Canine Vans PDF - Module 2

Module 2: SA Forelimb VANs Clinical Considerations Understanding the innervation of groups of muscles. E.g.: if an animal is unable to flex the elbow, you must consider musculocutaneous nerve damage as a cause....

Module 2: SA Forelimb VANs Clinical Considerations Understanding the innervation of groups of muscles. E.g.: if an animal is unable to flex the elbow, you must consider musculocutaneous nerve damage as a cause. Understanding the cutaneous autonomous zones. E.g.: if an animal loses sensation to the lateral aspect of 5th digit you would expect ulnar nerve damage. Brachial plexus avulsion, either complete or partial, may occur following severe trauma, where roots of the spinal nerves that contribute to the brachial plexus are torn. Examples: o Radial nerve root damage – animal cannot support weight on the forelimb o Suprascapular and subscapular nerve root damage – animal cannot stabilize shoulder/advance limb o Musculocutaneous nerve root damage – animal cannot lift limb off the floor; inability to flex the elbow The panniculus reflex, or cutaneous trunci reflex: This reflex will be discussed further in the neuro part of the course. This reflex is the expression of the lateral thoracic nerve stimulating contraction of the cutaneous trunci m. leading to a visible “skin twitch” (this is a useful test of neurologic function). List of Terms You are responsible for locating, identifying, and discussing the concepts for the following items. Terms in italics do not have to be identified/located on your canine cadaver, but you should understand the concepts relative to these terms. You should have a basic understanding of regional blood supply and collateral circulation. Arteries of the Thoracic Limb Overview: We will study the great vessels of the heart later in this semester. Until that time, understand that the main vessel that supplies blood to the forelimb is the axillary a. Axillary a. o External thoracic a. – supplies superficial pectoral m. o Lateral thoracic a. – supplies deep pectoral m., note affiliation with the axillary lymph node o Subscapular a. – found between the teres major and subscapularis mm.; supplies subscapularis m. o Thoracodorsal a. – supplies teres major and latissimus dorsi mm. o Caudal circumflex humeral a. – found between proximal humerus (head) and teres major m.; supplies muscles of the shoulder and proximal brachium o The subscapular a. continues dorsally between the teres major and subscapularis mm. after giving off the above 2 branches. o Cranial circumflex humeral a. – last branch off axillary a.; supplies cranial aspect of shoulder 18  Module 2: SA Forelimb VANs Brachial a. (continuation of axillary a.) o Deep brachial a. – supplies the triceps brachii m. (note relationship to radial nerve) o Bicipital a. – supplies biceps brachii m.; usually a very small branch observed distally, but there may be more than one bicipital artery in some dogs o Collateral ulnar a. – supplies caudal elbow area o Transverse cubital a. – supplies cranial elbow and adjacent muscles o Common interosseus a. – last branch of brachial a.; short common trunk: It has 3 branches which you are not responsible for identifying: o Ulnar a. o Caudal interosseous a. o Cranial interosseous a. o NOTE the main arterial supply to the limb changes name now to MEDIAN A. Median a. – Principal source of blood to the paw; passes through the carpal canal with the deep digital flexor tendon to supply the palmar surface of the paw. o Deep antebrachial a. o Radial a. o Superficial palmar arch Veins of the Thoracic Limb Note: For the most part, veins are named the same as the arteries they accompany. Only those veins of clinical relevance will be considered here: Cephalic v. – common site for venipuncture and catheter placement in the forelimb o Accessory cephalic v. – cranially located on dorsum of paw and distal antebrachium; can also be used for venipuncture Median cubital v. – forms connection between the cephalic v. and the median or brachial v. Median v. – drains into both median cubital and brachial vv. Brachial v. – is the continuation of the median v. in the brachial region Nerves of the Thoracic Limb (from brachial plexus) Note: Identification of these nerves is based on the muscles they innervate Cranial pectoral nerves – innervate superficial pectoral m. Caudal pectoral nerves – innervate deep pectoral m.; often combined with the lateral thoracic n. proximally Lateral thoracic nerve – innervates cutaneous trunci m.; involved in the panniculus reflex Suprascapular nerve – innervates lateral stabilizers of the shoulder (supraspinatus m., infraspinatus m.); loss of innervation could affect stability of the shoulder joint Subscapular nerve – innervates subscapularis m. 19  Module 2: SA Forelimb VANs Musculocutaneous