Introduction to the Upper Limb PDF

Organization of the Limbs DPM Program 1. For each region, or compartments, of the upper limb describe structural relationships within the context of sectional anatomy. 4.0 2. Describe the innervation of the upper extremity in terms of dermatomes and cutaneous domains. 4.0 3. Describe the superficial...

Organization of the Limbs DPM Program 1. For each region, or compartments, of the upper limb describe structural relationships within the context of sectional anatomy. 4.0 2. Describe the innervation of the upper extremity in terms of dermatomes and cutaneous domains. 4.0 3. Describe the superficial and deep venous drainage of the upper extremity. 4.0 4. Describe the structure and function of the joints of the upper extremity including associated bursae. 4.0 5. Describe the superficial and deep fascia of the upper extremity in terms of myofascial compartments and their contents. 4.0 6. Describe the superficial and deep lymphatic drainage of the upper extremity. 4.0 Development of the Limbs 1. Describe and compare hand and foot plates, and digital rays in upper and lower limb development. 4.0 2. Discuss the importance of limb axes and limb rotation. 4.0 3. Discuss the importance of myotome and dermatome formation in limb development. 3.0 4. Describe the development of the nerve distribution of the limbs. 4.0 5. Describe the anomalies in limb development (eg, amelia and meromelia, cleft foot/hand, polydactyly, and syndactyly. 4.0 1 Overview of the Upper Limb Regions of the upper limb and associated bones: Shoulder: scapula, clavicle, proximal end of humerus Arm-humerus Elbow Forearm-radius and ulna Wrist-carpals Hand-metacarpals and phalanges Main sub regions of the upper limb include: Shoulder: deltoid region, axillary region Arm: anterior arm, posterior arm Forearm: anterior forearm, posterior forearm Wrist: anterior carpal, posterior carpal Hand: palm (volar) of hand, dorsum of hand, metacarpal region, regions of digits, interdigital spaces of hand, anatomical snuffbox (radial foveola) Areas of transition of the upper limb: Important structures pass through, or are related to these areas Axilla: structures that pass between the neck and the arm Cubital fossa: structures that pass between the arm and forearm Carpal tunnel: structures that pass between the forearm and hand 2 Neurovasculature Pathways in the Upper Limb Major neurovasculature structures travel between regions of the upper limb by passing through spaces that are located near the joints. There are three spaces in the upper limb. To get into or out of the upper limb, structures pass through the ‘cervicoaxillary canal’ which connects the axilla to the neck. 1. Axilla (anterior to glenohumeral joint): almost all neurovasculature structures for the entire limb pass through the axilla before spreading out to reach the shoulder region or portions of the ‘free’ limb. 2. Cubital fossa (anterior to the elbow): A pathway for structures travelling between the arm and forearm. 3. Carpal tunnel (anterior to the wrist): a pathway for structures travelling between the forearm and hand 3 Regions of the Upper Limb Glenohumeral joint (head of humerus and glenoid fossa of scapula) The upper limb is adapted for mobility and manipulation. Elbow joint (distal humerus with proximal radius and ulna) Radiocarpal joint (wrist joint; distal radius with scaphoid and lunate) There are 4 regions in the upper limb: 1. Shoulder region: transitional between the trunk and the ‘free’ portion of the limb. Most of the muscles in the shoulder region have an attachment to the bones of the pectoral girdle and act at the glenohumeral joint. 2. Arm: the proximal segment of the upper limb, located between the glenohumeral joint and elbow joints. 3. Forearm: the second segment of the upper limb, located between the elbow and wrist joints. 4. Hand: the most distal segment of the upper limb. It is composed of the wrist, palm, dorsum of hand and digits. 