Patellar tendon augmentation after removal of its central third limits joint tissue changes

The central third of the patellar tendon is commonly used to reconstruct th e injured anterior cruciate ligament. Some studies have noted changes in jo int tissues following this procedure. It has been postulated that these cha nges may be associated with increased stress on the remaining tendon follow ing harvest of the graft. III our study, the central third of the patellar tendon was excised in three groups of rabbits. The central tendon defects i n two of the three groups were fitted with different augmentation devices t o augment the host tendon during the healing process, All rabbits followed a daily treadmill exercise regimen for 12 weeks following the operation. Bi omechanical testing of the tendon revealed that in nonaugmented tendons the cross-sectional area and the length of the patellar tendon significantly i ncreased 112 and 16%, respectively. There was histological evidence of host -tendon remodeling throughout the cross section and extensive fibrosis in t he infrapatellar fat pad. Augmentation of the tendon significantly reduced these changes, with the least change noted in the group with the greatest a ugmentation. The rabbits with augmentation devices retained tendon dimensio ns similar to those of the contralateral intact tendon, and tendon remodeli ng occurred only in the defect area. The rabbits with augmentation devices exhibited little to no fibrosis of the fat pad. Structural properties of au gmented and nonaugmented tendons were similar despite the size differences, indicating higher tissue quality in the augmented tendons. This study sugg ested that complications of the knee joint (i.e., tendon proliferation and fat pad fibrosis) noted after anterior cruciate-ligament reconstruction wit h the autogenous patellar tendon may be limited by the implantation of an a ugmentation device.