Thumb Extensor Research Articles

Restoration of key grip and release in the C6 tetraplegic patient through functional electrical stimulation

Electrical stimulation of selected paralyzed forearm and hand muscles in C6 spinal cord injury patients provides control of lateral pinch (key grip) and release. The movement augments tenodesis grip or the grip achieved through tendon transfer procedures. Chronically indwelling percutaneous coiled wire electrodes were implanted with hypodermic needles into thenar (adductor pollicis and/or opponens pollicis), finger flexor (flexor digitorum superficialis and profundus), and thumb extensor (extensor pollicis longus) muscles. The strength of contraction is controlled by changing the stimulus pulse width and frequency, which determine the number of active muscle fibers and their rate of activation, respectively. Finger flexor activation always precedes thumb adduction /opposition to provide a stable platform for lateral pinch; release is provided by stimulation of the thumb extensor. The patient controls the timing and the strength of the contraction from a single control signal. This control signal is a myoelectric signal (MES) from a muscle which retains voluntary function, e.g., sternocleidomastoid. Electrical activity from the muscle is processed (rectified and averaged) and used to activate the stimulator. Each command to control the muscle is proportional in time, i.e., once a lower threshold bound is exceeded with the MES, the command increases (or decreases) linearly until the MES falls below threshold again. A zero level MES maintains the stimulus; exceeding the upper bound reverses the direction of stimulus change or deactivates stimulation if the level is held long enough. Five subjects have been involved in the development of this system for periods of up to 2 years, and three are presently involved in its evaluation. The function the electrical stimulation provides has been beneficial in performing tonic tasks such as eating and writing.

Hydrocephalus and Congenital Clasped Thumbs: a Case Report with Electromyographic Evaluation

A one-month-old male infant with hydrocephalus, aqueductal stenosis and congenital clasped thumbs is reported. Electromyographic evaluation supported the hypothesis that the clasped thumbs were a consequence of flexion-extension imbalance, with subsequent muscle contracture secondary to hypoplasia or aplasia of the thumb extensors.

Unusual congenital anomalies of the thumb extensors: Report of two cases

A case of rare hereditary anomaly of the extensor tendons of the thumb and a case of congenital duck-neck deformity of the thumb are reported.

The carpal tunnel syndrome

ERIPHERAL NERVES may be affected by a variety of injuries. If a peripheral nerve is injured in a specific location as the result of a mechanical irritation by some anatomical phenomenon, the condition is called an entrapment neuropathy. This type of nerve injury has been described by the term neuropraxia’ to characterize absence of action in an otherwise intact nerve. Neuropraxia may be caused by contusion, concussion, traction, or compression. Most peripheral nerves in their anatomic course pass through tough inelastic fibro-osseous tunnels, and are accompanied by tendons and/or blood vessels. These areas are well known and are frequently the landmarks used for local anesthetic nerve blocks. The best known of all these potential entrapment points is the carpal tunnel. Located on the volar aspect of the wrist joint it contains the median nerve. It is at this point in its peripheral course that the median nerve is most frequently injured so that it exhibits the physical symptoms and signs of neuropraxia. Although Paget in 1854 described median nerve compression at the wrist secondary to fracture callus, only in thhe past two decades has compression of the median nerve been appreciated as a distinct clinical entity and aggressively treated.*13 FUNCTIONAL ANATOMY The usual muscular distribution of the median nerve in the hand is to four and one-half muscles. They are: lumbricals I and II (the two most radial lumbricals), the abductor pollicis brevis, the opponens pollicis, and the superficial (main head) of the flexor pollicis brevis. These muscles act in conjunction with the long thumb flexor, thumb extensors, and abductor to produce almost all motions at the thumb metacarpophalangeal and carpometacarpal joints.4 The usual sensory supply of the median nerve is to the volar (palmar) side of the hand. This includes the radial half of the palm, most of the volar skin of the thumb, index, middle fingers, and radial half of the ring finger. Recently considerable attention has been given to the anatomical course of the motor branch of the median nerve which supplies the bulk of the thenar musculature. Its course may be variable both within the carpal tunnel and as it passes terminally to innervate the thenar muscles .5-7 The carpal canal also contains all the long flexor tendons to the fingers and thumb. Occasionally aberrant blood vessels are also present in the canal. All of these structures are covered by the strong transverse carpal ligament (flexor retinaculum) which extends across the concavity of the carpal arch. This ligament is attached medially to the pisiform bone and to the hamulus of the hamate bone; laterally it is attached to the tubercle of the navicular and to the greater multangular. The floor of the carpal tunnel is formed by the central carpal bones.

Prosthetic replacement of the trapezium. Technical aspects.

Affections of the first carpometacarpal joint are often accompanied by chronic radial subluxation of the metacarpal base. It is suggested that the dislocation is caused by the pull of the abductor pollicis longus and thumb extensors being unopposed because of loss of ulnar capsular support. This situation is commonly found in degenerative arthrosis of the first carpometacarpal joint, for example, a lesion which can now be treated by prosthetic replacement of the trapezium. However, a primarily good result of implant arthroplasty may easily be spoilt by recurrent dislocation of the first metacarpal by thumb motion and power grip. Proper correction requires not only a satisfactory range of motion of the joint but also stability and retention in reduction. A procedure is described which seems to meet these functional requirements.

Congential aplasia or hypoplasia of the thumb and finger extensor tendons

Congential aplasia or hypoplasia of the thumb and finger extensor tendons