Biomechanical strength of deep-frozen versus lyophilized large cortical allografts

Biomechanical strength of deep-frozen versus lyophilized large cortical allografts
June 2004
Received 18 July 2003; accepted 20 January 2004. Available online 9 April 2004.
A. Nather, , A. Thambyah and J. C. H. Goh
Clinical Biomechanics
Volume 19, Issue 5 , June 2004, Pages 526-533
ScienceDirect
Department of Orthopaedic Surgery, National University of Singapore, 5 Lower Kent Ridge Road, 119074, Singapore, Singapore
Abstract
Objective. To compare biomechanical strength of deep-frozen versus lyophilized large cortical allografts.
Design. In vivo transplantation studies performed in tibia of adult cats using 4 cm deep-frozen and lyophilized, gamma-irradiated allografts to bridge large cortical defect model.
Background. Bridging large cortical bone defect is a challenging problem. Options include autografts, allografts, bioceramics and prostheses. Allografts provide a suitable option.
Methods. Forty mature cats were used. A large defect (4 cm) was created in mid-diaphysis of right tibia. In 16 cats, cortical defect was reconstructed using deep-frozen allografts (-80 ?C) with intra-medullary rodding. In another 16 cats, lyophilized, gamma-irradiated allografts were used. Observation periods include 8, 12, 16 and 24 weeks. The specimens were procured together with unoperated legs as controls. Mechanical testing was performed using a materials testing machine with torsion test device of up to 500 N m at speed of 0.18 rpm. Parameters studied included maximum torque, torsional stiffness and energy of absorption.
Results. Deep-frozen allografts did not reach 100% strength, achieving only 64% at 6 months. In marked contrast, lyophilized allografts were significantly weaker with only 12% maximum torque strength at 6 months. Lyophilized allografts were significantly weaker than deep-frozen allografts in all observation periods (p<0.05).
Conclusion. Deep-frozen allografts did not reach 100% normal strength and were significantly weaker than non-vascularised autografts. Lyophilized allografts were significantly weaker than deep-frozen allografts.
Relevance
For the reconstruction of massive cortical bone defects, only deep-frozen cortical allografts should be used. Lyophilized allografts are not suitable.
Author Keywords: Biomechanical strength; Deep-frozen; Lyophilized; Large; Cortical; Allografts
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