Patellar Tendon and Infrapatellar Fat Pad Healing after Harvest of an ACL Graft

Clinical studies have documented proliferation of the host patellar tendon and fibrosis extending into adjacent tissues after reconstruction of the injured anterior cruciate ligament (ACL) using the central one-third of the patellar tendon (PT) as the graft. Such generalized arthrofibrosis has been implicated in knee locking and as possible source of anterior knee pain. However, it is not clinically feasible to measure changes in tendon morphology and mechanical properties and degeneration of peripheral tissues over time following graft harvest. In a rabbit experimental model proliferative changes in the tendon and the infrapatellar fat pad have been documented following harvest of a central third tendon graft without ACL reconstruction. Studies in larger animals have shown significant reductions in the strength and stiffness of the healing patellar tendon, but without assessment of the peripheral tissue response. In the current study an ACL reconstruction was performed in a goat model using an autogenous patellar tendon graft. Extensive tendon and fat pad proliferation were observed along with significant reductions in the biomechanical properties of the host tendon. Significant fat pad fibrosis was documented using biochemical methods. The current data confirm that harvest of an autogenous PT graft for reconstruction of the ACL results in significant changes in the PT and adjacent tissues. These data may help explain some of the clinical complications documented in the reconstructed joint.