Use of a hydroxyapatite-coated stem in patients with Dorr Type C femoral bone.

Type C bone, as described by Dorr, exhibits both cellular and structural compromise, which presents a challenge for fixation of a total hip arthroplasty (THA). We evaluated the performance of the Omnifit HA stem, a hydroxyapatite-coated titanium alloy stem, by retrospectively reviewing the clinical and radiographic data of 15 patients with femoral Type C bone who received the stem during primary THA between 1991 and 1994. The patients were followed a minimum of 9 years (mean, 11.5 years; range, 9-14 years). The average age at surgery was 54 years and the average body mass index was 28. Eight of the patients were men. The median Harris hip score was 94.5 points. Radiographically, two independent reviewers identified all patients as Type C bone. The average canal to calcar isthmus ratio was 0.74 (range, 0.65-0.95). At most recent followup, four patients demonstrated proximal osteolysis. Using plain radiography we detected no patients with distal osteolysis or subsidence. At 9 to 14 years, the stem has performed well in a selected series of patients with poor bone quality and the outcomes compare favorably with previously reported findings using this design of stem in other bone types. These results support the decision to use a hydroxyapatite-coated stem in patients with Type C bone.