Motion
Nerve
Cord
Division
Trunk
Root
Arm abduction
Suprascapulara
Upper
C5, C6
Arm abduction
Axillary
Posterior
Posterior
Upper
C5, C6
Elbow flexion
Musculocutaneousb
Lateral
Posterior
Upper
C5, C6
Anterior
Extension (dorsiflexion) of the elbow, wrist, hand, and fingers
Radial
Posterior
Posterior
Upper
C5, C6
Posterior
Middle
C7
Latissimus dorsi twitch (shoulder shrug)
Thoracodorsal
Posterior
Posterior
Middle
C7
Forearm pronation and wrist flexion
Median (lateral head)
Lateral
Anterior
Upper
C5, C6
Medial
Anterior and posterior
Middle
C7
Anterior
Lower
C8, T1
Thumb flexion and opposition (flexion middle and ring finger)
Median
Medial
Anterior
Lower
C8, T1
Thumb flexion and opposition
Anterior interosseous
Medial
Anterior
Lower
C8, T1
Fifth finger flexion and opposition, ulnar deviation of the wrist
Ulnar
Medial
Anterior
Lower
C8, T1
14.1.3 Osteotomes
Osteotomes refer to specific regions of the bones throughout the extremities that are innerved by the terminal nerves (rather than by spinal segments as with dermatomes). The innervation of bones can be significantly different from that of the muscles and skin. A good knowledge of joint innervation is important for orthopedic surgery as well as other surgical specialties and neurology.
14.2 Innervation of the Upper Extremity
14.2.1 Dermatomes and Cutaneous Distribution of the Peripheral Nerves (Figs. 14.1, 14.2, 14.3, and 14.4)
Fig. 14.1
Dermatomes; anterior view
Fig. 14.2
Dermatomes; posterior view
Fig. 14.3
Cutaneous distribution of the peripheral nerves of the upper extremity; anterior view
Fig. 14.4
Cutaneous distribution of the peripheral nerves of the upper extremity; posterior view
Segmental Cutaneous Innervation of the Upper Extremity
C3 and 4: upper shoulder region (supraclavicular nerves)
C5: deltoid and lateral aspect of the arm
C6: lateral arm, forearm, and thumb
C7: the hand and middle three fingers
C8: fifth finger and medial side of both the hand and lower forearm
T1: medial side of the lower arm and upper forearm
T2: medial side of the upper arm (intercostobrachial nerve)
14.2.2 Myotomes
For clinical practice, it is important to understand that there is a specific distribution of innervation to skeletal muscles that is derived from the terminal nerves (Figs. 14.5 and 14.6). Table 14.1 summarizes the origin of each terminal nerve and its objective movement upon electrical stimulation.
Fig. 14.5
Distribution of muscular innervations by the terminal nerves of the upper extremity; anterior view
Fig. 14.6
Distribution of muscular innervations by the terminal nerves of the upper extremity; posterior view
Segmental Motor Responses Associated with Nerve Stimulation
C5: lateral rotation and abduction of the arm at the shoulder joint
C6: pronation and supination of the forearm
C5 and 6: elbow flexion
C6-8: medial rotation and adduction of the arm at the shoulder
C6 and 7: elbow extension
C6 and 7: wrist flexion and extension (long flexor and extensor muscles of the wrist)
C7 and 8: digit flexion and extension (long flexors and extensors of the fingers), opposition of the thumb
T1: intrinsic movements of the hand
Muscular Distribution of the Spinal Segments
C5: rhomboids, supraspinatus, infraspinatus, anterior portion of deltoid, long head of biceps
C6: teres major and minor, middle and posterior deltoid, short head of biceps, coracobrachialis, brachialis, brachioradialis, extensor carpi radialis longus and brevis, supinator, pronator teres
C7: triceps, anconeus, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis longus and brevis, extensor indicis, flexor carpi radialis
C8: flexor digitorum superficialis and profundus, flexor carpi ulnaris, flexor pollicis longus, pronator quadratus, abductor and flexor pollicis brevis, opponens pollicis
T1: flexor digitorum superficialis, abductor digiti minimi, adductor pollicis, flexor digiti minimi brevis, opponens digiti minimi, palmar and dorsal interossei, lumbricals
14.2.3 Osteotomes
Terminal nerves, rather than spinal cord segments, distribute sensory innervation to specific regions of bones throughout the extremities. These terminal nerves also send articular branches to specific joints in the extremity. These regions of the bones, each supplied by a specific branch of a terminal nerve, are termed osteotomes; those for the upper extremity are summarized in Figs. 14.7 and 14.8.
