Effect of Dynamic Changes in Anterior Cruciate Ligament In Situ Graft Force on the Biological Healing Response of the Graft-Tunnel Interface

Background:Anterior cruciate ligament (ACL) grafts that are placed for reconstruction are subject to complex forces. Current “anatomic” ACL reconstruction techniques may result in greater in situ graft forces. The biological effect of changing magnitudes of ACL graft force on graft-tunnel osseointegration is not well understood.Purpose:The research objective is to determine how mechanical force on the ACL graft during knee motion affects tendon healing in the tunnel.Study Design:Controlled laboratory study.Methods:Male rats (N = 120) underwent unilateral ACL reconstruction with a soft tissue flexor tendon autograft. ACL graft force was modulated by different femoral tunnel positions at the time of surgery to create different graft force patterns with knee motion. External fixators were used to eliminate graft load during cage activity. A custom knee flexion device was used to deliver graft load through controlled daily knee motion. Graft-tunnel healing was then assessed via biomechanical, micro–computed t...