Abstract
Introduction: There has been a lack of general agreement on how successful unicompartmental knee arthroplasty has been. The purpose of this study is to report the results of revision total knee arthroplasties performed for failure of unicompartmental knee arthroplasty and to determine the factors that led to failure of the unicompartmental knee arthroplasty.
Materials and method: Between September 1992 and June 1999, 12 knees(10 patients) among 106 primary unicompartmental knee arthroplasties, had revision of a failed unicompartmental knee arthroplasty. The average age of the patients was 61 years(range, 43 to 73 years). The average follow-up period was 3.6 years. Diagnosis before initial unicompartmental knee arthroplasty included osteoarthritis in eight patients and osteonecrosis in two patients. The medial compartment was involved in all knees. The type of prosthesis used in the 12 knees before revision was one Modular II, seven Microlocs and four Allegrettoes. The initial unicompartmental knee prosthetic components had been in place for an average of 4.3 years(range, 1, 2 to 7.5 years). The clinical findings were assessed using the Hospital for Special Surgery scoring system. Radiographic measurements were done with Bauer’s method. ANOVA test was used for statistical analysis.
Results: The cause of revision was wear in six, loosening in five and one deep infection. The implant type used for revison was posterior stabilized type of Press Fit Condylar prosthesis. Eight knees had a bone defect at revision. Bone defects were filled with autogenous bone graft in six knees and metal wedges were used in two knees. At the last follow-up after revision, the average HSS knee score significantly improved from 58 to 83. And the Bauer’s angle was corrected from preoperative varus 6.3 degrees to valgus 6 degrees after revision. Radiographically, three knees had partial radiolucency. There was no complication such as postoperative hematoma, deep or superficial infection and peroneal nerve palsy.
Conclusion: Good or excellent results were achieved in all of the knees after revision. Successful salvage of the failed UKA could be achieved by revision arthroplasty. The design of prosthesis, proper selection of patients, and surgical technique were important factors for succes of unicompartmental knee arthroplasty.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
