Fracture Remodeling

Remodeling is the 3rd and final phase in biology of fracture healing, preceded by the inflammatory and reparative phases. This occurs from a combination of appositional bone deposition on the concavity of deformity, resorption on the convexity, and asymmetric physeal growth. Thus, reduction accuracy is somewhat less important than it is in adults (Fig. 675-2). The 3 major factors that have a bearing on the potential for angular correction are skeletal age, distance to the joint, and orientation to the joint axis. The rotational deformity and angular deformity not in the axis of the joint motion are less likely to remodel. The amount of remaining growth provides the basis for remodeling; younger children have greater remodeling potential. Fractures adjacent to a physis undergo the greatest amount of remodeling, provided that the deformity is in the plane of the axis of motion for that joint. The fractures away from the elbow and closer to the knee joint have greater potential to remodel because this physis provides maximal growth to the bone. One can expect remodeling to occur over the next several months following injury throughout skeletal maturity. Skeletal maturity is reached in girls between 13 and 15 yr and in boys between 14 and 16 yr of age.

Figure 675-2 Remodeling in children is often extensive, as in this proximal tibial fracture (A) and as seen 1 yr later (B).

(From Dormans JP: Pediatric orthopedics: introduction to trauma, Philadelphia, 2005, Mosby, p 38.)

Overgrowth

Physeal stimulation from the hyperemia associated with fracture healing causes overgrowth. It is usually prominent in long bones such as the femur. The growth acceleration is usually present for 6 mo to 1 yr following the injury and does not present a continued progressive overgrowth unless complicated by a rare arteriovenous malformation. Femoral fractures in children <10 yr of age often overgrow by 1-3 cm. Bayonet apposition of bone is preferred to compensate for the expected overgrowth. This overgrowth phenomenon will result in equal or near equal limb lengths at the conclusion of fracture remodeling. After 10 yr of age, overgrowth is less of a problem and anatomic alignment is recommended. In physeal injuries, growth stimulation is associated with use of implants or fixation hardware that can cause chronic stimulus for longitudinal growth.

Progressive Deformity

Injuries to the physes can be complicated by progressive deformities with growth. The most common cause is complete or partial closure of the growth plate. As a consequence, angular deformity, shortening, or both, can occur. The partial arrest may be peripheral, central, or combined. The magnitude of deformity depends on the physis involved and the amount of growth remaining. CT and MRI are important for assessing partial arrests and formulating treatment (Fig. 675-3).

Figure 675-3 MRI with gradient echo sequence, illustrating distal femoral physeal bar.

(From Dormans JP: Pediatric orthopedics: introduction to trauma, Philadelphia, 2005, Mosby, p 43.)

Rapid Healing

Children’s fractures heal quickly compared with those of adults. This is due to children’s growth potential and thicker, more active periosteum. As children approach adolescence and maturity, the rate of healing slows and becomes similar to that of an adult.

Plastic Deformation

Plastic deformation is unique to children. It is most commonly seen in the ulna and occasionally the fibula. The fracture results from a force that produces microscopic failure on the tensile side of bone and does not propagate to the concave side (Fig. 675-4). The concave side of bone also shows evidence of microscopic failure in compression. The bone is angulated beyond its elastic limit, but the energy is insufficient to produce a fracture. Thus, no fracture line is visible radiographically (Fig. 675-5). The plastic deformation is permanent, and a bend in the ulna of <20 degrees in a 4 yr old child is expected to correct with growth.

Figure 675-4 Graphic relation of bony deformation (bowing) and force (longitudinal compression) showing that the limit of an elastic response is not a fracture but plastic deformation. If the force continues, a fracture results. A, reversible bowing with stress; B, microfractures occur; C, point of maximal strength; between C and D, bowing fractures; D, linear fracture occurs.

(Modified from Borden S IV: Roentgen recognition of acute plastic bowing of the forearm in children, Am J Roentgenol Radium Ther Nucl Med 125:524–530, 1975; from Slovis TL, editor: Caffey’s pediatric diagnostic imaging, ed 11, vol 2, Philadelphia, 2008, Mosby, p 2777.)

