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CHAPTER 8 • Fractures of the Distal Radius and Ulna

are treated with closed reduction and there is failure to either obtain or maintain reduction of the radial fracture. The ulna remains subluxed and heals with an incongruent joint. Treat- ment of this requires proper recognition and corrective oste- otomy. If physical examination is not definitive for diagnosis, then a CT scan in pronation, neutral rotation, or supination may be helpful. MRI or wrist arthroscopy will aid in the diag- nosis and management of associated ligamentous, chondral, or TFCC injuries that will benefit from debridement or repair. It is important to understand that if the DRUJ subluxation is caused by a radial malunion, a soft tissue reconstruction of the DRUJ alone will fail. In the true soft tissue disruption, repair of the TFCC will often stabilize the DRUJ. If there is no TFCC tear, soft tissue reconstruction of the DRUJ ligaments with extensor retinaculum or local tendon is appropriate. NONUNION Nonunion of a closed radial or ulnar fracture is rare. In children, nonunion has been universally related to a pathologic condi- tion of the bone or vascularity. 27,84 Congenital pseudarthrosis or neurofibromatosis (Fig. 8-53) should be suspected in a young patient with a nonunion after a benign fracture. 111 This occurs most often after an isolated ulnar fracture. 81,185 The distal bone is often narrowed, sclerotic, and plastically deformed. These fractures rarely heal with immobilization. Vascularized fibular bone grafting usually is necessary for healing of a nonunion associated with neurofibromatosis or congenital pseudarthrosis.

If the patient is very young, this may include a vascularized epiphyseal transfer to restore distal growth. Vascular impairment also can lead to nonunion. Distal radial nonunion has been reported in a child with an ipsilateral supra- condylar fracture with brachial artery occlusion. Revasculariza- tion of the limb led to eventual union of the fracture. Nonunion also can occur with osteomyelitis and bone loss. 25 Debridement of the necrotic bone and either traditional bone grafting, osteo- clasis lengthening, vascularized bone grafting, or creation of a single-bone forearm are surgical options. The choice depends on the individual patient. CROSS-UNION Cross-union, or posttraumatic radioulnar synostosis, is a rare com- plication of pediatric distal radial and ulna fractures. It has been described after high-energy trauma and internal fixation. 198,199 A single pin crossing both bones increases the risk of cross-union. 199 Synostosis take-down can be performed, but the results usually are less than full restoration of motion. It is important to deter- mine if there is an element of rotational malunion with the cross- union because this will affect the surgical outcome. Soft tissue contraction across both bones also has been described. 66 Contracture release resulted in restoration of fore- arm motion. REFRACTURE Fortunately, refractures after distal radial fractures are rare and much less common than after pediatric diaphyseal level radial and ulna fractures and fractures in adults. This is likely due to the unique biology in children where, as opposed to adults, remin- eralization after forearm fractures in children occurs rapidly with a transient elevation in bone mineral density. 71 Most commonly, refracture occurs with premature discontinuation of immobiliza- tion or early return to potentially traumatic activities. It is advis- able to protectively immobilize the wrist until full radiograph and clinical healing (usually 6 weeks) and to restrict activities until full motion and strength are regained (usually an additional 1 to 6 weeks). Individuals involved in high-risk activities, such as downhill ski racing, snowboarding, or skateboarding, should be protected with a splint during those activities for much longer. PHYSEAL ARREST OF THE DISTAL RADIUS Distal radial physeal arrest can occur from either the trauma of the original injury (Fig. 8-54) 3,8,96 or late reduction of a displaced fracture. The incidence of radial growth arrest has been shown to be 4% to 5% of all displaced radial physeal fractures. 12,27,126 The trauma to the physeal cartilage from displacement and compression is a significant risk factor for growth arrest. How- ever, a correlation between the risk of growth arrest and the degree of displacement, type of fracture, or type of reduction has yet to be defined. Similarly, the risk of further compromising the physis with late reduction at various time intervals is still unclear. The current recommendation is for an atraumatic reduction of a displaced physeal fracture less than 7 days after injury. When a growth arrest develops, the consequences depend on the severity of the arrest and the amount of growth remaining.

Figure 8-53.  This 3 year old presented to the emergency room with pain after an acute fall on his arm. The ulna is clearly pathologic with thinning and deformity before this injury. This represents neurofibroma- tosis. (Courtesy of Children’s Orthopaedic Surgery Foundation.)