Fig. 14.7
Osteomes of the upper extremity; anterior view
Fig. 14.8
Osteomes of the upper extremity; posterior view
14.2.4 Innervation of the Major Joints of the Upper Extremity
In general, the nerve supplying a joint also supplies the muscles which move the joint and the skin covering the articular attachments of those muscles (Hilton’s law).
Table 14.2 outlines the innervation of the joints of the upper extremity joint innervation and associated motor responses associated with nerve stimulation during nerve block procedures.
Table 14.2
Innervation of the joints of the upper extremity joint innervation and motor responses associated with nerve stimulation
Joint | Nerve | Root | Motion |
|---|---|---|---|
Shoulder | |||
Anterior and posterior | Suprascapular | C5, C6 | Arm abduction |
Axillary | C5, C6 | Arm abduction | |
Elbow | |||
Anterior | Musculocutaneous | C5, C6 | Elbow flexion |
Radial | C5–C7 | Extension of the elbow, wrist, and fingers | |
Median | C5–T1 | Thumb flexion and forearm pronation | |
Posterior | Radial | C5–C7 | Extension of the elbow, wrist, and fingers |
Ulnar | C8, T1 | Fifth finger flexion and opposition | |
Wrist | Radial (superficial) | C5–C7 | Extension of the elbow, wrist, and fingers |
Median | C5–T1 | Thumb flexion and forearm pronation | |
Ulnar | C8, T1 | Fifth finger flexion and opposition | |
14.2.4.1 Innervation of the Shoulder
The nerve supply to shoulder joint nerve supply is derived from the axillary, suprascapular, and lateral pectoral nerves, from branches arising from the posterior cord of the brachial plexus, possibly the radial nerve. Sympathetic innervation is derived directly from the stellate and perhaps from other lower cervical and/or upper thoracic sympathetic ganglia (Table 14.2). Recommended block(s) is/are shown in Fig. 14.9.
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Fig. 14.9
Innervation of the major joints
Axillary nerve (articular branch): after leaving the posterior cord of the brachial plexus and descending laterally across the subscapularis muscle, the articular branch of the axillary nerve innervates mainly the inferior aspect of the joint capsule
A portion of the articular branch innervates the bicipital sulcus and forms anastomoses with fiber bundles from the posterior cord.
The branch leaves the plexus in proximity to where the axillary nerve forms and courses obliquely across the subscapularis muscle to reach the bicipital sulcus and inferior and superior aspects of the anterior surface of the joint capsule.
Terminal twigs course superiorly from the inferior aspect of the capsule to reach the anterior and posterior surfaces of the capsule.
Nerve fibers largely penetrate the fibrous layer of the capsule, while there is some penetration into the synovial layer and adjacent portions of the humerus.
Fibers which reach the posterior capsule join the lower articular branch of the suprascapular nerve; those coursing toward the anterior capsular surface jointly innervate this area with the branch from the posterior cord of the plexus.
Lateral pectoral nerve: articular branches arise mainly from the lateral pectoral nerve.
Articular branch travels superior to the coracoid process to reach the acromioclavicular joint, with its terminal portion supplying the anterosuperior region of the shoulder joint capsule, as well as synovial tissue.
Sympathetic fibers which innervate the joint arise from both the stellate ganglion and the sympathetic trunk just superior to the stellate ganglion.
Fibers descend within the adventitia of the subclavian and axillary arteries to the point where the arteries enter the vascular area of the joint.Related posts:
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