Figure 675-5 Plastic deformation is a microfailure in tension without a visible fracture line.

(Courtesy of Dr. John Flynn, Children’s Hospital, Philadelphia.)

Buckle or Torus Fracture

A compression failure of bone usually occurs at the junction of the metaphysis and diaphysis, especially in the distal radius (Fig. 675-6). This injury is referred to as a torus fracture because of its similarity to the raised band around the base of a classic Greek column. They are inherently stable and heal in 3-4 wk with simple immobilization.

Figure 675-6 Buckle fracture is a partial failure in compression: anteroposterior (A) and lateral (B) radiographs of the distal radius.

(From Dormans JP: Pediatric orthopedics: introduction to trauma, Philadelphia, 2005, Mosby, p 37.)

Greenstick Fracture

These fractures occur when the bone is bent, and there is failure on the tensile (convex) side of the bone. The fracture line does not propagate to the concave side of the bone. The concave side shows evidence of microscopic failure with plastic deformation. It is necessary to break the bone on the concave side because the plastic deformation recoils it back to the deformed position.

Complete Fractures

Fractures that propagate completely through the bone are called complete fractures. These fractures may be classified as spiral, transverse, or oblique, depending on the direction of the fracture lines. A rotational force usually creates the spiral fractures, and reduction is easy due to the presence of an intact periosteal hinge. Oblique fractures are in the diaphysis at 30 degrees to the axis of the bone and are inherently unstable. The transverse fractures occur following a 3-point bending force and are easily reduced by using the intact periosteum from the concave side.

Epiphyseal Fractures

The injuries to the epiphysis involve the growth plate. There is always a potential for deformity to occur, and hence long-term observation is necessary. The distal radial physis is the most commonly injured physis. Salter and Harris (SH) classified epiphyseal injuries into 5 groups (Table 675-1 and Fig. 675-7). This classification helps to predict the outcome of the injury and offers guidelines in formulating treatment. SH type I and II fractures usually can be managed by closed reduction techniques and do not require perfect alignment, because they tend to remodel with growth. SH type II fractures of the distal femoral epiphysis need anatomic reduction. The SH type III and IV epiphyseal fractures involve the articular surface and require anatomic alignment to prevent any step off and realign the growth cells of the physis. SH type V fractures are usually not diagnosed initially. They manifest in the future with growth disturbance. Other injuries to the epiphysis are avulsion injuries of the tibial spine and muscle attachments to the pelvis. Osteochondral fractures are also defined as physeal injuries that do not involve the growth plate.

Table 675-1 SALTER-HARRIS CLASSIFICATION

Figure 675-7 Salter-Harris classification of physeal fractures, types I-V.

Child Abuse

The orthopedic surgeon sees 30-50% of physically abused children. Child abuse should be expected in nonambulatory children with lower extremity long bone fractures (Chapter 37). No fracture pattern or types are pathognomonic for child abuse; any type of fracture can result from nonaccidental trauma. The fractures that suggest intentional injury include femur fractures in nonambulatory children, distal femoral metaphyseal corner fractures, posterior rib fractures, scapular spinous process fractures, and proximal humeral fractures. A skeletal survey is essential in every suspected case of child abuse, because it can demonstrate other fractures in different stages of healing. Radiographically, some systemic diseases mimic signs of child abuse, such as osteogenesis imperfecta, osteomyelitis, Caffey disease, and fatigue fractures. Many hospitals have a multidisciplinary team to evaluate and treat patients who are victims of child abuse. It is mandatory to report these cases to social welfare agencies.

