30.4 Sensory & motor block
- The infraclavicular block results in anesthesia of the arm below the shoulder (Fig-1).
- Although the axillary nerve is also anesthetized, complete anesthesia and analgesia of the shoulder are not achieved with this technique alone.
- As with other techniques to block the brachial plexus, an infraclavicular block will not anesthetize the skin of the medial side of the proximal arm (territory of the intercostobrachial nerve, T2).
Lateral cord: Response after stimulation will be pronation of the forearm, flexion of the fingers or flexion and opposition of the thumb (Fig-2).
The lateral cord branches into the following nerves:
- The lateral pectoral nerve to the pectoralis major muscle.
- The musculocutaneous nerve (C5, C6, and C7) which innervates the biceps muscle.
- The median nerve, partly (C5-C7). The other part comes from the medial cord (C7-T1).
Posterior cord: Motor responses after stimulation will be the abduction of the thumb and extension of the wrist and fingers (Fig-3).
The posterior cord branches into the following nerves:
- Subscapular nerve (C5-C6): Supplies the subscapularis muscle of the rotator cuff, and teres major muscle.
- Thoracodorsal nerve (C6-C8): Supplies the latissimus dorsi muscle.
- The axillary nerve (C5-C6): Supplies the shoulder joint, motor to the deltoid muscle, teres minor and long head of the triceps brachii muscle.
- The radial nerve (C5-C8, T1): Supplies the triceps brachii, brachioradialis, extensor muscles of the finger and wrist, supinator, and the extensor and abductor muscles of the thumb.
Medial cord: Motor responses after stimulation will generate the contraction of the fourth and fifth fingers and thumb adduction (ulnar), flexion of the first three fingers, and opposition of the thumb (median) (Fig-4).
The medial cord branches into the following nerves:
- The medial pectoral nerve (C8-T1): Supplies the pectoralis muscle.
- The medial brachial cutaneous nerve (T1)
- The medial antebrachial cutaneous nerve (C8-T1)
- The median nerve, partly (C7, C8, and T1). The other part comes from the lateral cord.
- The ulnar nerve (C8-T1, and occasionally C7).