Cementless total knee arthroplasty in ochronotic arthropathy: a case report with a 4-year follow-up.

Alkaptonuria is an inherited metabolic disorder characterized by the absence of the enzyme homogentisic acid oxidase, which leads to the accumulation of homogentisic acid, produced during normal metabolism of phenylalanine and tyrosine. Ochronosis, which is the dark pigmentation of connective tissues in patients with long-lasting alkaptonuria, can cause severe cartilage destruction in large joints and the vertebral column. Knee joint involvement, which occurs at relatively early ages, can be quite restrictive. Arthroplasty may be the treatment of choice in these patients because of limited mobility and diffuse involvement of the joint. We report a 48-year-old man who had been treated with cementless total knee arthroplasty. Theoretically, there are no bone ingrowth deficits that might be detrimental for the stabilization of cementless prostheses in ochronotic arthropathy because the bone tissue is not primarily affected by the disease. The 4-year follow-up of cementless total knee arthroplasty was satisfactory without any evidence of loosening.