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Where Should the Femoral Tunnel of a Posterior Cruciate Ligament Reconstruction Be Placed to Best Restore Anteroposterior Laxity and Ligament Forces?

From the Biomechanics Research Section, Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California

^* Address correspondence to Keith L. Markolf, PhD, Biomechanics Research Section, University of California at Los Angeles Rehabilitation Center, Room 21-67, 1000 Veteran Avenue, Los Angeles, CA 90095-6902 (e-mail: kmarkolf{at}mednet.ucla.edu).

Background: Objective results of posterior cruciate ligament reconstruction are often less than satisfactory, with many patients exhibiting excessive posterior laxity.

Hypothesis: Changes in the position of the femoral tunnel within the posterior cruciate ligament’s femoral footprint will significantly affect anteroposterior laxities and graft forces.

Study Design: Controlled laboratory study.

Methods: The posterior cruciate ligament’s femoral origin was mechanically isolated in 13 fresh-frozen knee specimens, and the bone cap containing the ligament’s insertion was attached to a load cell that recorded resultant force during tibial loading tests. Anteroposterior laxity (at +mn; 200 N applied force) was also measured. Cast acrylic replicas of the bone cap were fabricated, with tunnels placed in anterolateral, central, and posteromedial regions of the footprint. A graft reconstruction was tested in each tunnel.

Results: Mean laxities with the anterolateral tunnel were +0.9 mm to +1.7 mm greater than normal between 0° and 45° of flexion. Mean laxities with the posteromedial tunnel were –2.4 mm to –3.7 mm less than normal between 10° and 45° of flexion. Mean laxities with the central tunnel were not significantly different from intact knee values, except at 0° (0.9 mm greater). Mean graft forces with the anterolateral tunnel were normal for most modes of loading, whereas there were significant increases in graft forces with the posteromedial and central tunnels.

Conclusion: The anterolateral tunnel reproduced normal posterior cruciate ligament force profiles but produced a knee that was more lax than normal between 0° and 45° of flexion. The central tunnel best matched intact knee laxities, but graft forces were higher than posterior cruciate ligament forces between 0° and 45° of flexion. The posteromedial tunnel overconstrained anteroposterior laxity approximately 2 to 4 mm between 0° and 45° of flexion and generated higher graft forces in the same flexion range.

Clinical Relevance: This study suggests that a posteromedial tunnel should not be used for single-bundle posterior cruciate ligament reconstruction.

Key Words: posterior cruciate ligament (PCL) • knee ligament biomechanics • PCL reconstruction • PCL graft forces

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				K. L. Markolf, B. R. Graves, S. M. Sigward, S. R. Jackson, and D. R. McAllister How Well Do Anatomical Reconstructions of the Posterolateral Corner Restore Varus Stability to the Posterior Cruciate Ligament-Reconstructed Knee? Am. J. Sports Med., July 1, 2007; 35(7): 1117 - 1122. [Abstract] [Full Text] [PDF]