INTRODUCTION

Carpal fractures were originally thought to be relatively uncommon in children, but there has been an increasing recognition of such injuries over the past decade. However, it is still accurate to state that fractures and dislocations of the carpus in children are exceptionally rare. Indeed, only 10 lines in Mercer Rang’s classic textbook on children’s fractures are devoted to such injuries.

The fact that carpal injuries are relatively uncommon is due to the fact that the carpus in the child is largely cartilaginous and therefore relatively immune to injury. As a result, considerable forces are required to injure the essentially unossified carpal bones. Thus, biomechanically, a fall on an outstretched hand is more likely to result in an injury to the distal radius and physis rather than the individual carpal bones. However, as ossification progresses, the individual bones become more susceptible to fracture and soft tissue (ligamentous) injury, so that by early adolescence most of the carpus is completely ossified, and the fracture patterns become similar to the adult type of injury.

The most common fracture in a child is to the distal pole of the scaphoid, and it is most likely to be a dorsoradial avulsion. Fractures of the waist of the scaphoid are less common, whereas fractures of the proximal pole are virtually unknown. Fractures of the other carpal bones are relatively uncommon. Nafie reported a series of 82 fractures in children of which 71 of the fractures were isolated to the scaphoid. The remaining 7 carpal bones accounted for only 11 fractures, and 5 of these involved the triquetrum. There were no capitate fractures reported in this series, and indeed isolated capitate fractures are rare and are usually associated with fractures of the scaphoid, the so-called scaphocapitate syndrome.

It is perhaps more likely that despite the presence of the usual physical signs, the injury may be missed or diagnosis delayed owing to the difficulties in interpreting the radiographs in an immature skeleton. Nafie found that the initial radiograph failed to reveal the fracture in 37% of cases. This was further emphasized by Compson’s experience in reporting transcarpal injuries associated with distal radial fractures in which the extent of the original injury was not apparent on the original films. Therefore, one must have a high index of suspicion when faced with a wrist injury in a child.

SCAPHOID FRACTURES

As in the adult, scaphoid fractures in children are the most common of the carpal bone fractures, representing 0.45% of all upper limb fractures and 2.9% of hand and wrist fractures in children.

Fractures of the scaphoid are very rare in the first decade, but peak at around 15 years of age. This is probably because the ossification center is protected by thick peripheral cartilage. The ossification center usually appears in children by 5 to 6 years of age, and full ossification is complete by age 13 to 15 years.

A scaphoid fracture is generally the result of a fall onto an outstretched hand, with tensile forces coming to act across the scaphoid. The clinical presentation does not differ from that of adults, although the misdiagnosis rate is higher because the fractures are relatively rare in childhood and the index of suspicion is low. As with adult injuries, many of these fractures may not be immediately apparent on the initial films but are more obvious on radiographs performed 2 to 3 weeks later. However, one should be aware of the possibility of a congenital bipartite scaphoid. This condition is generally bilateral, and there is no history of trauma. Occasionally, advanced imaging studies such as magnetic resonance imaging (MRI) may be necessary to confirm the diagnosis.

The patterns of scaphoid fractures are somewhat different in the skeletally immature child. Thus, the classic mid-waist fracture is seldom seen in childhood, largely because of the eccentric ossification pattern. Only adolescents demonstrate patterns of scaphoid injuries similar to those shown in adults, and proximal pole fractures, when they occur, are usually associated with a more complex ligamentous injury involving the greater arc.

Fortunately, the majority (60% to 85%) of scaphoid fractures in children are nondisplaced or minimally displaced fractures of the distal pole (avulsion injuries), which heal successfully after 4 to 6 weeks of cast immobilization. Although a standard forearm cast, with or without the thumb included, is usually sufficient, an above-elbow cast may be appropriate in younger children to prevent the cast from falling off. Scaphoid fractures that are displaced may require open reduction and some form of internal fixation to minimize the risk of nonunion.

Tubercle or avulsion fractures should be treated by immobilization in a short-arm cast for 3 to 4 weeks. It may be necessary to immobilize distal pole fractures for up to 5 weeks, with 7 to 8 weeks necessary for fractures through the waist.

Nonunion of scaphoid fractures in children is rare and mainly clustered around the 11- to 15-year age group. It invariably involves the waist and is generally attributed to delay or indeed failure of diagnosis. Acute scaphoid fractures that are correctly treated by prompt immobilization have a very low (0.8%) nonunion rate.

Nonunion can be classified into two groups: (1) undiagnosed and therefore untreated fractures, and (2) diagnosed fractures that did not unite despite appropriate treatment. In cases of nonunion following a delay/failure to diagnose, cast immobilization supplemented by electromagnetic stimulation or extracorporeal shockwave has been shown to be beneficial.

