Slipped capital femoral epiphysis — branching viva

Branching framework

Open with the one-sentence problem representation. This is an overweight adolescent with knee pain and an acute inability to bear weight, and the slipped capital femoral epiphysis is the must-not-miss diagnosis until excluded by the frog-lateral radiograph. State the urgency aloud — the child who cannot bear weight has an unstable slip with an avascular necrosis risk approaching fifty per cent — before you discuss anything else. The examiner is listening for whether you reach for the non-weight-bearing and the theatre before you reach for the differential. [1] [7]

Classify the slip by the Loder stability criteria. The single determination is whether the child can bear weight: stable if yes, even with crutches, unstable if no. State the avascular necrosis prediction — approximately zero per cent in the stable, forty-seven per cent in the unstable — and be ready for the severity probe: the Southwick angle on the frog-lateral grades the slip into mild below thirty, moderate thirty to fifty, and severe above fifty. The stability drives the urgency, and the severity guides the surgical strategy. [1]

Branch to the single most important investigation. The frog-lateral radiograph of both hips, because the posterior displacement of the slip is invisible or subtle on the AP view alone. Name the Klein's line on the AP pelvis — drawn along the superior femoral neck, it normally intersects the epiphysis, and in the slip it misses it, the Trethowan sign — and the metaphyseal blanch sign of Steel as the confirmatory signs on the AP. State that the frog-lateral is never omitted, because the early or mild slip shows only a physeal widening on that view. [7]

Branch to the unstable slip as the orthopaedic emergency. The child is made strictly non-weight-bearing, given intravenous analgesia, and taken to theatre for the urgent gentle reduction and fixation or the modified Dunn procedure. Contrast this with the stable slip, which is fixed electively with single-screw in-situ pinning on the next available list. State the cardinal rule against forceful reduction of a chronic slip, because the rough manipulation tears the retinacular vessels from the medial circumflex femoral artery and causes the avascular necrosis the surgery was meant to prevent. [1] [10]

Branch to the contralateral prophylactic pinning question. Between twenty and forty per cent of children develop a contralateral slip, and the risk is higher in the younger child with an open triradiate cartilage. Some centres pin prophylactically at the index operation in the high-risk child, while others monitor with serial radiographs until physeal closure. The decision is individualised, and the examiner rewards the candidate who names both strategies and frames the risk-benefit. [7]

Close with the atypical child and the endocrine work-up. The Loder age-weight test flags the child below ten or above sixteen, or below the fiftieth percentile in weight, as atypical, and these children have a higher prevalence of endocrine, renal, and chromosomal disease. The bilateral slip in a young or thin child with a nodular neck is the classic clue to a thyroid or a pituitary lesion, and the work-up extends to the thyroid function, the growth hormone axis, the sex hormones, and the pituitary imaging. The examiner rewards the candidate who recognises that the slip may be the first manifestation of a systemic disease. [3] [7]