Rockwood Children CH8

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SECTION TWO • Upper Extremity

Because of the greater forces borne and imparted to the radius, as well as the increased porosity of the distal radial metaphysis, distal radial fractures are far more common than distal ulna fractures and so, isolated distal radius fractures do occur regularly. However, fractures of the distal ulna most often occur in association with fractures of the distal radius. 122,158 The metaphysis of the distal radius is the most common site of fore- arm fracture in children and adolescents. 13,116,122 The pediatric Galeazzi injury usually involves a distal radial metaphyseal frac- ture and a distal ulnar physeal fracture that result in a displaced distal radioulnar joint (DRUJ). Galeazzi fracture–dislocations are relatively rare injuries in children with a cited occurrence of 3% of pediatric distal radial fractures. 200 Given the frequency with which these injuries occur, the evaluation and management of distal radius and ulna fractures in children remain a fundamental element of pediatric orthope- dics. Despite established treatment principles, however, care of these injuries remains challenging due to the spectrum of injury patterns, issues of skeletal growth and remodeling, diversity of nonoperative and surgical techniques, evolving patient/family expectations, and increasing emphasis on cost-effective care.

forearm (Fig. 8-1). Conversely, axial loading on the flexed wrist will produce a volarly displaced fracture with apex dorsal angu- lation (Fig. 8-2). Occasionally, a direct blow sustained to the distal forearm may result in fracture and displacement. In addi- tion to the angular deformity caused by axial and bending loads applied to the distal forearm, rotational displacement may also occur, based on the position of the forearm and torsional forces sustained at the time of injury. Fracture type and degree of displacement are also dependent on the height and velocity of the fall or injury mechanism. 214 Indeed, the spectrum of injury may range from nondisplaced torus (or “buckle”) injuries (common in younger children with a minimal fall) or dorsally displaced fractures with apex volar angulation (more common in older children with higher-velocity injuries) (see Fig. 8-1). Displacement may be severe enough to cause foreshortening and bayonet apposition. Adult type inju- ries with intra-articular extension do occur. Rarely, a mechanism such as a fall from a height can cause a distal radial fracture asso- ciated with a more proximal fracture of the forearm or elbow (Fig. 8-3). 12,173 These “floating elbow” situations connote higher- energy trauma and as a result are associated with risks of neuro- vascular compromise and compartment syndrome. 12,173 Fractures of the distal forearm in children typically occur when the radius and/or ulna are more susceptible to fracture sec- ondary to biomechanical changes during skeletal development. Work based on load-to-strength ratio and other measures of bone quality has identified specific times during skeletal development where the biologic properties of the distal upper extremity pro- duce relatively weaker bone, making a child more susceptible to fracture. 65,109,118,147 In these studies, prepubescent boys and girls were found to have lower estimates of bone strength com- pared to same-sex postpubertal peers. From these studies, it can be concluded that children are uniquely susceptible for fracture when longitudinal growth outpaces mineral accrual during rapid

ASSESSMENT OF FRACTURES OF THE DISTAL RADIUS AND ULNA

MECHANISMS OF INJURY OF FRACTURES OF THE DISTAL RADIUS AND ULNA Distal Radius and Ulna Fractures

The mechanism of injury is generally a fall on an outstretched hand. Typically, the extended position of the wrist at the time of loading leads to tensile failure on the volar side of the distal

B

Figure 8-1.  A: Tension failure greenstick fracture. The dorsal cortex is plastically deformed ( white arrow ), and the volar cortex is complete and separated ( black arrows ). B: Dorsal bayonet.

A