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]