Influence of bone quality on femoral stress distribution after cemented stem insertion: an experimental thermoelastic stress analysis.

Abstract

With an ageing population, the number of total hip arthroplasty (THA) performed in osteoporotic patients is increasing. Cemented stems are often chosen for osteoporotic bone owing to their lower fracture risk. However, how bone quality influences stress distribution after cemented stem insertion remains unclear. This study compared femoral stress distribution between normal and osteoporotic femora using thermoelastic stress analysis (TSA). 6 composite femora were used: 3 normal adult male models (#3403) and 3 osteoporotic models (#3503). C-stem AMT cemented stems were implanted with a standardised technique. TSA was conducted before and after stem insertion under physiological loading (normal: 100-1900 N; osteoporotic: 100-1000 N). Stress distribution was analysed by Gruen zones and compared using linear mixed models. In the normal models, stress uniformly decreased after stem insertion with a distal shift of peak stress. In the osteoporotic models, proximal stress decreased markedly, while distal stress (zones 4L, 4M) increased, demonstrating a more pronounced distal shift. Bone quality strongly affects load transfer after cemented stem insertion. Osteoporotic bone demonstrated proximal stress loss and distal concentration, possibly underlying atypical periprosthetic femoral fractures. TSA provides useful insights for implant design and surgical planning in osteoporotic THA.