2015 ISAKOS Biennial Congress ePoster #1209

Graft Shift in the Femoral Bone Tunnel in Anterior Cruciate Ligament Reconstruction; An Experimental Study

Masataka Fujii, MD, PhD, Okayama JAPAN
Yusuke Sasaki, MD, asahikawa JAPAN
Daisuke Araki, MD, PhD, Kobe, Hyogo 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 Ortopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA

FDA Status Not Applicable

Summary: We measured the amount of graft shift in a simulated tunnel using human cadaveric semitendinosus tendons, and the center of the graft shifted more than 1mm inside 7-mm diameter simulated tunnel.

Rate:

Abstract:

Introduction

Precise tunnel placement is one of the most important factors for a successful anatomic anterior cruciate ligament (ACL) reconstruction. During ACL surgery with a soft tissue graft, a space is frequently observed between the posterior aspect of the femoral tunnel wall and the placed graft at the tunnel aperture. This may be attributable to a size mismatch between the graft and the tunnel and the graft deformity.
It is hypothesized that even though the femoral tunnel is positioned in the center of the footprint, the centroid of the graft may be deviated from the footprint center. However, this critical phenomenon has not been described in detail.
The purpose of this study was to evaluate the amount of graft shift in a tunnel model.

Methods

Twenty human cadaveric semitendinosus tendons were used in this study. The semitendinosus tendon was doubled over the loop of the EndoButton CL (Smith & Nephew Inc, Andover, MA). The diameter of the graft was measured using the graft sizing tube (Smith & Nephew Inc, Andover, MA) and the exact size of 7mm was verified. Eight of twenty grafts that had a diameter of 7mm were included. We used a custom made aluminum cube, the size was 40mm3, with 7-mm diameter hole as a simulated femoral tunnel. A 7-mm diameter graft was inserted into the tunnel, and EndoButton was flipped and fixed to the cube. The distal end of the graft was tensioned to 30 N at angles of 15, 30, 45, 60, and 75 degrees, reproducing the graft bending angle during knee range of motion. The picture of the tunnel aperture was taken by a digital camera at each graft bending angle. The photographs were downloaded to a computer, and the amount of graft shift in the simulated tunnel was analyzed using Image J (ImageJ 1.41o, National Institutes of Health, USA). The amount of the graft shift was defined as the distance between the center of the simulated tunnel and the center of the graft on the 2-dimensional coordinate.

Results

The maximum distance between the center of the simulated tunnel and the center of the graft was 1.10 ± 0.12 mm. The largest shift was observed at a graft bending angle of 75 degrees in all specimens.

Discussion

This is the first study to evaluate graft shift inside the tunnel. The most important finding of this study was that the center of the graft shifted more than 1mm inside the simulated tunnel. These results suggest that even if the femoral tunnel was created in the center of the ACL insertion site, the position of graft placement may not be optimal. This shift results in a lower proportion of the native ACL footprint being covered by the graft.

Conclusions

To restore the native ACL anatomy, tunnel positioning as well as graft positioning within the ACL footprint may be the most important factor in anatomic ACL reconstruction.