Revision Total Knee Arthroplasty of Failed Unicompartmental Knee Arthroplasty

ABSTRACT

PURPOSE: To analyze the failure mechanism, complexity of surgery, complication and outcome of revision of failed unicompartmental knee arthroplasty(UKA). MATERIALS AND METHODS: 14 patients(16 knees) were followed up a mean 70 months. The patients were a mean age of 58.2 years at time of UKA and predominantly female(85%). Revision surgery was done 14 to 104 months with an average time of 4 years 10 months after UKA. The UKA component that were revised include 10 Microloc, 4 Allegretto, 1 Oxford and 1 Marmor modular II. Clinical and radiographic evaluation were completed preoperatively and at last follow-up. The scoring system used in this study is Hospital for Special Surgery(HSS) knee score. Radiographic assessment was performed using Bauer's method(tibio-femoral angle) and American knee society roentgenographic evaluation system. RESULTS: The predominant failure mechanism was polyethylene wear and femoral component loosening. At the last follow-up, the average HSS knee score significantly improved from 60 to 86. Average tibio-femoral angle was corrected from varus 2o to valgus 5o. The implant type used for the revision was PFC-PS. 11 knees required local autograft but no allograft were used. Femoral block augment and tibial metal wedges with stem were also used to reconstruct the defect. There were 2 cases of complications, subluxation of patella and deep infection after intraarticular injection at local clinic. CONCLUSION: Polyethylene wear and femoral component loosening was common failure mechanism in revision of UKA. Bone defects needed to reconstruct were detected in 11 cases but autograft was enough to reconstruct the defect. Result of failed UKA compares favorably with those of total knee revision.