Phalangeal Fractures

The different phalangeal fracture patterns in children include physeal, diaphyseal, and tuft fractures. The mechanism of injury is a direct blow to the finger or typically a finger trapped in a door (Chapter 673). Crush injuries of the distal phalanx manifest with severe comminution of the underlying bone (tuft fracture), disruption of the nail bed, and significant soft-tissue injury. These injuries are best managed with antibiotics, tetanus prophylaxis, and irrigation. A mallet finger deformity is the inability to extend the distal portion of the digit and is caused by a hyperextension injury. It represents an avulsion fracture of the physis of the distal phalanx. The treatment is splinting the digit in extension for 3-4 wk. The physeal injuries of the proximal and middle phalanx are similarly treated with splint immobilization. Diaphyseal fractures may be oblique, spiral, or transverse in fracture geometry. They are assessed for angular and rotational deformity with the finger in flexion. Any malrotation or angular deformity requires correction for optimal functioning of the hand. These deformities are corrected with closed reduction, and if unstable, they need stabilization.

Forearm Fractures

Fractures of the wrist and forearm are very common fractures in children, accounting for nearly half of all fractures seen in the skeletally immature. The most common mechanism of injury is a fall on the outstretched hand. Eighty percent of forearm fractures involve the distal radius and ulna, 15% involve the middle third, and the rest are rare fractures of the proximal third of the radius or ulnar shaft. The majority of forearm fractures are torus or greenstick fractures. The torus fracture is an impacted fracture, and there is minimal soft-tissue swelling or hemorrhage. They are best treated in a short arm (below the elbow) cast and usually heal within 3-4 wk. Wrist buckle fractures have also been successfully treated with a removable splint. Impacted greenstick fractures of the forearm tend to be intrinsically stable (no cortical disruption) and may be managed with a soft bandage rather than casting.

Diaphyseal fractures could be more difficult to treat because the limits of acceptable reduction are much more stringent than for distal radial fractures. A significant malunion of a forearm diaphyseal fracture can lead to a permanent loss of pronation and supination, leading to functional difficulties. The physical examination focuses on soft-tissue injuries and ruling out any neurovascular involvement. The anteroposterior (AP) and lateral radiographs of the forearm and wrist confirm the diagnosis. Displaced and angulated fractures require manipulative closed reduction under general anesthesia. They are immobilized in an above-elbow cast for at least 6 wk. Loss of reduction and unstable fractures require open reduction and internal fixation.

Distal Humeral Fractures

Fractures around the elbow receive more attention because more aggressive management is needed to achieve a good result. Many injuries are intra-articular, involve the physeal cartilage, and can result in rare malunion or nonunion. As the distal humerus develops from a series of ossification centers, these ossification centers can be mistaken for fractures by inexperienced eyes. Careful radiographic evaluation is an essential part of diagnosing and managing distal humeral injuries. Common fractures include separation of the distal humeral epiphysis (transcondylar fracture), supracondylar fractures of the distal humerus, and epiphyseal fractures of the lateral or medial condyle. The mechanism of injury is a fall on an outstretched arm. The physical examination includes noting the location and extent of soft-tissue swelling, ruling out any neurovascular injury, specifically anterior interosseous nerve involvement or evidence of compartment syndrome. A transcondylar fracture in neonates should raise suspicion of child abuse. AP and lateral radiographs of the involved extremity are necessary for the diagnosis. If the fracture is not visible, but there is an altered relationship between the humerus and the radius and ulna or the presence of a posterior fat pad sign, a transcondylar fracture or an occult fracture should be suspected. Imaging studies such as CT, MRI, and ultrasonography may be required for further confirmation.

In general, distal humeral fractures need good restoration of anatomic alignment. This is necessary to prevent deformity and to allow for normal growth and development. Closed reduction alone, or in association with percutaneous fixation, is the preferred method. Open reduction is necessary for fractures that cannot be reduced by closed methods. Inadequate reductions can lead to cubitus varus, cubitus valgus, and rare nonunion or elbow instability.

