Slipped Capital Femoral Epiphysis (SCFE)

Introduction

Slipped capital femoral epiphysis, or SCFE, is one of the most common orthopedic hip disorders affecting adolescents. 

  • SCFE refers to the anterior and superior displacement of the femoral neck metaphysis in relation to the capital epiphysis.
    • This slip occurs through the physis, or growth plate, resulting in an unstable and very painful hip that many times presents with isolated thigh or knee pain.

History

  • Earliest report of SCFE is attributed to the 1572 French text Cinq Livres de Chirurgie where it was described as “bending of the neck of the femur in adolescence.”
  • In the late nineteenth century, investigators were already able to begin differentiating between traumatic and insidious proximal femoral epiphyseal separation and suggesting treatment with three or more months of hip spica casting.
  • Osteotomies (bone alignment surgeries) were done as early as 1900 as one of the treatments for SCFE.

 

Epidemiology

  • The most recent studies suggest that the incidence of SCFE is approximately 8.3 unilateral cases and 0.5 bilateral cases per 100,000 children.
    • The overall prevalence of SCFE has been reported to be as high as 10.8 per 100,000 depending on what part of the country is surveyed. 
  • Roughly 19% of patients go on to develop a slip in the contralateral hip at a mean of 166 days after the first slip. 
  • SCFE most often occurs in the obese prepubertal male.
    • More than 80% of children who develop SCFE are obese, making obesity the major precipitating factor for the disease.
    • Sex and race are important considerations as males are 1.5 times more likely to develop a SCFE than females.
    • African American children are nearly 4 times more likely to develop SCFE compared to Caucasians, and Hispanics are 2.5 times more likely compared to develop SCFE compared to Caucasians. 
    • The average age of onset is 12.7 to 13.5 years for boys and 11.2 to 12 years for girls. 
      • This age of onset is decreased compared to previous reports. 
    • Of most concern is that the incidence of SCFE is increasing compared to previous years.

 

Etiology

While the precise cause of SCFE remains unclear, the underlying pathology is thought to relate to a mechanical overload of the proximal femoral epiphysis, the translocation and external rotation of the metaphysis.

  • The causes of this mechanical overload are thought to be multifactorial. 
    • Increases in BMI, as a result of childhood obesity, likely promote a shear stress across a physis that is weakened by the hormonal milieu associated with normal childhood growth spurts. 
    • It is believed that testosterone weakens the physis and estrogen acts to strengthen the physis, thus explaining the difference in incidence between girls and boys. 
    • These disturbances in the normal hormonal balance in the setting of increased mechanical stress present an increased risk of developing a SCFE. 
    • In addition, SCFE is also occasionally associated with other endocrine disturbances like hypothyroidism, pituitary disorders, and renal failure. 
    • Thus, one can conclude that SCFE most commonly occurs in children with some alteration or disturbance of normal growth. 
    • Trauma is only noted to be a cause in 10% of cases.
    • Inflammatory changes and total body irradiation (as utilized in pediatric cancer) are even less common causes of SCFE than trauma.
    • Increasing research shows genetic predisposition might play a role, but to what extent is unknown.

 

Symptoms

SCFE can be a difficult diagnosis to make because the symptoms can often be vague and the onset can be insidious. Here are the major symptoms to look for if one is suspicious of SCFE:

  • Change in gait usually presenting as a limp.
    • Usually will have a positive Trendelenburg sign.
  • Non-radiating, dull, aching pain in the hip, groin, thigh, or knee with no preceding trauma.
    • The pain is usually exacerbated by physical activity.
  • Patients may also present with decreased range of motion     
  • A small percentage of patients can present with painless limp

 

