Bone-mineral content, surface hardness, and mechanical fixation in the human radius. A correlative study.

Abstract

The bone-mineral content of seventeen intact forearms from eleven cadavera was determined by the non-invasive photon-absorptiometric scanning technique (Norland-Cameron Bone-Mineral Analyzer). Each radius was then removed and three surgical screws were implanted. The forces required to push out the screws retrograde were used to represent the security of mechanical fixation and were correlated with bone-surface hardness and bone-mineral content. A high degree of correlation (r = 0.89 or more) was found between bone-mineral content and the force required for extraction. A much lower correlation existed between surface hardness and extraction force (r = 0.30). We concluded that surface hardness does not correlate well with the screw-holding capacity of bone but that bone-mineral content, as determined by a non-invasive means, does so within a 10 per cent error. This study demonstrates a high degree of positive correlation between bone density and the security of screw fixation in the human radius. Measuring bone density using a highly accurate, non-invasive, safe technique has clinical relevance in preoperative assessment of osteopathic patients who are being considered for internal fixation of the radius with plates and screws.