Radial nerve injury at axilla (e.g. crutch palsy - radial nerve continuously compressed against humerus) Because these types of injuries are "upstream" from all of the muscles that the radial nerve innervates, this lesion causes motor loss in the extension of the elbow (triceps), extension of the wrist (extensor carpi radialis longus), supination of the forearm (supinator), extension of the metacarpophalangeal joints of digits two through five (extensor digitorium) and the extension (extensor pollicis longus) and abduction (abductor pollicis longus) of the thumb. The denervation of the forearm extensor compartment causes wrist drop, a condition where a patient's hand hangs flaccidly because they cannot extend at the wrist. Wrist drop is a characteristic distal sign of proximal radial nerve palsy. Sensory loss on the posterior arm, forearm, and dorsum of the thumb also occur in axilla lesions of the radial nerve.
Radial nerve injury at radial groove (e.g. Saturday night palsy) Lesions on the shaft of the humerus are usually due to humeral fractures or compression lesions such as Saturday night palsy. Saturday night palsy is an acute retrohumeral compression palsy that occurs when a patient falls asleep curled over their arm. Upon waking up, the patient notices that they cannot extend their wrist, a hallmark of wrist drop. In addition to wrist drop, a radial nerve lesion in the spiral groove of the humerus shares all of the characteristics of lesions in the axilla, EXCEPT for loss of extension at the elbow and posterior arm cutaneous sensation. In other words, extension in the elbow and posterior arm cutaneous sensation is spared in spiral groove lesions, as the lesion is "downstream" from where the radial nerve innervates the tricep and posterior arm skin. Sensation on the posterior aspect of the forearm may or may not be spared.
1. Proximally, an imaginary line connecting the medial and lateral epicondyles. 2. Medially, the mass of forearm flexor muscles arising from the common flexor attachment on the medial epicondyle; most specifically, the pronator teres. 3. Laterally, the mass of forearm extensor muscles arising from the lateral epicondyle and supra-epicondylar ridge; most specifically, the brachioradialis
The floor of the cubital fossa is formed by the brachialis and supinator muscles of the arm and forearm, respectively. The roof of the cubital fossa is
formed by the continuity of brachial and antebrachial (deep) fascia reinforced by the bicipital aponeurosis, subcutaneous tissue, and skin.
• Terminal part of the brachial artery and the commencement of its terminal branches, the radial and ulnar arteries. The brachial artery lies between the biceps tendon and the median nerve.
• (Deep) accompanying veins of the arteries.
• Biceps brachii tendon.
• Median nerve.
• Radial nerve, deep between the muscles forming lateral boundary of the fossa (the brachioradialis, in particular) and the brachialis, dividing into its superficial and deep branches. The muscles must be retracted to expose the nerve.
Circumduction at wrist is a combination of flexion, extension, abduction, and adduction.
• Flexion of the wrist joint is produced by the FCR and FCU, with assistance from the flexors of the fingers and thumb, the palmaris longus and the APL
• Extension of the wrist joint is produced by the ECRL,ECRB, and ECU, with assistance from the extensors of the fingers and thumb.
• Abduction of the wrist joint is produced by the APL, FCR, ECRL, and ECRB; it is limited to approximately 15° because of the projecting radial styloid process.
• Adduction of the wrist joint is produced by simultaneous contraction of the ECU and FCU.