Cross-section radiographic analysis of 10 retrieved titanium alloy press-fit femoral endoprostheses

Ten cementless, press-fit, rectangular cross-section, titanium alloy prosthetic hips were implanted in the treatment of 9 displaced subcapital hip fractures and 1 case involving degenerative joint disease in 9 elderly patients (1 patient with bilateral implants) with varying Dorr bone types. Femur-implant constructs were retrieved postmortem for radiographic evaluation. Specimens remained in situ an average of 27 months (range, 6 weeks to 60 months). The mean patient age at retrieval was 87 years (range, 66-103 years). After retrieval, 2-mm-thick transverse sections were made at 5 levels along each implant. Radiographs were then made of each transverse section. Extensive bone-to-prosthesis apposition, remodeling, and the consistent mineralization of bony structures extending from the endosteal cortex to the implant were noted. The appositional bone index was measured for each patient, and the mean index (across all levels) between patients ranged from 15% to 74% overall mean, 48%. Radiographic and clinical findings demonstrated the ability of the titanium alloy material and the design of the press-fit implant to achieve satisfactory primary and secondary stability in elderly patients.