Rockwood Children CH8

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SECTION TWO • Upper Extremity

Metaphyseal Injuries

intact surrounding periosteum. Rarely, they may extend into the physis, putting them at risk for growth impairment. 157–159 Incomplete or greenstick fractures occur with a combination of compressive, tensile, and rotatory forces, resulting in com- plete failure of one cortex and plastic deformation of the other cortex. Most commonly, the combined extension and supina- tion forces lead to tensile failure of the volar cortex and dorsal compression injury. The degree of force determines the amount of plastic deformation, dorsal comminution, and fracture angu- lation and rotation. With greater applied loads, complete fracture occurs with disruption of both the volar and dorsal cortices. Length may be maintained with apposition of the proximal and distal frag- ments. Frequently, the distal fragment lies proximal and dorsal to the proximal fragment in bayonet apposition. Ulna fractures often associated with radial metaphyseal injuries may occur in the metaphysis, physis, or through the ulnar styloid. Similar to radial metaphyseal fractures, the ulnar fracture can be complete or incomplete. These inju- ries are also characterized according to fracture pattern and displacement. Distal radial fractures also can occur in conjunction with more proximal forearm fractures, 19,205 Monteggia fracture–dislocations, 18 supracondylar distal humeral fractures, 172,183 or carpal fractures. 32,41,91,119 The combination of a displaced supra- condylar distal humeral fracture and a displaced distal radial metaphyseal fracture has been called the pediatric floating elbow. This injury combination is unstable and has an increased risk for malunion and neurovascular compromise including compartment syndrome.

Distal Metaphyseal Fractures: CLASSIFICATION

Directional displacement Dorsal Volar Fracture combinations Isolated radius Radius with ulna

Ulnar styloid Ulnar physis

Ulnar metaphysis, incomplete Ulnar metaphysis, complete

Biomechanical patterns Torus

Greenstick One cortex Two cortices

Complete fracture Length maintained Bayonet apposition

Metaphyseal fracture patterns are classified as torus, incomplete or greenstick, and complete fractures (Fig. 8-17). This system of classification has been shown to have good agreement between experienced observers. 169 Torus fractures are axial compression injuries. The site of cortical failure is the transition frommetaph- ysis to diaphysis. 128 As the mode of failure is compression, these injuries are inherently stable and are further stabilized by the

A, B

C

Figure 8-17.  Metaphyseal biomechanical patterns. A: Torus fracture. Simple bulging of the thin cortex ( arrow ). B: Compression greenstick fracture. Angulation of the dorsal cortex ( large curved arrow ). The volar cortex is intact but slightly plastically deformed ( small white arrows ). C: Complete length maintained. Both cortices are completely fractured, but the length of the radius has been maintained. (Reprinted from Wilkins KE, ed. Operative Management of Upper Extremity Fractures in Children . Rosemont, IL: American Academy of Orthopaedic Surgeons; 1994:24, with permission.)