Proximal hamstring reconstruction with a semitendinosus tendon allograft exhibits superior time-zero biomechanical properties compared to reconstruction with an Achilles tendon allograft.

Abstract

Aims: Chronic proximal hamstring tendon injuries sometimes require surgical reconstruction using a certain type of tendon graft. Although a distal hamstring and an Achilles tendon are the previously reported allograft options for this procedure, it remains unclear which allograft has superior biomechanical properties. The objective is to biomechanically compare the failure load, elongation at failure, and stiffness of proximal hamstring reconstruction techniques, using a semitendinosus tendon allograft and an Achilles tendon allograft. We hypothesized that the reconstruction, using a semitendinosus tendon allograft, would result in superior biomechanical properties.

Methods: Eight pairs of fresh-frozen human cadaveric hemipelvises were obtained, along with Achilles tendon and semitendinosus allografts. Specimens first underwent non-destructive native-state testing to determine linear stiffness. Within each pair, specimens were randomly assigned to reconstruction with either an Achilles tendon or a semitendinosus allograft. Following repair, the specimens underwent uniaxial tension testing consisting of a preconditioning phase and pull-to-failure testing to determine failure load, elongation at failure, stiffness, and mode of failure.

Results: The Achilles tendon allograft group failed at a significantly lower mean load than the semitendinosus group (213 N (SD 48) vs 366 N (SD 85); p = 0.005). Failure in the Achilles group occurred exclusively via suture pullout at the proximal end of the graft. Repairs with semitendinosus grafts most often failed by the same mechanism. Mean percent difference of native stiffness was significantly higher in the Achilles group compared to the semitendinosus group (34.4% (SD 14.1%) vs 13.1% (SD 6.4%); p = 0.003).

Conclusion: Proximal hamstring reconstruction with a semitendinosus tendon allograft showed higher failure load and better preservation of native stiffness compared to an Achilles tendon allograft using the techniques described in this study. While construct differences may contribute to this result, these findings support semitendinosus as the strongest allograft option for proximal hamstring reconstruction.