It is recommended that patients who have not responded to appropriate immobilization are best treated by open reduction and Matti-Russe-type bone grafting. We have the experience of treating two cases of nonunion of the scaphoid in adolescents using percutaneous bone grafting and fixation. Overall, the results of open fixation and grafting are excellent with restoration of virtually normal motion and function. No major complications have been reported from surgical intervention of scaphoid fractures in children, nor have there been any reports about the possibility of growth disturbance of the scaphoid after screw fixation.

CAPITATE FRACTURES

Fractures of the capitate are the second most frequently encountered injury to the child’s wrist, but they rarely occur in isolation. These fractures either result from a hyperextension-type injury with compression of the capitate on the lunate or distal radius or from a high-energy trauma. Young reported a single case of an isolated fracture of the body of the capitate in a 10-year-old child, who was treated by cast immobilization. Fortunately, the injuries generally involve minimal displacement and heal with simple cast immobilization, although displaced fractures may require open reduction and internal fixation. It is interesting that there have been recent reports of MRI findings of edema in the capitate associated with scaphoid fracture, which suggests a forme fruste scaphocapitate-type injury.

Capitate fractures are generally associated with injuries to the other carpal bones, in particular fractures of the scaphoid—the so-called scaphocapitate syndrome. This is an injury in which there is a fracture through the waist of the scaphoid and a fracture through the neck of the capitate, often associated with 90 to 180 degrees of rotation of the head of the capitate. This injury has been well described in adults but is relatively rare in children and generally results when the child falls from a height, landing heavily on the wrist in a forced dorsiflexed position.

It has been proposed that the impact results in a trans-scaphoid transcapitate perilunate fracture-dislocation that reduces spontaneously but only partially, and hence causing the rotatory injury to the proximal capitate. Given the inherent elasticity of the soft tissues, this mechanism is likely in children. The diagnosis is often hampered by the fact that the carpal bones in children are only partially ossified. Thus, awareness of the rare injury in children is necessary to avoid misdiagnosis and to institute timely treatment.

Fortunately, most fractures of the capitate heal uneventfully with a period of cast immobilization, even when associated with other carpal injuries. However, significantly displaced or complicated injuries require prompt open reduction, restoration of normal anatomy, and internal fixation. This is due to the fact that both the capitate and the scaphoid have a retrograde blood supply, and delay may result in avascular necrosis of the proximal pole of both bones.

Nonunion of a capitate fracture is rare, and it has been treated by bone grafting and internal fixation.

FRACTURES OF THE LUNATE

Isolated fractures of the lunate are in general extremely rare, and case reports referring to this injury are only sporadic. De Smet and associates reported a case of a transverse fracture of the lunate with marked displacement, requiring open reduction and osteosynthesis. The lunate became necrotic with all the features of Kienböck’s disease. However, to the best of my knowledge, true Kienböck’s disease has not been described in children.

Most injuries are the classic perilunate injuries with a pattern of injury similar to that seen in the adult, either in the form of an isolated lunate dislocation, which may be combined with a distal radial epiphyseal fracture, or trans-scaphoid perilunate dislocations. The diagnosis may go unnoticed because of the patterns of ossification. Acute injuries can usually be reduced by closed reduction and then held with either simple cast immobilization or wire fixation. The associated ligamentous injuries usually heal uneventfully without progression to the classic instability patterns.

FRACTURES OF THE TRAPEZIUM AND TRAPEZOID

Fractures of either the trapezium or the trapezoid are rare injuries in children. It is possible that direct palmar trauma could result in a fracture of the trapezial ridge. A hyperextension-type force may result in a dorsal impaction fracture or ligament avulsion. Simple cast immobilization is all that is required.

FRACTURE OF THE HAMATE

Fractures of the hamate generally result from a fall with the impact on the ulnar border of an outstretched hand, a crush injury, or a direct blow to the ulnar border of the hand, as occurs when attempting to catch a hard ball such as a cricket ball or baseball. This mechanism of injury would generally result in a fracture of the hook of the hamate. The diagnosis is made by point-specific tenderness over the hook of the hamate in the palm and confirmed on carpal tunnel views or computed tomography (CT). Symptomatic support is all that is usually required, and although nonunion of the hook of the hamate is possible, there is usually no indication for surgical intervention.

The fractures of the body of the hamate may be associated with injuries occurring to the hamate-metacarpal articulation, where there is often an avulsion injury with associated displacement of the base of the fourth and/or fifth metacarpals equivalent to a Lisfranc-type fracture-dislocation.