Biomechanics of Intratunnel Anterior Cruciate Ligament Graft Fixation Neal C. Chen, MD a,b,c , Jeff C. Brand, Jr, MD d, * , Charles H. Brown, Jr, MD e a Combined Harvard Orthopaedic Residency Program, Boston, MA, USA b Hand and Upper Extremity Service, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA c Sports Medicine and Shoulder Service, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA d Alexandria Orthopaedics and Sports Medicine Asssociates, 1500 Irving, Alexandria, MN 56308, USA e Abu Dhabi Knee and Sports Medicine Centre, 6th Floor, Saif Tower, Electra Street, P.O. Box 43330, Abu Dhabi, United Arab Emirates I n 1983 Lambert [1] first introduced the technique of intratunnel anterior cru- ciate ligament (ACL) graft fixation by securing a vascularized bone-patellar tendon-bone ACL graft with 6.5-mm AO cancellous screws. Kurosaka and colleagues [2] demonstrated that fixation of a 10-mm bone-patellar tendon-bone ACL graft in human cadaveric knees with a custom-designed headless 9.0-mm fully threaded interference screw had better strength and stiffness than fixation with a 6.5-mm AO cancellous screw, staple fixation, or tying sutures over a but- ton. Because of the many biomechanical studies demonstrating superior initial fixation properties and clinical outcomes studies demonstrating a high rate of success, interference screw fixation of bone-patellar tendon-bone grafts now is considered the standard against which all ACL graft-fixation techniques are compared [3,4]. Based on the success of interference screw fixation of bone-patellar tendon-bone ACL grafts, Pinczewski [5] in 1996 introduced the use of blunt, threaded metal interference screws to fix four-strand hamstring tendon ACL grafts, and in 1997 Fu [6] described quadrupled hamstring tendon grafts (QHTGs) for ACL reconstruction secured with a bioabsorbable interfer- ence screw. Rigid initial graft fixation minimizes elongation and prevents failure at the graft-attachment sites, maintaining knee ligament stability during cyclical load- ing of the knee before biologic fixation of the ACL graft. The advantages of early joint motion, early weight bearing, and closed-chain exercises following ACL *Corresponding author. E-mail address: bjbrand@info-link.net (J.C. Brand, Jr). 0278-5919/07/$ – see front matter ª 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.csm.2007.06.009 sportsmed.theclinics.com Clin Sports Med 26 (2007) 695–714 CLINICS IN SPORTS MEDICINE