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Review
, 25 (4), 1316-1327

Tunnel Widening in Single- Versus Double-Bundle Anterior Cruciate Ligament Reconstructed Knees

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Review

Tunnel Widening in Single- Versus Double-Bundle Anterior Cruciate Ligament Reconstructed Knees

Cathrine Aga et al. Knee Surg Sports Traumatol Arthrosc.

Abstract

Purpose: The consequence of tunnel widening after ACL reconstructions is foremost of importance in case of revision surgery. Tunnel expansion leads to bone loss close to the joint, and additional surgery with bone grafting prior to revision surgery might be necessary. The purpose of the study was to measure widening of the tunnels in single-bundle (SB) and double-bundle (DB) ACL reconstructed knees during the first year after surgery, detected by a novel, semi-automated 3D CT imaging modality. Our hypothesis was that there would be a difference between the initial tunnel size and the size measured one year post-operatively due to the tunnel widening process. Further, the purpose was to evaluate whether there were any differences in the amount of tunnel widening between the two surgical techniques.

Methods: Twenty patients who underwent DB ACL reconstruction, and 22 patients who underwent SB ACL reconstruction, performed a CT scan of the bony tunnels, during their first days after surgery and one year post-operatively. The CT scans were transformed into 3D CT reconstructions, and the tunnels were measured with the "best-fit cylinder" method, measurements at the level of tunnel aperture and 10.0 mm from the joint line.

Results: All tunnels in the DB and SB ACL reconstructed knees exhibited widening during the first year after the operation (p < 0.001). The SB femoral tunnels showed more widening compared to the DB femoral AM tunnels (1.4 ± 0.9 vs. 0.5 ± 0.6 mm) (p < 0.001), and the SB tibial tunnels widened more compared to the DB tibial PL tunnels (1.0 ± 1.0 vs. 0.5 ± 0.6) (p < 0.043).

Conclusion: All tunnels widened during the first year after the ACL reconstruction with a larger amount of widening in the SB tunnels compared to the DB femoral AM tunnels and the DB tibial PL tunnels. This is the first study to detect tunnel widening in DB reconstructed knees through a semi-automated 3D CT imaging modality.

Level of evidence: Prospective cohort study, Level III.

Keywords: 3D CT; ACL reconstruction; Anterior cruciate ligament; CT; Double bundle; Revision; Tunnel widening.

Figures

Fig. 1
Fig. 1
a Single-bundle ACL reconstructed knee in a 3D CT model with one tunnel on each side of the joint. b Double-bundle ACL reconstructed knee in a 3D CT model with 2 tunnels in the femur AM (green) and femur PL (yellow) and two tunnels in the tibia AM (fuchsia) and tibia PL (cyan)
Fig. 2
Fig. 2
a Double-bundle ACL operated knee in a 3D model with the 4 segmented tunnels: femur AM tunnel (green), femur PL tunnel (yellow), tibia AM tunnel (fuchsia) and tibia PL tunnel (cyan). b The tibia AM tunnel extracted and imported to the 3D-matic software. c Measurements of best-fit cylinder (yellow); aperture measurements and 10 mm from joint line measurements (dotted lines)
Fig. 3
Fig. 3
Best-fit cylinder method: The 3D model of the segmented tunnels was exported to the 3D-matic software (a). A best-fit cylinder was generated semi-automatically by the software (b), and the cylinder diameter was measured (c) [5]

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