CHAPTER 19 The wrist and hand

The wrist area has a series of articulations between the distal end of the radius and the carpal bones (radiocarpal joint), and between the individual carpals themselves (intercarpal joints). The radiocarpal joint is formed between the distal end of the radius and the scaphoid, lunate and triquetral. The end of the radius being covered by a concave articular disc. The eight carpal bones are arranged in two rows, the junction between the rows forming the mid-carpal joint. This joint is convex laterally and concave medially, giving it an ‘S’ shape (Fig. 19.1).

Definition

The radiocarpal joint is formed between the ends of the forearm bones (radius and ulna) and the wrist bones (carpals). The mid-carpal joint is between the two rows of carpal bones themselves.

The wrist is strengthened by collateral, palmar and dorsal ligaments. The ulnar collateral ligament is a rounded cord stretching from the ulnar styloid to the triquetral and pisiform. The radial collateral ligament passes from the radial styloid to the scaphoid and then to the trapezium. The dorsal radiocarpal ligament runs from the lower aspect of the radius to the scaphoid, lunate and triquetral. On the palmar surface, the radiocarpal and ulnocarpal ligaments attach from the lower ends of the radius and ulna to the proximal carpal bones (Fig. 19.2).

Figure 19.2 The capsular and collateral palmer ligaments of the radiocarpal joint. (A) Anterior. (B) Posterior.

After Palastanga, Field and Soames (1994) with permission.

The available range of movement at the wrist is a combination of radiocarpal and mid-carpal movement. Flexion occurs more at the mid-carpal joint, while extension is greater at the radiocarpal joint, but the combined movement is about 85° in each direction. Abduction occurs mostly at the mid-carpal joint and has a range of about 15°, whereas adduction involves more movement of the radiocarpal joint and has a range of 45° (Palastanga, Field and Soames, 1989). The difference in range occurs because the radial styloid comes down further than the ulnar styloid, and so is more limiting to abduction.

The carpal bones form a transverse arch, concave on their palmar aspect (Fig. 19.3). This arch is maintained by the flexor retinaculum, which attaches medially to the pisiform and the hook of hamate. Laterally, the retinaculum binds to the scaphoid tubercle and to the groove of trapezium, through which runs the tendon of flexor carpi radialis. The space formed beneath the retinaculum is called the ‘carpal tunnel’, and the tendons of flexor pollicis longus, flexor digitorum profundus, flexor digitorum superficialis and the median nerve pass through it.

Figure 19.3 Transverse arch of the wrist.

Keypoint

The carpel tunnel (i) lies on the palmar (under) side of the wrist, (ii) has a roof formed by the flexor retinaculum, (iii) provides a passage for the flexor tendons and medial nerve.

On the posterior aspect of the wrist the extensor retinaculum stretches from the radius to the hamate and pisiform bones and extends inferiorly to form six longitudinal compartments for the passage of the extensor tendons.

Grip

Prehension (gripping) is an advanced skill in humans, resulting largely from the ability of the thumb to oppose the fingers. Two types of grip may be described, ‘precision’ involving the thumb and fingers and ‘power’, involving the whole hand.

Keypoint

Precision grip involves the finger tips; power grip uses the whole hand.

With precision grip, the object is usually small and light. The grip is applied with the nails or fingertips (terminal opposition), pads of the fingers (subterminal opposition), or the pad and side of another finger (subterminal−lateral opposition). This action involves rotation of both the carpometacarpal joints of the thumb and fingers involved in the gripping action. The small finger muscles work in combination with the flexor digitorum profundus and superficialis as well as the flexor pollicis longus.

In power grips the long flexors and extensors work to lock the wrist and grip the object. A balance must exist between these two sets of muscles to lock (stabilize) the wrist in its optimal gripping position. Where this balance breaks down pathology may result. In lateral epicondylalgia for example (see Chapter 18) the power of the long extensors is reduced allowing the flexors to dominate, giving an average of 11° less wrist extension (Bisset et al., 2006). The line of action of the finger flexor muscles (flexor digitorum superficialis and profundus) is at some distance to the axis of the wrist joint. This position creates a significant leverage force which tends to flex the wrist as well as the fingers. This tendency for wrist flexion is counterbalanced by the extensor carpi radialis muscles to give an optimal gripping position of 35° wrist extension and 5° ulnar deviation. During light grip the extensor carpi radialis brevis (ECRB) is most active, but as grip power increases and heavier objects are held the extensor carpi ulnaris (ECU) and extensor carpi radialis longus (ECRL) are activated (Neumann, 2002). Grip force is reduced as wrist flexion increases (Fig. 19.4) due to the shortened position of the finger flexors and the passive extension force created by the finger extensor muscles.

