Physeal Injuries
The Salter-Harris Classification
Salter-Harris Classification
Critical Must-Knows
- SALTR Mnemonic: Slip, Above, Lower (Through), Ram, Ruin (Crush).
- Type II is Most Common: Fracture through physis with metaphyseal fragment (Thurston-Holland).
- Type III/IV are Intra-Articular: Require anatomical reduction.
- Type V is a Crush Injury: Often diagnosed retrospectively by growth arrest.
- Distal Femur is High Risk: Accounts for 60-70% of leg length discrepancy from growth arrest.
Examiner's Pearls
- "Know the Salter-Harris classification perfectly
- "Understand which types require ORIF
- "Know the high-risk physes (Distal Femur, Proximal Tibia)
- "Recognize growth arrest patterns (Bar, Complete)
Clinical Imaging
Imaging Gallery
The Distal Femoral Physis
The Distal Femoral Physis is HIGH RISK.
- It contributes 70% of femoral length and 35% of total leg length.
- Even minor physeal damage can cause significant leg length discrepancy.
- Angular deformity (varus/valgus) is also common.
- Any Salter-Harris injury to the distal femur should be treated with respect and followed long-term for growth disturbance.
Salter-Harris Types at a Glance
| Type | Fracture Line | Prognosis | Treatment |
|---|---|---|---|
| Physis only | Good | Casting | |
| Physis + Metaphysis | Good | Reduction + Casting | |
| Physis + Epiphysis | Fair (intra-articular) | ORIF | |
| All three layers | Poor (high arrest risk) | ORIF | |
| Crush injury | Very Poor (often missed) | Monitor for arrest |
SALTR Mnemonic
Memory Hook:SALTR - The classic mnemonic.
High-Risk Physes
Memory Hook:DPD - Distal Femur is Priority, but Distal Tibia is tricky.
Factors Affecting Prognosis
Memory Hook:ASTR - Assess these factors for prognosis.
Overview/Epidemiology
Physeal Injuries are fractures involving the growth plate (physis).
- Epidemiology:
- Account for 15-30% of all pediatric fractures.
- Boys are more commonly affected (2:1).
- Peak incidence during the adolescent growth spurt ("closing physes are vulnerable physes").
- Anatomical Weakness:
- The physis is weaker than bone, ligaments, and tendons in children.
- In adults, the same mechanism would cause a ligament sprain or dislocation.
- In children, it causes a physeal fracture.
Anatomy and Pathomechanics
Physeal Anatomy The physis has distinct zones (from epiphysis to metaphysis):
- Reserve Zone (Resting Zone): Storage of nutrients. Germinal cells.
- Proliferative Zone: Chondrocyte replication (columns of cells).
- Hypertrophic Zone: Chondrocyte enlargement. Weakest zone - fractures propagate here.
- Zone of Provisional Calcification: Chondrocytes undergo apoptosis, matrix calcifies.
- Primary Spongiosa: New woven bone formation.
Fracture Propagation
- Fractures typically propagate through the hypertrophic zone (Type I, II).
- This zone is weak because the chondrocytes are dying, and the matrix is transitioning.
- The germinal cells (Reserve and Proliferative zones) are typically preserved, allowing continued growth.
- In Type III, IV, and V injuries, the germinal layers are disrupted, leading to growth arrest.
Ring of LaCroix and Perichondral Ring
- These structures provide peripheral stability to the physis.
- Injury to these (e.g., in severe Type I) can contribute to instability and arrest.
Classification Systems
Salter-Harris Classification (1963)
The gold standard.
Type I: Fracture through the physis only. No metaphyseal or epiphyseal fragment. Often occult on X-ray (diagnosed by point tenderness over the physis).
Type II: Fracture through the physis with extension into the metaphysis. The metaphyseal fragment is called the Thurston-Holland fragment. Most common (75%).
Type III: Fracture through the physis with extension into the epiphysis. Intra-articular. Requires anatomical reduction.
Type IV: Fracture crosses all three layers (metaphysis, physis, epiphysis). Highest risk of growth arrest. Requires ORIF.
Type V: Crush injury to the physis. Often missed on initial X-rays. Diagnosed retrospectively when growth arrest is identified.
Clinical Assessment
History:
- Mechanism: Fall? Twisting? Direct blow?
- Location of Pain: Point tenderness over the physis is the key finding.
- Swelling: May be minimal in Type I.
Physical Exam:
- Inspection: Swelling, deformity, ecchymosis.
