Pediatric Distal Radius Fractures

INTRODUCTION

Children are not small adults, and pediatric distal radius fractures cannot always be treated by applying established principles for adult fractures. Children have unique anatomic structures particular to them. In addition, children have the capacity to remodel their bones, which influences fracture management. The surgeon must appreciate these unique characteristics when determining appropriate management, especially because pediatric distal radius fractures are common. The preponderance of severe wrist fractures has increased with the advent of the X Games and high-risk activities such as BMX (bicycle motocross) biking, skateboarding, and snowboarding. Many of these fractures are high velocity and widely displaced and include a large soft tissue element compared with low-energy injuries. Another contributing factor to distal radius fractures is childhood obesity. Overweight adolescents have poorer balance than healthy-weight adolescents, which explains their propensity for fracture.

Salter described a classification scheme for injuries to the epiphyseal plate that has received universal acceptance ( Box 66-1 ). As a general rule, the risk of growth arrest increases with each type. Most distal radius fractures are mildly displaced Salter-Harris type II fractures and are treated without surgery. In general, acceptable reduction is angulation less than 20 degrees with 2 years of growth remaining. In the young child, complete bayonet apposition is totally acceptable. In the older adolescent, lesser angulation is accepted. Operative intervention is indicated in certain fracture types. This chapter highlights fractures that require surgical intervention with an emphasis on indications and operative technique. The management of complications, such as growth arrest, is also discussed in detail.

BOX 66-1

Type I—fracture through the physis (widened physis)

Type II—fracture partway through the physis extending up into metaphysis

Type III—fracture partway through the physis extending down into the epiphysis

Type IV—fracture through the metaphysis, physis, and epiphysis; can lead to angulation deformities when healing

Type V—crush injury to the physis

SALTER-HARRIS CLASSIFICATION

PERTINENT ANATOMY

The pediatric skeleton has many distinctive features compared with that of adults. First and foremost is the presence of the physis, or growth plate, which provides longitudinal growth. The physis is divided into four zones: germinal, proliferative, hypertrophic, and provisional calcification. The hypertrophic and provisional calcification zones are relatively weaker than the germinal and proliferative layers. Classically, fracture lines tend to pass through the hypertrophic and provisional calcification zones. However, high-energy injuries may undulate through all four zones and cause considerable growth plate destruction.

The existence of secondary ossification centers is another distinguishing feature that can complicate fracture detection. The surgeon should be aware of the characteristics of the distal radius epiphysis. The distal radius epiphysis is absent at birth and appears when the child is approximately 1 year of age. Specifically, its appearance is between 0.5 and 2.3 years in boys and between 0.4 and 1.7 years in girls. The configuration of the epiphysis also changes with age. Initially, the epiphysis is transverse and becomes more triangular with time. The radial physis closes at approximately 16 years of age in girls and 17 years of age in boys. When there is doubt about the normal appearance of the radial epiphysis and the presence of a fracture, comparison x-rays or consulting a skeletal atlas is pivotal. The distal radius and ulnar physes contribute approximately 75% to 80% of the forearm growth and 40% of the entire upper extremity growth.

INDICATIONS FOR SURGERY

The primary surgical indications for pediatric distal radius fractures are irreducible fractures, displaced intra-articular fractures, and Galeazzi fracture-dislocations. Irreducible fractures require open reduction to remove the offending structure from the fracture site. In children, the interposed structure is most often the periosteum. Intra-articular fractures are relatively uncommon in children and often the result of high-intensity sports, such as BMX biking or snow- or skateboarding. The fracture pattern is usually a Salter-Harris III or IV fracture. The fracture can also occur through a closing physis in older children and can resemble an adult configuration with three or four distinct fracture fragments. As with adults, articular congruity must be restored to prevent traumatic arthritis and to reduce the chances of a physeal arrest. Galeazzi fractures are less common in children than in adults, but the treatment principles in adults and children are similar. The radius and distal radioulnar joint (DRUJ) require reduction. Unfortunately, the pediatric Galeazzi fracture-dislocation is often misdiagnosed and treated as an isolated radius fracture without appreciation of the DRUJ component. Subsequently, the patient fails to regain forearm rotation, and further evaluation reveals DRUJ injury.

