Abstract

Background/Objectives: Hamstring tendon (HT) autografts are commonly used for anterior cruciate ligament reconstruction (ACLR), traditionally combining semitendinosus and gracilis (ST + GR) tendons to achieve adequate graft length and diameter. More recently, four-strand semitendinosus (ST-only) constructs have been adopted to avoid gracilis harvest and reduce donor-site morbidity when sufficient ST tendon length is available. However, to our knowledge, the intrinsic biomechanical properties of four-strand ST-only and ST + GR grafts have not been directly compared. Methods: Twenty-five hamstring allografts (17 ST, 8 GR) from a single provider were prepared into two four-strand configurations: ST-only (n = 9) and ST + GR (n = 8). Manufacturer-reported folded tendon diameters were used to estimate four-strand graft diameters. Grafts underwent preconditioning, cyclic loading (80–250 N), and load-to-failure testing using a servomechanical testing apparatus. Ultimate failure load, stiffness, cyclic elongation, and elongation at failure were recorded. Groups were compared using the Mann–Whitney U test. Results: Mean donor age was 55.8 years (range, 27–72 years). Estimated mean graft diameter was significantly greater for ST-only constructs compared with ST + GR constructs (8.88 ± 0.62 mm vs. 7.70 ± 0.38 mm; p < 0.001). ST-only constructs demonstrated greater stiffness than ST + GR constructs (458.99 ± 54.51 vs. 364.67 ± 57.18 N/mm; p = 0.007) and lower elongation at failure (5.67 ± 1.25 vs. 7.42 ± 0.86 mm; p = 0.01). Cyclic elongation (0.259 ± 0.045 vs. 0.256 ± 0.049 mm; p = 0.89) and ultimate load to failure (1689.84 ± 121.36 vs. 1626.59 ± 324.92 N; p = 0.64) did not differ between groups. Conclusions: When tested in isolation, four-strand ST-only grafts are not biomechanically inferior to ST + GR grafts and demonstrate greater stiffness and larger estimated diameter. When sufficient semitendinosus length is available, ST-only grafts represent a biomechanically viable option for ACLR without the need for gracilis harvest.

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