Slipped Capital Femoral Epiphysis (SCFE): Diagnosis and Management Controversies

Slipped Capital Femoral Epiphysis (SCFE) is the most common hip disorder affecting adolescents, yet it remains one of the most challenging conditions to manage perfectly. The classic analogy of "ice cream falling off the cone" belies the potential for catastrophic complications like Avascular Necrosis (AVN) and Chondrolysis.

This article explores the etiology, diagnosis, and the raging controversies in surgical management.

Visual Element: Cover image demonstrating Klein's Line on an AP pelvis X-ray, highlighting the "Trethowan's sign" where the line fails to intersect the epiphysis.

1. Etiology and Pathophysiology

SCFE is a failure of the proximal femoral physis (growth plate). It is a Salter-Harris Type I fracture that occurs slowly (usually).

• Mechanical Factors: Obesity is the strongest risk factor. The increased load on the hip joint exerts excessive shear stress on the physis. The slip occurs through the hypertrophic zone of the physis, which is the weakest layer.
• Endocrine Factors: The physis is weakened by hormonal imbalances.
  • Hypothyroidism: Delays physeal closure.
  • Growth Hormone: Increases physeal width and proliferation.
  • Renal Osteodystrophy.
  • Pearl: If a patient is <10 years old or >16 years old, or is underweight, screen for endocrine disorders.

2. Clinical Presentation: The Knee Pain Trap

The diagnosis is frequently missed.

• The Classic Patient: Obese adolescent male (10-16 years).
• Symptoms: Groin pain, thigh pain, or—crucially—Knee Pain.
• The Trap: The obturator nerve supplies both the hip and the knee. Up to 15-20% of SCFE patients present solely with knee pain. Always examine the hip in a child with knee pain.
• Physical Exam:
  • Antalgic gait (Trendelenburg).
  • External Rotation deformity: The foot points outward.
  • Obligatory External Rotation: When you flex the hip, it automatically goes into external rotation. Limited internal rotation is the hallmark sign.

3. Classification Systems

Loder Classification (Stability)

This is the most clinically relevant classification as it predicts the risk of AVN.

• Stable SCFE: The patient can walk (even with crutches).
  • AVN Risk: <10% (some studies say 0%).
• Unstable SCFE: The patient cannot walk or bear weight. This is effectively an acute fracture.
  • AVN Risk: Extremely high (20-50%).

Temporal Classification

• Acute: < 3 weeks symptoms.
• Chronic: > 3 weeks.
• Acute-on-Chronic: Exacerbation of pain in a patient with long-standing symptoms.

Southwick Angle (Severity)

Measured on the frog-leg lateral view.

• Mild: <30°
• Moderate: 30-50°
• Severe: >50°

4. Management: The Gold Standard

In-Situ Pinning

For Stable SCFE, in-situ pinning with a single cannulated screw is the gold standard globally.

• Goal: Prevent further slippage. We accept the deformity to avoid the risk of AVN associated with reduction.
• Technique:
  • Percutaneous screw from the anterior-lateral thigh.
  • Screw should be perpendicular to the physis.
  • Center-Center: Ideally in the center of the epiphysis on both AP and Lateral views.
  • Pin Penetration: The screw must stop 5mm short of the joint. Penetration causes Chondrolysis (rapid cartilage death).

Visual Element: Internal 3D render showing the ideal screw trajectory for in-situ pinning.

5. Controversy 1: Prophylactic Pinning

Should we fix the other (normal) hip?

• The Risk: The risk of a contralateral slip is 20-40% (higher in patients with endocrine issues).
• The Debate:
  • Proponents: Pinning is a minor surgery; a slip is a major disaster. Fix it before it happens.
  • Opponents: You are operating on a normal hip. Complications (infection, fracture, chondrolysis) can occur. Close follow-up is safer.
• Consensus: Most surgeons advocate prophylactic pinning for "high risk" patients (young age, endocrine disease, high Southwick angle on the first side).

6. Controversy 2: The Unstable Slip

This is an orthopaedic emergency.

• Urgent Decompression: There is consensus that the intracapsular hematoma raises pressure and tamponades the retinacular vessels. Urgent capsulotomy (release) is recommended.
• Reduction?: Gentle reduction is controversial. Forceful reduction stretches the vessels and causes AVN. However, leaving the hip in severe displacement also kinks the vessels. Most accept an "incidental" gentle reduction during positioning but avoid forceful maneuvers.

7. Controversy 3: The Modified Dunn Osteotomy

For Severe slips, in-situ pinning leaves a major deformity. This deformity causes Femoroacetabular Impingement (FAI) and early arthritis.

• The Procedure: Developed by Reinhold Ganz. It involves a surgical dislocation of the hip, developing a retinacular flap to protect the blood supply, removing the callus/bump, and realigning the epiphysis anatomically.
• The Promise: A normal hip. No FAI. No arthritis.
• The Peril: It is technically demanding. In inexperienced hands, the AVN rate is high.
• Current Stance: In expert centers, Modified Dunn is becoming the treatment of choice for severe slips. In general practice, it is risky.

8. Complications

• Avascular Necrosis (AVN): The death of the femoral head. Leads to collapse and early Total Hip Replacement.
• Chondrolysis: Acute dissolution of articular cartilage. Linked to pin penetration. Causes a stiff, painful, fused hip.
• Slip Progression: If the screw is not placed well, the slip can continue.
• Impingement (FAI): The residual bump on the femoral neck ("Pistol Grip Deformity") jams against the acetabulum, causing labral tears and arthritis.

Conclusion

SCFE is a diagnosis you cannot afford to miss.

• The Rule: Every child with knee pain needs a hip exam.
• The Treatment: Pin it where it lies (usually).
• The Future: Anatomical reduction (Modified Dunn) is the future, but only if we can solve the AVN problem.

Clinical Pearl: Klein's Line. On an AP pelvic X-ray, a line drawn along the superior neck of the femur should intersect the epiphysis. If it doesn't, that is a SCFE (Trethowan's Sign).