Total knee arthroplasty in a patient with thrombocytopenia-absent radius syndrome.

Thrombocytopenia-absent radius (TAR) syndrome is a rare genetic condition with a complex inheritance pattern. This syndrome is classically characterized by hypomegakaryocytic thrombocytopenia as well as bilateral absent radii, shortened ulna, and radially deviated 5-digit hands. During infancy, the predominant manifestations are hemorrhagic complications. Later in life, the bleeding disorder typically improves, but the musculoskeletal abnormalities become of greater concern because of the effects on quality of life. Although the classic musculoskeletal manifestations of TAR syndrome involve the upper extremity, multiple lower-extremity abnormalities have been described, especially dysplasia of the knee. Knee abnormalities include genu varum, varying degrees of laxity or stiffness, patellar abnormalities, concave distal femur, convex medial tibial plateau, and/or absence of the anterior cruciate ligament and posterior cruciate ligament. Several management strategies for lower-extremity abnormalities in TAR syndrome have been described, especially for pediatric patients. Management strategies have not halted the natural progression of knee disease in these patients, and the effect that these knee abnormalities have in adulthood is unclear. Management of knee abnormalities in adults with TAR syndrome is poorly described in the current literature. The authors report a 59-year-old patient with TAR syndrome and knee abnormalities who underwent successful total knee arthroplasty. The patient was followed to the 3-year postoperative visit. At various postoperative time points (7 weeks, 6 months, 1 year, and 3 years), Knee Society Scores and 12-Item Short Form Health Survey scores were recorded. Radiographs obtained at each clinical visit showed well-positioned, well-fixed components. The authors concluded that total knee arthroplasty may be a safe and effective surgical intervention for adults with TAR syndrome and associated knee osteoarthritis.