Figure 19.4 Grip force with changing wrist position.

Adapted from Neumann (2002).

Keypoint

Optimal grip force is produced with the wrist in 35° extension and 5° ulnar deviation. As the wrist is flexed, grip force is reduced.

In the palmar grip, the whole hand surrounds the object, and the thumb works against the fingers. The shape taken up by the hand is largely determined by the size of the object, but the grip is strongest when the thumb can still touch the index finger. This is the type of grip used when holding a racquet or javelin. When the fingers are closed firmly, the fourth and fifth metacarpals move over the hamate bone to further tighten the grip and prevent a smooth object from slipping out of the hand. The hook grip is used when lifting something with a handle, such as a suitcase. Now, the object is held between the flexed fingers and palm, the thumb not being used. Although the grip is quite powerful, the power is in one direction only.

Screening examination

Initial examination of the wrist utilizes a number of movements to cover all the joints involved in wrist articulation. The superior and inferior radioulnar joints are stressed by passive pronation and supination. The wrist itself is assessed by flexion, extension, abduction and adduction performed both passively and against resistance.

Keypoint

When the wrist is examined, the superior and inferior radioulnar joints should also be assessed, using passive pronation and supination of the forearm.

At the same time as the wrist is examined, the fingers are also assessed as the two areas are intimately linked. Passive and resisted movements are performed at the thumb and finger joints. Again, flexion, extension, abduction and adduction are used. The capsular pattern for the wrist joint is an equal limitation to passive flexion and extension. Painful resisted movement at the wrist indicates that the lesion is not local, but higher up in the muscle bellies, whereas pain to resisted finger movements may give local pain. In addition to pain, crepitus to active movements is an important sign for the long finger tendons.

This examination, described by Cyriax (1982), provides the examiner with enough information to establish whether a lesion is intracapsular or not, and whether contractile tissue is affected. For the physiotherapist, further assessment is usually required to assess and record range of motion and accessory movements. Movements of the individual carpal bones gives more detail about the exact site of the lesion, and the sequence for testing is shown in Table 19.1. In addition, specific tests are used once the initial examination has focused the therapist’s attention onto a specific area or series of tissues.

Table 19.1 Assessing motion of individual carpal joints

Movements around the capitate

Fixate capitate and move

1 trapezoid

2 scaphoid

3 lunate

Fixate capitate and move

4 hamate

Movements on the radial side

Fixate scaphoid and move

5 the two trapezii

Movements of the radiocarpal joint

Fixate radius and move

6 scaphoid

7 lunate

Fixate ulna (including the disc) and move

8 triquetrum (triquetral)

Movements on the ulnar side

Fixate triquetrum and move

9 hamate

10 pisiform (position the patient’s hand in palmar flexion)

From Kaltenborn, F.M. (1993) The Spine. Basic Examination and Mobilisation Techniques, 2nd edn. Olaf Norlis Bokhandel, Oslo, Norway. With permission.

Keypoint

A screening examination of gross movements allows the examiner to distinguish between pathology at the joint and soft tissues. Examination of individual carpal motion refines the examination and gives an indication of manual therapy required.

Scaphoid fracture

The important feature of this fracture is not the frequency with which it occurs, but the number of times it is missed, with pain so often being put down to ‘just a sprain’. The usual history is of a fall onto the outstretched arm with the wrist fully extended. When the hand is locked into extension, the athlete is more likely to sustain a scaphoid fracture; this can occur with a vertical fall from gymnastic apparatus for example. When the hand is more relaxed and the force has some horizontal component, as with a fall when running, the distal radius will usually break (Colles’ fracture). The scaphoid fracture is common in the young athlete while the Colles’ fracture is seen more frequently in the elderly. This is partially due to the weakness of the radius with the onset of osteoporosis in the aged.

Keypoint

With a fall onto the outstretched hand, if the wrist is locked a scaphoid fracture is common. Where the wrist is more relaxed and some sliding force is present (fall onto the outstretched hand when running) the distal radius will more commonly break.

