Biomechanical study on the effect of twisted human patellar tendon

Objective. To compare the stiffness and maximum strength between the untwis ted and twisted free-tendon. Design. 22 twisted and untwisted sectioned-specimens of human cadaver patel lar tendons were used and pulled to failure to obtain load-deformation prof iles from which stiffness, maximum load to failure and elastic elongation l imit were derived. Background. In the reconstruction of the deficient anterior cruciate ligame nt, the use of the central one-third of the patellar tendon is a well-estab lished procedure in which, prior to insertion, the tendon graft may be twis ted to mimic the natural orientation of the anterior cruciate ligament in t he 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/m m), with maximum load at 363.5 kg (SD, 109.9 kg), an increase of over 100%. The elastic elongation limit, or allowable elongation before permanent def ormation or failure, was significantly larger in twisted tendons by 35%. Conclusion. Twisting increased the resistance to deformation of the tendon in this study.