Cemented bipolar hemiarthroplasty in osteoporosis for failed femoral neck fixation.

From the Department of Surgery, University Health Network, Toronto, Ont. O steopetrosis refers to a group of disorders characterized by severe impairment of osteoclast-mediated bone resorption. Other terms that are often used for this disease are marble bone disease, which describes the solid radiographic appearance of the involved skeleton, and Albers–Schonberg disease, which refers to the milder, adult form of osteopetrosis, or autosomal dominant osteopetrosis type 2. The major types of osteopetrosis include malignant (severe, infantile, autosomal recessive) osteopetrosis and benign (adult, autosomal dominant) osteopetrosis types I and II. A third form is a rare autosomal recessive type characterized by a carbonic anhydrase II deficiency; it is associated with renal tubular acidosis and cerebral calcification. Radiographically, there is a generalized, symmetric increase in bone mass with thickening of both cortical and trabecular bone. Despite the excess bone formation, osteopetrosis bone tends to be brittle in nature. There is presently no cure for the disease, but bone marrow transplant is an option for some children. Osteoarthritis and periarticular nonunions are indications for jointreplacement surgery in these patients. Most reports of hip-replacement surgery performed in this population focus on total hip arthroplasty (THA) for osteoarthritis. One previous report discusses THA for femoral neck nonunion with retained hardware. Most authors recommend the use of cemented femoral fixation and uncemented acetabular fixation. There are no reports of bipolar hemiarthroplasty in osteopetrosis patients. We describe a case of cemented bipolar hemiarthroplasty as a salvage option for failed femoral neck fixation with retained hardware, despite end-stage acetabular cartilage degeneration.