Synergetic effect of freeze-drying and gamma irradiation on the mechanical properties of human cancellous bone.

Freeze-drying and irradiation are common process used by tissue banks to preserve and sterilize bone allografts. Freeze dried irradiated bone is known to be more brittle. Whether bone brittleness is due to irradiation alone, temperature during irradiation or to a synergetic effect of the freeze-drying-irradiation process was not yet assessed. Using a left-right femoral head symmetry model, 822 compression tests were performed to assess the influence of sequences of a 25 kGy irradiation with and without freeze-drying compared to the unprocessed counterpart. Irradiation of frozen bone did not cause any significant reduction in ultimate strength, stiffness and work to failure. The addition of the freeze-drying process before or after irradiation resulted in a mean drop of 35 and 31% in ultimate strength, 14 and 37% in stiffness and 46 and 37% in work to failure. Unlike irradiation at room temperature, irradiation under dry ice of solvent-detergent treated bone seemed to have no detrimental effect on mechanical properties of cancellous bone. Freeze-drying bone without irradiation had no influence on mechanical parameters, but the addition of irradiation to the freeze-drying step or the reverse sequence showed a detrimental effect and supports the idea of a negative synergetic effect of both procedures. These findings may have important implications for bone banking.

Outcome of total knee arthroplasties after renal transplantation.

The fate of total knee arthroplasty in renal graft recipients is unknown. We retrospectively reviewed the outcome of 16 total knee arthroplasties (TKAs) performed after renal transplantation in 12 renal graft recipients from February 1997 to December 2003. The patients (mean age 63) were submitted to a clinical evaluation using the Knee Society Score (KSS) and a radiological evaluation using the Knee Society Total Knee Arthroplasty Roentgenographic Evaluation. The follow-up period averaged 65 (range 25-107) months. No knee had to be revised and one patient died during the follow-up period. The mean knee score was 97.1 (range 93-100) and the mean function score was 87.7 (range 60-100). The alignments of the prosthetic components were correct for all but one patient who, however, kept a good knee score (95). No case of aseptic loosening or osteolysis was detected at last X-rays examination. We conclude that TKA is a safe and symptomatically effective treatment of knee osteonecrosis or severe osteoarthritis in renal graft recipients and should thus be proposed in this population when symptomatology becomes significant. Long-term follow-up studies are necessary to confirm this initial report.