Hip and Knee Arthroplasty in Hypophosphatemic Rickets

There is very limited published information about the technical aspects and durability of lower extremity arthroplasty in hypophosphatemic rickets. Between 1972 and 2006, 8 total hip arthroplasties (THAs) and 6 total knee arthroplasties (TKAs) were performed in 8 patients with degenerative arthritis and bone deformity secondary to hypophosphatemic rickets. Two hips required osteotomies at the time of arthroplasty, and 1 TKA patient required postoperative osteotomies. Specialized implants were required in 3 hips and 1 knee. At average follow-up of 7 years, mean Harris hip scores improved to 21 points, and mean Knee Society pain and function scores improved to 48 points and 27 points, respectively. One cemented THA failed due to femoral aseptic loosening at 13 years postoperatively; all other implants remained well fixed. Lower extremity arthroplasty is effective and durable for patients with arthritis associated with hypophosphatemic rickets, but corrective osteotomies and use of special implants should be anticipated with more severe deformities.