- Palpation: Point tenderness over the physis = physeal injury until proven otherwise (even if X-ray is negative).
- ROM: May be limited by pain.
- Neurovascular: Document status (especially for displaced fractures).
Investigations
Imaging:
- X-ray (AP and Lateral): Standard. May be normal in Type I or V.
- Comparison Views: Of the contralateral (uninjured) side can be helpful for subtle widening.
- MRI: If X-ray is negative but clinical suspicion is high. Shows physeal edema.
CT Scan:
- Useful for complex intra-articular fractures (Type III, IV) to map the fracture and plan surgery.
- 3D reconstruction is helpful.
Management Algorithm
Type I and II (Extra-Articular)
- Closed Reduction and Casting is the mainstay.
- Gentle manipulation. Avoid repeated reduction attempts (damages physis).
- If stable: Cast immobilization.
- If unstable after reduction: Consider percutaneous pinning (smooth K-wires that do not cross the physis).
- Do NOT cross the physis with threaded hardware (exception: very localized Type IV with screw well away from the rest of the physis).
Surgical Techniques
Percutaneous K-Wire Fixation
Indications: Unstable Type I/II after reduction, or Type III/IV after open reduction.
Technique: Closed or open reduction under fluoroscopic guidance. Pass smooth K-wires, avoiding crossing the physis if possible. For Type III/IV, place pins through the epiphysis, parallel to the physis. Bury or leave percutaneous. Immobilize in cast and remove pins at 3-4 weeks.
Key Technical Points When performing ORIF for physeal injuries, the surgeon must balance the need for rigid fixation against the risk of iatrogenic physeal damage. The following principles guide technique selection:
- Use the smallest effective implants.
- Place hardware parallel to the physis when possible.
- If screws must cross the physis, use small diameter (less than 4.0mm) and remove early.
- Minimize soft tissue stripping to preserve blood supply.
Reduction Maneuvers by Type
- Type I: Gentle traction and reduction. Avoid aggressive manipulation.
- Type II: Reverse the mechanism (e.g., apex posterior = flex and apply posterior force). Use the Thurston-Holland fragment as a guide.
- Type III/IV: Open reduction to visualize the articular surface. The physis cannot be adequately assessed closed.
Postoperative Immobilization
- Long leg cast for lower limb physeal injuries.
- Above elbow cast for upper limb physeal injuries.
- Duration: 4-6 weeks for most injuries, longer for distal femur.
Deep Dive: Hardware and the Physis
Can you cross the physis with hardware?
- Smooth K-wires: Yes. They cause minimal localized damage. Remove early (3-4 weeks).
- Threaded screws: Avoid if possible. They create a "tether" that can cause asymmetric growth (angular deformity).
- Exception: In Type IV fractures, a single 4.0mm screw placed perpendicular to the fracture line (crossing the physis) may be acceptable if placed centrally and only one or two small holes are made. The risk is lower than leaving a malreduced fracture.
Key Principle The bigger the physis (younger the child, more growth remaining), the more cautious you must be about crossing it.
Complications
| Complication | Rate | Prevention/Management |
|---|---|---|
| Growth Arrest | Variable (1-10% Type II, up to 50% Type IV) | Anatomical reduction. Avoid physis damage. |
| Angular Deformity | Common with partial arrest | Bar excision if less than 50% physis affected, osteotomy if complete. |
| Leg Length Discrepancy | Depends on site and age | Epiphysiodesis or lengthening depending on discrepancy. |
| Avascular Necrosis | Rare (except specific sites like femoral head) | Gentle reduction. Minimize soft tissue stripping. |
| Nonunion | Very Rare | Good blood supply in children. |
Postoperative Care
- Immobilization: Cast or splint for 3-6 weeks depending on location.
- Weight Bearing: Usually non-weight bearing initially for lower limb injuries.
- Follow-up: X-rays at 1-2 weeks to confirm alignment, then at 6-12 months to screen for growth disturbance.
- Long-Term Surveillance: Any patient with a SH III, IV, or high-risk location (distal femur) should be followed for at least 1 year for growth arrest.
Outcomes/Prognosis
- Type I/II: Generally excellent. Growth arrest is rare (less than 2% for Type II).
- Type III/IV: Fair to poor if malreduced. Good if anatomically reduced. Arrest rate 10-50%.
- Type V: Poor. Often missed initially. Growth arrest is common.
- Site Matters: Distal femur has the worst outcomes regardless of type.
