Long-Term Outcomes of the Knee and Hip Arthroplasties in Patients with Alkaptonuria

Alkaptonuria is a rare autosomal recessive metabolic disorder. It is characterized by the accumulation of homogentisic acid in the body due to a lack of enzymes that degrade it. Over time, it results in joint degeneration and eventually leads to ochronosis. Ochronosis refers to bluish-black discoloration of connective and other tissues within the body. In this study, we present 5 distinct cases diagnosed with alkaptonuria. They have undergone 8 total joint replacement surgeries (4 hips and 4 knees) within 8 years (2010-2018). All patients had an excellent outcome over several years. The follow-up period ranged from 2 to 10 years. Although none of the presented cases had intraoperative or postoperative adverse sequelae, we must take care when dealing with patients with ochronotic arthropathy. They carry a higher risk of complications than other patients with osteoarthritis disease. These complications include fractures due to fragile bone quality, muscle or tendon rupture, joint instability, and anesthesia-related complications. Total joint arthroplasty is a valid and safe option in the management of hip and knee ochronotic arthropathy.