Spatial Variation in Material Properties in Fascicle-Bone Units from Human Patellar Tendon

Abstract

An understanding of the mechanical responses of the patellar tendon (PT) subunits should aid in determining which portion of the tissue might best be used as a cruciate ligament replacement. Human cadaveric knees were obtained from young donors. Fascicle groups with patellar and tibial bone blocks (subunits) were cut to provide six equally-spaced test specimens for each PT. After potting each bone end in PMMA, specimens were mounted in a saline-filled chamber, preloaded to 0.26 N and then subjected to 40 cycles of preconditioning to 2.5 % of the initial length at a strain rate of 1.25 %/sec, and then preloaded to 0.26 N again and failed at a strain rate of 100 %/sec using an Instron. The moduli and maximum stresses were generally greater in the lateral and mid subunits than in the medial subunits. The strains to maximum stress were similar between the lateral and medial subunits, but mid subunits had larger strains. Most strain values were distributed between 10 % to 20 %. Mechanical responses of human PT do vary from location to location. In general, the mid and lateral subunits were stiffer and carried greater stresses than the medial subunits. The results of this research should eventually be important, e.g. in selecting which portion of the PT would be the most suitable for cruciate ligament replacements to use as an autograft. On the basis of strength and stiffness, the more lateral portion of the PT would seem to be more advantageous.