Evidence Base
- Original description of the classification
- Based on mechanism and prognosis
- Type I/II have better prognosis than III/IV/V
- Added Type VI (injury to perichondral ring)
- Peripheral injuries have high arrest risk
- Lawnmower injuries are classic
- Risk factors for growth arrest after distal tibial physeal fractures
- Greater displacement = greater arrest risk
- Type III/IV are higher risk
- MRI can detect physeal injuries when X-ray is negative
- MRI shows physeal bar formation early
- Useful for Type I and V fractures
- Described physeal bar excision and interposition
- Effective if bar is less than 50% of physis
- Requires at least 2 years of growth remaining
Viva Scenarios
Practice these scenarios to excel in your viva examination
The Limping Child with a Normal X-ray
"9-year-old with ankle pain after a twisting injury. X-ray is normal. Point tenderness over the distal fibular physis."
This is a **Salter-Harris Type I fracture** of the distal fibula (analogous to a lateral ankle sprain in adults). Even though the X-ray is normal, point tenderness over the physis is diagnostic. Management: **Below-knee cast or walking boot** for 3-4 weeks. Prognosis is excellent. No specific follow-up for growth arrest is needed for this location.
The Displaced Type IV Distal Tibia
"12-year-old with a Salter-Harris Type IV fracture of the distal tibia. 3mm of articular step-off on CT."
This is **unacceptable**. Type IV fractures are intra-articular, and greater than 2mm of step-off leads to both joint incongruity (arthritis) and high risk of growth arrest. This requires **ORIF**. I would perform anatomical reduction via an appropriate approach (anterolateral or anteromedial), visualize the articular surface, reduce, and fix with screws placed within the epiphysis (parallel to the physis). This patient needs long-term follow-up for growth disturbance.
Growth Arrest After a Distal Femur Fracture
"8-year-old presents 1 year after a Salter-Harris II distal femur fracture. Now has 2cm of LLD and progressive valgus."
This is a **growth arrest** with a **physeal bar** causing both shortening and angular deformity. MRI will confirm the bar location and size. If the bar is less than 50% of the physis AND the child has greater than 2 years of growth remaining, **bar excision with fat or PMMA interposition** is an option. If the bar is greater than 50% or growth is nearly complete, bar excision will fail. In that case, I would perform **contralateral epiphysiodesis** (to equalize leg length) and correct the angular deformity with an **osteotomy** or **guided growth** (hemi-epiphysiodesis).
The Lawnmower Injury
"5-year-old with a lawnmower injury to the foot. Significant soft tissue loss over the lateral malleolus and visible physis."
This is a **Peterson Type VI** physeal injury - injury to the **perichondral ring**. This is a high-risk injury for peripheral physeal bar formation and subsequent angular deformity. Management: **I&D**, **Stabilization** (of any associated fractures), **Soft tissue coverage** (may need flap). Long-term surveillance for growth arrest is mandatory.
MCQ Practice Points
Classification MCQ
Q: Which Salter-Harris type is most common? A: Type II (75% of physeal fractures). Fracture through physis with a metaphyseal (Thurston-Holland) fragment.
Prognosis MCQ
Q: Which Salter-Harris type has the worst prognosis for growth arrest? A: Type IV and V. Type IV crosses all layers. Type V is a crush injury.
Anatomy MCQ
Q: Which zone of the physis is the weakest? A: Hypertrophic zone. This is where Type I and II fractures propagate.
Management MCQ
Q: What is the maximum acceptable step-off for a Salter-Harris Type III or IV fracture? A: 2mm. Greater than 2mm requires ORIF.
Hardware MCQ
Q: Can threaded screws be placed across the physis? A: Avoid if possible. Threaded hardware creates a tether causing asymmetric growth. Use smooth K-wires and remove early (3-4 weeks).
Distal Femur Risk
Q: What is the significance of the distal femoral physis? A: High risk location. Contributes 70% of femoral growth and 35% of leg length. Even Type II injuries have 30-50% arrest risk.
Australian Context
- Imaging: Low-dose EOS imaging is increasingly available for follow-up.
- Bar Excision: Performed at major pediatric centres with fluoroscopic or navigation guidance.
- Guided Growth: Tension band plating for angular deformity is widely used.
- Surveillance: Children with high-risk physeal injuries should be followed for at least 1-2 years.
