A LIMPING CHILD
A 13-year-old boy presents to his general practitioner with an 8-week history of an ache in the left thigh. Over the last few days this has got worse and now he is complaining of groin pain and has developed a pronounced limp. He is unsure, but his worsening symptoms may have coincided with a fall while playing football. He is feeling well and reports no back or neurological symptoms. His past medical history is unremarkable and he takes no regular medication.
His pulse and blood pressure are within the normal range and he is afebrile. He is overweight and has a body mass index of 33. His abdominal examination is normal and there are no detectable abnormalities of the back or left knee. His left leg is held in slight external rotation. There is a restriction in abduction and internal rotation. When the hip is flexed the leg is forced into external rotation. There is no distal neurovascular deficit.
• What is the diagnosis?
• What further plain X-rays should be requested?
• What are the other causes of a ‘limping child’?
This boy has a (acute-on-chronic) slipped capital femoral epiphysis.
This refers to a weakening or fracture of the proximal femoral epiphyseal growth plate.Continued shear stresses on the hip cause the epiphysis to move posteriorly and medially.
This condition has a peak presentation in adolescent boys. There are a number of risk factors including obesity,hypothyroidism and renal failure.
There are three different types described:
• acute slip: normally secondary to significant trauma
• chronic slip: the commonest (60 per cent) presentation with symptoms 3 weeks
• acute-on-chronic: duration of symptoms >3weeks with sudden deterioration.
This scenario is also an excellent example of the orthopaedic mantra of examining the ‘joint above and below’ the suspected origin of the pathology. Up to half of the patients with a chronic slipped capital femoral epiphysis present with thigh or knee pain. In this case one of the important clues in the examination is the finding of obligatory external rotation when the hip is flexed.
The anterior-posterior X-ray demonstrates Trethowan’s sign. When a line (Klein line) is drawn along the superior surface of the neck, it should pass through part of the femoral head. If the line remains superior to the femoral head then this is termed Trethowan’s sign. A frog-lateral view of the hip is normally requested to further aid diagnosis, although caution should be applied in acute presentations as this can worsen the slip. It is also worth noting that when a patient is diagnosed with a slipped capital femoral epiphysis,an X-ray of the opposite hip should be performed as a bilateral presentation occurs in
one-third of patients.
At any age, a limp in a child should always be taken seriously. General points to note are: if the child is febrile or unwell then the diagnosis of a septic arthritis or osteomyelitis should be considered. In the well child, trauma and neoplasia can occur in all age groups.
The limping infant should make the clinician think of a developmental hip dysplasia, whereas in the 4–10-year age range, one should think of Perthes’ disease.
• The joints above and below the presumed source of the pain should always be