Physeal injury

Physeal Injuries and Bar Formation

Aetiology of Bridging

  • Definition: Bridging occurs when there is any direct contact or communication between the metaphysis and epiphysis, often resulting in ossification and bar formation.

Most Common Causes

  1. Trauma
    • High-energy injuries.
    • Displaced fractures, especially Types 3, 4, and 5.
    • Axial compression injuries.
  2. Surgery
    • Pin placement: Thin, smooth, perpendicular pins are safest. Risks increase with threaded, large, oblique pins or multiple passes.
    • Interference with perichondrial ring: This ring stabilizes the physis, and disruption can destabilize it.
    • Physeal violation with implants (e.g., nails for femur fractures).
  3. Specific Physes Susceptibility
    • Distal femur is highly susceptible due to its wavy structure, which increases surface area, allowing fractures to cross multiple physeal parts.

Non-Fracture Causes

  • Irradiation
  • Tumors
  • Infections
  • Congenital disorders (e.g., Madelung’s deformity, Blount’s disease)

Pathophysiology of Physeal Injury & Growth Arrest

Physis Zones Characteristics
Hypertrophic Zone Avascular, poor healing potential, mostly cellular with minimal matrix
Osseo-Cartilaginous Junction Metaphysis and physis are supported by the perichondrial ring of LaCroix; damage here disrupts the physis
  • Growth Arrest: Occurs in about 10% of physeal fractures, more common in Type 4 and 5 fractures.
  • Adolescents: Higher likelihood of arrest due to the thickness of the physis and weaker cartilage, though with minimal remaining growth potential, impact is less significant.

Bar Formation

  • Begins around 6 weeks post-injury but may not be clinically evident for some time.
  • Requires follow-up until skeletal maturity, especially in:
    • Types 4 and 5 fractures.
    • High-risk and lower limb physes due to potential impacts on leg length and mechanical alignment.
  • Bridging threshold: Damage needs to exceed 7% of physis cross-section for bridging to occur.

Classification of Physeal Bars

Classification Description
Position Central, Linear, Peripheral
Size Critical size is 50% of physeal area, which is the upper limit for resection; measured on axial CT or MRI for precision.

X-Ray Evaluation

  • Signs:
    • Angular deformity.
    • Visible bar.
    • Asymmetry in Harris growth recovery lines:
      • These sclerotic lines indicate calcification post-physeal injury.
      • Growth lines should ideally be parallel to the physis; convergence towards a bar suggests arrest.
      • The gap between growth lines and the physis shows growth since the injury. Complete arrest shows no growth lines.
  • Imaging:
    • CT scan: Offers better definition of bony structures.
    • MRI scan: Ideal for identifying fibrous bars.

Factors Affecting Bridge Resection

Factor Impact on Treatment
Aetiology Trauma-related bars have better outcomes than those from infections.
Physeal Location & Growth Contribution Higher growth potential enhances remodeling.
Age & Growth Potential Younger children benefit more from resection; growth charts help assess potential.
Bar Size Optimal outcomes with bars <25%; resectable up to 50%.
Bar Location - Peripheral: Causes angular deformity; resection recommended.
- Central: Harder to resect, causes limb length discrepancy if large.

Resection Criteria: 1. Child has at least 2 years or 2 cm of remaining growth. 2. Bar size <25%, ideally, but maximum resection up to 50%.

Alternative Treatments to Bar Resection

  1. Epiphysiodesis
    • Prevents angular deformity in older children.
    • May include contralateral epiphysiodesis for symmetry.
  2. Osteotomy
    • Corrects angulation; can be combined with bar resection or delayed to observe bar resection’s effect on angulation.
  3. Limb Lengthening
    • Conducted at skeletal maturity.
    • Option if bar is irresectable, too large, or resection fails.
  4. Delayed Hemiepiphysiodesis
    • Performed opposite the bar to correct angulation once resected area shows growth.

Resection Technique

  • Approach: Based on bar type and location.
    • Central bars often need access through osteotomy or a metaphyseal window.
    • Use curettes or burrs for bar resection, with continuous irrigation.
  • Interposition Grafts: Fill space with a fat or PMMA graft; both materials show equivalent results.
  • Corrective Osteotomy: For irreparable angular deformities.
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