Kinematik des kraniozervikalen Übergangs beim Chihuahua : eine Untersuchung mittels biplanarer Röntgenvideographie und Scientific Rotoscoping

Zur Biomechanik des kraniozervikalen Übergangs vom Hund ist wenig bekannt. Bisherige Erkenntnisse stützen sich auf Untersuchungen an anästhesierten Hunden oder auf Untersuchungen an herausgelösten Wirbelsäulenabschnitten. Erkrankungen des kraniozervikalen Übergangs, wie die atlantoaxiale Instabilität und das atlantookzipitale Overlapping, für die die Zwergrassen prädisponiert sind, sind mit respektiven Positionsveränderungen der gelenkbildenden Knochen zueinander verbunden und gehen daher vermutlich mit einer pathologischen Beweglichkeit bezüglich Bewegungsmuster und/oder –ausmaß einher. Physiologische Bewegungsmuster des kraniozervikalen Übergangs und deren Größenordnung sind in vivo bisher jedoch nicht untersucht worden. Ziel der Arbeit war eine dreidimensionale nicht invasive in vivo Bewegungsanalyse des kraniozervikalen Übergangs beim klinisch gesunden Chihuahua (n=4), mit Fokus sowohl auf schrittzyklusassoziierte Bewegungen in Schritt und Trab als auch auf aktive Kopfbewegungen, die während der Fortbewegung gezeigt wurden. Die kinematische Untersuchung erfolgte mittels „Scientific Rotoscoping“, eines markerlosen Verfahrens der XROMM-Methodik (X-Ray Reconstruction of Moving Morphology). Beim Scientific Rotoscoping werden durch multiple Arbeitsschritte Bewegungsdaten erzeugt. Zu diesem Zweck wird eine knöcherne Gelenkkette konstruiert, die der Knochensilhouette der Röntgenvideos entsprechend der Bewegung angepasst wird. Grundlage für die knöcherne Gelenkkette sind Daten aus der computertomographischen Untersuchung der Probanden, Grundlage für die Röntgenvideos die Aufzeichnung von Bewegungen mittels biplanarer Röntgenvideographie. Die Daten beider Untersuchungen unterliegen verschiedener Arbeitsprozesse vor der eigentlichen Animation, also der Anfertigung des Videos, in dem die virtuelle Knochenmarionette die Bewegungen aus dem Röntgenvideo ausführt. Aus diesen Bewegungen der Knochenmarionette gehen die dreidimensionalen Bewegungsdaten hervor.Little is known about the biomechanics of the craniocervical junction of the dog. Previous findings are based on studies with anesthetized dogs or investigations on detached spinal sections. Craniocervical junction abnormalities, such as atlantoaxial instability and atlantooccipital overlapping, i.e. diseases the dwarf dog breeds are predisposed to, are associated with position changes of the joints among each other and are therefore likely to come along with pathological mobility. Physiological movement patterns of the craniocervical junction and their magnitude have, however, not yet been investigated in vivo. The aim of this study was a three-dimensional non-invasive in vivo motion analysis of the craniocervical junction in clinically sound chihuahuas (n = 4), with focus on gait-cycle-related movements while walking and trotting, as well as active head movements during locomotion. The kinematic analysis was realized by means of "Scientific Rotoscoping", a markerless method of XROMM methodology (X-Ray Reconstruction of Moving Morphology). In Scientific Rotoscoping, movement data are produced in a step-by-step process. For this purpose, a bone marionette is constructed to be matched with the bony silhouette on X-ray videos, according to the movement observed. Basis for the bone marionette are data obtained from a computertomographic examination of the subjects. The X-ray videos are based on recorded movements using biplanar X-ray videography. The data from both examinations undergo various work processes before animation begins, producing a video in which the virtual bone marionette performs the movements observed on the X-ray video. The three-dimensional motion data result from these movements of the bone marionette

Three-dimensional kinematics of the craniocervical junction of Cavalier King Charles Spaniels compared to Chihuahuas and Labrador retrievers.

