INCIDENCE

The most common upper extremity fractures are those of the metacarpals and phalanges. In a series of 4303 patients presenting to the emergency room with fractures, 19% had hand fractures.¹ The phalanges were most commonly fractured. Males between the ages of 15 and 35 were most commonly injured. Fractures of the little finger ray were most common.

Hove, in a series of 1000 consecutive patients, found that metacarpals, phalanges, and carpal bones accounted for 36%, 46%, and 18% of the fractures, respectively.² Chung and Spilson analyzed data from the 1998 National Hospital Ambulatory Medical Care Survey and estimated that in 1998, there were more than 600,000 metacarpal and phalangeal fractures in the United States.³

Fractures in children follow different patterns in various age groups because of differing mechanisms of injury. In a review of 242 hand fractures, Mahabir et al. found that 75% of injuries were in males, the mean age being 11 years.⁴ The incidence of fractures was very low in the very young, rose sharply at age 9, and peaked at 12 years. Forty percent were epiphyseal fractures, predominantly Salter-Harris II. The fifth metacarpal was the most frequently fractured bone.

The incidence of hand injuries in polytrauma was studied by Schaller and Geldmacher.⁵ They noted a 20% incidence of associated hand injuries, 75% of which were closed fractures. Ninety-three percent were involved in motor vehicle accidents.

MECHANISM OF INJURY

Chung and Spilson described the cause of injury in hand and forearm fractures.³ Forty-seven percent of injuries were due to falls, while 15% were due to being struck by a person or object. Ten percent were due to vehicular accidents. Other causes included being caught between objects, accidents involving machines or tools, injury due to another person, and nontraffic motor vehicle accidents.

De Jonge et al. studied the incidence and etiology of 6857 phalangeal fractures.⁶ They found that falls were responsible for most injuries in patients 70 years or older, while sports were the main cause in the age group 10–29 years. The highest incidence was in males aged 40–70 years, and the cause was machinery. Over 45% of hand fractures in children occurred either during sports or in a fight.

DIAGNOSIS

Management of hand injuries requires a good understanding of hand anatomy and biomechanics. The individual needs of the patient need to be taken into account before devising a treatment plan. A detailed history needs to be obtained. Key points to be elicited are noted in Table 2.

Table 2 History in Hand Injuries

Examination of the hand should assess deformity, tenderness, instability, sensation, and vascularity of the finger. The condition of the skin and soft tissues should be evaluated, including an assessment for injury to the tendons. It is particularly important to assess the finger cascade. On flexion of the fingers to make a fist, the tips of the fingers should converge toward the scaphoid. Scissoring of the fingers indicates rotational malalignment. Evaluation of stability is necessary to rule out ligamentous injury. This is done after administration of local anesthetic to prevent pain and reflex muscle spasm. The congruity of the joint is assessed during active motion and passive stress. Partial injuries can be treated by immobilization, while complete tears may require surgical repair.

Three views are necessary for adequate radiologic evaluation: anteroposterior, lateral (with the fingers fanned out), and an oblique view. The lateral view obtained in this manner, however, shows, at best, one finger in a true lateral position. Hence, it is better to get lateral views of individual fingers. Very rarely, special views of the hand are necessary to assess certain injuries. Occasionally, stress views of joints are used—for example, to evaluate collateral ligament injuries of the thumb metacarpophalangeal joint.

METACARPAL FRACTURES

The metacarpals are structurally divided into the head, neck, shaft, and base. The metacarpal head articulates with the base of the proximal phalanx. The collateral ligaments between the metacarpal and phalanx arise in an eccentric position. Hence, these ligaments are stretched in flexion and lax in extension, and the joint is stable in flexion (Figure 1). The thumb metacarpal and fourth and fifth metacarpals are mobile. Because of its unique anatomy, thumb fractures are dealt with separately. Common metacarpal fracture patterns are illustrated in Figure 2.

Figure 1 Metacarpophalangeal joint anatomy. The collateral ligaments arise in an eccentric fashion on the metacarpal head, resulting in a stable position in flexion.

Figure 2 Common fracture patterns. (A) Transverse. (B) Spiral. (C) Comminuted. (D) Neck. (E) Intra-articular.

Metacarpal Shaft Fractures

Transverse fractures are caused by axial loading or direct blows. Because of the pull of the interossei, the fracture angulates dorsally. Patients can accept some angulation of the fourth and fifth metacarpals because of mobility. Greater than 30-degree angulations of the fifth metacarpal, 20 degrees in the fourth metacarpal, and any angulation in the second and third metacarpals require reduction. Oblique and spiral fractures, on the other hand, cause rotational malalignment. This is poorly tolerated, because the fingers overlap each other when the fingers are flexed. Transverse fractures are inherently stable, while spiral and oblique fractures are not.

Most metacarpal shaft fractures can be managed nonoperatively. The fracture is reduced if needed, and the hand is immobilized in the so-called safe position, with the wrist in 30–40 degrees of extension, the metacarpophalangeal joints in 80–90 degrees of flexion, and the interphalangeal joints in extension. Immobilization is maintained for 3–4 weeks and is followed by active mobilization.

Open reduction is indicated when the fracture is malaligned or unstable. Open fractures and those with associated soft tissue injuries are also best treated by open reduction. This permits earlier mobilization to prevent stiffness. With multiple metacarpal fractures, the stabilizing influence of the adjacent metacarpals is lost, and such fractures may need open reduction and internal fixation. Various techniques are available to stabilize fractures. Spiral or long oblique fractures can be stabilized by lag screws (Figure 3). The length of the fracture line should be at least twice the diameter of the bone. The proximal hole is overdrilled to a diameter wider than the thread of the screw. As the screw is tightened and the threads grip the distal fragment, interfragmentary compression is achieved.

Figure 3 (A) Metacarpal shaft fracture sustained in a fist fight. (B) Fixation with three lag screws.

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