Bibliography

Hotchkiss RN. Fractures and dislocations of the elbow. In: Rockwood CA, Green DP, Bucholz RW, Heckman JD, eds. Fractures in adults, 4th ed. Philadelphia: Lippincott— Raven Publishers, 1996.

Morrey BF. The elbow and its disorders, 2nd ed. Philadelphia: WB Saunders, 1993.

Robert L. Merkow and Paul Pellicci

Anatomy.. and ..function History

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Disorders of the hand are common; the primary physician is frequently called on to evaluate, diagnose, treat, or refer these important problems. The diagnosis of hand disorders can usually be made by appropriate history, physical examination, radiographs, and laboratory data. A knowledge of basic functional anatomy and physiology, together with a systematic approach to examination, will enable the practitioner to arrive at a working diagnosis and plan a rational therapeutic regimen.

I. Anatomy and function Sir Charles Bell, the leading British anatomist, physiologist, and neurologist of the early nineteenth century, was among the first to recognize the unique qualities of the human hand: "It is in the human hand that we perceive the consummation of all; perfection, as an instrument. This superiority consists in its combination of strength, with variety, extent, and rapidity of motion . . . and the sensibility, which adapt it for holding, pulling, spinning, weaving, and constructing; . . . with the hands, the laborer supports a family, the parent loves and cares for a baby, the musician plays a sonata, the blind 'read' and the deaf 'talk.'" 1 The hand is an essential, complex organ comprising many specialized tissues. The hand-wrist unit integrates 27 bones and joints and 36 intrinsic and extrinsic muscles innervated by branches of three major nerves. The hand is supplied by two blood vessels and contains a variety of highly specialized retinacula and cutaneous structures.

A detailed description of hand anatomy and dynamics of function is beyond the scope of this chapter; however, certain generalities deserve emphasis, for they relate directly to the discussion of common hand disorders.

A. The bones of the hand are divided into three groups: the carpal bones, metacarpal bones, and phalanges. These are functionally grouped into fixed and mobile units. The hand is not flat but rather is shaped with structurally and functionally important transverse and longitudinal arches.

The fixed unit of the hand is central and consists of the index and long-finger metacarpals and the slightly mobile capitate, trapezium, and trapezoid bones, which form the bony keystone foundation of the hand. The flanking mobile units consist of the strong, mobile thumb on the radial side and the powerful ring and little finger on the ulnar side.

B. The muscles and tendons are divided into two groups: the intrinsic muscles (arising from within the hand) and the extrinsic muscles (arising from the forearm and elbow, but inserting into the hand via long tendons). The extrinsic muscles consist of the long flexors and extensors and provide movement and power to the fingers and thumb. The intrinsic muscles are grouped into the thenar and hypothenar muscles, the lumbricals, and the volar and dorsal interosseous muscles. These provide a strong thumb and a fine balance of flexor-extensor mechanisms for the precise and coordinated motions of the fingers.

C. The three major nerves supplying the hand are the median, ulnar, and radial nerves. The hand has an enormous share of sensory and motor representation in the brain. It should be appreciated that all purposeful hand function is initiated in the cerebral cortex.

1. The radial nerve innervates the extensor muscles in the forearm and provides dorsal sensation to the thumb, first web space, index finger, long finger, and radial half of the ring finger to the level of the proximal interphalangeal (PIP) joint.

2. The median nerve supplies all motor branches in the volar forearm except to the flexor carpi ulnaris (FCU) and the flexor digitorum profundus to the ring and little finger (FDP4+5). The median nerve enters the forearm through the two heads of the pronator teres at the elbow; it courses down the forearm volarly within the deep fascia of the flexor digitorum superficialis (FDS) muscle group. The median nerve enters the hand superficially at the wrist through the carpal canal. It also innervates the thenar muscles, except the adductor (via the recurrent motor branch at the base of the thumb), and supplies the lumbricals to the index and long fingers. The median nerve provides important sensation to the thumb, the index and long fingers, and radial half of the ring finger.

3. The ulnar nerve supplies only the FCU and FDP4+5 in the forearm. It runs deep to the FCU, entering the hand via the canal of Guyon between the pisiform and the hook of the hamate bone. In the hand, the ulnar nerve supplies the hypothenar muscles and the remaining intrinsic muscles, and its sensory branches innervate the little finger and the ulnar half of the ring finger.

D. The blood and lymphatic vessels supply the hand with two major branches of the brachial artery: the radial and ulnar arteries entering the hand at the wrist. These anastomose in the palm, forming superficial and deep arches that give off arterial branches to the thumb and fingers. The venous and lymphatic networks run from the palmar to the dorsal side of the hand (this, together with the loose dorsal skin, accounts for the prominent dorsal swelling that can occur in the hand and fingers). The dorsal veins coalesce into the cephalic (radial side) and basilic (ulnar side) systems.