Additional surgical indications for children are similar to those for adults, such as open fractures and fractures associated with nerve injuries such as carpal tunnel syndrome. Open fractures require thorough debridement and intravenous antibiotics to reduce the chances of infection. Regarding associated nerve injuries, the diagnosis is more difficult in children and adolescents than in adults ( Figs. 66-1 A and B and 66-2 A and B ). First, children do not recognize numbness as a sign of impending problems and do not relay the information to healthcare providers. Second, sensation is difficult to examine in the pediatric population, and two-point discrimination is unreliable until the child is about 9 years of age. Therefore, the physician must have a high index of suspicion for nerve compression after treatment of markedly displaced fractures. The treatment principles of fractures associated with nerve injuries are similar to those for adults. A distal radius fracture and concomitant acute carpal tunnel syndrome require nerve decompression and fracture stabilization.

Surgical considerations are subject to a variety of parameters unique to children. First, the timing of surgery is different in children compared with that for adults. Children heal much more quickly than adults and form abundant callus rapidly. Therefore, surgery should be performed within the first week after injury, if possible. Second, children have considerable potential to remodel, especially fractures about the physis. This remodeling is greater in young children and in the sagittal plane of motion. As a result, considerable angulation is acceptable in the young child compared with less angulation in the adolescent approaching skeletal maturity. Third, growth plate fractures directly injure the physis, and additional manipulation or surgery may further damage the growth potential. Repeat manipulations are particularly harmful to the physis and should be avoided. Children who present more than 1 week after injury or who have partially lost reduction represent a particular quandary. In such cases, the surgeon must compare and contrast the risk-benefit ratio of manipulation and/or surgical intervention on the growth plate with the inherent remodeling capacity of the child.

CONTRAINDICATIONS TO SURGERY

Contraindications to surgery stem from the indications noted in the previous section. The main factor that separates children from adults is the remodeling capacity of the immature skeleton. Displaced fractures that would require surgery in adults are often acceptable without surgery in children, especially fractures about the growth plate in the younger child and fractures that present late. At all costs, the surgeon must avoid doing more harm. Unnecessary surgery may further damage the growth plate and lead to considerable complications that are far greater than the initial fracture.

OPERATIVE TECHNIQUE

Standard Set-up for Children and Adolescents

General anesthesia is used for children undergoing fracture fixation. Airway control is a high priority, and children are less receptive to regional anesthesia. Adolescents are given the option of general or regional anesthesia. The child is placed in the supine position. An adult or pediatric tourniquet (Delfi Medical Innovations, Vancouver, Canada) is placed on the upper arm, depending on the size of the child. The pediatric-size tourniquet has a smaller diameter, prevents irritation in the antecubital fossa, and extends the surgical field. Preoperative antibiotics are routinely administered. The extremity is prepped and draped in sterile fashion.

Intra-articular Fractures

Fixation for Salter-Harris Fractures

Displaced Salter-Harris type III and IV fractures disrupt the joint surface and require surgery to restore anatomic alignment. The goal of internal fixation is intra-epiphyseal fixation with avoidance of the physis. Small-diameter screws are necessary, and use of a cannulated system may improve the accuracy of screw placement. If fixation must cross the physis, smooth pins are preferable to limit further physeal injury. Mini-fluoroscopy is an invaluable tool for assessing joint alignment and implant fixation. External fixation may be required to augment the internal fixation and to unload the joint surface until reasonable healing has occurred.

The specific approach varies according to the fracture configuration, and computed tomography (CT) may be necessary to delineate the precise fracture pattern ( Fig. 66-3 A–C ). In general, the approach is directed at the fracture fragment or fragments and direct visualization of the articular surface. A dorsal fragment requires a dorsal longitudinal incision along Lister’s tubercle. Sharp dissection is performed to the extensor retinaculum. Skin flaps are elevated from the retinaculum that contain the sensory nerves. The third compartment is opened, and the extensor pollicis longus is transposed in a radial direction. The posterior interosseous nerve is identified along the floor of the fourth compartment and resected. The second and fourth compartments are retracted radially and ulnarly, respectively.