A further cause of injury to the scaphoid is striking an object with the heel of the hand, a mechanism seen in contact sports such as the martial arts or in a collision with another player. In addition, scaphoid fracture can be seen as a punching injury. Horii et al. (1994) described a series of 125 patients with fractured scaphoid, 14% of whom had acquired the injury through punching. Normally it is a bending force within the scaphoid which creates the fracture line when falling onto the outstretched hand. With a punching scaphoid fracture, however, stress force creates the fracture, making displacement and delayed union more likely.

Examination

The major symptom of scaphoid fracture is one of well-localized pain to the base of the thumb, within the ‘anatomical snuffbox’. The athlete’s hand is pronated and gently stressed into ulnar deviation to make the scaphoid more superficial, as the snuffbox is palpated. Palpation of the scaphoid tuberosity with radial deviation of the wrist may also be painful. In addition, pain is exacerbated by axial (longitudinal) compression of the first metacarpal against the scaphoid by pressing the thumb proximally.

Keypoint

With a fracture of the scaphoid bone there is pain at the base of the thumb within the ‘anatomical snuffbox’. Pain is exacerbated by shunting the thumb into itself (longitudinal compression).

Radiographic examination is helpful, but a negative x-ray does not rule out fracture (Garrick and Webb, 1990). Non-displaced fractures are often normal to begin with and only become positive when some bone reabsorption has occurred, the fracture line beginning to show up 2–4 weeks after injury. Plain AP (anteroposterior) views of the wrist may easily miss a scaphoid fracture (Fig. 19.5A), while a specialist scaphoid view which focuses on the bone itself is more reliable (Fig. 19.5B).

Figure 19.5 The wrist showing the scaphoid bone. (A) Anteroposterior view. (B) Scaphoid view.

The scaphoid is ‘nut-shaped’ with a narrow waist and two poles (proximal and distal). On the palmar surface of the distal pole there is a tubercle for the attachment of the flexor retinaculum and the tendon of abductor pollicis brevis. The blood supply to the scaphoid enters through the waist (centre) of the bone (Fig. 19.6). Smaller arteries enter from the distal pole and retrograde flow from these supplies the proximal pole, this pole having no separate blood supply itself. This has an important clinical bearing, because fractures to the waist of the bone can sever the communicating vessels, starving the proximal segment of blood (Gutierrez, 1996). This situation makes non-union or malunion more likely.

Figure 19.6 Classification of scaphoid fracture.

From Gutierrez, G. (1996) Office management of scaphoid fractures. Physician and Sportsmedicine 24(8), 1–8. With permission.

Classification of injury is important as fractures occurring more proximally tend towards avascular necrosis. In addition, fracture orientation should be noted (see Fig. 19.5) as this will influence stability. Horizontal oblique fractures are generally stable, whereas transverse fractures are inherently unstable.

Management

Scaphoid fracture requires prolonged immobilization of the wrist and thumb. The cast usually extends to the interphalangeal (IP) joint of the thumb to just below the elbow. In some cases an above elbow splint is used to limit pronation and supination. Uncomplicated fractures of the scaphoid tubercle may heal in as little as 4 weeks, but fracture to the proximal part of the bone may take as much as 20 weeks. Complications to scaphoid fracture have a poor prognosis. Avascular necrosis may require excision of the avascular fragment, or prosthetic replacement of the whole bone. Non-union usually demands open reduction and internal fixation (ORIF), percutaneous screw fixation, or bone graft. However, failure rate can be high.

Definition

(i) Open reduction and internal fixation (ORIF) is surgery where bones are set, consisting of fixation with nails, screws or plates often made from titanium. (ii) Percutaneous procedures are those performed by inserting a needle or other instrument through the skin rather than cutting the skin open with a scalpel.

Successful union has been shown in 90% of patients treated with a Herbert differential pitch screw (which is completely buried in the bone) combined with bone grafting (Bunker, McNamee and Scott, 1987). This type of fixation significantly reduces the time to return to active sport. With fixation, return in some athletes is immediate, but on average 4.3 weeks. Athletes treated non-operatively with a playing cast return on average in 11 weeks (Rettig, Weidenbener and Gloyeske, 1994). In a systematic review (12 studies met the inclusion criteria out of 112 initially considered), Modi et al. (2009) found percutaneous fixation to give faster rates of union and an earlier return to sport (mean 7 weeks) compared with cast immobilization.