Slipped Capital Femoral Epiphysis

Overview

Definition

Slipped capital femoral epiphysis (SCFE) is a hip disorder common in adolescence that features the displacement of the capital epiphysis of the femoral head through the growth plate (physis) in relationship to the femoral neck.

Slipped capital femoral epiphysis (SCFE) is considered a Salter-Harris type 1 fracture, because SCFE is a transverse fracture through the growth plate or physis.

Classification

There are several classification systems for SCFE:

• Temporal classification: time of presentation:
  • Acute: < 3 weeks
  • Chronic: > 3 weeks
• Loder classification of stability: based on the ability to bear weight:
  • Stable: ambulation possible
  • Unstable: ambulation not possible
• Southwick slip angle classification: femoral epiphyseal-diaphyseal angle difference:
  • Mild: < 30° 
  • Moderate: 30°–50°
  • Severe: > 50°
• Gradation: based on the percentage of slippage:
  • Grade I: 0%–33%
  • Grade II: 34%–50%
  • Grade III: > 50%

Epidemiology

• Incidence 1 in 1,000–10,000 children in the United States
• Mean age of presentation is 12–13 years.
• Male : female ratio 2.5:1
• More common in Pacific Islanders, Latinx, and Black adolescents 
• Left hip more commonly affected in unilateral cases
• Bilateral in 20%–40% of cases (up to 100% of patients with endocrine disease) 
• Associated with:
  • Obesity (the severity of disease worsens in parallel with obesity)
  • Hypothyroidism
  • Hypogonadism
  • Panhypopituitarism 
  • Growth hormone disorders 
  • Several genetic disorders (e.g., Rubenstein-Taybi syndrome, Down’s syndrome)

Etiology

The causes of SCFE are multifactorial, a combination of endocrine and biomechanical factors. Excessive mechanical forces causing more shearing forces to be applied to the femoral neck result in the failure of a susceptible (weakened) physis.

• Increased mechanical forces: 
  • Increased body weight 
  • Trauma 
• Weakened physis:
  • Widening of the epiphysis and periosteal thinning during periods of rapid growth (e.g., pubertal growth) 
  • Chronic inflammation of the joint
  • Endocrine and metabolic disorders causing abnormal mineralization of cartilage and instability of the perichondrial ring:
    • Hypothyroidism
    • Renal osteodystrophy
    • Growth hormone deficiency 
    • Panhypopituitarism
  • Radiation exposure for treatment of bone cancers

Pathophysiology

Repetitive shear forces applied to a weakened physis result in fracture and slipping. As slippage progresses, the metaphysis translates anteriorly and superiorly while rotating externally; the epiphysis remains in the acetabulum.

Clinical Presentation

Children who present with SCFE typically complain of groin and anterior thigh pain, and demonstrate an altered gait.  

• History:
  • Chief complaint: hip pain without a history of trauma: 
    • May complain primarily of pain in the ipsilateral knee
    • Pain in the groin, hip, knee, or thigh aggravated by physical exertion
  • Acute cases: severe and sudden pain after injury or activity
  • Chronic cases: hip pain for weeks or months
  • May report difficulty in daily activities (tying shoes)
• Physical examination:
  • Limping while walking or running (inability to walk in severe cases)
  • External rotation of the affected leg and loss of range of motion (ROM)
  • Length discrepancy of lower limbs (the affected limb is shorter)
  • Gait becomes antalgic as slippage progresses.

Diagnosis

The diagnosis of SCFE is performed through a combination of history, physical examination, and plain film X-rays. 

• Hip X-rays (anteroposterior (AP) and frog leg lateral views of both hips):
  • Lateral X-ray is the primary way to identify a subtle slip:
    • Epiphysiolysis: growth plate widening or lucency
  • Klein’s line: In AP view, a line drawn along the superior border of the femoral neck will intersect less of the femoral head in a child with SCFE; asymmetry between sides is key.
• Computed tomography (CT), magnetic resonance imaging (MRI), and bone scans:
  • MRI may help diagnose a “preslip” condition.
  • If X-rays normal, but SCFE suspicion high, MRI can demonstrate widening of the growth plate with surrounding edema
• Hormone levels according to clinical suspicion of endocrinopathies

Management and Complications

Management

The treatment involves immediate non–weight-bearing status and referral to orthopedic surgery:

• Must be non–weight bearing to prevent further slippage
• Operative stabilization is the primary treatment:
  • Percutaneous screw fixation through the femoral neck, engaging the physis
  • Reduction of slipped epiphysis is not recommended because of increased risk of avascular necrosis.
  • Prophylactic pinning of the contralateral hip is controversial.
• Prognosis:
  • Mild cases with less slippage have a better prognosis.
  • More severe cases are at risk of developing osteoarthritis at a young age.

Complications

• Osteonecrosis or avascular necrosis of the hip: loss of blood supply to the femoral head leading to necrosis of cartilage and bone: 
  • Most concerning complication leading to worst outcome 
  • Increased risk seen with acute, unstable slips 
  • 10%–15% of children with SCFE develop osteonecrosis.
• Contralateral hip SCFE: increased risk in obese males with endocrine disorders
• Chondrolysis: destruction of hip cartilage: occurs with penetration of a stabilization pin into the joint during surgery
• Residual deformity with limb length discrepancy
• Femoroacetabular impingement (FAI): poor fit of the hip “ball in socket” causing grating and further injury with movement
• Degenerative arthritis with aging
• Non-union after surgical pinning

Clinical Relevance

• Avascular necrosis of the hip: necrosis and deformation of the femoral head due to impaired blood supply to the head of the femur. Development of avascular necrosis is a serious complication in SCFE or other conditions.
• Osteoarthritis or degenerative joint disease: progressive degeneration of the joint characterized by a loss of cartilage and growth of bone spurs. Patients with SCFE, due to femoral head deformity, are at risk of developing degenerative changes of the hip joint and osteoarthritis earlier in life.
• Legg-Calvé-Perthes disease (LCPD): idiopathic avascular necrosis of the femoral head. Exact mechanism is unknown and diagnosis is made by clinical findings and diagnostic imaging. Treatment can be conservative or surgical, depending on the severity and the patient’s age.