II. History. Because hand function is integral to all activities of daily living, the patient will usually be able to describe accurately the duration and degree of disability.

A. The general history should include the following:

1. The patient's age, occupation, hand dominance, and previous impairment.

2. Activities and hobbies.

3. Medical history, including any underlying systemic disorders, such as diabetes, vascular disease, and endocrine or collagen vascular disorders.

4. The distinction between traumatic and nontraumatic causes is useful; however, disorders may occur concomitantly or be noted after an unrelated injury.

B. The specific history regarding dysfunction of the hand should include duration of disability, precipitating causes, and specific loss of function. Cardinal symptoms include pain, swelling, deformity, and alteration in sensation or strength.

1. Type and severity of pain, as well as location and pattern, are important. What is its onset and progression? Is it constant or intermittent? Does it occur at night? Which specific acts make the pain worse? Is the pain well localized, or does it radiate in a nerve or root distribution? Pain in the neck or other joints may also be helpful in determining a remote or systemic cause. Finally, what treatments or medication have been tried, and what have been the results?

2. Swelling and deformity may be subjective. They may be subtle or obvious. Inquiries regarding onset, progression, and response to treatment should be made.

3. Numbness, weakness, and paresthesia may indicate neurologic dysfunction. The severity, anatomic distribution, duration, and progression of the symptoms are important. Identifying precipitating activities or positions can be very helpful in localizing neurocompressive problems. A history of neck pain or radiation should also be sought.

III. Physical examination.The patient should be sitting, and the entire upper extremity should be exposed and evaluated.

A. Surrounding joints. Begin at the neck; check range of motion, and palpate for areas of tenderness.

1. The shoulder and elbow should be fully examined because either may be the source of a hand disorder. Assessment of active motion at the shoulder and elbow as well as of forearm pronation and supination is important because motion at these joints is necessary for proper positioning of the hand for function. Note any discrepancy between active and passive motion. Closely examine the shoulder, arm, and forearm for evidence of muscle atrophy.

2. Wrist. Evaluate both active and passive range of motion, including supination and pronation. Compare right and left sides. Observe and palpate for localized swelling or tenderness. Note whether areas of swelling appear to arise from the carpal joints per se, from the distal radioulnar joint, or from the more superficial dorsal tendons crossing the wrist (in the last case, the swelling may move with digital flexion-extension).

B. Hand. Observe the resting posture of the hand, and record specific areas of muscle atrophy, discoloration, abnormal swelling, or deformity. Comparison with the contralateral hand (if normal) can be helpful. Accurate recording of the findings is important; a simple sketch of the hand with appropriate notations and measurements is often helpful.

1. The attitude or position of the hand should be inspected for loss of the normal transverse and longitudinal arches, loss of the flexion cascade of the fingers, abnormal posturing, or deformities of the fingers and thumb.

2. Circulation is assessed by observing the color of the skin and fingernails as well as blanching and flush of the nail bed. Patency of the radial and ulnar arteries can be assessed by use of Allen's test. This test can also be applied to the digital vessels.

3. Skin is normally thick and moist on the palmar surface and thin and mobile on the dorsal surface. Examine for the presence or absence of swelling, wrinkles, moisture, scars, or cutaneous lesions.

4. Joints should be inspected for evidence of effusion, synovitis, osteophytes, or loss of normal alignment and motion.

5. Motions of the hand as a unit and individual joints should be checked for stiffness or abnormal mobility. Have the patient make a fist and fully extend the fingers. Evaluate and record action range of motion at the metacarpophalangeal (MCP), PIP, and distal interphalangeal (DIP) joints. Gently check passive flexion and extension of the finger joints and record any fixed contractures.

6. Flexor tendon function is evaluated by asking the patient to flex at the DIP joints while holding the MCP and PIP joints in extension. This action evaluates the FDP function. To test the FDS function, hold the other fingers in extension at the MCP, PIP, and DIP joints, and allow free the digit to be tested. Flexion should occur at the PIP joint, and the DIP joint should be flaccid.

7. Sensation is best tested for light touch with cotton and for two-point discrimination with the prongs of a paper clip. Measure the distance at which the distinction between one and two points is not accurate, and compare with the other digits and contralateral hand. Normally, a patient can distinguish two points 6 mm apart on the pulp of the fingers.

8. Grip and pinch strengths are useful objective measurements and should be recorded and compared with the contralateral side.

9. Simple functional tasks. The patient's ability to use the hand for activities of daily living should also be evaluated and recorded.

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