Biomechanical evaluation of the stabilizing function of the atlantoaxial ligaments under shear loading: a canine cadaveric study.

OBJECTIVES: To evaluate the stabilizing function of atlanto-axial ligaments in dogs. STUDY
DESIGN: Cadaveric biomechanical study. ANIMALS: Beagle dog cadavers (n = 10).
METHODS: The craniocervical region was collected from 10 Beagle cadavers, and the occipito-atlanto-axial region was prepared and freed from the surrounding muscles. Care was taken to preserve integrity of the atlantoaxial ligaments and atlantoaxial joint capsule. The atlanto-occipital joints were blocked with 2 diverging transarticular 1.8 mm positive threaded K-wires. Specimen extremities were embedded in polymethylmethacrylate (PMMA) and mounted on a simulator testing shear load at the atlantoaxial joint. Range of motion (ROM) and neutral zone (NZ) were determined with all ligaments intact, after cutting the apical ligament, both alar ligaments, the transverse ligaments and finally after cutting the dorsal atlantoaxial ligament.
RESULTS: ROM increased similarly and stepwise during testing. The most significant increase was observed after transection of the alar ligaments.
CONCLUSION: The alar ligaments seem to be the most important ligamentous structures for stabilization of the atlantoaxial joint under shear load. © Copyright 2013 by The American College of Veterinary Surgeons.