Biomechanical assessment of the healing response of the rabbit patellar tendon after removal of its central third.

The objective of this study was to determine the biomechanical properties of the healing patellar tendon after removal of its central third. This was accomplished by removing the central third of the patellar tendon from the right limb of 30 mature New Zealand White rabbits. The tendon of the contralateral normal limb served as the unoperated control. The rabbits were separated into five test groups according to healing time: time of surgery and 1, 2, 3, and 6 months after surgery. The ultimate failure strength of the patellar tendons with the central third removed was significantly less than the failure strength of the contralateral normal patellar tendons at all time intervals after surgery. At the time of surgery, the ultimate failure strength values of the operated patellar tendons were on average 53% of the normal patellar tendons, increasing to 72% of normal at 6 months. There was a significant correlation between the ultimate failure strength of the operated tendons and healing time. The positive slope for this regression indicated that the ultimate failure strength of the operated tendons converged toward normal as healing progressed. Failure mode of the operated tendon did not depend on healing time.