Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Pamela BL The wrist is located at the junction of the forearm and hand. The hand, which is the manual part(used for grasping and holding) of the upper limb is located distal to the forearm, and consists of: 1. Wrist 2. Hand proper(palm) 3. The digits(fingers) Movements of the hand occurs at the wrist joint. The skeleton of the hand consists of carpals in the wrist, metacarpals in the hand proper, and phalanges in the digits. The skeleton of the wrist/carpus, is composed of eight carpal bones(carpals) arranged in two rows of four each. These bones give flexibility to the wrist. The carpus is markedly convex from side to side posteriorly and concave anteriorly. The carpals are attached to each other by interosseous ligaments. From lateral to medial, the four bones in the proximal row are: Scaphoid- a boat shaped bone that articulates proximally with the radius and has a prominent tubercle. Lunate- a moon shaped bone that articulates proximally with the radius and is broader anteriorly than posteriorly. Triquetrum- a three cornered pyramidal bone that articulates proximally with the articular disc of the distal radioulnar joint. Pisiform- a small, pea shaped bone that lies on the palmar surface of the triquetrum. From lateral to medial, the bones in the distal row of the carpus are: Trapezium- which is four sided Trapezoid- which is wedge shaped Capitate- which has a rounded head Hamate- which is wedge shaped and has a hooked process, the hook of hamate. Red part represents hook(hamulus) of hamate bone The proximal surfaces of the distal rows of carpal bones articulate with the proximal row of carpals, and their distal surfaces articulate with the metacarpals. The skeleton of the hand between the carpus and phalanges is composed of five metacarpal bones(metacarpals). Each bone consists of a body, a proximal end and distal end. The distal ends or heads of the metacarpals articulate with the proximal phalanges and form the knuckles of the fist. The proximal ends or bases of the metacarpals articulate with the carpal bones. The 1st metacarpal(of the thumb) is the thickest and shortest of the metacarpals. The 3rd metacarpal is distinguished by a styloid process on the lateral side of its base. Each digit has three phalanges except the 1st(thumb) which has only two. Each phalanx has a base proximally, a head distally and a body btwn the base and the head. The proximal phalanges are the largest, the middle ones are intermediate in size and the distal ones are the smallest. Each terminal phalanx is flattened and expanded at its distal end to form the nail bed. Fracture of the scaphoid- the scaphoid is the most frequently fractured carpal bone(common injury of the wrist) especially as a result of fall onto the palm when the hand is abducted. Pain occurs primarily on the lateral side of the wrist especially during dorsiflexion and abduction of the hand. Initial radiographs may not reveal a fracture of the scaphoid. An apparently severely sprained wrist is subsequently diagnosed as a fractured scaphoid after repeated radiographs 2-3 weeks alter revealing a fractured site because bone resorption has occurred there. Because of poor blood supply to the proximal part of the scaphoid, union of the fractured parts may take several months. Avascular necrosis of the proximal fragment of the scaphoid(pathological death of bone resulting from inadequate blood supply) may occur and produce degenerative joint disease of the wrist. Fracture of the hamate may result in non union of the fractured bony parts because of the traction produced by the attached muscles. Ulnar nerve may be injured by a hamate fracture because of its close proximity to the hook of hamate, causing decreased grip strength of the hand. Fracture of the metacarpals- fracture of the necks of the 1st and 2nd metacarpals are often referred to as “boxer’s fractures”. In unskilled street fighters, the neck of the more mobile 5th metacarpal is commonly fractured when they strike a blow with the fist clenched. Severe crushing injuries of the hand mat produce multiple metacarpal fractures resulting in instability of the hand. The hand is involved in the following activities: Power grasping Precision handling Pinching The power grip(palm grip) refers to forcible motions of the digits acting against the palm, the fingers are wrapped around an object with counter pressure from the thumb, e.g. when grasping a cylindrical structure. The precision handling grip involves a change in position of a handled object that requires fine control of the movements of the fingers and thumb(e.g. holding a pen or winding a watch). In precision grip, the wrist and the fingers are held firmly by the long flexors and extensor muscles, and the intrinsic hand muscles perform fine movements of the digits e.g. when treading a needle or buttoning a shirt/blouse. Pinching refers to compression of something btwn the thumb and index finger(e.g. handling a teacup), or btwn the thumb and adjacent two fingers(e.g. when snapping the fingers). The fascia of the palm is continuous with the antebrachial fascia of the dorsum of the hand. The palmar fascia is thin over the thenar and hypothenar eminences but it is thick centrally where it forms the fibrous palmar aponeurosis and in the digits where it forms the digital sheaths The palmar aponeurosis a strong well defined part of the deep fascia covers the soft tissues and overlies the long flexor tendons. The proximal end/apex of the triangular palmar aponeurosis is continuous with the flexor retinaculum and the Palmaris longus tendon. When the muscle is present, the palmar aponeurosis is the expanded tendon of the Palmaris longus. Distal to the apex, the palmar aponeurosis forms four longitudinal digital bands that radiate from the apex and attach distally to the bases of the proximal phalanges and become continuous with the fibrous digital sheaths. 