Proximal Humerus Fractures

Fractures of the proximal humerus account for <5% of fractures in children. They usually result from a fall onto an outstretched arm. The fracture pattern tends to vary with the age group. Children <5 yr of age have an SH I injury, those 5-10 yr of age have metaphyseal fractures, and children >11 yr have SH II injury. Examination includes a thorough neurologic evaluation, especially of the axillary nerve. The diagnosis is made on AP radiographs of the shoulder. An axillary view is obtained to rule out any dislocation. SH I injuries do not require reduction because they have excellent remodeling capacity, and simple immobilization in a sling for 2-3 wk is sufficient. The proximal humerus contributes 80% of the growth to the humerus. The metaphyseal fractures usually do not need reduction unless the angulation is >50 degrees. A closed reduction with sling immobilization adequately treats this fracture. SH II fractures with <30 degrees of angulation and <50% displacement are managed in a sling. Displaced fractures are treated with closed reduction and further stabilization if unstable. Occasionally, open reduction is required because of button-holing of the fracture spike through the deltoid or interposition of the tendon of biceps.

Clavicular Fractures

Neonatal fractures occur as a result of direct trauma during birth, most often through a narrow pelvis or following shoulder dystocia. They can be missed initially and can appear with pseudoparalysis. Childhood fractures are usually the result of a fall on the affected shoulder or direct trauma to the clavicle. The most common site for fracture is the junction of the middle and lateral 3rd clavicle. Tenderness over the clavicle will make the diagnosis. A thorough neurovascular examination is important to diagnose any associated brachial plexus injury.

An AP radiograph of the clavicle demonstrates the fracture and can show overlap of the fragments. Physeal injuries occur through the medial or lateral growth plate and are sometimes difficult to differentiate from dislocations of the acromioclavicular or sternoclavicular joint. Further imaging such as a CT scan may be necessary to further define the injury. The treatment of most clavicle fractures consists of an application of a figure-of-eight clavicle strap. This will extend the shoulders and minimize the amount of overlap of the fracture fragments. For older adolescents with fracture fragments tinting the skin, operative management is increasingly more advised. The physeal fractures are treated with simple sling immobilization without any reduction attempt. Often, anatomic alignment is not achieved, nor is it necessary. The fractures heal rapidly usually in 3-6 wk. Usually a palpable mass of callus is visible in thin children. This remodels satisfactorily in 6-12 mo. Complete restoration of shoulder motion and function is uniformly achieved.

Hip Fracture

Hip fractures in children account for <1% of all children’s fractures. These injuries result from high-energy trauma and are often associated with injury to the chest, head, or abdomen. Treatment of hip fractures in children entails a complication rate of up to 60%, an overall avascular necrosis rate of 50%, and a malunion rate of up to 30%. The unique blood supply to the femoral head accounts for the high rate of avascular necrosis. Fractures are classified as transphyseal separations, transcervical fractures, cervicotrochanteric fractures, and intertrochanteric fractures. The management principle includes urgent anatomic reduction (either open or closed), stable internal fixation (avoiding the physis if possible), and spica casting.

Toddler Fracture

Toddler fractures occur in young ambulatory children. The age range for this fracture is typically from around 1-4 yr. The injury often occurs after a seemingly harmless twist or fall and is often unwitnessed. The children in this age group are usually unable to articulate the mechanism of injury clearly or to describe the area of injury well. The radiographs may show no fracture; the diagnosis is made by physical examination. The classic symptom is refusal to bear weight, which can manifest as pulling up the affected extremity or florid display of protest. The AP and lateral views of the tibia-fibula might show a nondisplaced spiral fracture of the distal tibial metaphysis. An oblique view is often helpful because the fracture line may be visible in only 1 of the 3 views. A 3-phase technetium bone scan can be helpful in excluding infections such as septic arthritis and osteomyelitis. The fracture is treated with an above-knee cast for approximately 3 wk.

Tibia and Fibula Shaft Fractures

The tibia is the most commonly fractured bone of the lower limb in children. This fracture generally results from a direct injury. Most tibial fractures are associated with a fibular fracture, and the mean age of presentation is 8 yr. The child has pain, swelling, and deformity of the affected leg and is unable to bear weight. Distal neurovascular examination is important in assessment. The AP and lateral radiographs should include the knee and ankle. Closed reduction and immobilization are the standard method of treatment. Most fractures heal well, and children usually have excellent results. Open fractures need to undergo irrigation and debridement multiple times. The fractures with more-severe soft tissue injury are best treated with external fixation. The fracture healing in open fractures takes longer than closed injuries.

