A novel transverse talar tunnel achieved less vessel damage and better drilling safety for ATFL reconstruction: a cadaveric study with three-dimensional microCT.

Purpose To introduce a novel transverse tunnel (TT) in anterior talofibular ligament (ATFL) reconstruction, and assess whether it was superior to the tunnels currently used. Methods Thirteen fresh cadaveric lower extremities were perfused with lead-based contrast. Talar tunnels were drilled from the ATFL insertion in the following directions: transversely towards the medial side (TT), towards the talar neck (TNT), and towards the anterior, distal, and posterior points of the medial malleolus (AMMT, DMMT, and PMMT, respectively). MicroCT was used to reconstruct the tali, and virtual transosseous and 20-mm blind-ended tunnels were generated. The graft bending angle, vascular compromise caused by the tunnels, and the minimum distances from the tunnels to the chondral surfaces were evaluated. Results The bending angles between the ATFL and the TT, TNT, AMMT, DMMT, and PMMT were 47.3±7.9°, 41.5±7.7°, 57.0±6.0°, 63.9±11.7°, and 87.9±6.2°, respectively. The proportion of damaged intraosseous vessels was significantly less for the TT (7.8±2.7%) compared with the AMMT (10.0±5.2%), DMMT (15.5±6.5%), and PMMT (16.9±3.9%). Both the TNT and the AMMT carried a high risk of joint penetration, with respective minimum distances of 2.2±1.7 mm and 1.4±1.0 mm from the tunnel to the cartilage; in contrast, the TT, DMMT, and PMMT had larger safety margins, with minimum distances of 5.4±0.8 mm, 8.9+2.7 mm, and 6.0±1.2 mm. The blind-ended tunnels caused less vascular compromise and had larger minimum distances to the cartilage (better drilling safety) than the transosseous tunnels for all tunnel directions. Conclusion The TT achieves a superior graft bending angle and intraosseous blood supply protection than the AMMT, DMMT, and PMMT, and is less likely to result in cartilage damage than the TNT. The 20-mm blind-ended tunnels achieve less vessel damage and better drilling safety than transosseous tunnels.