Two pegs are better than one: rare mode of femoral component failure in unicompartmental arthroplasty requiring revision to total knee arthroplasty.

Femoral component fracture is a rare complication in unicompartmental knee arthroplasty, especially in cemented prostheses. We present a 75-year-old man who presented with a fractured single-peg Vanguard component 9 years postoperatively. He was revised to a total knee arthroplasty with an excellent functional outcome at 1 year. The components were additionally examined at an outside biomechanical engineering laboratory. Theories as to the cause of the component fracture include aseptic loosening due to a thin anterior cement mantle and the single-peg Oxford design.