Wrist extensors

Lateral (wrist extensor) and supinator Supplied by the radial and the posterior interosseous nerve, this group consists of the supinator, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum communis, and the extensor carpi ulnaris. 

Epicondylitis is a common elbow problem, generally called tennis elbow if the lateral epicondyle is involved and golfer s elbow if the medial epicondyle is involved. This is an overuse syndrome that is associated with any activity that requires repetitive pronation and supination, such as gripping a tennis racquet, golf club, screwdriver, or doorknob. The wrist extensor muscles are involved in lateral epicondylitis. 

The wrist is crossed by flexor and extensor tendons which course along its ventral and dorsal aspects respectively. Among them, nine flexor tendons and nine extensor tendons move toward the fingers without any attachment to the carpal bones two primary wrist flexors and three wrist extensors insert onto the distal carpal row and the metacarpals and one tendon, the palmaris longus tendon, attaches to the transverse carpal ligament and to the palmar aponeurosis. 

Denman 1979) and leads to considerable tendon weakness, partial and complete tears if untreated. In extensor pollicis longus tenosynovitis, the synovial sheath effusion is typically found just proximal to the Lister tuberde and after the tendon has crossed the extensor carpi radialis longus (Fig. 10.40). Due to the restricted space under the fasda, the synovial sheath of this tendon maybe distended with fluid in the area of the Lister tuberde and over the radial wrist extensors only wflien the amount of effusion is remarkable. 

Occasionally the alimentary symptoms are relatively slight and are overshadowed by neuromuscular dysfunction, accompanied by signs of motor weakness, which may progress to paralysis of the extensor muscles of the wrist ( wrist drop ) and less often of the ankles ( foot drop ). Encephalopathy, the most serious result of lead poisoning, frequently occurs in children due to the ingestion of inorganic lead compounds, but rarely in adults, except from exposure to organic lead. " ... 

Peripheral neuropathy may appear after chronic high-dose lead exposure, usually following months to years of blood lead concentrations higher than 100 mcg/dL. Predominantly motor in character, the neuropathy may present clinically with painless weakness of the extensors, particularly in the upper extremity, resulting in classic wrist-drop. Preclinical signs of lead-induced peripheral nerve dysfunction may be detectable by electrodiagnostic testing. 

As the disease progresses, the ankle jerk reflex is lost, and the muscular weakness spreads upward, involving first the extensor muscles of the foot, then the muscles of the caff, and finally the extensors and flexors of the thigh. At fins stage, there is pronounced toe and foot drop - the patient is unahle to keep either the toe or the whole foot extended off the ground. When the arms are affected, there is a similar inahUity to keep the hand extended - wrist drop. 

Peripheral motor neuropathy, affeoting mainly the upper extremities, oan cause severe extensor muscle weakness ( wrist drop ). 

Lieber, R.L., Fazeli, B.M., and Botte, M.J. (1990). Architecture of selected wrist flexor and extensor muscles. /. Hand Surg. 15 244-250. 

For prosthetic arms to be more than just position controllers for portable vices, multifunctional mechanisms that have the ability to have multiple degrees of freedom controlled simultaneously (in parallel) in a subconscious manner need to be developed. Current commercially available multifunctional controllers are generally sequential in nature and take the form of two site, three state multifunctional controllers. Motion Control, Inc., in the ProControl hand-wrist controller, uses rapid cocontraction of the forearm extensors and flexors to switch control between hand opening and closing to wrist rotation. Otto Bock uses a similar control strategy in its wrist-hand controller. Motion Control, Inc., in its elbow controller, uses dwell time (parking) to switch from elbow flexion and extension to hand opening and closure and cocontraction of biceps and triceps to switch control from the hand back to elbow. 

A tourniquet applied to the upper arm induces carpopedal spasm due to contraction of the flexors of the arm and wrist, the extensors of the phalanges, and the abductor of the thumb. These combinations of muscle contractions lead to a position of the hand referred to as Trousseau s sign. The application of a mild galvanic current (below 6 milliamps) to the motor nerves leads to contraction of the muscles controlled by these nerves (Erb s sign). 

Carpal T mnel An internal passage in the wrist between the extensor retinaculum and the carpal bones through which the median nerve, finger flexor tendons, and blood vessels pass from the arm to the hand. 

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