The Effects of Freezing on the Tensile Properties of Repaired Porcine Flexor Tendon

Purpose When conducting complex testing of tendon repairs, it is essential that the samples are adequately preserved to prevent degradation. Freezing of samples is the most convenient method of preservation; however, there is no evidence in the literature to prove that freezing tendon before or after repair is acceptable. We aimed to prove that freezing tendons does not significantly alter the results of linear load-to-failure testing of tendon repairs. Methods After a power study, 150 tendons were harvested from porcine forelimbs and randomized into 5 groups of 30 tendons. After division, tendons were repaired using a Pennington modified core technique with a Silfverskiöld peripheral cross-stitch. Tendons in group 1 were divided, repaired, and tested within 3 hours postmortem. Tendons in group 2 were refrigerated at 4°C for 24 hours prior to repair and testing. Tendons in group 3 were frozen at −25°C for 3 months prior to repair and testing. Tendons in group 4 were frozen at −25°C for 6 months prior to repair and testing. Tendons in group 5 were frozen at −25°C for 6 months, repaired, refrozen for 1 month, and then tested. All repairs were linear load tested to ascertain the ultimate strength and force to produce 3-mm gap in the repair. Results Analysis of variance analysis of the results did not demonstrate any significant differences between groups. Conclusions Freezing tendons both before and after suture repair is an acceptable method of preservation when investigating the force to produce 3-mm gap and ultimate strength of tendon repairs.