Neck fracture femoral heads for impaction bone grafting: evolution of stiffness and compactness during impaction of osteoarthrotic and neck-fracture femoral heads.

BACKGROUND: The need for safe bone allografts is increasing and preservation of femoral heads from patients being operated on with hip arthroplasty should be encouraged. However, should we preserve femoral heads from patients operated on for neck fracture as tissue mechanical quality may not be satisfactory? MATERIAL AND METHODS: We compared the evolution of stiffness and compactness of fresh-frozen morselized bone obtained from osteoarthrotic femoral heads and those from neck fractures. Both materials were also compared after freeze-drying and irradiation. We used 6 osteoarthrotic and 6 neck-fracture femoral heads to prepare 4 batches of morselized bone. 18 samples from each batch were impacted in a contained cylinder. Frozen bone grafts were tested after thawing at room temperature for 2 hours and freeze-dried grafts were tested after 30 minutes of rehydration. RESULTS: The stiffness of fresh-frozen neck fracture bone was lower than that of fresh-frozen osteoarthrotic bone at 150 impactions. The stiffness of freeze-dried irradiated bone was higher than that of the fresh-frozen bone and did not differ between osteoarthrotic and neck-fracture bone. INTERPRETATION: Solvent-treated freeze-dried bone from femoral heads procured during arthroplasty for sub-capital hip fractures represents a valuable source of material for allografts, addressing concerns regarding serological testing, medical history and bone quality.

Freeze-dried irradiated bone brittleness improves compactness in an impaction bone grafting model.

BACKGROUND: Defatted bone chips with or without freeze-drying and irradiation have mechanical advantages as compared to fresh-frozen controls in in vitro models of impaction. These improved results have been ascribed to replacement of viscous bone marrow by saline and embrittlement of the freeze-dried bone by irradiation. MATERIAL AND METHODS: To determine which of these hypotheses is correct, we compared the development of stiffness and compactness of morselized bone graft that had been: 1) fat-reduced with saline, and 2) fresh-frozen, solvent-detergent defatted, 3) freeze-dried irradiated and 4) not irradiated. We used 12 osteoarthrotic femoral heads to prepare these four batches of morselized bone, and impacted 18 samples from each batch in a cylinder. The frozen bone grafts were tested after thawing at room temperature for 2 hours and the freeze-dried grafts were tested after 30 minutes of rehydration. We monitored the development of compactness and stiffness of the material during impaction. RESULTS: The stiffness of the freeze-dried irradiated bone was greater than that of the other three series after 10, 50 and 150 impactions. The freeze-dried bone chips that were not irradiated and the chips defatted with saline alone were less stiff than the fresh-frozen control after 150 impactions. INTERPRETATION: The brittleness of freeze-dried irradiated bone, caused by loss of the capacity to absorb energy in a plastic way, increases the compactness and stiffness of the morselized grafts. Washing bone with saline alone or treating bone with solvent-detergent but no irradiation had no similar mechanical advantage and the bone did not impact better than fresh-frozen undefatted bone in our model.