2015 ISAKOS Biennial Congress ePoster #2011

Changes in Cross-Sectional Area of the Human Posterior Cruciate Ligament During Knee Motion

Masataka Fujii, MD, PhD, Okayama JAPAN
Yoshimasa Fujimaki, MD, Tokyo JAPAN
Yusuke Sasaki, MD, asahikawa JAPAN
Takayuki Furumatsu, MD, PhD, Okayama JAPAN
Shinichi Miyazawa, MD, PhD, Okayama JAPAN
Toshifumi Ozaki, MD, PhD, Prof., Okayama JAPAN
Monica A. Linde, MS, RN, Pittsburgh, PA UNITED STATES
Patrick J. Smolinski, PhD, Pittsburgh, PA UNITED STATES
Freddie H. Fu, MD, Pittsburgh, PA UNITED STATES

Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA

FDA Status Cleared

Summary: We investigated the morphological characteristic of the in situ PCL by measuring the CSA of the PCL and evaluated the changes in the in situ CSA of the PCL under knee loading using a laser scanner.

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Abstract:

Introduction

To restore the native PCL anatomy, several anatomic studies have been done to measure the cross-sectional area (CSA) of the ligament. Although one of the most important factors, which affects the ligament shape and CSA, is the position of the tibia relative to the femur, it has not been considered in previous studies.
The objectives of this study were to investigate the morphological characteristic of the in situ PCL by measuring the CSA of the PCL and to evaluate the changes in the in situ CSA of the PCL under knee loading. The acquired data will provide accurate information of PCL anatomy and thereby lead to improved anatomic PCL reconstruction techniques.

Methods

Ten fresh-frozen non-paired human cadaveric knees were used. The path of passive flexion-extension of the intact knee was first determined from 0° to 90° of flexion and this is defined as neutral loading. Then, an 89 N posterior tibial load was applied at 0°, 30°, 60°and 90° of knee flexion to simulate the clinical examination of the PCL which is defined as posterior tibial translation (PTT) position. After robotic testing, the knees were dissected free of all musculature, patella and joint capsule leaving the PCL intact. The dissected knee was place back in the robot and repositioned. Then the PCL was scanned using a three-dimensional scanner (Faro Inc.) at the neutral and PTT knee positions and the images were analyzed with software (Geomagic, Inc.). The shape of the PCL and the change of the mean CSA along its midsubstance at each knee state was evaluated.

Results

The CSA of the PCL was the smallest at middle level of the midsubstance at every flexion angle and under both neutral and PTT loading. At the middle level, the CSA of the PCL became significantly smaller with knee flexion and PTT.

Discussion

The most important finding of this study was that the in situ CSA of the PCL became smaller with knee flexion and PTT. This is the first study to evaluate the effect of the knee position on the CSA of the PCL. In vitro studies have reported increased PCL forces with increasing flexion up to 90°, suggesting a lengthening of the PCL with flexion. This corresponds to the results of the present study where the CSA of the PCL became smaller with knee flexion and PTT apparently by lengthening of the PCL through the Poisson effect.

Conclusion

The present study revealed that the position of the tibia relative to the femur is the critical factor of CSA measurement.