Continuing Education Activity

This activity describes the evaluation and management of physeal injuries in the pediatric population. It explains the role of the interprofessional team in diagnosing and treating these injuries in the best possible manner to avoid growth arrest and lifelong complications.

Objectives:

• Describe the pathophysiology of pediatric physeal injuries.
• Outline the typical presentation of physeal injuries and highlight the unique presentation of pediatric patients.
• Describe the treatment of physeal injuries, explaining the differences between operative and non-operative management.
• Explain the importance of an interprofessional team to diagnose and treat physeal injuries.

Introduction

Pediatric fractures include the growth plate 15 to 18% of the time. Foucher first described injuries to the growth plate back in 1863, with the first classification system described by Poland in 1898. The most popular, descriptive anatomical classification system used today, the Saltar-Harris classification, was described by Dr. Salter and Dr. Harris in 1963. They were the first to recognize that the injury occurred through the zone of provisional calcification of the physis; this is a weaker zone in the physis due to it being a transition between the calcified and non-calcified parts of the growth plate.[1]

Etiology

Fractures may occur after mechanical falls, during sporting events, MVA, etc. 

Epidemiology

Physeal injuries are common in the pediatric population, accounting for approximately 30% of all bony injuries.[2][3] Most fractures occur in ambulatory children and are especially common in the adolescent population. Those who participate in sporting activities have a higher incidence of injury. Overall, they are twice as prevalent in boys as girls. The most common physeal injury seen is in the phalanges, accounting for 30% of these injuries.

Pathophysiology

Injection studies demonstrate that there are two main blood supplies to the growth plate: the vessels from the epiphysis that end at the layer of resting cells, and the vessels from the metaphysis that end at the layer of enchondral ossification.[4] Research has also shown that the vessels may enter the plate in one of two ways: most commonly from the periosteum covering the epiphysis, or from the rim of the plate if the entire epiphysis is intra-articular.[5] It stands to reason that injuries may easily damage this type of nutrient system, resulting in growth arrest.

The arrangement of cells of the physis is in layers or zones. These layers include the reserve, proliferative and hypertrophic zones. The reserve zone serves as the storage area for lipids, proteoglycans, and glycogen for growth and matrix production later. The proliferative zone has the highest rate of extracellular matrix production and accounts for the most abundant longitudinal growth. The hypertrophic zone has three phases: maturation allows for preparation for calcification, degenerative further prepare the matrix, and provisional calcification zone is where chondrocyte death occurs, allowing for calcium release. Physeal fractures most commonly occur in the zone of provisional calcification, as it is the weakest in response to shearing stress.[6][7]

The physis is weaker than ligaments or periosteum in children, causing injury to the growth plate before other structures.

Histopathology

Zones of the physis:

1. Resting zone - located closest to the epiphysis, location of germinal matrix, inactive chondroblasts 
2. Proliferative zone - active chondroblasts, like the name sounds, chondroblasts create proteins for the extracellular matrix (ECM)
3. Hypertrophic Zone - more organized chondroblasts, decreased production of ECM, the zone subdivides further:
   1. Zone of maturation
   2. Zone of provisional degeneration
   3. Zone of provisional calcification - weakest zone, where physeal injuries occur
4. Zone of calcification - the level that cartilage becomes calcified/becomes bone[1][7]

Two other important structures surround the physis:

• The groove of Ranvier - located on the diaphyseal side of the growth plate, supports peripheral growth of growth plate, made up of osteoblasts, fibroblasts, and chondroblasts. 
• Ring of LaCroix - makes the physis more stable, fibrous, connects metaphysis, and epiphyseal periosteum.

Blood supply located on epiphyseal end via periosteum.[1]

History and Physical

It is important to start with the history prior to the presentation. In all high trauma situations, it is important to begin with the trauma basics - the ABCs (airway, breathing, circulation). Once assessed and addressed, evaluation of other injuries may occur.  Mechanism of injury should be obtained from the history to determine the level of trauma to the extremity.  The skin should be assessed for any evidence of open fracture - especially looking for subtle signs such as poke holes or impending open fractures with skin tenting. A neurovascular exam is necessary to assess for any disruption before any type of intervention. Compartments should undergo an assessment to look for compressibility and to check for signs of developing compartment syndrome in high energy mechanism injuries.[8] 

In all pediatric fractures, it is crucial to look for signs of possible non-accidental trauma.  Non-accidental trauma can present as an orthopedic injury and which commonly include:  metaphyseal corner fractures, various states of healing of fractures, multiple fractures, patients who are not ambulatory with long bone fractures, epiphyseal separation.[9][10]

Evaluation

Following the physical exam, imaging studies should be obtained to evaluate injuries further.[11] Ultrasound may be used in very young patients before cartilage ossification. Plain radiographs will usually suffice to demonstrate fractures of the physis. Physeal fractures are classified using Salter-Harris I-V. Each subsequent number indicates a more substantial risk of growth arrest. Studies have shown moderate interobserver reliability using this classification, which is improved with the seniority of the reviewer.[12]

 Salter-Harris Classification:

• Salter-Harris I: fracture through the growth plate, epiphyseal and metaphyseal separation
• Salter-Harris II: through physis with extension into the metaphysis, the name of the metaphyseal fragment a Thurston-Holland fragment
• Most common
• Salter-Harris III: through physis with extension into the epiphysis, risk of post-traumatic arthritis
• Salter-Harris IV: extension of fracture line through metaphysis, physis, and epiphysis
• Wide range of incidence of growth disturbance based on the location of the fracture in the extremities [13]
• Salter-Harris V: physeal crush injury.[1][6][7]

Treatment / Management

As with all traumatic injuries, it is important to start with trauma principle basics by starting with the ABCs (airway, breathing, circulation) and treating any injuries found. After addressing those, treatment of the fracture can begin. 

