2017 ISAKOS Biennial Congress ePoster #1103

 

Optimal Entry Point of the Tibial Bone Tunnel for Minimizing the Graft Bending Angle at the Tibial Tunnel Aperture for Anterior Cruciate Ligament Reconstruction

Yoshimasa Fujimaki, MD, Tokyo JAPAN
Christopher D. Murawski, MD, Pittsburgh, PA UNITED STATES
Eric Thorhauer, BS, Seattle, WA UNITED STATES
Patrick J. Smolinski, PhD, Pittsburgh, PA UNITED STATES
Scott Tashman, PhD, Pittsburgh, PA UNITED STATES
Freddie H. Fu, MD, Pittsburgh, PA UNITED STATES

University of Pittsburgh Medical Center, Pittsburgh, PA, UNITED STATES

FDA Status Not Applicable

Summary

Seven cadaveric knees were tested using a six degrees-of-freedom robotic arm. The crossing point of the trajectory of AM and PL bundles and the anterior surface of the tibia were recognized as the optimal tunnel entry point at which the minimum graft bending angle at the aperture could be achieved. The crossing points for the AM were consistently located medially and proximally when compared to th

Abstract

Objectives
The size and position of the anterior cruciate ligament (ACL) insertion sites, as well as the technique used to create the bone tunnel apertures within the insertion site have been widely studied. In this regard, the graft bending angle at the aperture of the bone tunnel is thought to be a major factor in the phenomenon of bone tunnel enlargement after ACL reconstruction. As it turns out, optimal placement of bone tunnel to thereby eliminate or reduce bending of the graft at the tunnel aperture is largely unknown, particularly for tibial side.
The purpose of this study was to investigate the optimal entry point for the tibial tunnel aperture at which a minimum graft bending angle could be achieved.

Methods

Seven cadaveric knees (mean age 57.5±8.0 years) with no signs of osteoarthritis, previous injury or surgery were tested using a six degrees-of-freedom robotic arm. First, normal tibio-femoral kinematic paths were recorded. After dissection, bone surface morphology as well as the positional data of insertion sites boundaries the of anteromedial (AM) and posterolateral (PL) bundles of the ACL were acquired using a 3D laser scanner digitizer at 0, 30, 60 and 90 degrees of knee flexion on the robotic motion simulator. The trajectory of the AM and PL bundles were defined as the line connecting the centroids of the femoral and tibial insertion site boundaries. The crossing point of this trajectory and the anterior surface of the tibia were recognized as the optimal tunnel entry point at which the minimum graft bending angle at the aperture could be achieved (fig1a). The crossing points were evaluated on a square grid reference system based on a medial-lateral line on the tibial plateau (fig 1b).

Results

The crossing points of both AM and PL bundles were located distally when the knees were extended (32.2% from the proximal border for AM and 38.4% for the PL at 0 degrees), and moved proximally in a serial fashion as the knee flexion angle increased (15.6% from proximal boarder for AM and 18.1% for PL at 0 degrees). The crossing points for the AM were consistently located medially and proximally when compared to the crossing points of the PL bundle at each of the tested angles of knee flexion.

Conclusions

The crossing points of both AM and PL bundles were located distally when the knees were extended and moved proximally in a serial fashion as the knee flexion angle increased. The results of this study may be valuable for surgical planning, specifically for choosing an entry point for the tibial tunnel that minimizes the graft bending angle at its aperture.