Femoral Shaft Fractures

Fractures of the femur in children are common. All age groups, from early childhood to adolescence, can be affected. The mechanism of injury varies from low-energy twisting type injuries to high-velocity injuries in vehicular accidents. Femur fractures in children <2 yr should raise the concern for child abuse. A thorough physical examination is necessary to rule out other injuries and assess the neurovascular status. In the case of high-energy trauma, any signs of hemodynamic instability should prompt the examiner to look for other sources of bleeding. AP and lateral radiographs of the femur demonstrate the fracture. An AP radiograph of the pelvis is obtained to rule out any associated pelvic fracture. Treatment of shaft fractures varies with the age group, as described in Table 675-2.

Triplane and Tillaux Fractures

Triplane and Tillaux fracture patterns occur at the end of the growth period and are based on relative strength of the bone-physis junction and asymmetric closure of the tibial physis. The triplane fractures are so named because the injury has coronal, sagittal, and transverse components (Fig. 675-8). The Tillaux fracture is an avulsion fracture of the anterolateral aspect of the distal tibial epiphysis. Radiographs and further imaging with CT and 3-dimensional reconstructions are necessary to analyze the fracture geometry. The triplane fracture involves the articular surface and hence anatomic reduction is necessary. The reduction is further stabilized with internal fixation. The Tillaux fracture is treated by closed reduction. Open reduction is recommended if a residual intra-articular step off persists.

Figure 675-8 The triplane fracture is a transitional fracture: anteroposterior (A) and lateral (B) radiographs.

(From Dormans JP: Pediatric orthopedics: introduction to trauma, Philadelphia, 2005, Mosby, p 38.)

Metatarsal Fractures

Metatarsal fractures are common in children. They usually result from direct trauma to the dorsum of the foot. High-energy trauma or multiple fractures of the metatarsal base are associated with significant swelling. A high index for compartment syndrome of the foot must be maintained and compartment pressures must be measured if indicated. Diagnosis is obtained by AP, lateral, and oblique radiographs of the foot. Most metatarsal fractures can be treated by closed methods in a below-knee cast. Weight bearing is allowed as tolerated. Displaced fractures can require closed or open reduction with internal fixation. Percutaneous, smooth Kirschner wires generally provide sufficient internal fixation for these injuries. If the compartment pressure is increased, complete release of all compartments in the foot is necessary.

Toe Phalangeal Fractures

Fractures of the lesser toes are common and are usually secondary to direct blows. They commonly occur when the child is barefoot. The toes are swollen, ecchymotic, and tender. There may be a mild deformity. Diagnosis is made radiographically. Bleeding suggests the possibility of an open fracture. The lesser toes usually do not require closed reduction unless significantly displaced. If necessary, reduction can usually be accomplished with longitudinal traction on the toe. Casting is not usually necessary. Buddy taping of the fractured toe to an adjacent stable toe usually provides satisfactory alignment and relief of symptoms. Crutches and heel walking may be beneficial for several days until the soft-tissue swelling and the discomfort decrease.

Surgical Techniques

It is important to take great care with soft tissues and skin. The other indications for open reduction and internal fixation are unstable fractures of the spine, ipsilateral fractures of the femur, neurovascular injuries requiring repair, and, occasionally, open fractures of the femur and tibia. Closed reduction and minimally invasive fixation are specifically used for supracondylar fractures of the distal humerus, phalangeal fractures, and femoral neck fractures. Failure to obtain anatomic alignment by closed means is an indication for an open reduction.

The main indications for external fixation are summarized in Table 675-3. The advantages of external fixation include rigid immobilization of the fractures, access to open wounds for continued management, and easier patient mobilization for treatment of other injuries and transportation for diagnostic and therapeutic procedures. The majority of complications with external fixation are pin tract infections, chronic osteomyelitis, and refractures after pin removal.

Table 675-3 COMMON INDICATIONS FOR EXTERNAL FIXATION IN PEDIATRIC FRACTURES