Mechanical considerations in impaction bone graftingN. T. Brewster, FRCS Ed(Orth), Senior Lecturer in Orthopaedic Surgery; W. J. Gillespie, FRACS Orth, Professor of Orthopaedic Surgery; and C. R. Howie, FRCS Ed(Orth), Consultant Orthopaedic SurgeonPrincess Margaret Rose Orthopaedic Hospital, Fairmilehead, Edinburgh EH10 7ED, UK. S. P. G. Madabhushi, PhD, Lecturer in Civil and Environmental Engineering; A. S. Usmani, Lecturer in Civil and Environmental Engineering; and D. R. Fairbairn, PhD, Senior Lecturer in Civil and Environmental Engineering Department of Civil Engineering, Kings Buildings, University of Edinburgh, West Mains Road, Edinburgh, UK. Correspondence should be sent to Mr C. R. Howie. In impaction grafting of contained bone defects after revision joint arthroplasty the graft behaves as a friable aggregate and its resistance to complex forces depends on grading, normal load and compaction. Bone mills in current use produce a distribution of particle sizes more uniform than is desirable for maximising resistance to shear stresses. We have performed experiments in vitro using morsellised allograft bone from the femoral head which have shown that its mechanical properties improve with increasing normal load and with increasing shear strains (strain hardening). The mechanical strength also increases with increasing compaction energy, and with the addition of bioglass particles to make good the deficiency in small and very small fragments. Donor femoral heads may be milled while frozen without affecting the profile of the particle size. Osteoporotic femoral heads provide a similar grading of sizes, although fewer particles are obtained from each specimen. Our findings have implications for current practice and for the future development of materials and techniques. This article has been cited by other articles:
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