In SUFE, the femoral neck subluxes away from the epiphysis which can result in a severely altered geometry of the hip and sometimes catastrophic avascular necrosis. This is usually an adolescent condition, more common in boys and the overweight. Rarely, children as young as six or seven can be affected and endocrinopathies such as hypothyroidism or hypogonadism can predispose to SUFE. The presentation can be acute, chronic or acute-on-chronic.
A limp is common and sometimes associated with inability to weight bear. Examination will show a shortened, externally rotated limb but findings can be subtle – often asymmetric internal rotation is the only finding (see figure below). Bilaterality should be suspected and the diagnosis is confirmed radiographically. As mentioned the frog-lateral view is paramount as the diagnosis is often missed on the AP view – figure 5. Urgent paediatric orthopaedic referral is called for and surgical intervention is normally required.
The red lines on the AP view represent ‘Klein’s lines’ – this is drawn along the superior aspect of the femoral neck – normally it should pass through the epiphysis. Here it does not on the left, giving the diagnosis of SUFE. This helps to make the diagnosis on the AP view as findings are often subtle. The diagnosis is more obvious on the frog-lateral view.