Document Title: Curran-AJSM-Jul04.shtml
Article Title: The Biomechanical Effects of Low-Dose Irradiation on Bone–Patellar Tendon–Bone Allografts
Authors: Andrew R. Curran, DO, Douglas J. Adams, PhD, Julie L. Gill, PA-C, Mark E. Steiner, MD and Arnold D. Scheller, MD
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: July 2004
Volume 32, pages 1131-1135
Keywords: Allografting, irradiation, sterilization of graft, micro-scale biomechanics, microbiomechanics, histological structure, cellular biology, cellular biomechanics.

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Comments: This study shows that irradiating (using ionizing radiation) an allograft (cadaver graft) results in diminished strength and increased likelihood of graft failure. The typical amount used in North America is between 1 and 2.5 Mrad (megarads), despite the fact that about 3.5 megarads are needed in order to reliably destroy the DNA of an extremely worrisome pathogen such as the AIDS virus. Unfortunately, the reduced radiation dose, while unreliable in terms of disinfection, is still enough to detrimentally affect the structure and stregth of the graft.

ABSTRACT

Background: Despite evidence that low-dose irradiation of 2 Mrad (20 kGy) is not virucidal for patellar tendon allografts and reduces tissue strength, many tissue bank protocols include low-dose irradiation.

Hypothesis: Maintaining tissue mechanical integrity may be particularly relevant toward accelerated rehabilitation of the injured knee, where the cyclic function of patellar tendon allografts is critical.

Study Design: Controlled laboratory study.

Methods: The cyclic and failure mechanical properties of paired bone-patellar tendon-bone allografts, with and without current low-dose irradiation of 20 kGy, were evaluated. Specimens were loaded from 50 N to 250 N for 1000 cycles at 0.5 Hz and subsequently loaded to failure at a strain rate of 100% per second.

Results: After 1000 cycles, grafts elongated 27% more when irradiated than when not (4.4 ± 1.5 mm vs 3.4 ± 1.0 mm; P = .03). Failure load averaged 1965 ± 512 N for irradiated grafts and 2457 ± 647 N for nonirradiated grafts (P = .007).

Conclusions: The diminished strength of irradiated grafts may contribute to overt anterior cruciate ligament graft failure, and the increase in cyclic elongation may also be detrimental to graft function.

Clinical Relevance: These results suggest that one should consider the use of nonirradiated allografts as an alternative to irradiated grafts in anterior cruciate ligament reconstruction.

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