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Some BTB allografts maintain biomechanics after sterilization
Two proprietary tissue sterilization methods did not appear to affect collagen compared to controls.
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CHICAGO — Researchers at the University of Southern California’s Keck School of Medicine found that different allograft sterilization and processing methods do not appear to affect the properties of bone-tendon-bone allografts typically used for ACL reconstruction surgery.
For these types of cases, orthopedic surgeons have always been faced with a dilemma: Use an autograft and maybe later deal with donor site morbidity problems, or implant an allograft that might be associated with reduced performance or increased risk of disease transmission.
The researchers hoped to address some of those concerns with their biomechanical study, which analyzed whether certain sterilization methods affected bone-tendon-bone (BTB) graft properties, such as strength, toughness and size.
MTS cycling
Researchers studied the effects of three sterilization techniques on the tendons. The first group, a control group, consisted of 14 aseptically harvested BTB tendons placed through a chemical wash and gamma irradiation. The second group included 11 tendons that underwent the BioCleanse process (Regeneration Technologies Inc.), a low-temperature chemical wash. The third group featured 15 tendons processed with the Clearant process (Clearant Inc.), which involves a pathogen-inactivating wash and coating method.
The width of each graft using digital calipers was 10 mm.
Researchers potted all the BTB allografts in a material testing system, performed cyclic loading tests on them, and then put the allografts through time-to-failure testing via strain-gauge loading at a rate of 100% per sec. They analyzed such data as graft dimensions at both ends of the tendon and in the medial aspect, donor age and sex, 2% yield stress, Young’s modulus or elasticity, elongation time, strain fracture, ultimate stress and toughness.
Factors: graft age, length
“The only differences we had were the age of the controls and the length of the controls,” Jim Reid, MD, said.
Reid presented the study results at the American Academy of Orthopaedic Surgeons 73rd Annual Meeting, here. He is a now a fellow at the Palo Alto (Calif.) Medical Foundation in Sports Medicine.
The average donor age in the control group was 54.2 years, compared to 40.2 and 52.5 years, respectively, for the second and third groups. The average tendon length in the Clearant-treated group was 45.4 mm compared to 52.5 mm for the controls and 56 mm for the BioCleanse-treated tendons.
Researchers detected no significant statistical differences in any other parameters, such as elongation to failure, strain to failure, ultimate stress and toughness (P>.05). None of the differences in other factors, such as yield stress and Young's modulus reached statistical significance (P>.05).
Yield stress ranged from 19.34 to 25.4 MPa. Young’s modulus ranged from 171.87 to 219.38 MPa.
In discussing the results in the tendons processed via the BioCleanse and Clearant methods, Reid said, “neither appeared to affect the collagen.”
For more information:
- Vangsness CT, Sikka R, Vu C, et al. Sterilization effects on the biomechanical properties of human bone-tendon-bone (BTB) allografts. #165. Presented at the American Academy of Orthopaedic Surgeons 73rd Annual Meeting. March 22-26, 2006. Chicago.