Three-dimensional kinematics of the normal and dysplastic canine elbow joint

Conventional three-dimensional kinematic gait analysis of the canine elbow joint is limited because of skin movement artifacts, similar to the situation reported for the canine stifle joint.(1) Biplanar fluoroscopic kinematography allows precise assessment of the 3D motion of the bones involved, while dogs are walking on a treadmill.(2,3) With the aid of bone embedded markers (0.8 mm , at least 3 per segment) skeletal motion can be measured with sub-millimeter accuracy.

Guillou et al. were the first to report in vivo 3D kinematics of the canine elbow joint at walk and trot using dynamic radiostereometric analysis (RSA).(4) They documented significant varus angulation as well as axial movement of the radius and ulna relative to each other, resulting in dynamic change of the radio-ulnar transition. The latter could be of special interest as radio-ulnar incongruity has been cited to be one entity of elbow dysplasia (ED), potentially leading to fragmentation of the medial coronoid process. One could argue that ED might be, similar to hip dysplasia, more a soft tissue instability rather than a primary bone deformation. A hypothesis could be that the soft tissue attachments, of dysplastic elbow joints, between radius and ulna are weaker than normal allowing increased axial translation of both bones and thus resulting to dynamic radio-ulnar step during stance phase.

Based on our preliminary dynamic RSA studies in normal and dysplastic canine elbow joints axial translation of the radius relatively to the ulna does not seem to play a significant role. The most consistent finding is relative motion of the humeral condyle in respect to the radio-ulnar joint cup in the dysplastic elbows (see fig. 1). At the beginning of stance phase the humeral condyle translates from medial to lateral while the humeral trochlea rotates cranially. This forces the trochlea against the cranio-lateral aspect of the medial coronoid process. The latter could explain why fragmentation along the radio-ulnar incisure or at the tip of the coronoid process is commonly observed. The mechanism by which the humeral motion is induced remains unknown.

3D elbow kinematics

Figure 1: Image sequence of a dysplastic elbow (right side, medial view) while walking on a treadmill (Images 1-6)
At the beginning of stance phase (image 2) the humeral trochlea translates cranially, while the condyle moves from medial to lateral (not visible in this view).
Image A and B illustrate the resulting contact pattern between the lateral border of the medial coronoid process and the trochlea in another dysplastic elbow (right side, frontal view. Image A - before stance phase, Image B - during stance phase)

1. Böttcher P, Rey J: In vivo kinematics of the canine stifle, Proceedings, 3rd World Veterinary Orthopaedic Congress, Bologna, Italien, September 15th - 18th, 2010
2. Brainerd EL, Baier DB, Gatesy SM, et al: X-ray reconstruction of moving morphology (XROMM): precision, accuracy and applications in comparative biomechanics research. J Exp Zool A Ecol Genet Physiol 2010;313:262-279
3. Tashman S, Anderst W: In-vivo emasurement of dynamic joint motion using high speed biplane radiography and CT: application to canine ACL deficiency. J Biomech Eng 2003;125:238
4. Guillou RP, Déjardin LM, Bey MJ, et al: Three Dimensional Kinematics of the Normal Canine Elbow at the Walk and Trot. Vet Surg 2011;40:E30

Ms. Rommy Pertersohn for her technical assistance during fluoroscopic gait analysis at the Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität, Jena, Germany. This study was supported by a grant of the Gesellschaft zur Förderung Kynologischer Forschung e.V., Bonn, Germany.