A longitudinal capsulotomy is performed, and any hemarthrosis within the joint is evacuated. The capsulotomy may require extension into a T configuration to increase joint and fracture line exposure. The distal radial surface is exposed, and a reverse retractor is placed on the volar lip. The joint surface is examined and the fracture line delineated. Hematoma is removed from the fracture site using a small curet. The fracture is then reduced and the joint surface realigned. Provisional fixation is obtained using multiple Kirschner (K) wires (0.035 or 0.045-inch) drilled from dorsal to palmar.

Mini-fluoroscopic imaging is used to confirm joint reduction and wire position. Preferably, the fixation is intra-epiphyseal and avoids crossing the physis. Direct joint inspection avoids intra-articular wire placement, since imaging can be ambiguous. In sequential fashion, the pins are removed and replaced with compression screws across the fracture ( Fig. 66-4 A and B ).Another option is to use small cannulated screws over the K wires. After screw placement, the fixation is assessed for rigidity. A determination is made regarding the necessity of an external fixator to unload the joint surface until healing has occurred. In active and noncompliant children, I have a low threshold to apply an external fixator. The external fixator is placed by means of standard open incisions. Distraction is applied until the scaphoid and lunate are slightly elevated from the articular surface to eliminate longitudinal compressive forces until fracture union. Standard closure is performed with absorbable suture, and the external fixator is securely tightened. The tourniquet is deflated to ensure capillary refill. A long-arm splint is applied. The external fixator is removed 5 to 6 weeks after surgery. Active and active-assisted range of motion is instituted. Formal therapy is usually not required in children despite this fracture being intra-articular ( Fig. 66-5 A and B ).

Fixation for High-Energy Injuries

The closing physis remains an area prone to injury, similar to a Tillaux fracture of the anterolateral tibial epiphysis about the ankle. High-energy injuries create a combination of axial load and tension across the stout volar carpal ligaments. Fracture patterns are similar to adult high-energy injuries, but the fracture line propagates across the closing physis ( Fig. 66-6 ). Many of these fractures are irreducible and require operative fixation to restore articular congruity. Advanced imaging studies are helpful to fully define the fracture pattern and the fracture fragments ( Fig. 66-7 A and B ). The advent of volar locking plates has greatly enhanced our ability to achieve rigid fixation and allow earlier motion.

The fracture is approached via a volar trans-FCR (flexor carpi radialis) approach. Sharp dissection is carried out down to the level of the flexor carpi radialis tendon sheath. The sheath and subsheath of the flexor carpi radialis tendon are incised, and the deeper carpal contents are mobilized in an ulnar direction. The pronator quadratus is visualized and is sharply elevated from its radial attachment. The radial metaphysis and the fracture fragments are identified. The fracture hematoma and debris are removed. The fracture fragments must be handled carefully to preserve the volar radiocarpal ligament attachments. Reduction of the fracture fragments proceeds in a stepwise fashion until articular congruity has been restored. Once satisfactory reduction is obtained, percutaneous 0.045-inch K wires are placed across the fracture fragments to obtain provisional fixation. A locking plate is carefully situated along the radius into a position that allows fixation of each fracture fragment. Using x-ray guidance and the locking pin guide, locking screws or pins are placed into each fracture fragment with careful attention to ensure that the screws do not violate the joint surface. After articular congruity has been restored, the plate is secured along the proximal radius using standard bicortical screw placement ( Fig. 66-8 A and B ). The pronator quadratus is re-attached and the wound closed in standard fashion. The patient is placed into a well-padded sugar-tong splint with the forearm in neutral rotation for 2 weeks. The institution of active motion is dependent on the ability of the child to cooperate and the rigidity of the fracture fixation. Formal therapy is usually not required in children despite this fracture being high energy and intra-articular ( Fig. 66-9 A–D ).