THE ANATOMY of the canine elbow has been fully

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1 Veterinary Surgery 38: , 2009 INVITED REVIEW A Clinically Oriented Comprehensive Pictorial Review of Canine Elbow Anatomy GHEORGHE M. CONSTANTINESCU, DVM, PhD, mult Dr h c and ILEANA A. CONSTANTINESCU, DVM, MS The clinically oriented canine elbow anatomy in its complexity earned a high importance in surgery especially after multiple imaging modalities have been used in the benefit of diagnosis and treatment of canine elbow disorders. The bony, joint, and muscular structures, the arteries, the veins and the nerves supplying the elbow are described and illustrated in textbooks and atlases in the context of the comparative anatomy. Nevertheless, there is no publication focused on all of these structures described together from the skin to the bones in a systematic and topographic order, nor through cross and/or sagittal and coronal sections. The figures used in this article are original and drawn after dissection, cross, sagittal, and coronal sections of the elbow structures. The sections are correlated to the multiple imaging modalities shown in the next article. r Copyright 2009 by The American College of Veterinary Surgeons Keywords: clinical comprehensive anatomy, elbow, canine INTRODUCTION THE ANATOMY of the canine elbow has been fully presented in a number of texts, 1 7 but with one exception, 4 illustration and description from a diagnostic and therapeutic perspective is not readily available. We provide a comprehensive review of the anatomy of the canine elbow for clinical reference. Presentation of anatomic features of the canine elbow is presented so that it can be readily correlated to diagnostic imaging, used for understanding disease mechanisms, and applied to current and novel treatment strategies. A comprehensive review is provided covering all tissues from superficial to deep, cross-sectional anatomy to correspond to diagnostic imaging, and functional relationships to address disease mechanisms and treatment strategies, which are the topics of the subsequent articles in this issue. CANINE ELBOW ANATOMY Fasciae, Cutaneous Blood Vessels, and Cutaneous Nerves Just beneath the skin, a subcutaneous olecranon bursa may be present to facilitate the smooth gliding of the skin over the olecranon. The elbow is entirely surrounded by the brachial and antebrachial fasciae and on the medial aspect, the superficial antebrachial fascia is added. The arteries are cutaneous branches of the caudal circumflex humeral A. (cranially), thoracodorsal A. (caudolaterally and caudomedially), and superficial brachial A. (craniolaterally and craniomedially). Cutaneous branches of the recurrent interosseous A. reach the elbow caudoventrally. The superficial veins are branches of the collateral ulnar V. (caudally), cephalic V. (cranially), median cubital V. (medially), and branches of the collateral radial and From the Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO. Address reprint requests to Dr. Gheorghe Contantinescu, DVM, PhD, mult Dr h c, Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, 1600 E. Rollins, Columbia, MO constantinescug@missouri.edu. Submitted April 2008; Accepted September 2008 r Copyright 2009 by The American College of Veterinary Surgeons /09 doi: /j x x 135

2 136 CANINE ELBOW ANATOMY Fig 1. Muscles, arteries, nerves lateral elbow of a dog. middle collateral Vv. (laterally). The recurrent interosseous V. may also supply the elbow. The cranial cutaneous antebrachial N. (branch of the axillary N.) runs on the cranial aspect of the elbow, in front of, and close to, the lateral cutaneous antebrachial N. (from the superficial branch of the radial N.); the latter splits into a lateral branch for the craniolateral aspect of the elbow, and a medial branch for the craniomedial aspect of the elbow. The medial cutaneous antebrachial N. (from the musculocutaneous N.) supplies the craniomedial aspect of the elbow, caudal to, and close to, the medial branch of the lateral cutaneous antebrachial N. The proximal branch of the caudal cutaneous antebrachial N. (from the ulnar N.) supplies the caudolateral and caudomedial aspects of the elbow. Branches of the intercostobrachial N., and lateral cutaneous branches of the intercostal N. II can also be found on the laterocaudal extent of the elbow. The arteries and nerves of the elbow, superficial and deep, in topographic relationship with the muscles are shown in Fig 1 (lateral aspect), Fig 2 (medial aspects), and Fig 3 (cranial aspect). Fig 2. Muscles, arteries, nerves medial elbow of a dog.