4 Dermatome vs Myotome of the Upper Limb More ventral rami contribute to the dermatomal innervation of a limb than to its myotomal innervation. Therefore: -Upper limb muscles are innervated by C5-T1 -Upper limb skin is innervated by C4-T2 -Cutaneous nerves are patterned such that the more central dermatomes are represented distally. -Muscular nerves are patterned such that the more proximal nerves innervated the more proximally positioned muscles (and vice versa) Therefore: -skin of the hand is innervated by C6-C8 -intrinsic muscles of the hand are innervated by C8, T1 5 Innervation of the Upper Limb Major nerves that ultimately innervate the arm, forearm, and hand originate from the brachial plexus in the axilla. Clinical signs of problems related to lower cervical nerves—pain; pin-and-needles sensations, or paresthesia, and muscle twitching—appear in the upper limb Clinical testing of lower cervical and T1 nerves is carried out by examining: -Dermatomes (often tested for sensation) -Myotomes (often tested by selected joint movements) (relies on patient being conscious) -Abduction of the arm at the glenohumeral joint (controlled by C5) -Flexion of forearm at the elbow (C6) -Extension of the forearm at the elbow (C7) -Flexion of the fingers (C8) -Abduction and adduction of the index, middle, and ring fingers is controlled predominantly by T1 -Tendon reflexes in the upper limb (can be used if patient is unconscious) -tap on tendon of the biceps in the cubital fossa test mainly for spinal cord level C6 -tap on the tendon of the triceps posterior to the elbow tests mainly for C7 Major peripheral nerves that carry somatic sensory information from patches of skin can be used to test for peripheral nerve lesions: -Musculocutaneous nerve: innervates skin on the anterolateral side of the forearm -Median nerve: innervates the palmar surface of the lateral three and on-half digits -Ulnar nerve: innervates the medial one and one-half digits -Radial nerve: skin on the posterior surface of the forearm and the dorsolateral surface of the hand 6 Cutaneous Innervation of the Upper Limb Dermatome Map Anterior Posterior There is always considerable overlap between adjacent dermatomes. The regions with the least amount of overlap with adjacent dermatomes are used for testing nerves /sensations/ spinal cord segments. These regions are: C5-upper/lateral arm C6-pollex (thumb) C7-3rd digit (middle finger) C8-5th digit (pinky) T1-medial aspect of elbow Cutaneous Nerve Map Musculocutaneous nerve -all muscles in the anterior compartment of arm Median nerve -most flexors in forearm -thenar muscles in hand Radial nerve -all muscles in posterior compartment of arm and forearm Ulnar nerve -most intrinsic muscles in hand -flexor carpi ulnaris and medial half of flexor digitorum profundus in forearm Posterior Anterior Axillary nerve -superior lateral cutaneous nerve of arm Axillary nerve -superior lateral cutaneous nerve of arm Radial nerve -inferior lateral cutaneous nerve of arm T2 Musculocutaneous nerve -lateral cutaneous nerve of forearm T1 Radial nerve -superficial branch Radial nerve -inferior lateral cutaneous nerve of arm -posterior cutaneous nerve of arm -posterior cutaneous nerve of forearm Musculocutaneous nerve -lateral cutaneous nerve of forearm T2 T1 Radial nerve -superficial branch Ulnar nerve Ulnar nerve Median nerve Median nerve 7 Major Peripheral Nerves Myotome Testing 8 Deep Fascia of the Upper Limb Clavipectoral fascia - lies deep to the Pectoralis major muscle, descends from the clavicle and encloses subclavius and pectoralis minor muscles. Brachial fascia - deep fascia of the arm Antebrachial fascia-deep fascia of the forearm Palmar fascia-deep fascia of the hand Forearm Arm Intermuscular septa extend inward from the deep fascia of the arm and forearm to create fascial compartments of the upper limb. Each compartment is associated with its own nerve and contains muscles with similar actions. In the forearm, the interosseous membrane assists in dividing the limb into compartments. Compartment Primary Blood Supply Innervation Main Muscle Actions Anterior Brachial artery Musculocutaneous nerve Flexors of shoulder and elbow Posterior Profunda brachii artery Radial nerve Extensors of the shoulder and elbow Anterior Ulnar, radial and interosseous arteries Median nerve Ulnar nerve Flexors of elbow, wrist, and digits Pronators of radioulnar joint Posterior Radial & posterior interosseous arteries Posterior interosseous nerve Extensors of elbow, wrist, and digits Supinators of radioulnar joint Ulnar nerve Act on 5th digits Median and ulnar nerves Digit flexion, IP extension Median nerve (recurrent branch) Act on pollex Ulnar nerve Digit adduction and abduction Medial (palmar) Hand Central (palmar) Lateral (palmar) -Superficial palmar arterial arch and branches (blood primarily from ulnar artery) -Deep palmar arterial arch and branches (blood primarily from radial artery) Interosseous (palmar) Posterior (dorsal) Radial artery There are no intrinsic muscles on the dorsum of the hand. 9 Upper Limb Fascial Compartments 10 