Rockwood Children CH8

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CHAPTER 8 • Fractures of the Distal Radius and Ulna

Distal Ulna Fractures Isolated ulnar physeal fractures are rare, as most ulnar physeal injuries occur in association with radial metaphyseal or phy- seal fractures. 1,184 Physeal injuries are classified according to the Salter–Harris classification. 158 Ulnar physeal fractures may also be seen with the pediatric Galeazzi injuries, 171 which usually involve an ulnar physeal fracture rather than a soft tissue dis- ruption of the DRUJ. Avulsion fractures of the ulnar styloid also represent epiph- yseal avulsion injuries. Most commonly associated with distal radial fractures, 1,184 these styloid fractures typically represent soft tissue avulsions of the ulnar insertion of the TFCC or ulno- carpal ligaments 12 and are rarely associated with growth-related complications.

progressively elongates with advancing skeletal maturity. The secondary center of ossification for the distal ulna appears at about age 7 years. 149 Similar to the radius, the ulnar styloid appears with the adolescent growth spurt. It also becomes more elongated and adult-like until physeal closure. On average, the ulnar physis closes at age 16 in girls and age 17 in boys, whereas the radial physis closes on average 6 months later than the ulnar physis. 174,222 The distal radial and ulnar physes con- tribute approximately 75% to 80% of the growth of the forearm and 40% of the growth of the upper extremity (Fig. 8-18). 150 The distal radius articulates with the distal ulna at the DRUJ. 179 Both the radius and ulna articulate with the carpus, serving as the platform for the carpus and hand. The radial joint surface has three concavities for its articulations: the scaphoid and lunate fossa for the carpus and the sigmoid notch for the ulnar head. These joints are stabilized by a complex series of volar and dorsal radiocarpal, ulnocarpal, and radioulnar liga- ments. The volar ligaments are the major stabilizers. Starting radially at the radial styloid, the radial collateral, radioscapho- capitate, radiolunotriquetral (long radiolunate), and radios- capholunate (short radiolunate) ligaments volarly stabilize the radiocarpal joint. The dorsal radioscaphoid and radial triquetral ligaments are less important stabilizers. The complex structure of ligaments stabilize the radius, ulna, and carpus through the normal wrist motion of 120 degrees of flexion and extension, 50 degrees of radial and ulnar deviation, and 150 degrees of forearm rotation. 152 The TFCC is the primary stabilizer of the ulnocarpal and radioulnar articulations. 152 It extends from the sigmoid notch of the radius across the DRUJ and inserts into the base of the ulnar styloid. It also extends distally as the ulnolunate, ulnotriquetral, and ulnar collateral ligaments and inserts into the ulnar carpus and base of the fifth metacarpal. 152 The volar ulnocarpal liga- ments (V ligament) from the ulna to the lunate and triquetrum are important ulnocarpal stabilizers. 22,180 The central portion of the TFCC is the articular disk (Fig. 8-19). The interaction between the bony articulation and the soft tissue attachments accounts for stability of the DRUJ during pronation and supina- tion. 153 At the extremes of rotation, the joint is most stable. The compression loads between the radius and ulna are aided by the tensile loads of the TFCC to maintain stability throughout rotation. The interosseous ligament of the forearm (Fig. 8-20) helps stabilize the radius and ulna more proximally in the diaph- ysis of the forearm. The ulna remains relatively immobile as the radius rotates around it. Throughout the mid-forearm, the interosseous ligament connects the radius to the ulna. It passes obliquely from the proximal radius to the distal ulna. However, the interosseous ligament is not present in the distal radius. Moore et al. 142 found that injuries to the TFCC and interos- seous ligament were responsible for progressive shortening of the radius with fracture in a cadaveric study. The soft tissue component to the injury is a major factor in the deformity and instability in a Galeazzi fracture–dislocation. The length relationship between the distal radius and ulna at the wrist is defined as ulnar variance. In adults, this is mea- sured by the relationship of the radial corner of the distal ulnar articular surface to the ulnar corner of the radial articular

Galeazzi Fracture

Galeazzi Fractures: CLASSIFICATION

Type I: Dorsal (apex volar) displacement of distal radius Radius fracture pattern Greenstick Complete Distal ulna physis Intact Disrupted (equivalent) Type II: Volar (apex dorsal) displacement of distal radius Radius fracture pattern Greenstick Complete Distal ulna physis Intact Disrupted

Galeazzi fracture–dislocations are most commonly described by direction of displacement of either the distal ulnar dislocation or the radial fracture. 126 Letts preferred to describe the direc- tion of the ulna: volar or dorsal. 77,200 Others classified pediatric Galeazzi injuries by the direction of displacement of the distal radial fracture. Dorsally displaced (apex volar) fractures were more common than volarly displaced (apex dorsal) injuries in their series. Wilkins and O’Brien 211 modified the Walsh and McLaren method by classifying radial fractures as incomplete and complete fractures and ulnar injuries as true dislocations versus physeal fractures. DRUJ dislocations are called true Galeazzi lesions and distal ulnar physeal fractures are called pediatric Galeazzi equivalents. 109,121,126

PATHOANATOMY AND APPLIED ANATOMY RELATING TO FRACTURES OF THE DISTAL RADIUS AND ULNA

The distal radial epiphysis normally appears between 0.5 and 2.3 years in boys and 0.4 and 1.7 years in girls. 73,138,149 Ini- tially transverse in appearance, it rapidly becomes more adult- like with its triangular shape. The contour of the radial styloid