Early failure of a press-fit carbon fiber hip prosthesis with a smooth surface.

We investigated a press-fit anatomically shaped hip stem made of carbon fiber-reinforced composite material in a prospective clinical study. The intention of the design was that a surface of interlaced carbon fibers in the proximal part would achieve metaphyseal fixation. A total of 51 carbon stems were implanted in 48 patients (30 women and 22 men). Mean age at operation was 59 years. The patients were followed clinically, radiologically, and with computed tomography. At 6-year follow-up, aseptic loosening was observed in 47 hips (92%). Forty stems were revised on average 30 months (range, 9-58 months) postoperatively. All revised carbon stems showed fibrous fixation without any bony on-growth. No osteolysis was seen. Histologically, no carbon wear or inflammatory reactions were observed. Only 4 cases had a good clinical result with bony fixation on computed tomography scan. The carbon fiber prosthesis without effective ingrowth or on-growth irregularities showed a high rate of early loosening.