An acute fracture requires initial treatment with a closed reduction with appropriate anesthesia. Salter-Harris 1 and 2 fractures that present 7 to 10 days out from injury should be given more leniency in acceptance of fracture displacement due to possibly causing more injury to the physis.[14] 

The risk of causing growth arrest after the fracture has begun healing is higher, and any deformities encountered later can be addressed by osteotomies. SH1 and SH2 injuries with greater than 3mm of displacement are also at increased risk of growth arrest. Salter-Harris 3 or 4 fractures should be reduced regardless of acute or late presentation due to the involvement of the joint. SH3 and SH4 fractures should have less than 2mm step off at the articular surface. Post-reduction CT may be considered to assess reduction quality.[8]  After performing reduction, the fracture should be stabilized initially with cast immobilization (4 to 6 weeks). Unstable fractures may require closed reduction and percutaneous pinning or fractures where interposed periosteum is blocking reduction may require open reduction and internal fixation. If an open reduction is necessary, the fracture should be approached from the tension side to reach the interposed tissue easily.[8]  

In patients who develop physeal bars and growth arrest, there are multiple options for treatment based on the amount of growth remaining. Skeletal age must be determined to help guide treatment. Boys typically grow until 16, while girls grow until 14 years old. Green and Anderson came up with growth grafts that can be used based on the patient's skeletal age to determine the amount of skeletal growth left in the patient.  

• Observation:
  • The entire physis is involved.
  • Limb length inequality acceptable
  • Acceptable angular deformity [15]
  • Minimal growth remaining in contralateral extremity
• Completion of bar:
  • Angular deformity is acceptable and may become unacceptable if growth continues.
  • Must evaluate limb length inequality before the procedure
    • If >2 to 2.5 cm growth remaining, perform contralateral epiphysiodesis. 
    • In ankle and wrist should consider doing epiphysiodesis of ulna or fibula to avoid ulnar impaction of the wrist or subfibular impingement due to continued growth of the other bone, respectively.[14][8]
• Resection:
  • Lots of growth remaining
  • partial arrest
  • must have large enough area of healthy physis left to continue growing 
    • Bony bar resection with interposition of fat autograft:
      • bar spans <50% of physis with two years of growth left or >2cm growth left[8]
      • >50% bar unlikely to do well
      • Type A bar - resect until area surrounded completely by healthy physis
      • Type B or C - make window or osteotomy to reach the area, may also consider using drill excision
      • Can evaluate growth postop if radiographic markers placed intraop[6]
• Osteotomy:
  • > 20-degree angulation 
  • < 20-degree angulation likely to correct with growth
    • Not always the case[15]

Differential Diagnosis

Physeal injuries often present with vague symptoms that can cause concern for an array of possible causes:

• Infection
• Non-accidental trauma
• Accidental trauma
• Muscle strain
• Metaphyseal/diaphyseal fracture
• Bone bruise
• Ligamentous injuries

Prognosis

The prognosis of physeal injuries is multifactorial. It is dependent not only on the initial fracture type, location, and time to treatment but also on the quality of reduction and subsequent orthopedic follow-up. Generally, the prognosis for pediatric physeal fractures is good. Most cases heal with good alignment with closed treatment. Inappropriate initial management increases the risk of growth arrest, malalignment, and lifelong difficulty for the patient.[16]

Complications

Physeal complications occur in 2 to 14% of patients after growth plate injury.  Growth arrest is relatively rare.  Certain areas in the body that sustain growth plate injuries do appear to have a higher incidence of premature growth plate closure, such as the distal tibia, with an incidence of close to 27.2%.  There is a higher risk of physeal bar formation if there is periosteal interposition within the fracture.  Physeal bar formation can cause complete growth arrest as well as partial arrest, which can result in angular growth.  MRI or CT can be useful to assess for physeal bar formation.[17]  Growth arrest may not be evident until many months after the injury occurs.  

Partial physeal arrest can be described by the Peterson classification:[15]

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

An important way to prevent physeal arrest is to limit the number of reduction attempts that occur. One reduction attempt increases the risk of arrest to 11%; two attempts increases the risk to 24%.[17]

After physeal injury, harris growth arrest lines may form and can be used to assess subsequent growth.  If the line appears transverse and parallel to the physis, then the growth plate is continuing to grow evenly.  If there is an asymmetry in the harris growth arrest line, this may indicate asymmetrical growth after injury.[14]

Other complications that can occur include infection, non-union, malunion, infection, neurovascular injury, and osteonecrosis.

Consultations

• Orthopedic surgeon 

Deterrence and Patient Education

Physeal injuries are frequently encountered in the pediatric population. It is important to review with the patient and family the risk of growth arrest and deformity after injury.  It is important to watch for leg length discrepancy and to plan for possible surgical intervention if needed based on the patient's age/growth left.[18][19]

Pearls and Other Issues

• Growth arrest can occur, patient's and family need to understand this 
• In all pediatric patients, it is essential to look for signs of non-accidental trauma and to report it.
• Make sure to perform a thorough neurovascular exam as well as check the skin for any evidence of open fracture.
• Initial reduction is important, but be mindful that multiple reductions can increase the risk of injury to the growth plate

Enhancing Healthcare Team Outcomes

Being aware of physeal injuries and appropriate treatment is vital to avoid complications. Emergency room providers, as well as primary care clinicians, need to be mindful of proper treatment and follow up to give patients the best care with the lowest risk of complications.  Referral to an orthopedic surgeon for further management/surgical intervention and follow up is important to assess for the development of complications.  Interprofessional communication is important so that patients with physeal injuries can be appropriately identified and treated.