Distal Femoral Physeal Injuries
Protecting the Critical Physis
Salter-Harris Classification
Critical Must-Knows
- High Risk: Even Type II injuries have 30-50% growth disturbance rate.
- Anatomical Reduction: Essential for all types.
- Long-Term Follow-Up: Mandatory for at least 1-2 years.
- Vascular Risk: Popliteal artery is close to the physis.
- Growth Arrest Management: Bar excision or epiphysiodesis depending on bar size.
Examiner's Pearls
- "This is NOT a benign fracture
- "Reduction must be anatomical
- "Follow for growth disturbance annually
- "Know bar excision indications
Clinical Imaging
Imaging Gallery
The Most Dangerous Growth Plate
Critical Growth Plate
70% of femoral length comes from this physis. Growth disturbance occurs in 30-50% of injuries (even Type II).
Mandatory Counseling
ALWAYS warn families about growth arrest, angular deformity (1°/year), and LLD (1cm/year). 2-year minimum follow-up is mandatory.
Distal Femoral Physis Key Facts
| Feature | Importance | Clinical Relevance |
|---|---|---|
| 70% of femur, 35% of leg | Highest of any physis | |
| 30-50% | Even for Type II | |
| Popliteal artery tethered | Hyperextension injury | |
| Minimum 2 years | Annual scanograms |
Distal Femur Dangers
Memory Hook:GROW - Distal femur must grow, protect it.
Complications to Watch
Memory Hook:LAV - Watch for these.
Treatment Principles
Memory Hook:APS - The treatment triad.
Overview/Epidemiology
Distal Femoral Physeal Injuries are relatively uncommon but HIGH STAKES injuries.
- Epidemiology:
- Account for 1-5% of all physeal injuries.
- Mean age 11-13 years (adolescent growth spurt).
- Boys greater than Girls (higher energy mechanisms).
- Mechanism:
- Hyperextension (popliteal artery at risk).
- Varus/Valgus Stress (sports injuries, MVA).
- Direct Trauma.
Anatomy and Pathomechanics
Physeal Anatomy
- The distal femoral physis is the largest physis in the body.
- It is undulating (mamillary processes interdigitate with metaphysis), providing some inherent stability but also predisposing to irregular arrest patterns.
- The physis is completely intracapsular (no perichondral ring protection medially and laterally near the collaterals).
Growth Contribution
- 70% of femoral length (approximately 1cm/year near peak growth).
- 35% of total lower limb length.
- Loss of even 1-2 years of growth equates to 1-2cm LLD.
Vascular Anatomy
- The popliteal artery is tethered by the genicular branches as it passes through the popliteal fossa.
- In hyperextension injuries, the artery can be stretched over the posterior metaphysis.
- Vascular injury rate: approximately 2% for displaced fractures.
Classification Systems
Salter-Harris Classification
Applied to the Distal Femur:
Type I: Rare in isolation. Usually seen in infants (birth injuries) or pathological bone.
Type II: Most common (approximately 60%). Metaphyseal (Thurston-Holland) fragment is usually posterolateral.
Type III: Intra-articular. Usually medial condyle. Requires anatomical ORIF.
Type IV: Crosses all layers. High arrest risk. Requires ORIF.
Clinical Assessment
History:
- Mechanism: Twisting? Hyperextension? Direct blow?
- Neurovascular Symptoms: Numbness, cold foot?
Physical Exam:
- Inspection: Swelling, deformity, skin tenting (posterior spike).
- Palpation: Tenderness around the distal femur.
- Neurovascular (CRITICAL): Popliteal pulse (may need Doppler), DP/PT pulses, capillary refill, foot warmth. Peroneal nerve function (foot drop).
- Compartments: Assess for compartment syndrome (especially with vascular injury).
Investigations
Imaging:
- X-ray (AP and Lateral): Standard. Include the knee and proximal tibia.
- Stress Views: May help identify occult Type I (with anesthesia if needed), but MRI is safer.
- CT Scan: For Type III/IV to map the intra-articular fracture.
- MRI: Useful for occult injuries or to assess physeal damage after reduction.
Vascular Assessment:
- Ankle-Brachial Index (ABI): If pulses are diminished.
- CT Angiography: If vascular injury is suspected (hard or soft signs).
Management Algorithm
Non-Displaced / Minimally Displaced Fractures
- Long Leg Cast: Knee in 20-30 degrees flexion. 6 weeks immobilization.
- Close follow-up with weekly X-rays for 2-3 weeks to monitor for displacement.
- Consider prophylactic pinning even for non-displaced fractures due to the high stakes.
Surgical Techniques
Closed Reduction and Percutaneous Pinning
Indications: Displaced Type I/II with acceptable closed reduction.
