ZONES OF HAND Rose Mary Antony

Tendons White fibrous connective tissue cords which connect muscles to bones. Tendon continuity is necessary for transmission of force from muscle bellies to hand. Disruption of a tendon causes loss of motion of the digit, diminished grip or pinch.

Tendon injuries In order to clarify the results of tendon repair , it is necessary to define the different anatomic regions of the tendons of hand .

Flexor system Muscle bellies originate from distal humerus and proximal ulna. Musculotendinous junction is located in the distal forearm and tendons pass to the wrist through the carpal tunnel & into the hand and digits.

2 tendons for each finger and 1 for thumb. Flexor digitorum superficialis divides into 2 tendon slips & inserts on the middle phalanx of each digit. Flexor digitorum profundus & flexor pollicis longus tendons insert on the base of distal phalanges of fingers & thumb.

FLEXOR ZONE SYSTEM MODIFIED VERDAN’S ZONE SYSTEM

Zone 1 From flexor superficialis insertion to the tip of finger. Involves only flexor digitorum profundus. Skin laceration- distal to mid finger crease.

Zone 2 Bunnell’s no man’s land - the results obtained were so poor that nobody should attempt to repair it.

Zone 2(contd) Begins proximal to the metacarpophalangeal joint & extends to the midportion of middle phalanx. 2 flexor tendons enclosed in the fibrous flexor sheath. Corresponds to distal palmar crease & mid finger crease.

Zone 3 From the distal end of transverse retinacular ligament to the distal palmar crease. Lumbrical muscle belly firmly attached to flexor profundus & superficialis.

Zone 4 Carpal tunnel – distal end of transverse retinacular ligament to the proximal margin. Lumbrical muscle belly thins out & flexor tendons to the fingers and thumb & median nerve.

Zone 5 From proximal transverse carpal ligament at the wrist to the musculotendinous junction of the flexor tendons in the distal third of forearm.

EXTENSOR SYSTEM Injuries to the extensor tendons are common owing to their relatively exposed and superficial location.

Extensor compartments 1 - extensor pollicis brevis and abductor pollicis longus. 2- extensor carpi radialis longus & brevis. 3- extensor pollicis longus. 4- 4 tendons of extensor digitorum + extensor indicis

5- extensor digiti minimi . 6 – extensor carpi ulnaris.

The extensor digitorum tendons are joined by oblique interconnections –juncturae tendinum. Intrinsic tendons from lumbricals & interossei join the extensor mechanism over the proximal phalanx & continue distally to the distal interphalangeal joint.

DORSAL DIGITAL EXPANSION Extensor mechanism at proximal interphalangeal joint can be described as a trifurcation of extensor tendon into the central slip & 2 lateral slips. Central slip attaches to the base of middle phalanx. Lateral bands pass on either side of proximal interphalangeal joint & get inserted at the base of distal phalanx.

EXTENSOR ZONES VERDAN’S ZONE SYSTEM 1- distal interphalangeal joint 2 - middle phalanx 3 - proximal interphalangeal joint 4 - proximal phalanx

5-metacarpophalangeal joint 6 – metacarpal 7 – dorsal retinaculum 8 – distal forearm

Zones of thumb 1 - interphalangeal joint 2 - proximal phalanx 3 -metacarpophalangeal joint 4 – metacarpal 5 – carpometacarpal joint or radial styloid

Resting posture of hand When relaxed, the hand lies in a characteristic posture with the thumb-tip held slightly flexed and fingers held in a cascade. Any change in the resting posture can suggest tendon or even nerve damage.

INJURIES injury to extensor tendons Inability to extend the fingers as in opening the hand.

Both flexor tendons of a finger severed Finger lies in an unnatural position of hyperextension compared with uninjured fingers.

Passive extension of wrist does not produce the normal tenodesis flexion of the fingers.

If the wrist is flexed , even greater unopposed extension of the affected finger is produced.

When both flexor tendons are severed, neither proximal nor distal interphalangeal joint can be actively flexed with the metacarpophalangeal joint stabilised.

Flexor digitorum profundus With proximal interphalangeal joint stabilised, active flexion of distal interphalangeal joint is not possible.

Flexor digitorum superficialis injury Maintaining the adjacent fingers in complete extension, flexion of the interphalangeal joints is not usually possible in the affected finger.

Thumb If flexor pollicis longus tendon is divided, flexion at the interphalangeal joint is absent when the metacarpophalangeal joint is stabilised.

MEDIAN NERVE INJURY Ochsner’s clasping test patient is asked to clasp the hands,index finger of the affected side fails to flex and remains as a pointing index.

ULNAR NERVE INJURY Froment’s sign Patient asked to grip a sheet of paper between thumb & index finger of both hands. Thumb of the affected side cannot remain straight & it flexes.

RADIAL NERVE INJURY Wrist drop Patient unable to extend the wrist if injury occurs in axilla & radial groove. Finger drop Injury to the nerve in fractures of the proximal radius.

Specific extensor tendon injuries. MALLET FINGER Loss of continuity of the extensor tendon over distal interphalangeal joint. Person is unable to actively extend the distal interphalangeal joint.

SWAN NECK DEFORMITY   Hyperextension at the proximal interphalangeal joints and flexion at the distal interphalangeal joints of the hands

BOUTONNIERE DEFORMITY Disruption of extensor tendon at the proximal interphalangeal joint . Loss of extension at proximal interphalangeal joint & compensatory hyperextension at distal interphalangeal joint.

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