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Biomechanical study on the effect of twisted human patellar tendon
A Thambyah1, P Thiagarajan, J C Goh
1Faculty of Medicine, Department of Orthopaedic surgery, National University of Singapore, Lower Kent Ridge Road, 119074, Singapore.
Objective:
To compare the stiffness and maximum strength between the untwisted and twisted free-tendon.
Design:
22 twisted and untwisted sectioned-specimens of human cadaver patellar tendons were used and pulled to failure to obtain load-deformation profiles from which stiffness, maximum load to failure and elastic elongation limit were derived.
Background:
In the reconstruction of the deficient anterior cruciate ligament, the use of the central one-third of the patellar tendon is a well-established procedure in which, prior to insertion, the tendon graft may be twisted to mimic the natural orientation of the anterior cruciate ligament in the knee joint.
Results:
The untwisted tendons had a mean stiffness of 36.5 kg/mm (SD, 16.6 kg/mm) and maximum load of 165.9 kg (SD, 86.8 kg). With a 90 degrees twist, the average stiffness of the twisted tendon was 66.5 kg/mm (SD, 25.4 kg/mm), with maximum load at 364.5 kg (SD, 109.9 kg), an increase of over 100%. The elastic elongation limit, or allowable elongation before permanent deformation or failure, was significantly larger in twisted tendons by 35%.
Conclusion:
Twisting increased the resistance to deformation of the tendon in this study. Relevance The finding supports the surgical practice of pre-twisting tendon grafts for anterior cruciate ligament reconstruction, based on the premise that a stronger and stiffer graft provides a more favourable outcome.