Technique: Reduction under fluoroscopy. Traction and reversal of the deforming force. For hyperextension injuries, flex the knee and apply posterior force to the distal fragment. Once reduced, pass 2-3 smooth K-wires (2.0-2.4mm) from the metaphysis into the epiphysis, crossing the fracture. Place pins divergently for stability. Avoid the intercondylar notch (ACL). Cut flush or bury.
Post-op: Long leg cast for 6 weeks. Pin removal at 4-6 weeks.
Key Surgical Points
- Single reduction attempt preferred to minimize additional physeal damage.
- Avoid excessive periosteal stripping to preserve blood supply.
- If crossing the physis is unavoidable, use smooth wires and remove early.
- Document neurovascular status before and after reduction.
Complications
| Complication | Rate | Prevention/Management |
|---|---|---|
| Growth Arrest | 30-50% | Anatomical reduction. Avoid iatrogenic damage. |
| Angular Deformity | Common (Varus/Valgus) | Bar excision if less than 50%, Osteotomy if more. |
| Leg Length Discrepancy | Common | Monitor. Epiphysiodesis or limb lengthening. |
| Vascular Injury | 1-2% | Vascular assessment. Urgent repair if injured. |
| Peroneal Nerve Palsy | Rare | Document pre-op. Avoid traction. |
| Stiffness | Variable | Early ROM after healing. |
Postoperative Care
- Immobilization: Long leg cast for 6 weeks minimum.
- Weight Bearing: Non-weight bearing initially, then protected WB.
- Pin Removal: 4-6 weeks (smooth wires). Screws can be left in situ.
- Follow-Up Schedule:
- Weekly X-rays for first 2-3 weeks.
- 6-week X-ray (assess healing).
- 6-month and 12-month X-rays (scanograms to assess growth).
- Annual follow-up until skeletal maturity.
Outcomes/Prognosis
- Growth Arrest: Occurs in 30-50% of cases, regardless of type.
- Type I/II: Still have significant arrest risk (25-35%).
- Type III/IV: Higher arrest risk (40-60%).
- Prognosis depends on: Quality of reduction, amount of growth remaining, and size of any physeal bar.
- Functional Outcomes: Generally good if LLD and angular deformity are managed.
Evidence Base
- Review of distal femoral physeal fractures
- Overall growth disturbance rate 52%
- No difference between SH types for arrest rate
- Anatomical reduction reduces arrest rate
- Non-anatomical reduction associated with higher LLD
- Recommend aggressive reduction
- Complications in distal femoral physeal fractures
- 52% overall complication rate
- 24% required secondary procedures
- Vascular injury in distal femoral fractures
- Hyperextension mechanism is highest risk
- Document vascular status diligently
- Long-term follow-up of distal femoral physeal injuries
- LLD and angular deformity are common
- Bar excision successful if less than 50%
Viva Scenarios
Practice these scenarios to excel in your viva examination
The Displaced SH II Distal Femur
"12-year-old with a Salter-Harris Type II distal femur fracture with posterior displacement of the distal fragment. Pulses palpable."
This is a **high-risk injury**. Even though pulses are palpable, I would document the vascular status carefully (ABI if any concern). This likely occurred via a **hyperextension mechanism**. I would perform **gentle closed reduction** under general anesthesia - flexing the knee and applying posterior force. Once reduced, I would **percutaneously pin** with smooth K-wires (2-3 wires, divergent). Post-op in a long leg cast. I would counsel the family about the **30-50% risk of growth disturbance** and arrange long-term follow-up with scanograms.
Absent Pulses After Distal Femur Injury
"Same patient as above. After closed reduction, the foot is cold and the DP pulse is not palpable."
This is a **vascular emergency**. The popliteal artery may be injured (stretched, intimal tear, thrombosis). I would immediately obtain an **ABI**. If less than 0.9, or if the foot remains cold, I would request an **urgent CT angiography** and involve the **vascular surgery team**. If there is clear arterial injury, **surgical exploration and repair** is needed urgently (within 6 hours to prevent irreversible ischemia). The fracture should be stabilized (external fixation if needed) to facilitate vascular repair. Fasciotomy may be required for reperfusion injury.
Growth Arrest After Treated Distal Femur Fracture
"10-year-old, 1 year post Type II distal femur fracture. Now has 2.5cm LLD and 10 degrees of valgus."
This is a **growth arrest** with a **physeal bar** causing both shortening and angular deformity. I would get an **MRI** to map the bar. The child has significant growth remaining. If the bar is **less than 50%** of the physis width, I would consider **bar excision** with fat interposition, combined with an **osteotomy** to correct the existing angular deformity. If the bar is **greater than 50%**, bar excision will fail. I would then perform **contralateral epiphysiodesis** (to equalize limb lengths) and a corrective **osteotomy** for the angular deformity.
