Biomechanical properties of an all-soft tissue quadriceps tendon autograft compared with a quadrupled semitendinosus autograft: a cadaveric study.

BACKGROUND

Anterior cruciate ligament (ACL) injuries are among the most frequent ligament injuries, with autograft reconstruction considered to be the gold standard treatment. The all-soft-tissue quadriceps tendon (ASTQT) autograft has gained popularity because of its favorable graft size, reliable biomechanical strength, and reduced donor site morbidity. However, graft strength depends on the preparation, fixation, and construct stiffness. Emerging techniques, such as suture tape augmentation, may further influence biomechanical outcomes. The aim of this study was to investigate the biomechanical properties of tape-augmented ASTQT construct compared with quadrupled semitendinosus construct (QST) for anterior cruciate ligament reconstruction (ACLR) using an established cadaveric biomechanical test protocol.

METHODS

A total of nine human cadaveric ASTQTs and 11 QSTs were obtained from the knees of body donors. For the ASTQTs, both ends were secured using a suture tape-integrated adjustable loop suspensory fixation device. For the QSTs, the semitendinosus tendons were quadrupled and attached to two adjustable loops and stitched using the buried-knot technique described by Lubowitz. Cyclic biomechanical testing was performed following an established protocol, and load-to-failure, mode of failure, and stiffness were reported.

RESULTS

QSTs revealed a significantly higher load-to-failure (806.1 N versus 577.9 N, P < 0.001), initial (120.7 N/mm versus 93.3 N/mm, P < 0.001) and final (153.9 N/mm versus 117.1 N/mm, P = 0.001) dynamic stiffness and higher stiffness at failure (173.8 N/mm versus 120.1 N/mm, P < 0.001) compared with ASTQTs. All ASTQTs exhibited suture tape cut-through (cheese wiring) at the proximal fixation site as their mode of failure. Conversely, suture rupture was the predominant failure mode in the QST group.

CONCLUSIONS

In an established cadaveric test setting, the QST construct exhibited higher load-to-failure and stiffness compared with the tape-augmented ASTQT construct. The consistent cheese-wiring failure at the proximal fixation site of the ASTQT indicates that the tape-tendon interface-not the substance itself-was the limiting structural element. These findings should be interpreted as construct-specific limitations of tape augmentation in degenerated tendon tissue, rather than as evidence of intrinsic inferiority of the quadriceps tendon graft.