How do growth fractures affect bone growth?

Impact of Growth Fractures on Bone Growth

Growth fractures can significantly disrupt normal bone growth, potentially leading to permanent deformities including limb length discrepancies, angular deformities, or complete growth arrest.

Types of Growth Plate Fractures and Their Impact

Growth plate (physeal) fractures are unique to children and can be classified using the Salter-Harris classification system, which helps predict the risk of growth disturbance 1:

• Type I: Fracture through the growth plate only

  • 36% risk of growth disturbance
  • Lowest risk among all types

• Type II: Fracture through growth plate and metaphysis

  • 58% risk of growth disturbance

• Type III: Fracture through growth plate and epiphysis

  • 49% risk of growth disturbance

• Type IV: Fracture through growth plate, epiphysis, and metaphysis

  • 64% risk of growth disturbance
  • Highest risk of significant leg length discrepancy

• Type V: Crush or compression injury of the growth plate

  • High risk of growth arrest due to direct damage to growth plate cells

Mechanisms of Growth Disturbance

When a growth plate is injured, the following pathological processes may occur:

1. Bone Bridge Formation: Following injury, damaged cartilage tissue within the growth plate can undergo premature ossification, forming a "bony bar" that connects the epiphysis and metaphysis 2.

2. Molecular Mechanisms: Bone bridge formation appears to be an early event after growth plate injury, involving pro-osteoblastic molecules like IL-6, BMP-2, OPG, and Collagen X 3.

3. Potential for Resolution: In some cases, bone bridges may eventually dissolve during the growth process, potentially linked to Wnt signaling inhibition and RANK/RANKL signaling activation 3.

Risk Factors for Growth Disturbance

Several factors influence the likelihood and severity of growth disturbance:

1. Fracture Displacement: Displaced fractures have 4 times greater odds of developing growth arrest compared to non-displaced fractures 4.

2. Location: Distal femoral growth plate fractures are particularly concerning, with 52% developing some form of growth disturbance and 22% developing leg length discrepancy greater than 1.5 cm 4.

3. Treatment Method: While fixation slightly increases the overall incidence of growth disturbance (63% vs. 58% without fixation), it decreases the incidence of clinically significant growth disturbance (27% vs. 37%) 4.

Clinical Implications and Management

1. Monitoring: Children with growth plate fractures require close follow-up to detect early signs of growth disturbance.

2. Differential Diagnosis: When evaluating multiple fractures in children, it's important to distinguish between:

   • Accidental injuries
   • Child abuse (the leading cause of fractures in infancy) 5
   • Underlying bone disorders like Osteogenesis Imperfecta 5

3. Potential Therapeutic Approaches: Growth hormone (GH) has been investigated as a potential therapeutic agent for fracture healing, with evidence suggesting a positive role in bone metabolism and fracture repair 6.

Special Considerations

• Underlying Bone Conditions: Children with conditions like osteopenia of prematurity, vitamin D deficiency, or osteogenesis imperfecta may be more susceptible to fractures and subsequent growth disturbances 5.

• Growth Hormone Deficiency: Endogenous and exogenous glucocorticoids can inhibit GH secretion, potentially worsening complications such as bone loss and growth deficits 5.

• Radiographic Evaluation: For suspected growth plate injuries, appropriate imaging is crucial. While skeletal surveys are often used to evaluate for multiple fractures, CT may provide better visualization of complex fractures 5.

Growth plate fractures require careful assessment, appropriate treatment, and vigilant follow-up to minimize the risk of permanent growth disturbance and optimize long-term outcomes.