Diagnosis

  • The diagnosis of SCFE is based on the symptoms at presentation, clinical suspicion, and careful examination of radiographs.
  • A careful physical exam is important.
    • Examination will typically demonstrate an obese body habitus or very tall and slender habitus with a history of a recent growth spurt in the case of atypical SCFE. 
    • Gait examination will reveal an antalgic gait with a positive Trendelenburg (unilateral SCFE) or waddling gait (bilateral SCFE). 
    • Foot is usually turned out (externally rotated foot procession angle).
    • Examination of the hip ROM will reveal decreased internal rotation, flexion, abduction, and obligatory external rotation when the hip is passively flexed to 90 degrees. 
    • In any case where SCFE is suspected, AP radiographs of the pelvis and a frog leg lateral view of the affected hip must be obtained.
      • The frog leg lateral view should be avoided in patients with an acute slip (slip occurs suddenly with severe pain, child is unable to bear weight on affected limb), as further slipping of the epiphysis is possible. 
      • A cross table lateral view is the best alternative in these patients.  SCFE can be as subtle as a widening of the epiphysis without apparent slippage (pre-slip). 
      • These cases are best evaluated with MRI. 
      • On an AP film, a line drawn along the superior femoral neck, Klein’s line, should normally intersect a portion of the femoral head.
        • In a patient with SCFE, the femoral head will drop below this line.
        • In a frog leg lateral view, the slip is generally more obvious, with the femoral head displacing posterior and medial to the femoral neck. 
      • Studies have shown that frog leg lateral views detect approximately 15% more cases of SCFE than AP views. 
      • Equivocal plain films with a high suspicion for SCFE are best evaluated with MRI.
      • Examples of both views of a SCFE on X-ray are located below.

SCFE1_0.pngA is AP radiograph, while B demonstrates the frog leg lateral projection. Both demonstrate SCFE in the right physis. Adapted from Georgiadis AG et al 2014.

 

Treatment

  • As soon as a SCFE is diagnosed, the patient should be made completely non-weight bearing and an urgent orthopedic consultation is mandatory.
    • The slip can often progress if left untreated.
  • The goals of treatment are to prevent any further slippage and to stimulate early physeal closure, while avoiding any possible complications.
  • The usual technique for repair of a SCFE is in situ pinning of the epiphysis without reduction with one or two cannulated screws (depending on whether the slip is determined to be stable or unstable).
  • The screw should be placed perpendicular to the epiphysis, crossing the physis into the geometric center of the femoral head. (image C)  
  • Outcome after surgical repair is generally good, but depends on the degree of the slip. 
  • The prophylactic pinning of contralateral hips in the patient presenting with a unilateral SCFE remains controversial but is being considered in cases caused by endocrine disease.
  • In chronic SCFE, a Dunn procedure can be performed which involves an intracapsular wedge osteotomy of the femoral neck with reduction of the head (image D), but this procedure is not performed often.

Image CSCFEC.pngAdapted from Georgiadis AG et al 2014

 

Image D: Dunn ProcedureSCFEDunn.pngAdapted from Georgiadis AG et al 2014

 

Complications

  • Chondrolysis, a loss of the cartilaginous surface of the femoral head and acetabulum, has been reported following all methods of treatment for SCFE.
    • Chrondrolysis occurs most commonly after non-operative treatment and can occur in up to seven percent of cases.
  • Osteonecrosis is the most serious complication of SCFE.
    • It should be suspected in a patient who has a history of SCFE who complains of persistent pain and stiffness in his hip.
  • Femoro-acetabular impingement is abnormal contact between the proximal femoral epiphysis and the acetabular rim and is the last major complication of SCFE.
    • It can lead to premature osteoarthritis in SCFE patients.
  • In general, patients with SCFE have an increased risk of premature osteoarthritis. 
  • SCFE can also reoccur in patients or slippage can progress.

 

References

  1. Georgiadis AG, Zaltz I. Slipped capital femoral epiphysis: how to evaluate with a review and update of treatment. Pediatr Clin North Am. 2014 Dec;61(6):1119–35.
  2. Slipped Capital Femoral Epiphysis: Prevalence, Pathogenesis, and Natural History - Springer. [cited 2015 Aug 10]; Available from: http://link.springer.com.proxy.uchicago.edu/article/10.1007/s11999-012-2...
  3. Loder RT, Skopelja EN. The epidemiology and demographics of slipped capital femoral epiphysis. ISRN Orthop. 2011;2011:486512.
  4. Kienstra et al. “Slipped Capital Femoral Epiphysis.” www.uptodate.com. Last update Aug 05, 2014.  Accessed Aug 3, 2015.

 

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