Three-Dimensional Kinematic Motion of the Craniocervical Junction of Chihuahuas and Labrador Retrievers

Abstract

All vertebrate species have a distinct morphology and movement pattern, which reflect the adaption of the animal to its habitat. Yet, our knowledge of motion patterns of the craniocervical junction of dogs is very limited. The aim of this prospective study is to perform a detailed analysis and description of three-dimensional craniocervical motion during locomotion in clinically sound Chihuahuas and Labrador retrievers. This study presents the first in vivo recorded motions of the craniocervical junction of clinically sound Chihuahuas (n = 8) and clinically sound Labrador retrievers (n = 3) using biplanar fluoroscopy. Scientific rotoscoping was used to reconstruct three-dimensional kinematics during locomotion. The same basic motion patterns were found in Chihuahuas and Labrador retrievers during walking. Sagittal, lateral, and axial rotation could be observed in both the atlantoaxial and the atlantooccipital joints during head motion and locomotion. Lateral and axial rotation occurred as a coupled motion pattern. The amplitudes of axial and lateral rotation of the total upper cervical motion and the atlantoaxial joint were higher in Labrador retrievers than in Chihuahuas. The range of motion (ROM) maxima were 20°, 26°, and 24° in the sagittal, lateral, and axial planes, respectively, of the atlantoaxial joint. ROM maxima of 30°, 16°, and 18° in the sagittal, lateral, and axial planes, respectively, were found at the atlantooccipital joint. The average absolute sagittal rotation of the atlas was slightly higher in Chihuahuas (between 9.1 ± 6.8° and 18.7 ± 9.9°) as compared with that of Labrador retrievers (between 5.7 ± 4.6° and 14.5 ± 2.6°), which corresponds to the more acute angle of the atlas in Chihuahuas. Individual differences for example, varying in amplitude or time of occurrence are reported.

Keywords: cervical spine; craniocervical motion; dog locomotion; scientific rotoscoping; three-dimensional kinematics.

Figure 1

Fluoroscopy 90° experimental setup. (A): 90° fluoroscopy setting to record the-laterolateral and ventrodorsal beam path. The treadmill is located in the center. (B): Chihuahua walking on the treadmill located in the beam path. (C): X-ray video view of the laterolateral beam path.

Figure 2

Fluoroscopy 63° experimental setup. (A): 63° fluoroscopy setting to record the oblique-laterolateral beam path. The treadmill is located in the center. (B): Labrador retriever walking on the treadmill located in the beam path. (C): X-ray video view of the oblique-laterolateral beam path.

Figure 3

Stride-phase-normalized gait-cycle-dependent movements of the total upper cervical motion (TUCM), atlantoaxial joint, and atlantooccipital joint. Six walking stride cycles (step 1 to step 6) for each dog are presented. X-axes represent the stride cycle from touch-down (0%) to subsequent touch-down of the reference limb (100%). The vertical line indicates the duty factor. (A) Horizontal, (B) vertical, and (C) lateral translations of the TUCM. (D) Axial, (E) lateral, and (F) sagittal rotations of the TUCM. (G) Axial rotations of the atlantoaxial joint, (H) sagittal rotations of the atlantooccipital joint.

Figure 4

Images of C3 illustrating (A) horizontal translations, lateral perspective, (B) vertical translations, lateral perspective, (C) lateral translations, cranial perspective. Images of C2 illustrating (D) axial, (E) lateral, and (F) sagittal rotations.