The anterior cruciate ligament: a study on its bony and soft tissue anatomy using novel 3D CT technology.
OBJECTIVE
The purpose of this study is twofold: first, to visualize both the tibial and femoral bony insertion surfaces and second, to describe the anterior cruciate ligament (ACL) geometrically, using novel 3D CT imaging. In addition, new concepts of best-fit cylinder and central axis are introduced and evaluated.


METHODS
Eight unpaired knees of embalmed cadavers were used in this study. Following the dissection process, the ACL was injected with a contrast medium for CT imaging. The obtained CT images in extension, 45°, 90° and full flexion were segmented and rendered in 3D allowing morphological and morphometric analysis of the ACL. Anatomical footprint centres, femoral and tibial footprint surface area, best-fit ACL-cylinder intersection area, best-fit ACL-cylinder/footprint coverage ratio, best-fit ACL-cylinder central axis projections at the tibial and femoral footprint in the four positions were used to describe the anatomy of the ACL, based on the Bernard, Hertel and Amis grid.


RESULTS
Based on these parameters, with the best-fit cylinder representing the bulk of the ACL, a changing fibre-recruitment pattern was seen with a moving position of the central axis from posterior to anterior on the femoral and tibial footprint, going from extension to flexion. Furthermore, the numerical data show an increase in tibial footprint coverage by the best-fit cylinder through the ACL when the knee is progressively flexed, whereas an inverse relationship was seen on the femoral side.


CONCLUSIONS
This study is the first to describe the detailed anatomy of the human ACL with respect to its course and footprints using a 3D approach. It confirms the large difference and inter-patient variability between the tibial and femoral footprint area with the former being significantly smaller. The best-fit cylinder concept illustrates the recruitment pattern of the native ACL where in extension the postero-lateral fibres are recruited and in flexion rather the antero-medial bundle, which can be valuable information in reconstructive purposes. The best-fit cylinder and central axis concept offers additional insights into the optimal tunnel placement at the tibial and femoral footprint in order to cover the largest portion of the native ACL soft tissue, aiming for optimal ACL reconstruction.
Department of Orthopaedic Surgery and Traumatology, Faculty of Medicine, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium. ttampere@gmail.com.
Thomas
http://orcid.org/0000-0001-6033-5943
T
Tampere
Department of Anatomy, Ghent University, Ghent, Belgium.
Tom
T
Van Hoof
Department of Orthopaedic Surgery and Traumatology, Faculty of Medicine, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium.
Michiel
M
Cromheecke
Department of Orthopaedic Surgery and Traumatology, Sint Lucas Ghent, Groenebriel 1, 9000, Ghent, Belgium.
Hans
H
Van der Bracht
Steadman Philippon Research Institute, 181W Meadow Dr, Vail, CO, 81657, USA.
Jorge
J
Chahla
Department of Orthopaedic Surgery, Monica Hospitals, Harmoniestraat 68, 2018, Antwerp, Belgium.|Faculty of Medicine, Ghent University, Ghent, Belgium.|Department of Orthopaedic Surgery, Antwerp University, Ghent, Belgium.
Peter
P
Verdonk
Department of Orthopaedic Surgery and Traumatology, Faculty of Medicine, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium.
Jan
J
Victor
D000368:Aged; D000369:Aged, 80 and over; D016118:Anterior Cruciate Ligament / Q000000981:diagnostic imaging*; D002102:Cadaver; D004210:Dissection; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008297:Male; D013977:Tibia / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed
3D; Anatomy; Anterior cruciate ligament; Computerized tomography