Femoral Tunnel Widening After Double-Bundle Anterior Cruciate Ligament Reconstruction With Hamstring Autograft Produces a Small Shift of the Tunnel Position in the Anterior and Distal Direction: Computed Tomography–Based Retrospective Cohort Analysis

Abstract

Purpose: To determine whether the femoral tunnel position remains in an anatomical footprint after tunnel widening and shifting. Methods: Patients who underwent unilateral double-bundle anterior cruciate ligament reconstruction with hamstring autograft and performed computed tomography scan evaluation at the time of 5 days and 1 year postoperatively were included in this retrospective cohort study. Three-dimensional models of the femur and femoral tunnels were reconstructed from computed tomography scan data. The location of the tunnel center and tunnel margins in the anatomical coordinate system, and the mean shifting distance of tunnel center and margin were measured with image analysis software during the period. The change of tunnel center location in Bernard quadrant was confirmed if the tunnel center remained within the boundaries of anatomical position after tunnel widening. Results: A total of 56 patients satisfied the inclusion criteria. The mean shifting distance of AM and PL tunnel centers were 1.7 AE 0.9 mm and 1.6 AE 0.6 mm. The Tunnel margin of the anteromedial (AM) and posteromedial (PL) tunnels were shifted to 2.5 AE 1.3 mm and 2.6 AE 1.4 mm in the anterior direction, and 1.4 AE 0.9 mm and 1.0 AE 0.7 mm in the distal direction, respectively. Among the anatomical located tunnel, 97% (32/33) and 87.1% (27/31) of AM and PL tunnel centers remained in a range of anatomical footprint. The tunnel center was shifted from the anatomical position into a nonanatomical position in 3% (1/ 33) of the AM tunnel and 12.9% (4/31) of PL tunnel after tunnel widening. The tunnel location which shifted nonanatomically were relatively anterior and distal position. Conclusions: Tunnel widening shifts the tunnel position to the anterior and distal direction, which could change the initial tunnel position. Nevertheless, the majority of tunnel positions remained in the anatomical position after tunnel widening and shifting. Level of Evidence: Level III, retrospective cohort study.

Lateral posterior tibial slope does not affect femoral but does affect tibial tunnel widening following anatomic anterior cruciate ligament reconstruction using a Bone–Patellar Tendon–Bone graft

“…It has been demonstrated that femoral tunnels enlarge anteriorly and distally (i.e., the direction in which the mechanical traction force of the graft works) rather than concentrically after anatomical ACL reconstruction. 37 , 38 , 39 This finding suggests that the wall supporting the graft moves closer to the direction of the pull, resulting in increased laxity of the knee joint due to TW. To clarify whether these factors influence clinical results after ACL reconstruction, future studies involving a large number of patients are required.…”

Editorial Commentary: Tunnel Widening After Anterior Cruciate Ligament Reconstruction May Increase Laxity and Complicate Revision

“…Additionally, it has been reported stress distribution at the femoral tunnel aperture is not equal in different directions, while the distal part dominantly bears the stress from the ACL graft. 13 From the results of previous studies and the study by Lee et al, 7 we can conclude that femoral tunnels enlarge due to the stress exerted on the wall in the direction where the graft runs and pulls in the knee joint. This indicates that the wall supporting the graft moves closer to the direction of the pull, which may lead to increased laxity of the knee joint due to TW.…”

“…8,9 This study showed how much and in which directions the walls of the femoral tunnel shifted postoperatively. Lee et al 7 demonstrated that the margins of the anteromedial and posterolateral tunnels were shifted by 2.5 mm and 2.6 mm to the anterior direction and by 1.4 mm and 1.0 mm to the distal direction, respectively. I think these are not a small values that can be ignored, considering that the footprints on the femoral side of the ACL reported by micro-or macroscopic studies are 3.5 to 8.0 mm wide and 16.0 to 17.7 mm long.…”

Arthroscopic Revision of Attenuated Anterior Cruciate Ligament Graft With Enlarged Bone Tunnels Using Injectable Bone Graft Substitute

“… 1 , 2 , 4 The tunnel-enlargement phenomenon occurs primarily with hamstring autografts, suspension fixation devices, and absorbable implants, and it commonly progresses within 24 weeks postoperatively. 5 , 6 , 7 The prevalence of tunnel enlargement ranges from 25% to 100% in femoral tunnels and 29% to 100% in tibial tunnels after ACL reconstruction. 6 The mechanism of tunnel enlargement is not well understood; mechanical and biological factors have been suggested as the etiology of tunnel enlargement.…”

“… 6 The mechanism of tunnel enlargement is not well understood; mechanical and biological factors have been suggested as the etiology of tunnel enlargement. 5 Biological factors include osteolytic cytokines that enter the space between the graft and the bone through the synovial fluid. Mechanical factors include longitudinal graft motion by extra-cortical femoral fixation (bungee effect), transverse graft motion (windshield-wiper effect), improper graft placement, higher initial graft tension and accelerated rehabilitation.…”