3 CONSTANTINESCU AND CONSTANTINESCU 137 Fig 3. Muscles and nerves cranial elbow of a dog. Muscles The muscles surrounding the elbow belong to the brachial and antebrachial groups of muscles. From the brachial group, the biceps brachii and brachialis Mm. run on the cranial aspect, the long and lateral heads of the triceps brachii M., and the anconeus M. cover the lateral aspect of the elbow, and the medial head of triceps runs on the medial aspect of elbow accompanied by the tensor fasciae antebrachii M. (Figs 1 3). A subtendinous bursa (of the triceps brachii M.) is located between the tendon of this Fig 5. Bicipitoradial bursa of a dog medial elbow. Fig 6. Elbow joint of a dog lateral aspect. Fig 4. Tricipital bursa of a dog lateral elbow. Fig 7. Elbow joint of a dog medial aspect.

4 138 CANINE ELBOW ANATOMY Fig 8. Elbow joint of a dog caudal aspect full flexion. muscle and the olecranon (Fig 4). Another subtendinous (bicipitoradial) bursa is located between the radius and the insertion of the biceps brachii M. (Fig 5). From the antebrachial group, starting on the cranial aspect and continuing laterally, caudally and medially, the muscles around the elbow are the brachioradialis M., the extensor carpi radialis M., the common digital extensor M., the lateral digital extensor M., the extensor carpi ulnaris M., the ulnar head of the deep digital flexor M., the ulnar and the humeral heads of the flexor carpi ulnaris M., the superficial digital flexor M., the humeral head of the deep digital flexor M., the flexor carpi radialis M., and the 2 deep muscles: the pronator teres M. and the supinator M. (Figs 1 3). Within the tendon of origin of the supinator M. an inconstant sesamoid bone can be found and is outlined as an interrupted circle in Fig 3. Fig 10. Radius and ulna in pronation cranial view. The insertions of the triceps brachii M. and its olecranon bursa, as well as the insertions of the biceps brachii and brachialis Mm. are shown in Figs 4 and 5. Fig 9. Elbow joint of a dog cranial aspect. Blood Vessels (Figs 1 3) The arteries supplying structures of the elbow accompanied by veins are the brachial A.V.; collateral radial A.V.; middle collateral A.V. forming an articular arterial network caudally and medially (medial cubital articular rete); collateral ulnar A.V. building an articular arterial network caudally and laterally (lateral cubital articular rete); recurrent interosseous A.V. contribute to the lateral cubital articular rete; recurrent ulnar A.V.; transverse cubital A.V.; and superficial brachial A.V. which continue as superficial antebrachial A.V. The veins without arterial satellite are the cephalic and the median cubital Vv.

5 CONSTANTINESCU AND CONSTANTINESCU 139 Fig 13. Distal humerus caudal view. Fig 11. Radius and ulna in supination cranial view. Nerves (Figs 1 3) The nerves around the elbow are the median N., deep and superficial branches of the radial N., and ulnar N. Fig 14. The Elbow Joint Distal humerus distal view. The elbow joint is a compound joint, consisting of the humeroradial, humeroulnar, and proximal radioulnar joints. There is a joint capsule, collateral ligaments, and other ligaments. The joint capsule covers only the cranial aspect of the elbow. The fibrous joint capsule is attached on humerus proximal to the radial fossa and foramen supratrochleare, and under the head of radius after blending with the annular ligament. The fibrous joint capsule ends laterally and medially at the lateral and medial collateral ligaments, respectively. The collateral ligaments attach proximally to the lateral and medial epicondyles of humerus, respectively, and are divided dis- Fig 12. Distal humerus cranial view. Fig 15. Capitulum of radius articular view.

6 140 CANINE ELBOW ANATOMY Fig 16. Proximalulna cranial view. tally into 2 crura. The crura of the lateral collateral ligament blend with the annular ligament and often contain a sesamoid bone. The cranial crura of both ligaments attach to the radius, whereas the caudal crura attach to the ulna. They are considered thickenings of the fibrous joint capsule. There is no fibrous joint capsule on the caudal aspect of the elbow in the dog. Despite the fact that the oblique ligament is not listed in the Nomina Anatomica Veterinaria (NAV), 8 it is a constant structure listed in books and atlases. It attaches proximal to the lateral aspect of the radial fossa and distally on the medial side of the neck of radius. The distal attachment is bifurcated to allow the passage of the tendons of biceps brachii and brachialis Mm. An additional elastic ligament joins the medial border of the olecranon Fig 18. Elbow in neutral caudal position. Fig 17. Elbow in neutral lateral position. Fig 19. Elbow in neutral medial position.

