Comparative mechanical strength of quadriceps tendon grafts

BACKGROUND: Selection of the optimal autograft for anterior cruciate ligament reconstruction remains one of the key challenges in contemporary orthopedics. Despite accumulated experience with traditional graft sources, comparative evaluation of the mechanical properties of different harvesting techniques for both the quadriceps tendon and the peroneus longus tendon remains insufficiently studied. This limits objective selection of an optimal graft combining high mechanical strength with minimal donor-site morbidity. AIM: This study aimed to compare mechanical strength and elastic–deformation characteristics of grafts derived from the peroneus longus tendon, full-thickness quadriceps tendon, and superficial layer of the quadriceps tendon under controlled experimental biomechanical testing (uniaxial quasi-static tensile loading to failure). METHODS: An experimental, controlled, laboratory biomechanical study was conducted on tendon specimens obtained from cadaveric material of 24 donors (mean age 50 ± 5 years). Specimens were allocated into three groups, 8 specimens each: peroneus longus tendon grafts, superficial-layer quadriceps tendon grafts, and full-thickness quadriceps tendon grafts. Mechanical testing was performed using a universal testing machine under uniaxial quasi-static tensile loading to failure at a deformation rate of 0.17 mm/s. The following parameters were assessed: ultimate load to failure, elastic modulus, stiffness, elongation at failure, and failure mode. RESULTS: Grafts derived from the superficial layer of the quadriceps tendon demonstrated the highest ultimate load to failure (1043.2 ± 4.2 N), stiffness (155.9 ± 13.0 N/mm), and elastic modulus (94.5 ± 8.6 MPa), significantly exceeding both other groups (p 0.001). Full-thickness quadriceps tendon grafts showed intermediate strength values (ultimate load 728 ± 39 N; elastic modulus 52.8 ± 9.4 MPa; stiffness 83.5 ± 15.4 N/mm), comparable to peroneus longus tendon grafts (ultimate load 908 ± 74 N; elastic modulus 78.2 ± 9.2 MPa; stiffness 101.1 ± 11.7 N/mm). Peroneus longus tendon grafts demonstrated the greatest elongation at failure (35.9% ± 8.8%), significantly exceeding that of superficial-layer quadriceps tendon grafts (23.5% ± 2.7%; p 0.001) and full-thickness quadriceps tendon grafts (26.6% ± 4.4%; p 0.01). No adverse reactions related to the studied intervention were observed. CONCLUSION: Grafts harvested from the superficial layer of the quadriceps tendon exhibit superior mechanical strength and may be considered a promising autograft option, combining sufficient biomechanical properties with potentially lower donor-site morbidity compared with full-thickness tendon harvesting.