Consent for Distal Femoral Physeal Fracture Surgery
"You are consenting a family for CRPP of a displaced SH II distal femur. What specific risks do you discuss?"
I would explain that this is a **high-risk growth plate injury**. Specific risks I would discuss include: **Growth disturbance (30-50% chance)** leading to leg length discrepancy or a crooked leg, even with perfect surgery. **Vascular injury** (the artery is close). **Nerve injury** (peroneal nerve). **Stiffness** of the knee. **Infection** (low risk). **Need for further surgery** (bar excision, osteotomy, epiphysiodesis). I would emphasize that **long-term follow-up with X-rays for at least 2 years** is essential.
The Birth Injury
"A neonate is noted to have decreased movement of the right leg after a difficult delivery. X-ray shows physeal widening at the distal femur."
This is a **birth-related distal femoral physeal injury** - typically a Type I fracture. The mechanism is usually hyperextension during breech delivery. The epiphysis may appear displaced on ultrasound due to lack of ossification. Management: **Splinting in comfortable flexion** for 2-3 weeks. Prognosis is generally excellent with rapid healing and minimal growth disturbance risk, though follow-up is still advisable.
The Adolescent Athlete
"16-year-old footballer with a valgus stress injury to the knee. Tender over the medial femoral condyle physis. X-ray shows a Salter-Harris III pattern."
This is a **Type III physeal injury** of the distal femur (medial condyle). It is intra-articular. I would obtain a **CT scan** to map the fracture. Management: **Anatomical ORIF** is mandatory. I would perform open reduction via a medial approach and fix with cannulated screws placed within the epiphysis, parallel to the joint. Post-op in a long leg cast for 6 weeks. This patient has minimal growth remaining (age 16), but I would still arrange follow-up scanograms.
The Polytrauma Patient
"8-year-old polytrauma after MVA. Bilateral distal femoral physeal fractures (Type II). Hemodynamically stable after resuscitation."
This is a **bilateral high-risk physeal injury** in the setting of polytrauma. Once the patient is hemodynamically stable and ATLS resuscitation is complete, I would prioritize **fracture stabilization** to facilitate nursing care and reduce pain. I would perform **closed reduction and percutaneous pinning** of both sides in a single surgery. Post-op in bilateral long leg casts. Given the bilateral nature and young age, I would counsel the family extensively about the high risk of growth disturbance and arrange meticulous long-term follow-up.
MCQ Practice Points
Anatomy MCQ
Q: What percentage of femoral length does the distal femoral physis contribute? A: 70%. This is the highest of any physis in the body.
Prognosis MCQ
Q: What is the approximate growth arrest rate for distal femoral physeal fractures? A: 30-50%, regardless of Salter-Harris type.
Vascular MCQ
Q: What vascular structure is at risk in distal femoral physeal injuries? A: Popliteal Artery. It is tethered by genicular branches and can be injured in hyperextension.
Treatment MCQ
Q: What fixation method is preferred for Type II distal femoral physeal fractures? A: Smooth K-wire percutaneous pinning (avoids crossing intact physis with threaded hardware).
Bar Excision MCQ
Q: What is the maximum physeal bar size amenable to bar excision? A: Less than 50% of the physis width, with at least 2 years of growth remaining.
Follow-up MCQ
Q: How long should patients with distal femoral physeal injuries be followed? A: At least 2 years with annual scanograms to skeletal maturity to detect growth disturbance.
Australian Context
- Tertiary Care: Complex distal femoral physeal injuries should be managed at tertiary pediatric centers.
- Vascular Surgery: Immediate vascular surgery availability is essential for displaced injuries.
- Imaging: EOS for scanograms is increasingly available for growth monitoring.
- Medicolegal: Failure to warn about growth disturbance is a common source of complaints.
DISTAL FEMORAL PHYSEAL INJURIES
High-Yield Exam Summary
KEY FACTS
- •70% Femoral Growth
- •35% Leg Length
- •30-50% Arrest Rate
- •Popliteal Artery Risk
TREATMENT
- •Anatomical Reduction
- •Smooth Pin Fixation
- •Avoid Crossing Physis
- •6+ Week Immobilization
COMPLICATIONS
- •Growth Arrest
- •LLD
- •Angular Deformity
- •Vascular Injury
FOLLOW-UP
- •Weekly X-rays (2-3 wks)
- •6-Month Scanogram
- •Annual to Maturity
- •Warn Family
Deep Dive: Managing Growth Arrest
Types of Arrest
- Complete Arrest: Entire physis stops growing. Results in shortening only (no angular deformity).
- Partial (Central) Arrest: Bar in the center. Causes shortening and may cause "tenting" of the physis.
- Partial (Peripheral) Arrest: Bar on one side. Causes angular deformity as the unaffected side keeps growing.
