THE EFFECTS OF DONOR AGE AND STRAIN-RATE ON THE BIOMECHANICAL PROPERTIES OF BONE-PATELLAR TENDON-BONE ALLOGRAFTS

Over 50% of all knee injuries involve partial or complete tear of the anterior cruciate ligament. Surgical reconstruction of this ligament u sing an isometrically placed bone-patellar tendon-bone autograft is th e current technique of choice; however, harvest of patellar tendon as a free graft can lead to increased morbidity. To address this issue, a llogenic patellar tendon grafts have been introduced as alternatives t o autogenic graft material. The purpose of this study was to examine e ffects of age and strain rate on tensile strength, modulus, and failur e mode of bone-patellar tendon-bone allografts from a typical populati on of tissue donors. Eighty-two, fresh-frozen, bone-patellar tendon-bo ne allografts were harvested from 25 different donors, aged 17 to 54. Paired grafts from individual patellar tendons were assigned randomly to tensile testing at either 10% or 100% elongation per second. Tensil e strength, modulus, and failure mode were not significantly different for tests conducted at these 2 strain rates. Correlations between ten sile strength and age were not significant for tests conducted at eith er strain rate. Specimens tested at a strain rate of 100% per second e xhibited weak but significant negative correlation between modulus and age, with modulus decreasing 25% over the age range examined.