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ACL Graft Fixation

 - Discussion:
    - see Arthrex, Mitek, Linvatec, Smith-Nephew
    - in choosing a fixation technqiue consider the need for the following:
             - circumferential (360 deg) healing of graft against tunnel wall (interference screws do not permit this);
             - bioabsorbable material
             - strong initial fixation (greater than 120-140 Newtons) 
    - interference screw insertion:  
             - typically a 8 x 25 mm screw will be selected;
             - nitinol guide wire can be inserted thru the medial arthroscopic portal, or may be inserted thru a stab incision made in fat pad, below the portal;
             - knee is flexed an additional 30 deg to facilitate insertion of Nitinol guide wire;
             - a sheath is required to protect the tendinous portion of the graft from the screw threads; 
    - appropriate graft tension:
             - usually about 40 N or 10 lbs of tension is applied;
             - typically graft is secured in 20-30 deg of knee flexion; 
             - references
                    - Initial tension and anterior load-displacement behavior of high-stiffness anterior cruciate ligament graft constructs.
                    - A prospectively randomized double-blind study on the effect of initial graft tension on knee stability after anterior cruciate ligament reconstruction.   
                    - Viscoelasticity and temperature variations decrease tension and stiffness of hamstring tendon grafts following anterior cruciate ligament reconstruction.
                    - Effects of initial graft tension on the tibiofemoral compressive forces and joint position after anterior cruciate ligament reconstruction.
                    - Effects of initial graft tension on clinical outcome after anterior cruciate ligament reconstruction. Autogenous doubled hamstring tendons connected in series with polyester tapes. 
                    - The effect of initial graft tension in anterior cruciate ligament reconstruction on the mechanical behaviors of the femur-graft-tibia complex during cyclic loading. 
                    - A survey of the tension applied to a doubled hamstring tendon graft for reconstruction of the anterior cruciate ligament 
                    - Graft tension in anteror cruciate ligament reconstruction. An in vivo study in dogs. 
                    - Effect of Different Preconditioning Protocols on Anterior Knee Laxity After ACL Reconstruction with Four Commonly Used Grafts
                    - Pretensioning of Soft Tissue Grafts in Anterior Cruciate Ligament Reconstruction.
   - degree of knee flexion during fixation:
             - if patient has gross instability to lachman and pivot shift then tensioning at 15 lbs at 30 deg is indicated;
             - if patient has hyperextension of the knees on both sides or if graft tightens or shortens 5 mm or more with knee extension, then
                    tension closer to full extension; 
             - dual fixation
                    - using the same concept as double tunnel reconstruction, consider fixation of the 2 posterior hanstring ends with a staple at 15 deg flexion,
                             and then interference screw fixation at 40 deg flexion;
             - references:
                    - Loss of Knee Extension After Anterior Cruciate Ligament Reconstruction: Effects of Knee Position and Graft Tensioning

- references: 

- Multistranded hamstring tendon graft fixation with a central four-quadrant or a standard tibial interference screw for anterior cruciate ligament reconstruction

- Reconstruction of the anterior cruciate ligament using bone-patellar tendon-bone graft with double biodegradable femoral pin fixation.

- The effect of soft-tissue graft fixation in anterior cruciate ligament reconstruction on graft-tunnel motion under anterior tibial loading.

- Is Supplementary Fixation Necessary in Anterior Cruciate Ligament Reconstructions?

- Lateral Femoral Cortical Breach During Anterior Cruciate Ligament Reconstruction: A Biomechanical Analysis

- Accidental Perforation of the Lateral Femoral Cortex in ACL Reconstruction: An Investigation of Mechanical Properties of Different Fixation Techniques

- Effect of PEEK Polymer on Tunnel Widening After Hamstring ACL Reconstruction

- Fixation devices in ACL surgery: what do I need to know?

- Popliteal artery pseudoaneurysm after anterior cruciate ligament re-revision using a rigidfix cross pin