MusculoSkeletal Exam

Figure 10.57 Testing wrist extension.

extensor carpi ulnaris by having the patient extend the wrist in an ulnar direction while applying resistance to the fourth and fifth metacarpals.

Testing wrist extension with gravity eliminated is performed with the patient’s forearm in a midposition

between pronation and supination and the hand resting on the table. The patient attempts to extend the wrist through the range of motion while the table supports the weight of the hand and forearm.

Painful resisted wrist extension may be due to lateral epicondylitis (see p. 228).

Weakness of wrist extension results in a weakening of the grip due to loss of the tenodesis effect. Extension of the wrist is necessary for the finger flexors to be in a stretched position so that they can function properly. Note that your grip strength is very weak with a fully flexed wrist. Grip strength is maximal at about 20 degrees of wrist extension.

The Hand

Flexion, extension, abduction, and adduction of the second through fifth fingers should be examined. The superficial and deep finger flexors should be tested in isolation.

Special attention should be devoted to the thumb and its movements of flexion, extension, abduction, adduction, and opposition.

Distal Interphalangeal Joint Flexion

The long finger flexor muscle is the flexor digitorum profundus (Figure 10.58). This is the only muscle that flexes the distal interphalangeal joint. It also can flex the wrist and the proximal joints of the fingers. Note that the flexor digitorum profundus to the index and middle fingers is innervated by the median nerve. The flexor digitorum profundus to the ring and fifth fingers is innervated by the ulnar nerve.

Figure 10.59 Testing distal interphalangeal joint flexion.

•Position of patient: Sitting.

•Resisted test: Test each finger individually by supporting it with one hand. Ask the patient to flex the distal phalanx while you apply resistance on the palmar surface of the finger over the distal finger pad (Figure 10.59).

Pain located in the region of the metacarpopha-

langeal joint associated with a swelling may be due to tenosynovitis of the flexor tendon, and may cause a “triggering” of the finger. A clicking sensation may be palpated along the flexor tendon where the inflammation exists. The patient may be unable to extend the finger independently due to a ball-and-valve phenomenon (Figure 10.60).

Proximal Interphalangeal Joint Flexion

The flexor digitorum superficialis attaches to the middle phalanx of the finger and flexes the proximal interphalangeal and metacarpophalangeal joints, and the wrist (Figure 10.61). It is assisted by the flexor digitorum profundus.

•Position of patient: Sitting.

•Resisted test: The goal of the test is to isolate the flexor digitorum superficialis. This can be accomplished by stabilizing the patient’s metacarpophalangeal joint with one hand and asking the patient to flex the proximal interphalangeal

joint while the distal interphalangeal joint is maintained in extension. Apply resistance to the palmar aspect of the middle phalanx (Figure 10.62).

Figure 10.62 Testing flexion of the proximal interphalangeal joint.

Figure 10.63 Testing flexion of the proximal interphalangeal joint by the flexor digitorum superficialis only.

This test can also be performed by hyperextending all of the patient’s fingers except for the thumb and the one being tested. Due to the mechanical disadvantage of the flexor digitorum profundus in this position, only the flexor digitorum superficialis will flex the finger being tested (Figure 10.63).

Weakness of finger flexion results in the inability to grip or carry objects with the fingers.

Finger Extension

The extensors of the metacarpophalangeal joints are the extensor digitorum, extensor indicis, and extensor digiti minimi (Figure 10.64). The interphalangeal

Extensor

indicis

Extensor digitorum

Extensor digiti minimi

Figure 10.64 The extensor digitorum, extensor indicis, and extensor digiti minimi.

joints are extended with the help of the lumbricals and interossei. The finger extensors also assist in wrist extension.

•Position of patient: Sitting. The pronated forearm is supported on a table.

•Resisted test: Ask the patient to extend the fingers at the metacarpophalangeal joints. Apply resistance with your fingers to the posterior aspect of the proximal phalanges (Figure 10.65).

