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Wrist extension is achieved by muscles in the forearm contracting, pulling on tendons that attach distal to (beyond) the wrist. If the tendons, muscles, or nerves supplying these muscles are damaged or otherwise not working as they should be, wrist drop may occur. The following situations may result in wrist drop:
The extensor carpi radialis longus is a wrist extensor that is innervated by the radial nerve, [2] [3] from spinal roots C6 and C7. [4] All other major extensor muscles in the superficial layer of the posterior compartment (the extensor digitorum , extensor carpi radialis brevis , extensor carpi ulnaris , and extensor digiti minimi ) are ...
The ED inserts into the middle and distal phalanges to extend the fingers and wrist. Opposite the head of the second metacarpal bone, the EI joins the ulnar side of the ED tendon to extend the index finger. The EDM has a similar role for the little finger. The ECU inserts at the base of the 5th metacarpal to extend and
The median nerve innervates the flexors of the wrist and digits, the abductors and opponens of the thumb, the first and second lumbricals. The ulnar nerve innervates the remaining intrinsic muscles of the hand. [3] [4] All muscles of the hand are innervated by the brachial plexus (C5–T1) and can be classified by innervation: [1] [4] [5]
Injuries (such as by an external flexion force during active extension) may allow the tendon to dislocate into the intermetacarpal space; the extensor tendon then acts as a flexor and the finger may no longer be actively extended. This may be corrected surgically by using a slip of the extensor tendon to replace the damaged ligamentous band. [6]
There are generally twelve muscles in the posterior compartment of the forearm, which can be further divided into superficial, intermediate, and deep. Most of the muscles in the superficial and the intermediate layers share a common origin which is the outer part of the elbow, the lateral epicondyle of humerus.
It is an extensor, and an abductor of the hand at the wrist joint. That is, it serves to manipulate the wrist so that the fingers moves away from the palm. The muscle, like all extensors of the forearm, can be strengthened by exercise that resist its extension; Reverse wrist curls with dumbbells can be performed.
It is innervated by the deep branch of the radial nerve (C8-T1). [4] The tendons of the extensor pollicis longus and extensor pollicis brevis form what is known as the anatomical snuff box (an indentation on the lateral aspect of the thumb at its base) The radial artery can be palpated anteriorly at the wrist(not in the snuffbox).