Pediatric Physeal Injuries Overview

Etiology

The growth plate is 5 times more brittle than the surrounding ligaments. Fractures may occur after mechanical falls, direct trauma, or during sporting events. Other possible causes of pediatric physeal injuries include iatrogenic surgical injuries, radiotherapy, chemotherapy, infection, bone tumors, and metabolic disorders.[6]

Epidemiology

Physeal injuries are common in the pediatric population, accounting for approximately 30% of all bony injuries.[7][8] Most fractures occur in ambulatory children and are especially common in the adolescent population. Those who participate in sports activities have a higher incidence of injury. Overall, physeal injuries are twice as prevalent in boys than in girls. The most commonly involved location is the phalanges, accounting for 30% of these injuries.

Pathophysiology

The growth plate is a key site of chondrocyte proliferation, and injuries to this area can disrupt its blood supply. Epiphyseal blood vessels nourish the zones of active chondrocyte growth, and damage to these vessels may result in necrosis, leading to the arrest of longitudinal bone growth. The growth plate may also close, and a secondary ossification center may anomalously develop at this site. Meanwhile, metaphyseal arterial damage can disrupt endochondral ossification, leading to chondrocyte persistence within the metaphysis and growth plate widening. 

Injuries that allow the epiphyseal and metaphyseal arteries to communicate, eg, Salter-Harris fractures, can produce transphyseal bone bridges, also known as physeal bars.[41] These abnormal structures can lead to length discrepancies between paired bones and angular deformity.[42] Growth plate cartilage is less resilient to shearing forces than ligament or adult articular cartilage. Injuries that can cause ligamentous tears or bone dislocation in adults can produce physeal injuries in children. 

Histopathology

The physis is divided into the following zones:

• Resting zone: The region closest to the epiphysis that houses the germinal matrix and inactive chondroblasts 
• Proliferative zone: Contains active chondroblasts, which synthesize extracellular matrix (ECM) proteins
• Hypertrophic zone: The zone that houses more organized chondroblasts and contributes less to ECM formation; this zone subdivides further into the zones of maturation, provisional degeneration, and provisional calcification
• Calcification zone: The level where cartilage calcifies and becomes bone

The zone of provisional calcification is the growth plate's weakest region. This site is most commonly involved in physeal injuries. 

Two other important structures surround the physis:

• Groove of Ranvier: This is located on the diaphyseal side of the growth plate and is composed of osteoblasts, fibroblasts, and chondroblasts. The groove of Ranvier supports horizontal epiphyseal growth. 
• Ring of LaCroix: This is a fibrous structure that makes the physis more stable. The ring of LaCroix securely connects the metaphysis to the epiphysis.

Epiphyseal arteries terminate at the periosteum.

History and Physical

In all high-trauma situations, assessment of the ABCs (airway, breathing, and circulation) must be prioritized. Once emergency conditions have been ruled out, other injuries may be examined. On history, the mechanism of trauma must be elicited to determine the potential extent of damage; for example, a recent sports-related collision, motor vehicular crash, fall from a height, or assault may be reported. The patient may present with multiple injuries or be brought to the emergency department unconscious. Initiate resuscitation if the patient is unconscious, apneic, and pulseless. Physical examination may reveal deformity, swelling, and tenderness in the affected area, and sensorimotor weakness distal to the site may indicate nerve damage in the fractured region.

A wound or skin tenting on the site may signify an open fracture or an impending one. Compartment syndrome—with symptoms of pain, pallor, paralysis, paresthesia, and pulselessness—must be ruled out. Refer to an orthopedic surgeon immediately if these signs are present, as these conditions are surgical emergencies.[9] Non-accidental trauma must be ruled out in all pediatric fractures. Non-accidental trauma presenting as orthopedic injuries include metaphyseal corner fractures, fractures in various states of healing, multiple fractures, long-bone fractures producing inability to ambulate, and epiphyseal separation.[10][11]

Evaluation

Imaging studies help elucidate the type and severity of injury. Plain radiography is enough to locate the fracture and assess its severity in most cases. Physeal fractures are classified using the Salter-Harris classification (see Image. Salter-Harris Classification of Physeal Injuries), which is as follows:

• Salter-Harris I: Fracture through the growth plate, with epiphyseal and metaphyseal separation
• Salter-Harris II: Break through the physis with extension into the metaphysis
  • The name of the metaphyseal fragment is "Thurston-Holland fragment." This type is the most common.
• Salter-Harris III: Physeal disruption with epiphyseal extension
  • This type predisposes to post-traumatic arthritis.
• Salter-Harris IV: Extension of fracture line through the metaphysis, physis, and epiphysis
  • This injury may predispose to growth disturbance, depending on the fracture location.[12]
• Salter-Harris V: Physeal crush injury
• Salter-Harris VI: Physeal fracture that includes the periphery of the physis
  • This injury is also called "perichondral ring fracture."
• Salter-Harris VII: Isolated injury to the epiphyseal plate

Higher-numbered injuries in the Salter-Harris classification have a greater risk of growth arrest. Study results have shown moderate interobserver reliability using this classification, which improves with experience.[13] Ultrasound may be used in young patients whose cartilage ossification has not started.[14] The inability to rule out a physeal injury despite normal x-ray findings warrants computer tomography (CT) or magnetic resonance imaging (MRI).

