Slipped Capital Femoral Epiphysis (SCFE)

Definition: Medial or posterior slippage of the femoral capital epiphysis relative to the metaphysis

Epidemiology:

• Classic patient group: overweight adolescent boys
  • Over 80% of SCFE involves children with a BMI > 95^th percentile (Manoff 2005).
  • Average age of onset: 12 years old
• Bilateral SCFE is fairly common
  • 23% will have contralateral disease at the time of initial presentation, despite only complaining of unilateral pain (Hagglund 1988, Loder 1993).
  • Up to 60% of patients will go on to develop bilateral SCFE in their lifetime
  • 88% of subsequent slips occur within 18 months of diagnosing the first slip
• Influenced by bone maturation, strength, and weight mismatch.
• SCFE has also been associated with endocrine disorders such as hypothyroidism, hypogonadism, pan-hypopituitarism, but this is not as common.

Presentation:

• Groin, hip and thigh pain most common (85%) – constant or intermittent
• Isolated knee pain (15%)
• Limited internal rotation
• +/- Limp
• Immobility or refusal to bear weight
• Weakness
• Abnormal gait alignment
• May have no complaints of pain at time of presentation/examination

Differential Diagnoses:

• Muscle strain
• Pelvic fracture
• Acute Rheumatic Fever
• Developmental dysplasia of hip
• Juvenile idiopathic arthritis
• Legg-Calve-Perthes disease
• Septic arthritis
• Transient synovitis
• Osteosarcoma

Complications:

• Usually secondary to delays in diagnosis due to:
  • Vague, nonspecific symptoms as discussed above or delayed patient presentation
  • Failure to obtain appropriate imaging
    • SCFE can present as isolated knee or distal thigh pain in up to 15% of cases (Matava 1999).
  • Subtle diagnostic findings in mild cases missed by inexperienced radiologists or orthopedists
    • One retrospective study showed SCFE to be the second most commonly missed pediatric orthopedic diagnosis behind fracture (Skaggs 2002)
• Numerous retrospective studies demonstrate that the average time of symptom onset to diagnosis is eight weeks
• Subsequent complications
  • Avascular necrosis (AVN) of the femoral head
  • Femoroacetabular impingement (FAI)
  • Limb-length discrepancy
  • Decreased range of motion
  • Osteoarthritis

Diagnosis:

• Plain Radiography (gold standard for diagnosis)
  • Views to obtain: XR Pelvis AP and Frog-Leg Lateral
    • Bilateral imaging should be obtained due to the high rate of bilateral disease on initial presentation
  • SCFE identified on XR has been traditionally described as ice cream slipping off the cone
    • Similar Salter Harris Type I Fracture due to disruption of physeal plate
  • Southwick Head Shaft Angle (SHSA) is used to classify the degree of slip
    • Mild: < 30^o
    • Moderate: 31-50^o
    • Severe: > 51^o 
  • Klein’s Line/S-Sign
    • Klein’s Line
      • Line drawn along the femoral neck and passes through the epiphysis.
      • With SCFE, Klein’s Line does not include the epiphysis and instead will pass lateral to the epiphysis.
    • S-Sign
      • Smooth S-shaped line drawn along the femoral head-neck junction from lesser trochanter to the midpoint of the femoral head.
      • If the line is asymmetric, discontinuous, or has sharp turns the likelihood of SCFE is significantly increased.
      • The combination of Klein’s line and the S-Sign are 96.5% sensitive and 85% specific for all cases of SCFE (Rebich 2018)
        • Accurate and easily reproducible compared to SHSA making them more useful in early diagnosis and improving overall prognosis.

• Ultrasound
  • 95% sensitivity (Magnano 1998)
  • Can show hip effusion or metaphyseal step-off when radiographs are negative
  • Operator dependent

• MRI
  • Sensitivity as high as 88% (Magnano 1998).
  • Useful in detecting early SCFE in “pre-slip” phase by identifying physeal abnormalities of those at risk of slippage even without radiographic evidence (Khaladkar 2015)

• CT
  • Generally not indicated given the other available imaging modalities
  • Avoid excessive and unnecessary radiation in children

Management:

• All patients should be immobilized and made non-weight bearing
• Obtain orthopedic consultation to determine need for early surgical intervention vs clinic referral for delayed repair
• Simple (non-operative) closed reduction
  • Contraindicated in stable SCFE
  • Manipulation of an intact epiphyseal-metaphyseal interface without visualization can result in worsening instability and additional complications.
• Identify avascular necrosis if present as this has been shown to be a complication of both delayed diagnosis as well as surgical repair of unstable SCFE
  • Preoperative
    • MRI with contrast
    • Bone scintigraphy
  • Intraoperative
    • Visual confirmation of bleeding by drilling into femoral head
    • Laser Doppler Flowmetry to measure pressure within the femoral head
• Treatment options include open or closed surgical fixation via:
  • Percutaneous in situ fixation
  • Osteotomy
  • Capsulotomy

Take Home Points

• Always consider SCFE in the differential diagnosis of a patient with non-traumatic hip, groin, thigh or knee pain
• Early recognition and diagnosis are crucial to avoid complications
• Immediate immobilization and urgent orthopedic consultation is crucial in management
• Surgical repair is the only definitive treatment modality

Guest Post By

C. Blair Gaines, MD
Emergency Medicine, PGY-3
Jackson Memorial Hospital
Miami, FL

References

1. Asad I et al. Point-of-Care Ultrasound Diagnosis of Slipped Capital Femoral Epiphysis. Clin Pract Cases Emerg Med 2019. PMID: 30775677
2. Kim TY et al. Limping: Evaluation, Diagnosis, and Management in the Pediatric ED. Pediatric Emergency Medicine Practice 2006. [Link is HERE]
3. Lien J et al. Pediatric Orthopedic Injuries: Evidence-Based Management in the Emergency Department. Pediatric Emergency Medicine Practice 2017. PMID: 28825959
4. Millis MB. SCFE: Clinical Aspects, Diagnosis, and Classification.  Journal of Children’s Orthopaedics 2017. PMID: 28529655
5. Otani T et al. Diagnosis and Treatment of Slipped Capital Femoral Epiphysis: Recent Trends to Note. Journal of Orthopedic Science 2018. PMID: 29361376
6. Rahme D et al. Consequences of Diagnostic Delays in Slipped Capital Femoral Epiphysis. Journal of Pediatric Orthopaedics 2006. PMID: 16436942
7. Rebich EJ et al. The S Sign: A New Radiographic Tool to Aid in the Diagnosis of Slipped Capital Femoral Epiphysis. JEM 2018. PMID: 29550284

Post Peer Reviewed By: Anand Swaminathan, MD (Twitter: @EMSwami) and Salim R. Rezaie, MD (Twitter: @srrezaie)