1.Deep antebrachial fascia 2.Superficial fascia and dorsal venous network 7.Cephalic vein 8.Basilic vein 3.Palmar aponeurosis 4.Thenar muscles 5.Hypothenar muscles 6.Palmaris brevis. Bwtn the flexor tendons and the fascia covering the deep palmar muscles are two potential spaces, the thenar space and midpalmar space. The spaces are bounded by fibrous septa passing from the edges of the palmar aponeurosis to the metacarpals. Btwn the two spaces is the specially strong lateral fibrous septum that is attached to the 3rd metacarpal. Hand infections Because the palmar fascia is thick and strong, swellings resulting from hand infections usually appear on the dorsum of the hand where the fascia is thinner. The potential fascial spaces of the palm are important because they may be infected. The fascial spaces determine the extent and direction of the spread of pus formed by these infections. 1. Depending on the sites of infection, pus will accumulate in the thenar, hypothenar or adductor compartments. An untreated infection can spread proximally through the carpal tunnel into the forearm, anterior to the pronator quadratus and its fascia. 2. Dupuytren’s contracture of palmar fasciais a progressive shortening, thickening and fibrosis of the palmar fascia and aponeurosis. The fibrous degeneration of longitudinal bands of the palmar aponeurosis on the medial side of the hand pulls the ring and little finger into partial flexion at the metacarpophalangeal and proximal interphalangeal joints. The contracture is frequently bilateral and is common in men older than 50 yrs. Its cause is unknown but evidence points to a hereditary predisposition. First the disease manifests itself as painless nodular thickenings of the palmar aponeurosis that adhere to the skin. Gradually, progressive contracture of the longitudinal bands produces raised ridges in the palmar skin that extend from the proximal part of the hand to the base of the ring and little fingers. Treatment of Dupuytren’s contracture usually involves surgical excision of all fibrotic parts of the palmar fascia to free the fingers. The intrinsic muscles of the hand are in 4 compartments: Thenar muscles in the thenar compartmentabductor pollicis brevis, flexor pollicis brevis and opponens pollicis. Adductor pollicis in adductor compartment Hypothenar muscles in the hypothenar compartment- abductor digiti minimi, flexor digiti minimi and opponens digiti minimi. Short muscles of the hand ,the lumbricals in the central compartment and the interossei are btwn the metacarpals. The thenar muscles form the thenar eminence on the lateral surface of the palm and are chiefly responsible for opposition of the thumb. The movement begins with the thumb in extended position and initially involves a medial rotation of the 1st metacarpal produced by the action of the opponens pollicis muscle at the carpometacarpal joint and then abduction, flexion and usually adduction. The reinforcing action of the adductor pollicis and flexor pollicis longus increases the pressure that the opposed thumb can exert on the fingertips. Abductor pollicis brevis-short abductor of the thumb, forms the anterolateral part of the thenar eminence. It abducts the thumb at the carpometacarpal joint and assists the opponens pollicis during the early stages of opposition by rotating its proximal phalanx slightly medially. To test the abductor pollicis brevis, abduct the thumb against resistance. Opponens pollicis- a quadrangular muscle lying deep to abductor pollicis brevis and lateral to flexor pollicis brevis. It opposes the thumb, most important thumb movement, that is flexes and rotates the 1st metacarpal medially at the carpometacarpal joint during opposition. This movement occurs when picking up an object. Flexor pollicis brevis- short flexor of the thumb located medial to the abductor pollicis brevis. Its tendon usually contains a sesamoid bone. It flexes the thumb at the carpometacarpal and metacarpophalangeal joints and aids in opposition of the thumb. To test flexor pollicis brevis, flex the thumb against resistance. Adductor pollicis-a fan shaped adductor of the thumb that is located in the adductor compartment. Has two heads of origin that are separated by the radial artery as it enters the palm to form the deep palmar arch. Its tendon usually contains a sesamoid bone. The adductor pollicis adducts the thumb, moves the thumb to the palm of the hand thereby giving power to the grip. Produce the hypothenar eminence on the medial side of the palm and move the little finger. They are in the hypothenar compartment. Abductor digiti minimi-most superficial of the three muscles. Abducts the 5th digit and helps flex its proximal phalanx. Flexor digiti minimi brevis-short flexor of the little finger lying lateral to the abductor digiti minimi. Flexes the proximal phalanx