Femoral tunnel enlargement after anatomic ACL reconstruction: a biological problem?

Abstract

Tunnel enlargement after anterior cruciate ligament (ACL) reconstruction may compromise revision surgery. The cause of this tunnel enlargement is not yet fully understood, but it is thought to be multifactorial, with biomechanical and biological factors playing a role. Tunnel enlargement has been described particularly in patients who underwent ACL reconstruction with hamstring tendons with extracortical fixation devices. The purpose of our study was to evaluate prospectively with magnetic resonance imaging (MRI) the changes in femoral tunnel diameter following arthroscopic anatomic ACL reconstruction with hamstring tendons. At 3-month post-op, all tunnels had enlarged compared to the diameter of the drill and most tunnels enlarged more in the midsection than at the aperture. In the posterolateral tunnels, the entrance increased 16% in diameter and the middle of the tunnel increased 30% in diameter. In the anteromedial femoral tunnels, the tunnels enlarged 14% at the aperture and 35% in the midsection. All femoral tunnels enlarged and most of them enlarged in a fusiform manner. The biological factors explain better our findings than the mechanical theory, although mechanical factors may play a role and the cortical bone at the entrance of the tunnel may modify the way tunnels respond to mechanical stress.

Revision of anterior cruciate ligament reconstruction with patellar tendon allograft and autograft: 2- and 5-year results

“…Tunnel widening of more than 1.5£ the initial tunnel was less observed in the aperture Wxation of BPTB (29%) than with the non-aperture Wxation of the hamstrings (47%) after initial surgery. Silva et al [48] conclude that "tunnel enlargement" is more often of biological than of mechanical origin. The patients in the present study whose drill holes were not evaluable radiographically at the Wrst follow-up could be readily assessed at the second follow-up because of the sclerosis that had evolved in the meantime.…”

How to evaluate bone tunnel widening after ACL reconstruction - a critical review

“…The widest tunnel diameter was noted at different levels in relation to the joint 3,9,10,17,18,20,22,38,44 . The percentages of the absolute values to the original drill bit size were calculated 3,9,10,17,18,20,22,38,44 . Susceptibility artifacts, caused by metallic implants such as buttons, screws or pins, which are commonly used in ACL surgery, can limit 17 .…”

“…The percentages of the absolute values to the original drill bit size were calculated 1, 7, 8, 15, 26, 31-33, 37, 39, 41-43, 46, 47 . In contrast to CT, MRI promises not only structural information on the tunnels, but also allows evaluation of the ACL graft itself 3,9,10,17,18,20,22,38,44 . Major drawback is the limited assessment of osseous structures in MRI.…”

“…Silva et al investigated femoral tunnel widening on contrast-enhanced MRI. Three different sequences of MR images were obtained for each tunnel (T1-weighted, proton-density-weighted fat-saturated and T1-weighted fat-saturated images after intravenous contrast administration) 38 . The diameters of each tunnel were measured perpendicular to the long axis of the tunnel at the tunnel aperture and at their widest point 38 .…”

“…Three different sequences of MR images were obtained for each tunnel (T1-weighted, proton-density-weighted fat-saturated and T1-weighted fat-saturated images after intravenous contrast administration) 38 . The diameters of each tunnel were measured perpendicular to the long axis of the tunnel at the tunnel aperture and at their widest point 38 . Buelow et al measured the tunnel diameter on radiographs (antero-posterior and lateral weight-bearing in extension) 3 .…”