Compaction of a bone dowel in the tibial tunnel improves the fixation stiffness of a soft tissue anterior cruciate ligament graft: an in vitro study in calf tibia

BACKGROUND: Despite increasing attention on fixation of a soft tissue anterior cruciate ligament graft in the tibia, there have been no studies on the use of a bone dowel as a joint line fixation device for promoting fixation properties, especially stiffness at the time of implantation. PURPOSE: To determine whether compacting a bone dowel into the tibial tunnel improves fixation stiffness, yield load, and resistance to slippage of a soft tissue anterior cruciate ligament graft. STUDY DESIGN: Controlled laboratory study. METHODS: A double-looped tendon graft was fixed at the distal end of the tibial tunnel with a WasherLoc in 24 calf tibias. The tibial tunnels were treated with or without a dowel of cancellous bone. The bone dowel was harvested from the tibial tunnel and then compacted into a tapered space anterior to the anterior cruciate ligament graft as a joint line fixation device. A cyclic load and measurement test was administered to determine fixation stiffness, yield load, slippage, and failure mode. RESULTS: The specimens with the bone dowel had 58 N/mm more stiffness (P = .04); however, the yield load and resistance to slippage were similar in specimens with and without the bone dowel. CONCLUSIONS: A bone dowel harvested from the tibial tunnel can be used as a joint line fixation device in series with a distal fixation method to improve initial fixation stiffness and increase the fit, which is known to enhance tendon graft-to-bone healing in the tibia.