of the 5th digit at the metacarpophalangeal joint. Opponens digiti minimi-quadrangular muscle lying deep to the abductor and flexor muscles of the 5th digit. Draws the 5th metacarpophalangeal joint anteriorly and rotates it laterally deepening the hollow of the palm and bringing the 5th digit into opposition with the thumb. Palmaris brevis- a small, thin muscle in the subcutaneous tissue of the hypothenar eminence. It wrinkles the skin of the hypothenar eminence and deepens the hollow of the palm thereby aiding the palmar grip. The Palmaris brevis covers and protects the ulnar nerve and artery. It is attached proximally to the medial border of the palmar aponeurosis and to the skin on the medial border of the hand. The short muscles of the hand are the lumbricals and interossei. Lumbricals-four slender muscles named so because of their wormlike form. Flex the digits at the metacarpophalangeal joints and extend the interphalangeal joints. Interossei- four dorsal interossei muscles are located btwn the metacarpals, three palmar interosseous muscles are on the palmar surfaces of the metacarpal bones. The 1st dorsal interosseous muscle is easy to palpate, oppose the thumb firmly against the index finger and it can be easily felt. The 4 dorsal interossei abduct the digits and three palmar interossei adduct them. Dorsal ABduct(DAB) Palmar ADduct(PAD). Acting together, the dorsal and palmar interossei and lumbricals produce flexion at the metacarpophalangeal joints and extension in the interphalangeal joints(the so called Z movement). The ulnar and radial arteries and their branches provide blood supply to the hand. Ulnar artery- enters the hand anterior to the flexor retinaculum btwn the pisiform bone and the hook of the hamate(Guyon’s canal). Lies lateral to the ulnar nerve. Divides into two terminal branches, the superficial palmar arch and deep palmar arch. The superficial palmar arch, the main termination of the ulnar artery give rise to three common palmar digital arteries that anastomose with palmar metacarpal arteries from the deep palmar arch. Each common palmar digital artery divided into a pair of proper palmar digital arteries that run along the adjacent sides of the 2nd4th digits. Radial artery-curves dorsally around the scaphoid and trapezium in the floor of the anatomic snuff box and enters the palm by passing btwn the heads of the 1st dorsal interossei muscle. It then runs medially and passes btwn the heads of adductor pollicis. The radial artery anastomoses with the deep branch of the ulnar artery to form deep palmar arch. The deep palmar arch, formed mainly by the radial artery, lies across the metacarpals just distal to their base. The deep arch gives rise to three palmar metacarpal arteries and the princeps pollicis arteries which supply the palmar surfaces and sides of the thumb. The superficial and deep palmar arterial arches are accompanied by superficial and deep palmar venous arches respectively. The dorsal digital vein drains into three dorsal metacarpal veins, which unite to form a dorsal venous network Superficial to the metacarpus, this network is prolonged proximally on the lateral side as the cephalic vein. The basilic vein arises from the medial side of the dorsal venous network. The median, ulnar and radial nerves supply the hand. Branches or communications from the lateral and posterior cutaneous nerves may contribute some fibers to supply the dorsum of the hand. Enters the hand through the carpal tunnel, deep to the flexor retinaculum along with nine tendons of the flexor digitorum superficialis and profundus and the flexor pollicis longus. The carpal tunnel is the passageway deep to the flexor retinaculum bwtn the tubercles of the scaphoid and trapezoid bones on the lateral side and the pisiform and hook of hamate on the medial side. Distal to the carpal tunnel, the median nerve supplies the three thenar muscles and the 1st and 2nd lumbricals. It also sends sensory fibers to the skin on the entire palmar surface, the sides of the 1st three digits, the lateral half of the 4th digit, and the dorsum of the distal halves of these digits. Results from any lesion(e.g. inflammation of synovial sheaths) that significantly reduces the size of the carpal tunnel. Fluid retention, infection and excessive exercise of the fingers may cause swelling of the tendons or their synovial sheaths. The median nerve is the most sensitive in the carpal tunnel and is therefore most affected. This nerve has two terminal sensory branches that supply the skin of the hand hence par aesthesia, hypoesthesia or anesthesia may occur in the lateral three and half digits. The nerve also has one terminal motor branch, the thenar or reccurrent branch which supply three thenar muscles. Progressive loss of coordination and strength in the thumb(owing to weakness of the abductor pollicis brevis and opponens pollicis) may occur if the cause of the median nerve compression is not alleviated. People with median nerve compression are unable to oppose the thumb. As the condition progresses, sensory changes radiate into the forearm and axilla. People with carpal tunnel syndrome have difficulty performing fine movements such as buttoning a blouse/shirt as well as gripping things such as a hairbrush. Partial or complete surgical division of flexor retinaculum(carpal tunnel release) may be necessary to relieve the symptoms.