This article is more than 5 years old. Information may no longer be current.

Extreme cryoprotection and rehydration changes tendon allograft characteristics

Extreme preparation methods may reduce predictability of performance andintegrity after ACL reconstruction.

Issue: August 2006

Add topic to email alerts

Receive an email when new articles are posted on

Please provide your email address to receive an email when new articles are posted on .

Subscribe

Added to email alerts

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

Back to Healio

We were unable to process your request. Please try again later. If you continue to have this issue please contact customerservice@slackinc.com.

Back to Healio

HOLLYWOOD, Fla. – Decellularized human anterior tibialis tendons prepared under extreme cryoprotectant incubation and rehydration conditions make it harder for surgeons to predict biomechanical performance and ACL reconstruction integrity compared to standardly prepared allografts.

In an in vitro biomechanical study, allografts prepared under extreme cryoprotection and rehydration methods and tested in porcine tibiae carried different biomechanical and qualitative characteristics than allografts prepared using standard conditions – decreasing a surgeon’s ability to detect performance and integrity after ACL reconstruction, according to researchers at the University of Louisville in Kentucky.

Although the researchers found some similar biomechanical properties, “decellularized tendon allograft constructs prepared under extreme conditions displayed lower stiffness during load-to-failure testing than constructs prepared using standardly prepared allograft tissue,” John Nyland, EdD, PT, of the University of Louisville, said at the Arthroscopy Association of North America 25th Annual Meeting.

He continued: “Decellularized tendon allografts must undergo cryoprotection prior to freezing for storage and later use. The ideal process for this has not been determined. If it’s done suboptimally it may affect the allograft properties.”

Three study groups

Researchers randomly divided paired decellularized human tibialis anterior tendon allografts from the same donor into two groups of 10.

Group 1 allografts underwent two-hour incubation and one hour of rehydration. Group 2 allografts underwent an eight-hour incubation and a 15-minute rehydration, Nyland said.

A third group – the control group – included 10 size-matched tendons that underwent standard preparation, using Allowash (LifeNet), and a 20-minute rehydration. All tendons received low-dose gamma irradiation (3-9 kGy), Nyland said.

An experienced, blinded surgeon evaluated the allografts’ tendon-handling properties, using a modified Visual Analog Scale. “After tendon-handling property evaluation, allografts were prepared and implanted in the equal-sized diameter tunnels in matched density (1.1 ± 0.2 g/cm²) porcine tibiae using 1-mm oversized, 35-mm-long bioabsorbable [Delta] screws (Arthrex),” Nyland said.

Surgeons used the same fixation method for all allografts, Nyland said. Researchers pretensioned the allograft constructs 10 N to 50 N at 0.1 Hz for 10 cycles, then cycled them between 50 N to 250 N at 0.5 Hz for 500 cycles. They finally tested for load to failure at 20 mm/minute.

The researchers used paired T-tests to compare Group 1 and Group 2 and used one-way Analysis of Variance (ANOVA) and Tukey post-hoc tests to evaluate differences among all three groups.

Using Pearson product moment correlations and coefficient of determination analyses they also identified tendon handling property-biomechanical test relationships (P<.05).

Researchers found that all three groups differed for compressive resilience and general graft “feel” (P<.0001). Group 2 and Group 3 differed from Group 1 for tensile stiffness, ease of graft preparation, color and slipperiness (P<.0001), Nyland said.

“Groups did not differ for displacement or stiffness during submaximal cyclic testing … [or] for load at failure or displacement,” Nyland said. “However, the control group displayed greater stiffness during load-to-failure testing.”

Researchers found the following related allograft characteristics in the control group but not for the experimental groups:

• Perceived tensile stiffness was strongly related to mechanical test cyclic displacement.
• Perceived compressive resilience was moderately related to load to failure.
• Perceived compressive resilience was moderately related to cyclic test displacement.
• Perceived tensile stiffness was weakly related to cyclic test stiffness.
• Perceived tensile stiffness was weakly related to load to failure.
• Perceived compressive resilience was weakly related to cyclic test stiffness.

“Only Group 1 displayed a significant relationship between perceived compressive resilience and stiffness during load to failure testing,” Nyland said. “However, this was an inverse relationship, meaning that the greater the perceived compressive resilience, the lesser was the actual construct stiffness during load to failure testing.”

Similarly, only Group 1 displayed a significant relationship between perceived tensile stiffness and stiffness during load-to-failure testing, Nyland said. Again the relationship was inverse, so the greater the perceived tensile stiffness, the lesser was the actual construct stiffness during load to failure testing.

For more information:

• Nyland J, Chang H, Caborn D. Tissue handling properties: A comparison of extreme human tibialis anterior allograft processing and rehydration methods. #SS-12. Presented at the Arthroscopy Association of North America 25th Annual Meeting. May 18-21, 2006. Hollywood, Fla.
• Dr. Nyland has no direct financial interest in the products discussed in this article, nor is he a paid consultant for any companies mentioned.