Role of the Wrist Extensors in Gripping Introduction: The main role of muscles of the wrist complex is to provide a stable base for hand while permitting positional adjustment that will allow for an optimal length tension relationship in the long finger muscles (Levangie and Norkins ,2005).
The major contributor of the wrist complex seams to be controlling length tension relationship in multiarticular hand muscles which in turn allows fine adjustment of grip (Levangie and Norkins, 2005).
The primovers of wrist extension are extensor carpi radialis longus(ECRL), extensor carpi radialis brevis(ECRB) and extensor carpi ulnaris .(Levangie and Norkins, 2005). Six muscles act secondarily on the wrist and are thumb muscles which are extensor digitorum communis, the extensor indices proprius, extensor digiti minimi, extensor pollicis longus and brevis and abductor pollicis brevis.( levangie and Norkins, 2005)
Anatomy: Extensor carpi radialis muscle arrises from the distal third of lateral supracondylar ridge of the humerus and adjacent part of the lateral intermuscular septum, extensor carpi radialis brevis originates from the lateral epicondyle of humerus and the fascia covering common extensor origin, both of them run through the second compartment of extensor retinaculum. The extensor carpi radialis longus is inserted base of the second metacarpal and extensor carpi radialis brevis into base of 3rd metacarpal (Nayak ,2006).
Extensor carpi radialis longus is innervated by radial nerve c6 c7 it acts as a extensor and abductor at the wrist and midcarpal joints also acts synergistically with finger flexors when making a fist (Stranding ,2004).
Extensor carpi radialis brevis innervated by posterior interosseus nerve c7 c8, along with extensor carpi radialis longus it acts as extensor and abductor of wrist and synergistically with finger flexors when making a fist (Strandring, 2004).
Extensor carpii ulnaris originates from the lateral epicondyle via the common extensor origin, posterior border of ulna and it attaches to tubercle on medial side of fifth metacarpal base, it is innervated by posterior interosseous nerve and along with ECRL and ECRB it acts synergistically with digital flexors to extend and fix the wrist when gripping a object (Strandring, 2004).
The role of wrist extensors in gripping: The two main types of grips are power and precision grip, in power grip there is cylindrical, spherical, hook grip and lateral prehension and in precision grip there is pad to pad , tip to tip , pad to side. The extensors have a role not only in providing balance force for flexor muscles but also essential for smooth and controlled opening of hand and release (Levangie and Norkins, 2005).
The fingers wind up to make a fist, the wrist tends to extend especially when force is applied, wrist extensors have marked effect on excursion of the long flexor tendons. If this effect of wrist extensor was absent, digital flexion would require the long tendons to move more proximally in their respective sheaths and these muscles in forearm would be shortened. Thus wrist extension tends to produce a lengthening effect of the same muscles, which in normal use is almost enough to balance the shortening due to finger flexion (Strandring, 2004).
The finger, palm and wrist musculature help in gripping, grasping and making a fist. The main function in gripping is finger flexion which is activated by finger flexors in forearm, but to maintain a straight wrist,