Superficial Veins of the Upper Limb All of the arteries are traveling with companion vv. that are responsible for draining the same structure. Some superficial veins do not travel with arteries. Superficial veins arise from the dorsal venous network of the hand. Here the dorsal venous network gives rise to two different veins superficially on the medial and lateral aspects: Superficial fascia: consists of fat that contains cutaneous nerves, superficial veins and superficial lymphatics. Cephalic vein-arises from the lateral aspect of the dorsal venous network of the hand, ascends on the lateral side of the forearm and arm, runs through the deltopectoral triangle, pierces the clavipectoral fascia and drains into the axillary vein. Basilic vein- begins on the dorsum of the hand (dorsal venous arch/ plexus), ascends on the medial side of the forearm and arm, pierces the brachial fascia, merges with the companion veins of the brachial artery to form the axillary vein. CLINICAL NOTE: frequent site for venipuncture and the insertion of I.V. needles Median cubital vein- runs diagonally across the anterior aspect of the elbow joint forming a communication between the basilic and cephalic veins. CLINICAL NOTE: It is a common site for venipuncture. Axillary vein- NOT a superficial vein—begins at the inferior border of the Teres Major m. as a continuation of the basilic vein Cutaneous innervation of the upper limb comes from: -supraclavicular nerves from the cervical plexus -intercostobrachial nerve (lateral cutaneous branch of T2 that joins with the medial cutaneous brachial n.) -branches of brachial plexus 11 Superficial Veins of the Upper Limb 12 Joints of the Shoulder Region Acromioclavicular Joint -synovial plane joint -the joint is primarily supported (reinforced) by extrinsic ligaments: Coracoclavicular ligament-two strong ligaments between the coracoid process and clavicle. Clavicle Sternoclavicular joint -synovial saddle shaped joint -articular surfaces: manubrium, first costal cartilage and the sternal end of the clavicle -only articulation between the upper limb and axial skeleton -strongly supported by ligaments and very rarely dislocated Coracoclavicular Ligament Manubrium 13 Glenohumeral Joint -Synovial ball and socket joint between the head of the humerus and glenoid fossa of the scapula -The area of contact and stability of the joint are increased by the glenoid labrum—a fibrocartilaginous ring that increases the depth of the glenoid fossa -primary support is from tendons of the muscles of the rotator cuff-reinforce the joint capsule posteriorly, superiorly and anteriorly. Their tonic contraction serves to hold the humeral head in the glenoid fossa. -weakest part is inferiorly—shoulder dislocations usually occur in the infero-anterior direction 14 Lymphatics Axillary lymph nodes (20-30) drain lymphatic vessels from the lateral part of the breast, superficial lymphatic vessels from the thoracoabdominal walls above the level of the umbilicus and vessels from the upper limb. They are divided into 5 main groups: Anterior (pectoral)-receive lymph from the lateral part of the breast and superficial vessels from the anterolateral thoracic wall above the level of the umbilicus Posterior (subscapular)-receive superficial lymph vessels from the back, down as far as the iliac crest Lateral (humeral)-receive most of the lymph vessels from the upper limb Central-receive lymph from anterior, posterior, and lateral nodes Apical-receives lymph from all other nodes, as well as lymph from the superficial arm that travels with the cephalic vein -efferent vessels from the apical group of nodes unite to form the subclavian lymphatic trunk. The right subclavian lymphatic trunk usually drains into the right lymphatic duct which in turn drains into the right venous angle. The left subclavian lymphatic trunk usually drains into the thoracic duct, which drains to the left venous angle. NOTE: most lymph from the breast (over 75%) drains into the axillary lymph nodes 15 16 Development of the Upper Limb 1. During the 4th week, development of the limbs begin as small elevations of the ventrolateral body wall. These elevations are called the limb buds. The initial stages of limb development are the same for the upper and lower limbs, except that development of the upper limb buds precedes that of the lower limb buds by a few days. We will only discuss the upper limb development in this course. 2. The upper limb bud appears opposite the lower cervical segments. 