Proximal Hamstring Repair: A Biomechanical Analysis of Variable Suture Anchor Constructs

Abstract

Background:Despite an abundance of literature regarding construct strength for a myriad of anchors and anchor configurations in the shoulder, there remains a paucity of biomechanical studies detailing the efficacy of these implants for proximal hamstring repair.Purpose:To biomechanically evaluate the ultimate failure load and failure mechanism of knotless and knotted anchor configurations for hamstring repair.Study Design:Controlled laboratory study.Methods:A total of 17 cadaveric specimens divided into 3 groups composed of intact hamstring tendons as well as 2 different anchor configurations (all-knotted and all-knotless) underwent first cyclic loading and subsequent maximal loading to failure. This protocol entailed a 10-N preload, followed by 100 cycles incrementally applied from 20 to 200 N at a frequency of 0.5 Hz, and ultimately followed by a load to failure with a loading rate of 33 mm/s. The ultimate failure load and mechanism of failure were recorded for each specimen, as was the maximal displacement of each bone-tendon interface subsequent to maximal loading. Analysis of variance was employed to calculate differences in the maximal load to failure as well as the maximal displacement between the 3 study groups. Holm-Sidak post hoc analysis was applied when necessary.Results:The all-knotless suture anchor construct failed at the highest maximal load of the 3 groups (767.18 ± 93.50 N), including that for the intact tendon group (750.58 ± 172.22 N). There was no statistically significant difference between the all-knotless and intact tendon groups; however, there was a statistically significant difference in load to failure when the all-knotless construct was compared with the all-knotted technique (549.56 ± 20.74 N) (P = .024). The most common mode of failure in both repair groups was at the suture-tendon interface, whereas the intact tendon group most frequently failed via avulsion of the tendon from its insertion site.Conclusion:Under biomechanical laboratory testing conditions, proximal hamstring repair using all-knotless suture anchors outperformed the all-knotted suture anchor configuration with regard to elongation during cyclic loading and maximal load to failure. Failure in the all-knotted repair group was at the suture-tendon interface in most cases, whereas the all-knotless construct failed most frequently at the musculotendinous junction.Clinical Relevance:No biomechanical studies have clearly identified the optimal anchor configuration to avert proximal hamstring repair failure. Delineating this ideal suture anchor construct and its strength compared with an intact hamstring tendon may alter the current standards for postoperative rehabilitation, which remain extremely conservative and onerous for these patients.

Biomechanical Evaluation of Proximal Hamstring Repair: All-Suture Anchor Versus Titanium Suture Anchor

“…Mean maximum load to failure was 474 N for the 2-S repair, 543 N for the 2-L repair, and 1164 N for the 5-S repair. 17 Gerhardt et al 14 evaluated a knotless anchor configuration with suture tapes and observed a mean peak load to failure of 767 N. Our data for mean peak load to failure of all-suture anchors as well as titanium anchors are within the range reported in current literature.…”

“…For the native proximal hamstring tendons, a mean peak load to failure between 750 and 1405 N has been reported. 14,17 The mean peak load to failure of all-suture anchors is within the observed range of native hamstring tendons. The load to failure of 1405 N for native proximal hamstring tendons 17 shows the magnitude of hamstring forces on their insertion and may warrant the use of early postoperative treatment with a hip and knee orthosis to prevent reruptures.…”

“…Recent biomechanical studies have reported loads to failure for proximal hamstring repairs using various constructs. 14,17,19 Harvey et al 19 found that specimens fixed with three 2.9-mm single-loaded biocomposite anchors withstood a mean maximum load of 326 N. In a study by Hamming et al, 17 specimens were tested after hamstring repair with two 2.9-mm anchors (2-S), two 5.5-mm anchors (2-L), or five 2.9-mm anchors (5-S). Mean maximum load to failure was 474 N for the 2-S repair, 543 N for the 2-L repair, and 1164 N for the 5-S repair.…”

Repair of Proximal Hamstring Tear Utilizing a Suture Bridge Knotless Construct

“…Gerhardt and colleagues [10] completed a biomechanical study comparing two common surgical repair techniques. They evaluated the ultimate failure load and failure mechanism of an intact hamstring tendon compared to knotless and knotted anchor configurations for hamstring repair.…”

“…Advancement to full weight bearing was allowed at a mean of 7.1 weeks [16]. Gerhardt eliminated postoperative bracing and allowed his patients, following knotless suture anchor construct fixation, to eliminate weight bearing assistance at two weeks [10]. Toe-touch weight bearing with a knee brace flexed to 40 degrees for 4 weeks is recommended by Arner et al to decrease the tension on the repair and is less cumbersome than a hip brace [1].…”