Evaluation of In Situ Graft Forces of a 2-Bundle Tibial Inlay Posterior Cruciate Ligament Reconstruction at Various Flexion Angles Eric W. Carson, M.D., Xiang Hua Deng, M.D., Answorth Allen, M.D., Thomas Wickiewicz, M.D., and Russell F. Warren, M.D. Purpose: The purpose of this study is to evaluate a posterior cruciate ligament (PCL) reconstruction using a 2-bundle (anterolateral [AL] and posteromedial [PM]) posterior tibial inlay reconstructive technique fixed at various degrees of flexion. Methods: Eight human cadaveric knee specimens underwent a 2-bundle/posterior inlay PCL reconstruction. A testing apparatus was developed with force gauges placed on the AL and PM bundles, respectively. The PCL 2-bundle complex was pretensioned and placed through an arc of motion from 0° to 105° with measurement obtained at 15° increments. Testing conditions included 3 different tension parameters of the AL and PM bundles: (1) AL and PM bundles both at 90°, (2) AL and PM bundles both at 45°, and (3) differential tensioning the AL bundle at 90° and the PM bundle at 0°. Results: The results revealed that tensioning of the AL bundle at 90° and PM bundle at 0° produced reciprocal in situ forces similar to the native PCL. Through a complete knee arc of motion, at least 1 of the 2 bundles maintained tension in a reciprocal fashion. Data from the other reconstructive conditions revealed there was significant and excessive in situ loads above the pretensioned loads transmitted through the PM bundle with increased extension. Conclusions: This in vitro PCL reconstructive study using an anatomic tibal inlay and 2-bundle (AL and PM) approach with the AL bundle fixed at 90° and the PM bundle at 0° flexion produces a symmetrical reciprocal force pattern with 1 limb of the graft under continuous tension throughout a full arc of motion, whereas the other 2 testing conditions (AL/PM at 45/45 and 90/90) produce excessive force in the PM bundle with lower degrees of flexion. Clinical Relevance: This cadaver study showed the PCL technique using 2-bundle/tibial inlay technique and fixation of the AL bundle at 90° of flexion and the PM bundle at 0° flexion reproduced anatomic in situ graft forces in a reciprocal pattern. Key Words: Posterior cruciate ligament— Reconstruction—Knee—Biomechanic—Posterior tibial inlay—2-bundle technique. T he posterior cruciate ligament (PCL) is located near the center axis of the knee and is widely recognized as the primary restraint against posterior tibia translation and secondary restraint to varus/val- gus and external rotation. 1-4 The bulk of the PCL has been described as nonisometric. 5 Traditionally, the PCL has been described as consisting of 2 components or bundles: a thicker anterolateral (AL) and a smaller posteromedial (PM) portion. 3 During passive flexion and extension, the AL bundle is tight in flexion and relatively lax in extension. The PM bundle (more posterior on the medial femoral condyle and medial on the tibia) is tight in extension and relatively lax in flexion. 6,7 Current reconstructive techniques for the PCL only address recreating the larger AL bundle tensioning the graft between 70° to 90° of knee flexion. Overall, follow-up studies have documented improved knee From the Department of Orthopaedics, Section of Sports Medicine, University of Virginia (E.W.C.), Charlottesville, Virginia; and The Hospital for Special Surgery, Sports Medicine and Shoulder Ser- vice (X.H.D., A.A., T.W., R.F.W.), New York, New York, U.S.A. The authors report no conflict of interest. Address correspondence and reprint requests to Eric W. Carson, Department of Orthopaedics/Section of Sports Medicine, Ray Hunt Drive, Suite 330, Charlottesville, VA 22911, U.S.A. E-mail: ewc6n@virginia.edu © 2007 by the Arthroscopy Association of North America 0749-8063/07/2305-4376$32.00/0 doi:10.1016/j.arthro.2007.01.019 488 Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 23, No 5 (May), 2007: pp 488-495