The relation between tunnel widening and bone mineral density after anterior cruciate ligament reconstruction: an experimental study in sheep.

Abstract

The aim of this study was to analyze the relation between bone mineral density (BMD) and femoral tunnel enlargement (TE) in a previously validated sheep model of soft-tissue anterior cruciate ligament (ACL) reconstruction. Thirty sheep underwent ACL reconstruction by use of a soft-tissue graft at the age of 4 months. Graft fixation was achieved with the EndoButton (Smith & Nephew Endoscopy, Andover, MA) and Suture Washer (Smith & Nephew Endoscopy). Six animals were killed at 0, 3, 6, 12, and 24 weeks postoperatively. Each ACL-reconstructed knee was examined both by computed tomography to analyze the bone tunnel cross-sectional area and by dual-energy x-ray absorptiometry to analyze BMD. There was a significant increase in tunnel cross-sectional area. BMD decreased significantly within the first 3 weeks after surgery and increased thereafter. A positive correlation between TE and BMD was found. However, a subgroup analysis showed that there is no influence of BMD on the development of a tunnel widening. The hypothesis that a TE would be associated with a loss in BMD was not confirmed. Tunnel widening during the first 6 months after ACL reconstruction is not affected by the transient changes in BMD. There is no correlation between TE and BMD in an experimental sheep model of ACL reconstruction. Translational investigations will determine whether this is also true in humans.