nerve – innervates extensors of the shoulder and flexors of the elbow (coracobrachialis, biceps brachii, brachialis mm.); autonomous (cutaneous) innervation to the medial aspect of the antebrachium via the medial cutaneous antebrachial n. o Communicating branch (to median nerve) Axillary nerve – innervates flexors of the shoulder (teres major, teres minor, deltoideus mm.) Thoracodorsal nerve – innervates latissimus dorsi m. Radial nerve – innervates all extensor muscles of the elbow, carpus, digits and supinator m.; autonomous innervation to the lateral antebrachium and dorsal paw o Radial n. damage at the brachial plexus leads to inability to bear weight! o Radial n. can be seen innervating and diving into the triceps brachii m. It should be viewed in 2 places: 1) Medially as it dives into the triceps brachii muscle group, 2) Lift the lateral head of the triceps to see the radial n. dividing into superficial and deep branches. o Superficial branch – provides sensory innervation to the craniolateral antebrachium and dorsum of the manus o Deep branch – innervates the extensor muscles of the carpus and digits and the supinator m. Median nerve – innervates pronators of the forelimb and flexors of the carpus and digits o Shares a common trunk with the ulnar n. proximally. o Passes through the carpal canal to supply sensation to the palmar surface of fore paw along with the ulnar nerve Ulnar nerve – innervates flexors of the carpus and digits on the lateral aspect; autonomous (cutaneous) innervation to the caudal antebrachium, lateral surface of the metacarpus, and the lateral aspect of the fifth digit. Passes through the carpal canal o Caudal cutaneous antebrachial n. Joint Innervation (Sensory only; remember joints cannot move by themselves!): Glenohumeral jt. – innervated by axillary and suprascapular nn. Elbow jt. – innervated by median, ulnar, musculocutaneous, and radial nn. Carpus and digital jts. – innervated by median, ulnar, and radial nn. 20  Module 2: SA Forelimb VANs Region Arterial Supply Nerve Motor Function Sensory Signs of Function Damage/Paralysis Atrophy of the supraspinatus Lateral Scapula and Shoulder Superficial cervical a. Suprascapular n. Supraspinatus Glenohumeral and infraspinatus mm. with Stabilizers, Extensors (and a and joint subsequent prominent flexor) of shoulder infraspinatus scapular spine; decreased mm. ability to laterally stabilize the shoulder Medial Scapula Subscapular a. Subscapular n. Subscapularis m. Decreased ability to medially Extensor and stabilizer of stabilize shoulder; no shoulder significant clinical signs Superficial cervical, Coracobrachialis, Medial Flexor reflex at the elbow is Cranial Muscles of Brachium Musculocutaneous axillary, and brachial aa. n. biceps brachii, and antebrachium; weak; loss of cutaneous Flexors of elbow, extensor of brachialis mm. sensation on the medial shoulder elbow joint aspect of the antebrachium Weakened ability to flex Caudal Scapula and Shoulder Deltoideus, teres Lateral shoulder shoulder. Decreased stability Flexors and stabilizers of Subscapular a. Axillary n. major, teres minor of the shoulder. shoulder mm. Loss of cutaneous sensation of the lateral shoulder region. Thoracodorsal n. Latissimus dorsi m. Ventral aspect Loss of skin twitching Lateral Thorax Thoracodorsal and (Panniculus) reflex lateral thoracic aa. Lateral thoracic n. Cutaneous trunci m. of the thorax and abdomen Triceps brachii, Injury of proximal Radial n. Caudal Brachium Axillary and brachial aa. anconeus, tensor Extensors of elbow Cranial and produces complete loss of fasciae antebrachii, lateral extension of all joints distal ECR, CDE, LDE, UL, antebrachium to the shoulder and loss of Common interosseus aa. Radial n. Cranial Antebrachium abductor digiti I and dorsal paw cutaneous sensation on the Carpal and digital extensors longus, and lateral antebrachium and supinator mm. dorsum of paw. Decreased ability to flex the Pronator teres, Elbow and carpus / digits. Median n. Common pronator quadratus, carpal joints; interosseous and FCR, SDF, and DDF palmar paw Caudal Antebrachium deep antebrachial mm. Carpal and digital flexors aa. Lateral aspect of Decreased ability to flex the Ulnar n. FCU and DDF mm. the metacarpus carpus / digits. Loss of and fifth digit, cutaneous sensation of the Caudal aspect of lateral aspect of the 5th digit antebrachium and caudal antebrachium. Radial n Autonomous to Superficial antebrachial branches. dorsum of paw; See radial nerve above aa. and radial a. Dorsal Paw Joints of carpus and digits Palmar paw Superficial palmar arch (median and (median a.) and deep Median and Ulnar ulnar nn.) and See median and ulnar nerves palmar arch (caudal nn. above Palmar Paw lateral aspect interosseous a.) ------> (ulnar n.) of palmar common digital paw; Joints of aa. carpus and digits 21