Our knowledge about the underlying pathomechanisms of craniocervical junction abnormalities (CCJA) in dogs mostly derives from measurements based on tomographic imaging. These images are static and the positioning of the dogs' head does not reflect the physiological in vivo position of the craniocervical junction (CCJ). Aberrant motion patterns and ranges of motion (ROM) in sound individuals of CCJA predisposed breeds may be a pathogenetic trigger. To further extend our limited knowledge of physiological motion of the CCJ, this prospective, comparative study investigates the in vivo motion patterns and ROM of the CCJ in walk and trot in sound Cavalier King Charles Spaniels and Chihuahuas. The Labrador retriever is used as a reference breed without predisposition for CCJA. This is the first detailed description of CCJ movement of trotting dogs. Biplanar fluoroscopy images, recorded in walking and trotting dogs, were matched to a virtual reconstruction of the skull and cranial cervical spine utilising Scientific Rotoscoping. Kinematic data reveal the same motion patterns among all breeds and gaits with individual temporal and spatial differences in each dog. A stride cycle-dependent lateral rotation of the cranial cervical spine and axial rotation of the atlantoaxial joint in trot in dogs is described for the first time. The ROM of the atlantoaxial and atlantooccipital joints in walk and trot were not statistically significantly greater in the CCJA-predisposed breeds CKCS and Chihuahua. ROM values of all translational and rotational degrees of freedom were larger in walk than trot, although this is only statistically significant for the atlantoaxial joint. Until proven otherwise, a more species-specific than breed-specific general motion pattern of the CCJ in walking and trotting, clinically sound dogs must be assumed. Species-specific anatomic properties of the CCJ seem to supersede breed-specific anatomical differences in clinically sound dogs

CCJ position in a walking Labrador retriever.

Images A–D: L1 in walk with an elevated neck position, E–H lowered neck position. A/E: fluoroscopy image with superimposed bone model, 63° oblique camera position. B/F: semi-transparent bone model and transparent atlas, 63° oblique camera position. C/G: semi-transparent bone model, laterolateral view, D/H: semi-transparent bone model in laterolateral view with illustration of the (modified) McRae’s line (green line), Wackenheim’s clivus baseline (rostral blue line) and clivus canal angle (both blue lines, angle in image D: 154°, in image H 153°). The contour of the dens is highlighted in yellow.</p

Fig 11 -

Comparative fluoroscopy images with superimposed bone model of a Chihuahua (A), a CKCS (B) and a Labrador retriever (C). The CKCS and Labrador retriever show a straight neck position in alignment with the withers while the Chihuahua shows an upright neck position and accordingly a steeper atlas angle. Images A and B: 90° camera position, image C: 63° oblique camera position.</p

Range of motion of the translations and rotations of the total cranial cervical spine (TCCS).

Range of motion of the translations and rotations of the total cranial cervical spine (TCCS).</p

Analysis of physiologic relative position of the occipitoatlantoaxial joints.

Sagittal CT image of the canine head with quantitative measurements as suggested by Waschk et al. [25]. McRae’s line (green): line drawn from basion to opisthion, no part of the dens or dorsal atlas arch is to cross this line. Wackenheim’s clivus baseline (rostral blue line): line drawn along the dorsal surface of the clivus, no more than one-third of the dens is to cross this line. Clivus canal angle (between both blue lines): angle formed by the junction of Wackenheim’s clivus baseline and the dorsal surface of the axis vertebral body.</p

Range of motion of the rotations of C2/C1 IVJ (atlantoaxial joint).

Range of motion of the rotations of C2/C1 IVJ (atlantoaxial joint).</p

Test for normal distribution of range of motion differences among the breeds.

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Treadmill speeds and phase normalisation of CKCSs, Chihuahuas and Labrador retrievers in walk and trot.

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Interobserver variability.

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