Treatment / Management

Pediatric physeal injuries may be managed conservatively or surgically, depending on factors like injury type and extent of involvement. This section explains pediatric physeal injury management.

Nonoperative Management

As previously mentioned, assessing patients with trauma must start with the ABCs. Emergent injuries like compartment syndrome and open fractures must also be ruled out immediately. A more thorough investigation and specific treatment may begin once emergencies have been ruled out. The therapeutic objectives for physeal fractures are maintaining normal limb function and physeal development. These goals can be accomplished by physeal and articular anatomic reduction.[15] Salter-Harris I and II fractures may be managed immediately by immediate reduction and immobilization. Patients must be given adequate pain control before the procedure. Muscle relaxation can make the bone more amenable to closed reduction. Forceful closed reduction and repeated manipulations must be avoided. Displacement in Salter-Harris I and II fractures presenting 7 to 10 days after injury should be assessed cautiously, as complications may have already developed at this time.[16][17](B3)

Operative Management

Physeal fracture displacement greater than 2 mm is an indication of open reduction, with pins and wires as the preferred fixation instruments.[18] Smooth pins are preferred over threaded ones, and small-diameter wires or pins are recommended.[19] Insertion at the physeal perimeter has a greater risk of growth arrest than insertion at the center. Titanium may cause physeal tethering more than stainless steel. Implants must be positioned parallel to the physis if the fracture geometry permits it. Additionally, positioning perpendicular to the physis will do less harm than placement at an oblique angle. Compression of transphyseal implants must be avoided.[20] Smith et al reported that 1 out of 5 patients who have had temporary transphyseal pinning for upper extremity fractures experienced physeal arrest.[21][22](B2)

Salter-Harris I and II fractures may be treated with closed manipulation, reduction, and 4 to 6 weeks of immobilization. Growth arrest risk after the fracture starts to heal is higher. Late-appearing deformities may be treated with osteotomy. Salter-Harris I and II injuries with greater than 3 mm of displacement are also at increased risk of growth arrest. Most Salter-Harris type I fractures may be successfully treated with closed reduction and casting. However, these fractures must be monitored for at least 3 months to ensure growth discrepancies do not develop. Soft tissue edema and pain may be the only initial symptoms of these injuries, although radiographs may reveal joint expansion or new bone growth at the anatomical borders.[23][24]

About 75% of physeal injuries are classified as Salter-Harris type II. Repeated reduction attempts of these injuries may damage the physis owing to the metaphyseal spike. The Thurston-Holland (metaphyseal) fragment may be internally fixated into the metaphysis if the fracture is unstable. Transphyseal internal fixation may be required if the metaphyseal segment is too small to hold an implant. Reduction performed more than 5 days following an extra-articular physeal fracture (Salter-Harris type I or II) should be avoided to reduce the risk of iatrogenic physeal damage and growth arrest. Instead, these injuries may be allowed to heal spontaneously, even if the process results in malunion, which is often simpler to treat than growth arrest.

Salter-Harris III and IV fractures should be surgically reduced regardless of the timing of presentation. Surgical reduction is recommended due to articular involvement. Salter-Harris type III fractures usually affect older children. Thus, the growth arrest risk is less. Potential complications of these injuries include posttraumatic arthritis, articular disruption, and minor growth arrest.[25] Salter-Harris type IV fractures require physeal and articular alignment during surgical reduction. Unstable fractures are internally fixated from epiphysis to epiphysis or metaphysis to metaphysis to minimize physeal damage. Regardless of the time of diagnosis, displaced intra-articular physeal fractures (Salter-Harris types III and IV) should be surgically treated with internal fixation.[26]

Joint arthrograms, fluoroscopy, direct visualization, and arthroscopic evaluation can help determine the adequacy of articular reduction after surgical treatment of Salter-Harris III and IV fractures. The appearance of asymmetric Park-Harris growth lines indicates growth impairment.[27] During open reduction, the fracture should be approached from the tension side to access interposed tissues easily; periosteal resection on each side of the physis may reduce the risk of bony bar development. Exposed or crushed physeal injuries may be covered with free fat grafts to avoid growth arrest.[28] Salter-Harris types III and IV fractures should be immobilized for 4 to 8 weeks after surgery.[29] Post-reduction CT may help assess reduction quality. Unstable fractures require closed reduction and percutaneous pinning. Open reduction and internal fixation (ORIF) may be necessary when treating fractures with an interposed periosteum.(B3)

Physeal Bar Development

Physeal bar formation can result in growth arrest. Physeal bar treatment depends on the patient's skeletal maturity and the amount of bone development remaining. Thus, skeletal age must be determined to help guide treatment. Boys typically grow until age 16, while girls grow until age 14. Green and Anderson growth graphs can help determine the amount of skeletal growth a patient has left.

