BACKGROUND: Transfemoral amputation is considered the last treatment option for failed knee arthroplasty. The extent to which this procedure is performed is not well known. The purpose of this study was to identify the incidence and causes of amputation following failure of knee arthroplasty in a nationwide population.

METHODS: Data were extracted from the Danish Civil Registration System, the Danish National Patient Register, and the Danish Knee Arthroplasty Register. With use of individual data linkage, 92,785 primary knee arthroplasties performed from 1997 to 2013 were identified. Of these, 258 were followed by amputation. Hospital records of all identified cases were reviewed. A competing-risk model was used to estimate the cumulative incidence of amputation. Differences in cumulative incidences were analyzed with use of the Gray test.

RESULTS: A total of 115 amputations were performed for causes related to failed knee arthroplasty. The 15-year cumulative incidence of amputation was 0.32% (95% confidence interval [CI], 0.23% to 0.48%). The annual incidence of amputation following arthroplasties performed from 1997 to 2002 was 0.025% compared with 0.018% following arthroplasties performed from 2008 to 2013 (p = 0.06). The causes of the amputation were periprosthetic infection in 95 cases (83%), soft-tissue deficiency in 26 (23%), severe bone loss in 21 (18%), extensor mechanism disruption in 11 (10%), intractable pain in 11 (10%), periprosthetic fracture in 10 (9%), and vascular complications in 9 (8%). In 92 (80%) of the cases, there were ≥2 indications for amputation.

CONCLUSIONS: The cumulative incidence of amputation within 15 years after primary knee arthroplasty was 0.32%, with a tendency toward a decreasing incidence in the last part of the study period.

LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.