Fractures of the distal radius account for 20% to 35% of all childhood fractures1–3 and 80% of pediatric forearm fractures. Up to one-third of these injuries involve the distal radial physis.4 The rapid growth of the distal radial physis, which accounts for 75% to 80% of the growth of the radius, and continual transformation of the metaphysis in part explains the propensity for fractures in this location and also explains the huge potential for fracture remodeling.5 Injuries of the distal ulnar physis are less common and are usually associated with fractures of the distal radius when they do occur. The most common cause of distal forearm injuries are a fall on an outstretched hand. Extension of the wrist at the time of injury causes the distal fragment to be displaced dorsally. Volar displacement of the distal fragment is usually the result of a fall on a flexed wrist. The degree of displacement is directly proportional to the energy transfer associated with a causative event. In general, these injuries are managed by closed reduction and casting with excellent results. Indications for pinning or open reduction of these fractures will be addressed. Complications are infrequent but not insignificant and usually treatable with early recognition and appropriate intervention.
DISTAL RADIUS METAPHYSEAL FRACTURES
Fractures of the distal radial metaphysis rarely require operative management. They tend to heal rapidly and remodel predictably. Nondisplaced fractures can be effectively treated closed with long-arm or short-arm cast immobilization for 4 to 6 weeks. Displaced fractures of the distal radius with less than 15 degrees angulation in children under 10 years of age (<10 degrees otherwise) can also be treated closed without manipulation in the expectation of remodeling by 6 to 9 months.6 On occasion, these fractures can displace further and so careful radiographic monitoring during healing is appropriate. Fractures with angulation of more than 15 degrees (any age), initial displacement of more than 30%, or shortening of more than 1 cm usually need to be reduced. These fractures tend to be unstable and repeat manipulation to address loss of reduction is necessary in up to one-third of patients.7–9 Poor cast technique and residual angulation/displacement after the initial reduction are 2 major factors that have been implicated in subsequent loss of alignment. Recent studies by Bohm et al10 and Webb et al11 have shown short arm casts to be sufficient to immobilize these injuries provided that the cast is molded to resist reangulation and displacement of the fracture.
Factors associated with loss of reduction include poor casting technique; the presence of an isolated, displaced fracture of the radius; concomitant displacement or plastic deformation of the ulna; and initial fracture angulation greater than 30 degrees. Chess et al reported a series of 761 distal fractures treated in a short-arm plaster cast following closed reduction. The average change in angulation during the course of treatment was 4.5 degrees, and in each instance that angulation changed more than 5 degrees, poor cast molding was evident.12 Proctor et al8 reported loss of reduction in 34% of patients that correlated most closely with complete initial displacement of the fracture or failure to achieve anatomic reduction. In a series reported by Mani et al,13 loss of reduction was noted in 29% of patients and over half (60%) were fractures with initial displacement of more than 50%. Gibbons et al published a prospective study of 23 patients with isolated radial fractures who were randomized to either closed reduction and casting or closed reduction, percutaneous pinning, and casting. Ten of the 11 fractures (91%) treated with closed manipulation and immobilization required repeat manipulation for the loss of reduction. The investigators recommended that strong consideration be given to treating isolated, displaced radial metaphyseal fractures by closed reduction and percutaneous fixation. McLaughlin et al14 and Miller et al15 in their prospective pinning versus cast treatment both found equivalent results at 2 years follow-up. Both studies conclude that surgeon preference for care by closed reduction and casting or closed reduction and pinning is reasonable.
On the basis of these observations, the following algorithm for the treatment of distal radius fractures is suggested. Fractures with less than 10 to 15 degrees angulation and less than 1 cm of shortening can be treated without manipulation. Fractures that are angulated more than 10 to 15 degrees usually need to be manipulated and immobilized in a well-molded long-arm or short-arm cast. In both situations, close radiographic monitoring for 3 weeks is appropriate to assess for unacceptable loss of alignment and need for realignment. Closed reduction and percutaneous pin fixation can be considered when initial angulation is greater than 30 degrees or initial displacement is greater than 50%. A “floating elbow” with ipsilateral distal forearm and elbow region injuries is an indication for pin stabilization of both fractures to prevent compartment syndrome. Primary open reduction is indicated in open fractures after debridement, in irreducible fractures with soft-tissue interposition,16 and in the rare instances of neurovascular compromise (acute median neuropathy, tunnel syndrome, or forearm compartment syndrome).17 Limited fixation with a single or crossed pins after closed or open reduction of the fracture is usually sufficient as an “internal splint” to maintain alignment in conjunction with a well-padded and molded cast or splint. Although it is preferable to avoid crossing the physis, transphyseal, small, smooth-pin placement may be unavoidable in distal metaphyseal fractures and is rarely problematic. The radial styloid and Lister's tubercle are both reliable bony landmarks for pin insertion.
