A prospective randomized trial of suture of the patellar tendon defect after harvesting

In a rabbit model, we studied the long-term biomechanical and biochemical effects of leaving the patellar tendon unsutured, or closing the defect with absorbable sutures, after harvesting one third. Using a prospective randomized design, after harvest of its central third, the patellar tendon was either sutured side to side with absorbable sutures, or left unsutured in 112 skeletally mature rabbits. The rabbits were killed at 2 and 6 weeks, and 6 and 9 months postoperatively. After an initial increase in both groups (.001 < P < .019), water content decreased from 2 weeks to 9 months after the operation (.02 < P < .0045), and remained significantly greater than in the control contralateral limb at all times (.00 1 < P < .003). Collagen content showed no significant differences between the two experimental groups. The operated tendons always showed a decreased collagen content at all time periods (.012 < P < .049). Failure load, ultimate stress, stiffness, and energy absorbed before failure tended to gradually return to normal over 9 months after a significant initial drop. There were no significant differences between the two experimental groups in failure load, ultimate stress stiffness, and energy absorbed before failure. At 9 months, the operated patellar tendon was significantly thicker (.0016 < P < .03) and had a greater cross-sectional area (.01 < P < .03) than the contralateral control regardless of whether it had been sutured or left open. After removal of the central third, closing the tendon gap with absorbable sutures or leaving it open makes little difference on the biomechanical and biochemical properties of the remaining patellar tendon.