7 CONSTANTINESCU AND CONSTANTINESCU 141 Fig 20. Elbow in extreme flexed medial position. Fig 22. level. Transverse section through a dog elbow oleranon Fig 21. oblique. Elbow cranial aspect craniolateral caudomedial Fig 23. Transverse section through a dog elbow humeral epicondyle level.

8 142 CANINE ELBOW ANATOMY Fig 24. Transverse section through a dog elbow proximal radioulnar level. fossa to the medial aspect of the olecranon, just distal to the olecranon tuberosity. This is the olecranon ligament. The proximal radioulnar joint is provided with the annular ligament, which attaches to the lateral and medial ends of the radial notch of ulna and is covered by the collateral ligaments. It blends its fibers with the fibrous joint capsule. The annular ligament does not attach to the radius, to allow it to rotate during pronation and supination (Figs 6 9). Figures 10 and 11 show the relationships between the radius and ulna during the maximal pronation and maximal supination, respectively. The synovial membrane intimately lines the fibrous joint capsule, and also the olecranon fossa. During flexion and extension, several recesses are formed (Figs 6 9). Cranially, 1 recess lies in the fossa radialis. It delegates 1 small recess under the attachments of the biceps brachii Fig 26. Coronal section through distal humerus and proximal radius and ulna left thoracic limb in pronation. M. (medially) and another small recess under the attachments of the extensor carpi radialis and common digital extensor Mm. Distally, the synovial membrane insinuates under the annular ligament. Caudally, 1 recess is found in the olecranon fossa, which sends a small recess under the medial epicondyle of humerus. The caudal recess is covered by the olecranon ligament. The recesses communicate with each other. The elbow joint as a whole is a trochlearthrosis or ginglymus (a hinge joint), allowing flexion and extension of the humerus over the radius and ulna. In dogs, the circumference of the radius (on the caudal aspect of the head of radius) is capable of rotating in the radial notch of the ulna during pronation and supination. Fig 25. Sagittal section through a dog elbow. The Bones The distal extremity of the humerus and the proximal extremities of the radius and ulna including the olecranon are illustrated in Figs Figures 17 and 18 show the neutral lateral view, and the caudal view of the elbow bones, respectively. The neutral medial aspect is shown in Fig 19, and the extreme flexed medial aspect in Fig 20. The craniolateral caudomedial oblique aspect is shown in Fig 21.

9 CONSTANTINESCU AND CONSTANTINESCU 143 Topography The topography of the bones, ligaments, muscles, vessels, and nerves is shown in 3 cross sections, 1 sagittal and 1 coronal section, in conjunction with computed tomography images. The cross sections are made in a proximodistal direction, as follows: at the level of the olecranon tuberosity (Fig 22), at the level of the lateral and medial epicondyles of humerus (Fig 23), at the proximal radioulnar level (Fig 24). The sagittal section is made through the humerus, ulna and radius at the level of the medial coronoid process (Fig 25). The coronal section is made in front of cranial part of the medial coronoid process with the limb in pronation (Fig 26). REFERENCES 1. Baum H, Zietschmann O: Handbuch der Anatomie des Hundes (ed 2). Berlin, Germany, Paul Parey, Budras K-D, McCarthy PH, Fricke W, et al: Anatomy of the Dog An Illustrated Text (ed 4). Hannover, Germany, Schlu tersche, Constantinescu GM, Cook JL: Clinical anatomy and surgical approach to the elbow joint in the dog, in the XXIVth Congress of the European Association of Veterinary Anatomists, Brno, Czech Republic, July Constantinescu GM: Clinical Anatomy for Small Animal Practitioners. Ames, IA, IA Iowa State Press, Done SH, Goody PC, Evans SA, et al: Color Atlas of Veterinary Anatomy. Vol. 3 The Dog and Cat. Philadelphia, PA, Mosby, Evans HE: Miller s Anatomy of the Dog (ed 3). Philadelphia, PA, Saunders, Ruberte J, Sautet J: Atlas d Anatomie du Chien et du Chat. Vol. 2 Thorax et Membre Thoracique. Barcelona, Spain, Multime dica, Nomina Anatomica Veterinaria (ed 5, electronic version) Editorial Committee: Hannover (Germany), Columbia (Missouri, USA), Gent (Belgium), Sapporo (Japan), 2005