DISTAL RADIAL PHYSEAL FRACTURES
Most injuries of the distal radial physis are preadolescent, Salter Harris II fractures. Standard treatment includes closed reduction and casting for fractures angulated at more than 10 to 15 degrees. Operative management is indicated for Salter Harris III and IV fractures to address both the physeal disruption and intra-articular displacement associated with theses injuries. Complications of these fractures are rare but potentially significant and include growth arrest and acute neurovascular compromise. Growth arrest may occur as a consequence of the fracture, reflecting a more severe injury mechanism, or as a result of treatment. In contrast to metaphyseal injuries, distal radial physeal fractures heal rapidly, and the remodeling potential of these injuries is far greater than injuries of the radial metaphysis, especially in children less than 10 years of age.18 For this reason, repeated closed or “late” (ie, after 7 d) open reductions of these fractures that risk iatrogenic injury to the physis should be avoided.19,20 Malunion of these fractures with residual deformity in the plane of motion of the wrist joint will predictably remodel as long as the physis is not damaged. Residual (often progressive) angulation and radioulnar length discrepancy are problems caused by partial or complete growth plate arrest. An osteotomy of the distal radius may be performed if there is symptomatic malunion with residual angulation of greater than 10 degrees (Fig. 1). Treatment of radioulnar length discrepancy may require physeal bar resection, ulnar epiphysiodesis, radial lengthening/ulnar shortening, or some combination of these procedures (Figs. 2 and 3).
Acute median neuropathy and, more rarely, acute forearm compartment syndrome are potential neurovascular complications of these injuries. Waters et al published a retrospective case series highlighting the occurrence of acute median neuropathy after physeal fractures of the distal radius. They noted that median nerve injury caused by the initial trauma can be potentiated by the use of hematoma block anesthesia for fracture reduction, additional iatrogenic trauma from forceful or repetitive attempts at reduction, external compression from a constricting cast or splint, or immobilization of the wrist in volar flexion. Acute carpal tunnel syndrome may occur by compression of the median nerve between the transverse carpal ligament and displaced distal radial metaphysis as the nerve enters the carpal canal (Fig. 4). These symptoms are sometimes hard to differentiate from acute forearm compartment syndrome, which is extremely rare following fractures of the distal radius, and can be diagnosed by the measurement of compartment pressures. An important caveat is to measure the compartment pressures away from the fracture site and hematoma, where pressures will always be elevated. When any of these causes of acute neurovascular compromise is present, the fracture should be treated by closed reduction and percutaneous pinning to stabilize the bony injury and relieve tension on the median nerve. If median nerve symptoms persist, exploration of the fracture and decompression of the median nerve to include the release of the carpal tunnel and/or Guyon's canal is indicated and prophylactic fasciotomy should be considered. If forearm compartment pressures are elevated, fasciotomy is obviously necessary.17
DISTAL ULNAR PHYSEAL AND GALEAZZI FRACTURES
Isolated injuries of the distal ulna physis are somewhat rare and are more frequently associated with fractures of the radius. Distal ulnar physeal arrest following trauma has been well documented in the literature, but symptoms are infrequent and minimal.19,21–23 True Galeazzi injuries—fracture of the distal radius and disruption of the ligamentous stabilizing system between the radius and ulna, which includes the triangular fibrocartilage complex, interosseous ligaments and periosteal tube of the ulna—are also relatively uncommon in children. Walsh et al24 found only 41 (3%) Galeazzi injuries in a series of 1453 distal radius fractures in children. More common than the classic presentation in children is the so-called “Galeazzi-equivalent” or “pseudo-Galeazzi” fracture wherein the injury to the ulna is a disruption (fracture or separation) of the distal ulnar physis without rupture of the ligamentous stabilizing system of the distal radioulnar joint (Fig. 5).25,26 The key to successful treatment of these fractures is to accurately diagnose the injury in a timely manner. In Walsh's series, 24 of the 41 Galeazzi injuries were initially missed.24 Most of these Galeazzi-equivalent injuries can be treated with closed reduction of the radius fracture, closed reduction of the ulnar physeal fracture, and immobilization of the forearm in supination to restore/maintain proper alignment of the distal radioulnar joint. On the rare occasions when the distal ulna cannot be acceptably aligned, the most common impediments to reduction are entrapped extensor tendons or interposed periosteum. In these instances, open reduction of the ulnar physeal fracture and pin fixation to stabilize the fracture and, indirectly, the distal radial ulnar joint is indicated. If after these maneuvers the radioulnar joint is unstable, reduction in supination and pin fixation may be necessary to address disruption of the ligamentous stabilizing system. Malunion of the radius with shortening and/or angulation of more than 10 degrees can result in loss of forearm rotation and painful subluxation or instability of the distal radioulnar joint, but these sequelae are rare in children.
CONCLUSION: PINNING INDICATIONS FOR DISTAL RADIUS AND ULNA FRACTURES
- “Floating elbow” injuries.
- Neurovascular compromise associated with distal radius and ulnar fractures.
- Relative indication of greater than 30 degrees angulation, or more than 50% displacement. Surgeon preference is acceptable.
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