Development of a femoral template for computer-assisted tunnel placement in anatomical double-bundle ACL reconstruction

Abstract

Femoral graft placement is an important factor in the success of anterior cruciate ligament (ACL) reconstruction. In addition to improving the accuracy of femoral tunnel placement, Computer Assisted Surgery (CAS) can be used to determine the anatomic location. This is achieved by using a 3D femoral template which indicates the position of the anatomical ACL center based on endoscopically measurable landmarks. This study describes the development and application of this method. The template is generated through statistical shape analysis of the ACL insertion, with respect to the anteromedial (AM) and posterolateral (PL) bundles. The ligament insertion data, together with the osteocartilage edge on the lateral notch, were mapped onto a cylinder fitted to the intercondylar notch surface (n ¼ 33). Anatomic variation, in terms of standard variation of the positions of the ligament centers in the template, was within 2.2 mm. The resulting template was programmed in a computer-assisted navigation system for ACL replacement and its accuracy and precision were determined on 31 femora. It was found that with the navigation system the AM and PL tunnels could be positioned with an accuracy of 2.5 mm relative to the anatomic insertion centers; the precision was 2.4 mm. This system consists of a template that can easily be implemented in 3D computer navigation software. Requiring no preoperative images and planning, the system provides adequate accuracy and precision to position the entrance of the femoral tunnels for anatomical single-or double-bundle ACL reconstruction.

Accuracy of a computer-assisted planning and placement system for anatomical femoral tunnel positioning in anterior cruciate ligament reconstruction

“…This value is constructed from the accuracies of (1) the planning procedure using the template implemented in the CAS system and (2) the placement procedure using the real‐time navigation function of the CAS system .The accuracy of the planning procedure with the template is related to the reproducibility of the positions of the AM and PL center locations within the template. In the process of defining the template by using 31 knee specimens, this reproducibility, reflected by the standard deviations of the mean center positions, appeared to be 2.2 mm (AM) and 2.0 mm (PL) . Performing the planning procedure with the template implemented in the CAS system at the 31 knee specimen of the development study resulted in slightly worse accuracy of the template positions relative to the anatomical centers (2.5 mm for AM and 2.2 mm for PL, Table ).…”

“…of the AM and PL center locations within the template. In the process of defining the template by using 31 knee specimens, this reproducibility, reflected by the standard deviations of the mean center positions, appeared to be 2.2 mm (AM) and 2.0 mm (PL) (25). Performing the planning procedure with the template implemented in the CAS system at the 31 knee specimen of the development study resulted in slightly worse accuracy of the template positions relative to the anatomical centers (2.5 mm for AM and 2.2 mm for PL, Table 4).…”

“…An arthroscopic system was used, providing the surgeons a surgical view in the notch, looking at the monitor. To determine the AM and PL planned tunnel positions with the templated CAS system, the steps in the implemented ACL‐module were followed . The total tunnel positioning procedure consists of two separate steps: (1) planning the anatomical locations using the template procedure and (2) virtually placing the tunnels by digitally marking the centre of the tunnel using CAS.For template alignment during the planning procedure, the notch was interactively digitized as a cloud of points by running the palpation device over the notch surface (avoiding the PCL insertion area) while viewing at the arthroscopic monitor.…”

“…An arthroscopic system was used, providing the surgeons a surgical view in the notch, looking at the monitor. To determine the AM and PL planned tunnel positions with the templated CAS system, the steps in the implemented ACL-module were followed (25). The total tunnel positioning procedure consists of two separate steps: (1) planning the anatomical locations using the template procedure and (2) virtually placing the tunnels by digitally marking the centre of the tunnel using CAS.…”

Computer-assisted anatomically placed double-bundle ACL reconstruction: An in vitro experiment with different tension angles for the AM and the PL graft

“…Since the QTB graft had one bone block, only one tunnel had to be made. Using the specifically developed 3D femoral template [24], incorporated in the ACL-module (MEM Institute for Biomechanics, Switzerland), the tunnel was positioned at the anatomical center of the ACL. Therefore the surface of the notch and the posterior joint cartilage edge at the medial wall in the lateral notch were digitized.…”