To identify the causes of failure after unicompartmental knee arthroplasty (UKA), and to evaluate considerations for surgical procedures and the results of revision total knee arthroplasty (TKA) performed after failure of UKA.

Eight hundreds and fifty-two cases of UKA were performed from January 2002 to June 2011. Forty-seven cases of failures after UKA were analyzed for the cause of the failures, and thirty-five cases of revision TKA after failure were analyzed for the operative findings and surgical technique. The clinical results were measured for thirty cases which were followed-up on at least two years after TKA. The mean duration of follow-up was four years and one month after revision TKA and the mean patient age at the time of surgery was sixty-five years.

For the cause of failures after UKA, there were twenty-two cases of early loosening of prosthesis, seventeen cases of simple mobile bearing dislocation, five cases of infection, one case of fracture of medial tibial condyle and two cases of unknown origin pain. In operative findings of thirty-five cases of TKA after failed UKA, there were twenty-seven cases of bone defect requiring treatment and the mean thickness of the defect was 10.6 mm. For the treatment of bone defect, there were five cases of autogenous bone graft, twenty-one cases of metal blocks, and one case of autogenous bone graft with metal block. The stem was used in tibial implants for nineteen cases, and one case of use in tibial and femoral implants. For thirty cases where follow-ups were possible at least two years after operation, the mean knee score was improved from 68.2 to 85.2 and the mean knee function score was improved from 67.7 to 78.0 at the last follow-up, respectively. The mean range of knee motion was 107.2° pre-operatively, which was recovered to 120.7° after the operation. The mean tibiofemoral angle was changed from 1.7° of valgus to 5.2° of valgus.

As shown in this study, the tibial bone defect was the most important problem in revision TKA after failure of UKA. Therefore, proper indication and accurate surgical technique using autogenous bone graft, metal block and stemmed implants would be able to achieve satisfactory results in revision TKA after failure of UKA.