Slipped capital femoral epiphysis

Slipped capital femoral epiphysis (SCFE) refers to the superior and anterolateral displacement of the femoral neck due to weakening of the proximal femoral epiphyseal growth plate. The name of the condition is a misnomer because the metaphysis, not the epiphysis, is displaced. It most commonly occurs in adolescent boys. The etiology is not fully understood, but risk factors include obesity and endocrine disorders. SCFE may have an acute or insidious onset and manifests with hip pain, limping, and restricted movement of the affected hip. If the patient is unable to walk, then the SCFE is considered unstable, which increases the risk of complications such as avascular necrosis. Conventional x-ray confirms the displacement. Surgical fixation is the only treatment option.

• Prevalence: most common hip disorder in adolescents ^[1]
• Peak incidence: : 10–16 years (often occurs during a growth spurt) ^[1]
• Sex: : ♂ > ♀

Epidemiological data refers to the US, unless otherwise specified.

The exact etiology is still unknown. However, there are some risk factors that increase the likelihood of SCFE: ^[2]

• Obesity
• Family history
• Endocrine or hormonal factors (e.g., hypothyroidism; , pituitary tumors, down syndrome, renal osteodystrophy, craniopharyngioma)
• Trauma (e.g., sports-related injury or fall)

• Puberty-induced hormonal changes, endocrine disorders, inflammation → poor cartilaginous organization and maturation → wide and unstable proximal femoral epiphyseal growth plate ^[3]
• Obesity, growth spurts, trauma → increased shear force
• Shear force > strength of the epiphyseal growth plate → superior and anterolateral displacement of the metaphysis distal to the growth plate

In SCFE, the metaphysis is displaced, not the epiphysis.

• Onset
  • Acute
  • Chronic (3 weeks to several months)
  • Acute on chronic (chronic with acute exacerbations)
• Location: bilateral in 20–40% of cases ^[4]
• Symptoms ^[2]
  • Dull pain in the medial thigh, knee , groin, or hip (often left > right)
  • Limping
  • Restricted range of motion
    • Reduced internal rotation and abduction
    • Patients may hold their hip in passive external rotation
    • Drehmann sign positive: external rotation and abduction during passive flexion of the affected hip in supine position ^[5]
• Stability of the physis
  • Stable: able to bear weight on affected hip, with or without crutches
  • Unstable : inability to ambulate and bear weight on affected hip, even with crutches and associated with a high risk of avascular necrosis

• Imaging ^[1][6]
  • Modality
    • AP pelvis x-ray
    • Frog leg lateral view (supine position, flexion of 45° and abduction of 45° in the hip): It allows for better evaluation of both hips, femoral head and neck.
  • Findings
    • Widening of the joint space
    • The femoral head appears to be displaced posteriorly and inferiorly relative to the femoral neck.
    • Klein line not passing the femoral head: It is a straight line drawn along the superior border of the femoral neck that normally passes through the femoral head.
    • Frog leg projection line not passing the femoral head: It is a line drawn through the center of the epiphysis that normally should pass through the center of the femoral neck.
    • Southwick method (for measurement of the slip angle/severity): refers to the tilt of the femoral neck in relation to the femoral head
    • Rules out underlying medical conditions (e.g., rickets)
    • Determines degree of displacement
• Laboratory tests: to exclude endocrinopathies in patients with an atypical age of onset or short stature

To visualize the displacement of the femoral head relative to the femoral neck as seen on x-ray, imagine a scoop of ice cream slipping from its cone.

• Avoid weight bearing before stabilization ^[1][6]
• Urgent surgical internal fixation with pinning of the femoral head
• Prophylactic fixation of the contralateral hip

• See “Differential diagnosis of pediatric hip pain.”
• Legg-Calvé-Perthes disease
• Transient synovitis
• Septic arthritis

Snapping hip syndrome ^[7]

• Definition: : snapping of the iliotibial band or gluteus maximus over the greater trochanter (external), or snapping of the iliopsoas tendon over the iliopectineal eminence (internal), typically seen in young athletes and dancers
• Epidemiology
  • Sex: ♀ > ♂
  • Peak incidence: 15–40 years
• Clinical features
  • Sensation of lateral or anterior snapping of the hip (possibly audible), with or without pain
  • Feeling of subluxing hip
  • Reduced or resolved with rest
  • May progress to trochanteric bursitis
• Treatment
  • Physical therapy, rest, ice
  • Injection of local anesthetic
  • If complaints persist: surgical treatment

The differential diagnoses listed here are not exhaustive.

• Avascular necrosis of the femoral head
• Early hip osteoarthritis ^[8]
• Chondrolysis of the hip: rapid degeneration of articular cartilage

We list the most important complications. The selection is not exhaustive.