complexity of surgery, and complications in UKA revisions.
A single surgeon performed 39 consecutive UKA revisions. Two patients died <2 years after revision, 4 had inadequate follow-up, and 1 was excluded due to infection before revision. Thirty patients (32 knees) were followed a mean interval of 53 months. Predominantly male, these patients were a mean age of 59 years at UKA.
Revisions were performed 9-204 months after UKA. The predominant failure mechanism was polyethylene wear; however, 9 implants failed due to loosening. The mean polyethylene thickness of the failed arthroplasties was 7.3mm. Revision procedures were straightforward. Ten cases required local autograft, but no allograft. Primary femoral components were used in all cases; 25 were cruciate-retaining. Fourteen cases had stemmed tibial components; 8 had wedge augments. The mean ROM after revision was 111°. Six patients had complications not requiring intervention, which included DVT, UTI, GI bleed, confusion, CVA, and an undisplaced tibial fracture. Two patients underwent manipulation. Two had arthroscopic surgery for patellar clunk. Three were re-revised for polyethylene wear at 76, 77, and 102 months after UKA revision of which two required polyethylene insert and patellar component revision, and the third also required tibial component revision for osteolysis.
This series demonstrated component wear and loosening as common failure mechanisms. The predominance of thin polyethylene suggests that 6 or 7 mm might be inadequate to withstand loads, particularly in males. The authors are encouraged by the simplicity of UKA revision. Although the number of cases in this series was small, the complications encountered in this series compared favorably with those of total knee revision.
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