Figure 132-1. Upper Extremity Dermatomes, Myotomes, and Sclerotomes
Adapted from Jochum D and Delaunay L, with permission from AstraZeneca France.
In the limbs, sensory fibers are distributed to an area further from the axis of the body than the motor fibers of the corresponding root. The skin innervation areas encroach on each other, which justifies the anesthesia of adjacent nerves.
Bones and joints are the main target for postoperative analgesia.
As a rule, joints receive innervation from the same nerves that innervate the muscles that act on them.
Figure 132-2. Shoulder Joint Innervation
The nerve fibers from C5 and C6 roots are the main ones involved for shoulder surgery.For the anterior capsule: branches of subscapular (1), axillary (2), and lateral pectoral nerves (3).For the posterior capsule: suprascapular nerve (4) and articular branches of the axillary nerve (2).
Figure 132-3. Elbow Joint Innervation
All major branches of the brachial plexus contribute to its innervation.The musculocutaneous nerve (1), through the anterior articular nerve of the elbow that comes out from either the main trunk of the nerve or the nerve to the brachialis muscle.The median nerve (2), through its articular rami (upper and lower rami, ramus of the nerve to the pronator teres muscle) to the anterior aspect of the joint.The ulnar nerve (3), through its articular rami (two to three) to the posterior and medial aspects of the joint.The radial nerve (4), through nerves for the medial head of the triceps and to the anconeus muscle, is distributed to the posterior and lateral aspects of the joint.
- Mainly the posterior interosseous nerve (deep branch of radial nerve)
- The anterior interosseous branch of the median nerve, after innervation of the pronator quadratus muscle, pierces the interosseous membrane and anastomoses with the posterior interosseous nerve