Abstract
Surgeons often protect Tendon-bone reconstructions such as rotator cuff repairs by off loading them. We investigated the effect of limb position and boundary conditions in an in-vitro rabbit patella tendon-bone repair model. Patella tendons were repaired back to the tibia in eight hindlimb cadavers with 2 mitek anchors(Mitek, Westwood, MA) and 3-0 Ethibond (Ethicon, Sommerville, NJ) using two techniques, one involving simple sutures and the other involving crossing over between the sutures. A loading mechanism through the patella tendon was constructed using static weights over a pulley mechanism. The contact area and force at the PT-bone interface were measured using a TekScan pressure sensor (6911, TekScan, South Boston, MA). The contact footprint (area and normal force) was acquired under four configurations: (1) knee full extension with interface unloaded, (2) knee 45° flexion with interface unloaded, (3) knee full flexion with interface loaded by limb weight alone, (4) tendon loaded with limb weight and 20N force applied through tendon loading mechanism. The contact area force footprint changed substantially between the different suture techniques and loading configurations. Crossing over of sutures appears to provide an increased and more evenly distributed force across the tendon-bone interface. Repair off-loading was accompanied by a decrease in the contact footprint force and pressure. The force in both suture techniques increased with increasing flexion angle and was substantially increased by both bearing the weight of the dependent limb and by an axial load in the patellar tendon. Off loading a repair may not provide optimal environment for healing.
The abstracts were prepared by David Stanley. Correspondence should be addressed to him c/o British Orthopaedic Association, Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PN.