Weakness of finger extension results in the fingers

remaining in a position of flexion at the metacarpophalangeal joints. Relative weakness of wrist flexion may also be noted.

The Interossei

It is said that the interossei function primarily to abduct and adduct the second through fifth digits. The palmar interossei adduct the fingers (Figure 10.66), and the dorsal interossei abduct the fingers (Figure 10.67). Mnemonics for these are “PAD” and “DAB.” Abduction and adduction of the digitis provides little functional advantage other than providing for a variety of hand grip sizes. A very important function of the interossei is to flex and rotate the proximal phalanx

Transverse metacarpal ligament

Palmar interossei

Figure 10.66 The palmar interossei.

Scaphoid tuberosity

Figure 10.68 The normal hand in a flexed posture shows all four fingers pointing toward the scaphoid tubercle.

of the finger. Note that when closing your hand, the four fingers point toward the scaphoid tubercle (Figure 10.68). This occurs because of the coordinated function of the interossei. Likewise, the rotation of the fingers as they extend also requires precise function of these muscles. Weakness or contracture of the interossei will prevent normal hand function. The rotational alignment of the metacarpals and proximal phalanges following a fracture is extremely important for preservation of normal function of the associated interossei muscles. Malalignment due to a fracture can result in overlapping of the fingers as the patient closes his or her fist (Figure 10.69).

•Position of patient: Sitting. The forearm is pronated.

•Resisted test: The palmar interossei are tested by attempting to abduct the fingers as the patient squeezes the fingers into adduction (Figure 10.70A–D). The dorsal interossei are tested by asking the patient to spread the fingers apart as you attempt to adduct them one on the other (Figure 10.71A–D).

The Thumb

Flexion

The flexors of the thumb are the flexor pollicis longus and flexor pollicis brevis (Figures 10.72 and 10.73). The flexor pollicis longus also assists in wrist flexion.

•Position of patient: Sitting. The forearm is supinated and the hand is in a relaxed posture.

•Resisted test: The flexor pollicis longus is tested by supporting the patient’s thumb on the palmar surface as the patient attempts to flex the interphalangeal joint (Figure 10.74). The flexor pollicis brevis is tested by applying pressure to the proximal

phalanx of the thumb on the palmar surface while the patient attempts to flex the thumb, keeping the interphalangeal joint extended (Figure 10.75).

Painful resisted thumb flexion may be due to tenosynovitis.

Weakness of the short thumb flexor will result in a weakened grip. Weakness of the long thumb flexor will result in difficulty holding a pencil or small objects.

Extension

The extensors of the thumb are the extensor pollicis and longus and extensor pollicis brevis (Figures 10.76 and 10.77).

Figure 10.78 Testing extension of the metacarpophalangeal joint of the thumb.

Figure 10.79 Testing extension of the interphalangeal joint of the thumb. The extensor pollicis brevis also extends the

metacarpophalangeal and carpometacarpal joints of the thumb.

•Position of patient: Sitting. The forearm is supinated and the wrist is in neutral.

•Resisted test: The patient’s hand is supported with your hand and you resist thumb movement away from the index finger in the plane of the palm, first proximally over the proximal phalanx, to test the extensor pollicis brevis and then distally, over the distal phalanx to test the extensor pollicis longus (Figures 10.78 and 10.79).

Painful extension of the thumb may result from

tenosynovitis at the wrist where the extensor pollicis brevis crosses the radial styloid process. This is called de Quervain’s syndrome. Associated tenosynovitis

in the abductor pollicis longus muscle may also be noted (see special test for de Quervain’s syndrome on

p.284).

Weakness of thumb extension results in a flexion

deformity of the thumb.

Abduction

The abductors of the thumb are the abductor pollicis longus, innervated by the radial nerve (Figure 10.80), and the abductor pollicis brevis, innervated by the median nerve (Figure 10.81).