PHYSEAL INJURIES (SALTER-HARRIS)
High-Yield Exam Summary
CLASSIFICATION
- •I: Physis only
- •II: + Metaphysis (Most Common)
- •III: + Epiphysis (Intra-art)
- •IV: All Three (Worst)
ANATOMY
- •Hypertrophic Zone (Weakest)
- •Reserve Zone (Germinal)
- •Perichondral Ring (Stability)
- •Thurston-Holland (Type II)
HIGH RISK SITES
- •Distal Femur (70% growth)
- •Proximal Tibia
- •Distal Tibia (Tillaux)
- •Type IV Anywhere
TREATMENT
- •I/II: Cast
- •III/IV: ORIF (greater than 2mm)
- •V: Monitor
- •Avoid crossing physis
Deep Dive: Physeal Bar Excision
What is a Physeal Bar?
- A bridge of bone that forms across the injured physis, tethering growth.
- Can be central (causes shortening only) or peripheral (causes angular deformity).
Indications for Bar Excision
- Bar less than 50% of physis width.
- At least 2 years (or 2cm) of growth remaining.
- Angular deformity that is progressive.
Technique
- Preoperative MRI to map the bar.
- Approach based on bar location.
- Excise the bar under fluoroscopy and direct vision.
- Interpose fat graft or PMMA (to prevent bar reformation).
- Consider concurrent osteotomy if significant angular deformity.
Outcomes
- Restoration of growth in 50-80% of cases.
- Better results with smaller bars and more growth remaining.
Self-Assessment Quiz
Parent's Guide: Understanding Physeal Injuries
What is a Growth Plate? A growth plate is a layer of cartilage near the end of a bone where growth occurs. Children's bones grow from these areas until they reach skeletal maturity (around age 14-16 for girls, 16-18 for boys).
What happens if the growth plate is injured? Most growth plate injuries heal completely without any problems. However, in some cases, the injury can damage the cells responsible for growth, leading to:
- Shorter limb: If growth slows or stops.
- Crooked limb: If one part of the growth plate is damaged but the rest keeps growing.
How is it treated?
- Most injuries are treated with a cast.
- Some injuries (especially those that go into the joint) may require surgery to realign the bones.
What are the warning signs? Your doctor will want to see your child for follow-up X-rays. Call them if you notice:
- One leg looking shorter than the other.
- A limb that seems to be growing crooked.
Long-term outlook Most children do very well. Your doctor may want to monitor your child with X-rays over the next 1-2 years to ensure the growth plate is healing normally.
Additional Evidence
- Risk of growth arrest with transphyseal screws
- Small diameter screws (less than 7% of physis) are safe
- Central placement is safer than peripheral
- Complications of distal femoral physeal fractures
- Overall complication rate 52%
- LLD and angular deformity are common
Rehabilitation Protocol
Phase 1: Immobilization (0-4 weeks)
- Cast or splint immobilization.
- Non-weight bearing for lower limb injuries.
- Gentle ROM of uninvolved joints.
Phase 2: Early Mobilization (4-6 weeks)
- Cast removal if healed.
- Progressive weight bearing.
- Gentle ROM exercises.
Phase 3: Strengthening (6-12 weeks)
- Progressive strengthening.
- Proprioception and balance.
- Return to activities.
Long-Term
- Follow-up X-rays at 6-12 months to screen for growth disturbance.
Differential Diagnosis
In a Child with Periarticular Pain and Normal X-ray:
- Salter-Harris Type I: Point tenderness over the physis. Treat as a fracture.
- Ligament Sprain: Rare in children (ligaments are stronger than physis).
- Stress Fracture: Overuse history. May need MRI/bone scan.
- Infection (Osteomyelitis/Septic Arthritis): Fever, elevated CRP.
- Tumour: Night pain, constitutional symptoms (rare).
Additional Self-Assessment Questions
Specific Physeal Injuries by Location
Distal Radius
- Most common pediatric physeal injury.
- Usually Type I or II. Excellent prognosis.
- Growth arrest is rare (less than 5%).
- Treatment: Closed reduction and casting.
Distal Femur
- High-risk injury. 70% of femoral growth from this physis.
- Growth disturbance in 30-50% of cases.
- Even Type II can lead to significant LLD or angular deformity.
- Requires close long-term follow-up.
Proximal Tibia
- Also high-risk. Contributes 55% of tibial growth.
- Risk of popliteal artery injury (tethered by genicular branches).
- Always perform thorough vascular examination.
Distal Tibia
- Transitional fractures (Tillaux, Triplane) occur as physis is closing.
- Type III (Tillaux) and Type IV (Triplane) are common patterns.
- Require anatomical reduction if displaced.