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Difficulty: Very hardPediatric Musculoskeletal Disorders

An 8-year-old boy is brought to the clinic by his parents due to a 1-month history of right knee pain and a worsening right-sided limp. He has no history of trauma, fever, or recent illnesses. His parents note that he has been growing at a slower rate than his peers, falling from the 50th percentile to the 5th percentile for height over the past two years. His current weight is at the 30th percentile. The parents also report that he has been more fatigued lately and has developed constipation. Vital signs are within normal limits. On physical examination, the right knee has no effusion, erythema, or tenderness; range of motion is full and painless. Evaluation of the right hip reveals limited internal rotation. When the right hip is passively flexed, the thigh obligatorily rotates externally. Radiographs of the right hip show widening of the proximal femoral physis and posterior displacement of the femoral head relative to the femoral neck. Which of the following is the most appropriate next step in the management of this patient?

  1. Referral for percutaneous in situ pinning and measurement of serum thyroid-stimulating hormoneAnswer
  2. B
    Reassurance, physical therapy, and routine follow-up for a benign growth variant
  3. C
    Immediate closed reduction of the femoral head and application of a spica cast
  4. D
    Admission for urgent hip arthrocentesis and administration of empiric intravenous antibiotics
  5. E
    Magnetic resonance imaging of the right knee to evaluate for internal derangement

Answer

Referral for percutaneous in situ pinning and measurement of serum thyroid-stimulating hormone
This patient's presentation of referred knee pain, obligatory external rotation of the hip during passive flexion, and radiographic evidence of posterior femoral head displacement is diagnostic of a slipped capital femoral epiphysis (SCFE). While idiopathic SCFE typically occurs in obese early adolescents (ages 10-16), this patient's young age (8 years old) and non-obese status (30th percentile weight) make this an atypical presentation. Atypical SCFE is strongly associated with endocrine disorders, most commonly hypothyroidism, which is further supported by his poor linear growth, fatigue, and constipation. The standard of care for all cases of SCFE is strict non-weight bearing and prompt surgical stabilization via percutaneous in situ pinning to prevent further slippage. In an atypical presentation, simultaneous evaluation of the underlying endocrinopathy with a thyroid-stimulating hormone (TSH) level is essential to manage the root cause.

Step-by-Step Solution

1
Interpret the physical exam and radiograph findings.
The obligatory external rotation on hip flexion (Drehmann sign) and radiographic posterior displacement of the femoral head confirm the diagnosis of slipped capital femoral epiphysis (SCFE).
Accurately identifying the primary orthopedic lesion is the requisite first step in determining management.
2
Analyze the demographic and systemic clues in the clinical vignette.
The patient is 8 years old, which is atypical for idiopathic SCFE. He also has poor linear growth (5th percentile), fatigue, and constipation.
Idiopathic SCFE typically occurs in obese early adolescents (ages 10-16). Atypical presentations (age < 10, weight < 50th percentile) warrant investigation for secondary causes.
3
Synthesize the systemic findings to identify the underlying etiology.
The combination of short stature, fatigue, constipation, and atypical SCFE strongly suggests undiagnosed hypothyroidism.
Endocrine disorders, particularly hypothyroidism, alter physeal chondrocyte maturation, weakening the physis and predisposing patients to SCFE.
4
Determine the most appropriate comprehensive next step in management.
The patient requires prompt orthopedic referral for percutaneous in situ pinning to prevent further slippage, alongside a serum TSH level to diagnose the underlying hypothyroidism.
Simultaneous orthopedic stabilization and medical diagnosis are critical to prevent avascular necrosis and correct the underlying metabolic derangement.

Key Concept

Diagnosis and management of atypical Slipped Capital Femoral Epiphysis (SCFE) associated with endocrinopathy (hypothyroidism).
Estimated Time:1m 30s
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Topics

Pediatric Musculoskeletal Disorders

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