3. Each limb bud is composed of mesenchyme derived from somatic mesoderm and covered by a layer of ectoderm. The ectodermal cells at the tip (apex) of each limb bud proliferate to form an apical ectodermal ridge which exerts an important inductive influence on the underlying mesenchyme, causing it to grow and differentiate. The ends of the flipper-like limb buds flatten into paddle-like hand plates (or foot plates in the case of the lower extremity). A portion of the mesenchyme in these plates condenses to form digital rays which give rise to the digits. Subsequently, the tissue forming the webbing between the digits breaks down to form separate digits, thereby giving the distal end of the limb a more hand-like (or foot-like) appearance instead of something from a Stephen King movie. 17 18 Development of the Upper Limb Continued 1. The limb projects outward from the body at a right angle with the thumb developing on the border toward the head (the cranial or preaxial border). The little finger develops on the caudal or postaxial border. 2. The upper limb rotates laterally 90 degrees during development so that the elbow faces posteriorly and the thumb is on the lateral side (The lower limb rotates 90 degrees in the opposite direction so that the knee faces anteriorly and the big toe is on the medial side. Therefore, the posterior compartments of the arm and forearm are homologous to the anterior compartments of the thigh and leg.). 3. The limb muscles develop from the mesenchyme (i.e., myoblastic cells) surrounding the developing bones. This developing musculature divides into dorsal (i.e., extensors) and ventral (i.e., flexors) parts, and the nerves which grow into these muscles divide similarly into dorsal and ventral components. 4. Recall that a dermatome is defined as the area of skin supplied by a single spinal nerve and its dorsal root ganglion. The peripheral nerves grow from the brachial plexus (i.e., the ventral rami of C5 - T1) into the mesenchyme of the limb buds during the 5th week. These spinal nerves (i.e., ventral rami) are distributed in segmental bands and supply both dorsal and ventral surfaces of the limb buds. This accounts for the initially orderly sequence of nerve 19 Preaxial border (becomes the cephalic vein) Postaxial border (becomes the basilic vein) Dermatomes with the highest segmental innervation (C5, 6) are nearest the preaxial border while the C8 and T1 dermatomes are nearest the postaxial border. This pattern holds for any location along the length of the limb. Notice that C6 is an important dermatome of the thumb. 20 Myotomes: the same ventral rami are responsible for muscular innervation of the limbs. The ventral rami of spinal nerves split into ventral and dorsal divisions. Ventral divisions=destined to supply muscles that developed on the ventral side of the limb (flexors) Dorsal divisions=destined to supply the developmentally dorsal muscles (extensors) Both divisions supply the skin Dorsal ramus Dorsal division of the ventral ramus (innervated muscles that develop on the dorsal surface of the limb) Ventral division of the ventral ramus (innervated muscles that develop on the ventral surface of the limb) Cross section of an embryo through the upper limb bud 21 To better understand limb development and limb rotation watch the following video: https://www.youtube.com/watch?v=VpbdqGJ9LWk 22 Malformations of the Upper Limb Abnormalities of the extremities vary greatly. Minor defects are comparatively common, whereas major malformations are usually rare. The critical period of limb formation is from days 24 to 42 after fertilization. Terminology Amelia: Complete absence of a limb or limbs. Meromelia: Partial absence of a limb or limbs. Cleft Hand and Cleft Foot (Lobster-Claw Deformities): In these rare deformities, there is an absence of one or more of the central digits which results from the failure of development of one or more of the digital rays. Consequently, the hand or foot is divided into two parts that oppose each other similar to lobster claws. The remaining digits are partially or completely fused (syndactyly - see below). Syndactyly (G. syn, with, together; G. daktylos, finger or toe) or Webbed Digits: a. Fusion of the fingers or toes is the most common of the limb defects. The toes are more frequently involved than the fingers. b. Webbing of the skin between the digits results from a failure of the tissue to break down between the digits during development. Polydactyly: extra fingers or toes (digits) that are present at birth 23 24 25 26