Patella position and biomechanical properties of the patellar tendon 1 year after removal of its central third

Objective. The aim of this study was to investigate how the removal of a patellar tendon graft for cruciate ligament reconstruction influences the mechanical properties of the remaining patellar tendon and the position of the patella at the knee joint. Design. The experimental model of this in vivo study was the anterior cruciate ligament reconstruction in sheep. Background. While the efficacy of a patellar tendon third as a ligament replacement has been extensively investigated, the consequences for the function of the remaining tendon and patella position remain unclear. Methods. The central third of the patellar tendon from the right knees of 10 animals was removed for cruciate ligament replacement. One year postoperatively, the position of the patella within the joint and the stiffness and modulus of elasticity of the remaining tendon were compared with the non-operated contralateral controls. Results. The patella position did not change in the operated knee joints in comparison with the controls. The cross-sectional area of the operated patellar tendon increased significantly by scar tissue formation at the defect site. Conclusion. Although the inferior mechanical properties of the scar tissue reduced the modulus of, elasticity of the tendon, the increase in cross-sectional area allowed it to develop a structural stiffness similar to the control tendons.