Evaluation
- Scanogram: Leg length measurement.
- MRI: Maps the physeal bar (location, size).
- Bone Age: Estimate remaining growth.
Management Options
- Bar less than 50%, Greater than 2 years growth remaining: Bar excision + fat/PMMA interposition.
- Bar greater than 50%, or Less than 2 years growth remaining: Bar excision will fail. Consider:
- Contralateral epiphysiodesis (for LLD).
- Limb lengthening (for significant LLD).
- Corrective osteotomy (for angular deformity).
- Guided growth (hemi-epiphysiodesis for angular correction if some growth remains).
Self-Assessment Quiz
Parent's Guide: Understanding Distal Femoral Injuries
What is the distal femoral growth plate? The distal femur (thighbone near the knee) has a growth plate that is responsible for 70% of the thighbone's growth. Injury to this growth plate is serious because it can affect how your child's leg grows.
Why is this injury different? Unlike most other growth plate injuries, the distal femoral growth plate has a HIGH chance (30-50%) of developing problems with growth, even if the treatment is perfect. This may lead to:
- One leg being shorter than the other.
- One leg growing crooked.
What are the treatment options if growth problems occur? If growth problems develop, your doctor may recommend:
- Surgery to remove the damaged area and allow growth to resume.
- Surgery on the opposite leg to slow its growth (so the legs end up the same length).
- Surgery to straighten a crooked leg.
What follow-up is needed? Your child will need regular X-rays for at least 2 years to monitor the growth plate. Please do not miss these appointments, as early detection of problems allows for better treatment.
Rehabilitation Protocol
Phase 1: Immobilization (0-6 weeks)
- Long leg cast. Knee in 20-30 degrees of flexion.
- Non-weight bearing on affected limb.
- Encourage toe wiggling and calf pumps to prevent DVT.
- Hip and ankle ROM exercises (within cast constraints).
Phase 2: Early Mobilization (6-10 weeks)
- Cast removal at 6 weeks if healing confirmed.
- Hinged knee brace initially.
- Partial weight bearing progressing to full weight bearing.
- Active and passive ROM for the knee.
- Quadriceps and hamstring isometrics.
Phase 3: Strengthening (10-16 weeks)
- Progressive resistance exercises.
- Closed kinetic chain exercises (squats, leg press).
- Proprioception and balance training.
- Gait normalization.
Phase 4: Return to Activity (4-6 months)
- Sport-specific training.
- Full ROM and greater than 90% strength.
- Clearance by surgeon (confirm no growth disturbance).
Differential Diagnosis
Knee Pain After Trauma in Adolescents:
- Distal Femoral Physeal Fracture: Point tenderness over the distal femoral physis.
- Patellar Dislocation: Apprehension sign positive. Patella may be back in place.
- ACL Tear: Hemarthrosis. Lachman positive. Usually post-skeletal maturity.
- Tibial Eminence Fracture: Extension block. X-ray shows avulsed tibial spine.
- Meniscal Injury: Locking, clicking. Usually after twisting.
- Proximal Tibial Physeal Fracture: Tenderness over the proximal tibial physis.
- Pathological Fracture: Through tumor. Night pain, constitutional symptoms.
Key Differentiators:
- Point tenderness over the physis indicates physeal injury.
- Hemarthrosis is common in ligament tears and intra-articular fractures.
- Always get a good lateral X-ray to assess the physis.
Surgical Pearls
Reduction Technique
- Apply longitudinal traction with the knee slightly flexed.
- For hyperextension injuries (posterior displacement of the distal fragment), flex the knee and push the distal fragment anteriorly.
- Avoid excessive force. One smooth reduction attempt is better than multiple aggressive attempts.
Pinning Technique
- Enter from the lateral and medial metaphysis, above the physis.
- Direct the wires across the fracture into the epiphysis.
- Diverge the wires for three-point fixation stability.
- Avoid the intercondylar notch (risk of ACL damage).
- Image in two planes (AP and lateral) to confirm position.
Avoiding Iatrogenic Damage
- Use smooth wires (not threaded).
- If threaded screws are used (for epiphyseal fixation), ensure they are parallel to the physis and do not cross it.
- Limit drill passes through the physis.
- Use small diameter implants.
Post-Reduction Checks
- Confirm neurovascular status immediately.
- Document pulses both before and after reduction.
- Obtain X-rays to confirm anatomical reduction.
Comparison: Distal Femur vs Other Physes
Distal Femur vs Other High-Risk Physes
| Feature | Distal Femur | Proximal Tibia | Distal Radius |
|---|---|---|---|
| 70% femur | 55% tibia | 75% radius | |
| 30-50% | 20-30% | Less than 5% | |
| Popliteal artery | Popliteal artery | Rare | |
| High | High | Low |