Comparison of single- versus double-tunnel tendon-to-bone healing in an ovine model: a biomechanical and histological analysis.

BACKGROUND The double-bundle technique has recently gained much interest in ligament reconstruction. In addition to potential kinematic advantages, perhaps double tunnels have the potential for faster and more secure tendon-to-bone healing. HYPOTHESIS Placement of tendons in 2 osseous tunnels, as opposed to 1, will enhance tendon fixation as determined biomechanically and histologically. STUDY DESIGN Controlled laboratory study. METHODS Fourteen sheep were used, and an extra-articular tendon graft reconstruction was performed on both knees of each sheep. In 1 randomly selected knee, the long digital extensor tendon was released from the femur and placed into a single tunnel in the proximal tibia. In the contralateral knee, the tendon was split and placed into 2 tibial tunnels. Ten sheep were analyzed by mechanical testing, and the remaining 4 were subjected to histologic evaluation at 6 weeks after surgery. Paired t tests were used for statistical analysis. RESULTS Mechanical testing demonstrated that the peak load (981.8 +/- 143.2 N, mean +/- SD) and stiffness (570.9 +/- 114.6 N/mm) at 6 weeks after surgery in the double-tunnel group were significantly greater than for the single-tunnel group (714.8 +/- 94.2 N and 432.2 +/- 56.7 N/mm, respectively; load, P = .007; stiffness, P = .03). Histologic analysis suggested similar tendon-to-bone healing for both groups. CONCLUSION This study demonstrated enhanced biomechanical fixation of the tendon to the surrounding bone in the double-tunnel compared with the single-tunnel technique in this ovine model. CLINICAL RELEVANCE The double-tunnel technique may provide better fixation and healing in human ligament reconstruction.