Rockwood Children CH8

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CHAPTER 8 • Fractures of the Distal Radius and Ulna

been shown to decrease the injury rate in snowboarders, espe- cially beginners and persons with rental equipment. 175 As cited above, there is seasonal variation, with an increase in both incidence and severity of fractures in summer. 203 Children who are overweight, have poor postural balance, ligamentous laxity, or less bone mineralization are at increased risk for distal radial fractures. 83,117,123,167,182,214 Although bone quality measures predict that boys had lower risk of fracture than girls at every stage except during early puberty, 147 these fractures have been reported to be three times more common in boys. This may be due to relative risk-taking behaviors or participation in higher risk of injury activities. However, the increased participation in athletics by girls at a young age may change this ratio. Radial Physeal Stress Fractures Repetitive axial loading of the wrist may lead to physeal stress injuries, almost always involving the radius (Fig. 8-4). These physeal stress injuries are most commonly seen in competi- tive gymnasts. 29,47,52,193,194 Factors that predispose to this injury include excessive training, poor techniques, and attempts to advance too quickly in competitive level. Stress injuries have been also observed in other sports including wresting, break dancing, and cheerleading. 76 Galeazzi Fracture Axial loading of the wrist in combination with extremes of forearm rotation (Fig. 8-5) may result in distal radius fractures with associated disruption of the DRUJ, the so-called “pediatric Galeazzi fracture.” 26,40,72,122,127,137,201 In adults, the mechanism of injury usually is an axially loading fall with hyperpronation. This results in a distal radial fracture with DRUJ ligament dis- ruption and dorsal dislocation of the ulna. However, in chil- dren, both supination (apex volar) and pronation (apex dorsal) deforming forces have been described. 126,200 The mechanism of injury is most obvious when the radial fracture is incomplete. With an apex volar (supination) radial fracture, the distal ulna is displaced volarly; whereas with an apex dorsal (pronation) radial fracture, the distal ulna is displaced dorsally. This is evi- dent both on clinical and radiographic examinations. In addi- tion, the radius is foreshortened in a complete fracture, causing more radial deviation of the hand and wrist. In children, this injury may involve either disruption of the DRUJ ligaments or, more commonly, a distal ulnar physeal fracture (Fig. 8-6). 1,172 B Figure 8-2.  Reverse bayonet. A: Typical volar bayonet fracture. Often the distal end of the proximal fragment is buttonholed through the extensor ten- dons ( arrows ). (Reprinted from Wilkins KE, ed. Operative Management of Upper Extremity Fractures in Children. Rosemont, IL: American Academy of Orthopaedic Surgeons, 1994:27, with permission.) B: Intact volar periosteum and disrupted dorsal periosteum ( arrows ). The extensor tendons are displaced to either side of the proximal fragment.

A

growth. 13 As 90% of the radius growth is from the distal physis and accounts for 70% of the loading across the wrist, the radius is more prone to fracture than the ulna during rapid growth. 202 Fractures occur at the biomechanically weakest anatomic loca- tion of bone, which also varies over time. As the metaphyseal cortex of the radius is relatively thin and porous, fractures of the metaphysis are most common, followed by physeal. 140,191 Usually, fractures occur during sports-related activities. Indeed, the trend toward increased sports participation in chil- dren has led to a substantial increase in the incidence of distal radius and/or ulna fractures. 102,213 Certain sports, such as skiing/ snowboarding, basketball, soccer, football, rollerblading/skating, and hockey have been associated with an increased risk of distal radial fracture, though a fall or injury of sufficient severity may occur in any recreational activity. 190 Protective wrist guards have

Figure 8-3.  A 10-year-old girl with an innocuous-appearing distal radial fracture associated with an ipsilateral angulated radial neck frac- ture ( arrows .)