The effect of the EndoPearl on soft-tissue graft fixation

This study determined whether EndoPearl (Linvatec Corp, Largo, Fla) secondary fixation to an interference screw increased the fixation strength of a soft-tissue tendon graft. Ten-millimeter porcine patellar tendon grafts with attached patellae were harvested without a tibial bone plug and inserted into 9-mm tibial tunnels to test a nonlooped solid tendon graft. Twenty grafts were fixed with a BioScrew (Linvatec Corp, Largo, Fla) and 20 with BioScrew/EndoPearl combinations. These were tested with straight line destructive loads at 60 mm/min without cycling and after 500 cyclic loads. Tendons were secured with nonlocking (Bunnell) sutures along both edges and then passed through the central hole of the EndoPearl. A significant decrease in stretch at maximum force was noted between specimens that were cyclically loaded prior to testing and those that were not (P<.001); a significant increase in energy absorption between specimens with and without EndoPearl in the straight destructive test (P<.02); and a significant increase in stiffness with cyclic loading (P<.001). A positive correlation also was noted between failure force and insertion torque (P=.02). The EndoPearl increased energy absorption at failure. Solid tendon grafts consistently failed due to the sutures tearing out of the tendon and the tendon sliding by the interference screw. The Bunnell stitch was the weakest link and is not effective for this graft.