Surgical reduction with or without internal fixation may remove physeal bars but does not always prevent growth arrest. Factors like deformity, remaining development, limb-length disparity, and injury extent, nature, position, and size affect how growth arrest is managed. Langenskiold surgery entails free fat graft interposition after removing the partially arrested physis, which prevents physeal re-tethering. Further, metaphyseal and epiphyseal metal markers can aid in tracking post-surgical growth.[30]

Another option to prevent bar reformation is polymethylmethacrylate, which is accessible, affordable, inert, and effective in providing bone structural support.[31] External fixation using Canadell and De Pablos distraction technique has also been used successfully to correct bony bars and malalignment. The technique can address these complications by physeal distraction, dispensing the need to remove the bone bridge.[32] Bollini et al reported that external fixation by the Ilizarov method can successfully treat a centrally positioned lower tibial bony bridge.[33](B3)

Early physeal closure, variable physeal growth, and pin site infection are possible complications of these physeal procedures, while physeal bar replacement with a healthy physis can induce development and treat growth arrest. The proximal fibula, distal ulna, phalangeal physis, costal cartilage, distal clavicle, and iliac crest apophysis are potential physeal cartilage donor sites.[34] Whole physeal impaction results in full growth arrest, resulting in delayed bone formation and limb shortening; perimeter physeal bars can cause angular deformity and slow bone growth. Centrally positioned physeal bars may be accessed by making a metaphyseal cortical window, preserving the perichondrial ring, and peripheral physeal bars may also be accessed through this window. The bony bar may be removed after periosteal excision until a healthy physis is seen. Hematoma formation may lead to bony bar reformation and must be avoided.[35](B3)

Other treatment approaches to physeal bar formation include the following:

• Observation: This is indicated when the entire physis is involved, and the degree of angular deformity or limb-length inequality is acceptable, ie, less than 2 cm. The patient must have minimal growth remaining in the contralateral extremity.
• Physeal bar completion: This is indicated when the angular deformity is acceptable but has a risk of progressing with continued growth. Limb-length inequality must be evaluated before the procedure. If the patient has greater than 2 to 2.5 cm growth remaining or a 2 to 5 cm leg-length discrepancy is present, contralateral epiphysiodesis may be performed. Ulnar and fibular epiphysiodesis must be considered to avoid ulnar wrist impaction and sub-fibular impingement, which result from the continued growth of neighboring bones.
• Resection: This may be considered in partial growth arrest, where the physis has substantial growth. Bony bar resection with fat autograft interposition may be performed when the physeal bar spans less than 50% of the physis. The technique may fail with greater than 50% involvement. Type A physeal bars must be resected until the area is surrounded completely by healthy physis. Type B or C physeal bars require osteotomy or drill excision to reach the area; intraoperative marker placement can aid in postoperative radiographic monitoring.
• Osteotomy: This is indicated if the physeal bar is accompanied by greater than 20° angulation. Normal growth may correct the angulation if it is less than 20°.[36]

Leg lengthening is required if the leg-length discrepancy is greater than 5 cm.

Differential Diagnosis

Physeal injuries often present with vague symptoms that can make them resemble the following conditions:

• Infection
• Muscle strain
• Metaphyseal or diaphyseal fracture
• Bone bruise
• Ligamentous injuries

Careful evaluation can help distinguish between these conditions.

Prognosis

The most important factors that impact the prognosis of physeal injuries include initial fracture type, location, time to treatment, quality of reduction, and orthopedic follow-up. The prognosis of extra-articular pediatric physeal fractures (Salter-Harris types I and II) is generally good. Most of these injuries heal with good alignment after closed reduction and conservative treatment. Inappropriate initial management increases the risk of growth arrest, malalignment, and lifelong mobility problems.[37] Salter-Harris types III and IV fractures have the greatest risk of growth arrest.

Complications

Physeal complications occur in 2% to 14% of patients after growth plate injury. Growth arrest is relatively rare. However, injuries to the distal tibia result in premature growth plate closure in 27.2% of the cases. This location has a high risk of physeal bar formation, especially if periosteal interposition is present. MRI or CT can help detect physeal bar formation. Growth arrest may not be evident until months after the injury. 

Partial physeal arrest can be categorized according to the Peterson classification:

1. Type A: Peripheral bar
2. Type B: Central bar that crosses entire physis (anterior to posterior) with healthy physis on the sides
3. Type C: Central bar surrounded by healthy physis

Limiting the reduction attempts can help prevent physeal arrest after a fracture treatment. One reduction attempt increases the growth arrest risk to 11%. Two attempts increase the risk to 24%.[38] Harris growth arrest lines may form after a physeal injury and can be used to assess subsequent growth. Lines transverse or parallel to the physis allow the growth plate to expand evenly. Asymmetric Harris growth arrest lines may result in uneven growth. Other possible complications of physeal injuries include infection, nonunion, malunion, infection, neurovascular injury, and osteonecrosis.