Vimarsha Gopal Swami BSC, Presenter: Nothing to Disclose

June Cheng-Baron PhD, Abstract Co-Author: Nothing to Disclose

Catherine Hui MD, Abstract Co-Author: Nothing to Disclose

Richard Thompson PhD, Abstract Co-Author: Nothing to Disclose

Jacob L. Jaremko MD, Abstract Co-Author: Nothing to Disclose

Anatomic placement of anterior cruciate ligament (ACL) grafts at arthroscopic reconstruction can be challenging. We developed a novel technique to localize ACL attachments on magnetic resonance imaging (MRI) sequences, and from these produce three-dimensional (3D) reconstructions to visualize the attachment sites in an interactive patient-specific "virtual arthroscopy" environment. ACL attachments can be identified on conventional two-dimensional (2D) MRI sequences, but slice thickness theoretically limits out-of-plane accuracy. We tested whether high-resolution 3D sequences improved reliability of ACL attachment localization compared to conventional 2D MRI.

Eight pediatric knees were scanned at 1.5 Tesla with multi-planar 2D proton density (PD) sequences (slice thickness 3-4 mm) and T2-weighted 3D multiple-echo data image combination (MEDIC) gradient echo (GRE) sequence (isotropic 0.8 mm voxels). Based on points identified separately by two observers, ACL attachment centre locations in 3D and their areas were calculated, and reliability assessed.

Inter-observer variation of centre locations of ACL attachments identified on 3D vs. 2D sequences were not significantly different (mean±SD): 1.3±0.5 vs. 1.6±0.7 mm at femoral attachments (p=0.44), 1.6±0.8 vs. 1.6±0.8 mm at tibial attachments (p=0.33), with 95% power to detect a difference of 1.5 mm between user-identified attachment centres. The 95% confidence interval for centre locations was <4 mm in all cases. Inter-observer reliability of attachment areas was not higher for 3D vs. 2D sequences. Intra-observer reliability was superior to inter-observer reliability in all cases.

ACL attachments were localized with high and similar reliability on 3D MEDIC GRE sequences and multi-planar routine 2D PD sequences.

MRI localization of ACL attachments for "virtual arthroscopy" based on 3D reconstruction has potential to assist anatomic ACL reconstruction, whether from 2D or 3D base sequences.

Swami, V, Cheng-Baron, J, Hui, C, Thompson, R, Jaremko, J, MRI-based 3D Virtual Arthroscopy for Anatomic ACL Reconstruction in Pediatric Patients: Does a High-resolution 3D Base MRI Sequence Improve ACL Attachment Site Localization?.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13011664.html