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SCFE - Slipped Capital Femoral Epiphysis
SCFE - Adolescents.
Legg-Calve-Perthes disease - younger child with hip pain.

SCFE - fracture through the proximal femoral growth plate (physis) - Salter-Harris type I fracture. Fractures typically occur with normal activity. Patients tend to be overweight and sedentary.

- Most common hip disorder in adolescence.
- Peak in girls between 11-13 yrs and boys 13-15 yrs.
- Boys are slightly more commonly afflicted.
- Bilateral disease is common at presentation (>10% of patients)
- Up to 50% will have a contra-lateral slip in the following 24 months

The symptoms are often referred most commonly to the knee.

The deformity is a fracture through the proximal physis and subsequent posterior and medial rotation of the epiphysis on the distal fragment. This is the one fracture in which the proximal fragment is described. For example, a report might read, "The epiphyseal fragment is posteriorly displaced by approximately 30 degrees."

As the epiphysis slips posteriorly and medially, the femoral neck will impinge on the superolateral acetabular margin with abduction. There will be limited motion and the patient will feel most comfortable in external rotation and slight abduction.

Radiographs are often the first test obtained and are usually positive. Capener's sign refers to absence of the normal triangular bony density created by the superposition of the medial aspect of the proximal femoral metaphysis on the posterior wall of the acetabulum in a patient with SCFE that would otherwise be missed on a frontal radiograph.

The acute slipped epiphysis may demonstrate a clear deformity of the femoral head as it has rotated in the acetabulum, but more typically there is only a subtle degree of physeal deformity related to the fracture and a slight asymmetry of the physes. Because of the subtle nature of the findings, a radiograph of both hips is preferred so a comparison is available.

There is a "blanching" of the physis meaning that the physis looks as if the calcium has been washed out.Often the epiphysis will show only a subtle medial slippage. This can be recognized by drawing a line along the lateral margin of the femoral neck on the AP view that should intersect approximately 1/5 of the femoral head. If the line does not intersect the head, slippage is evident.

In the chronic and sub-acute scenario there is often deformity of the femoral neck as well. The head may be clearly rotated, but the femoral neck is now thickened and curved, giving it a "pistol grip" deformity. This is the result of buttressing over weeks and months.
We suggest looking at the AP and if it is normal obtaining a frog-leg view.This view is often quite helpful although some children will not tolerate the position and some orthopedic surgeons believe it will cause further stress on the fracture. On this view, with the leg externally rotated, the degree of posterior slippage is evident. The movement posteriorly is often greater than medially and the slippage may only be seen on this view.

A line drawn along the longitudinal axis of the femoral neck should be perpendicular to a line drawn from the lateral margin to the medial margin of the femoral physis, known as the "Southwick method." An angle other than 90 degrees +/- 10 degrees is abnormal. As bilateral disease is so common, evaluation of both hips is recommended. As the clinical scenario is not always clear, patients often come for investigations other than radiographs. Radiographs are often deceptively normal, prompting further imaging. Slippage is evident on CT, Ultrasound, MRI and can even be suggested on Bone Scan.

Bone Scan is often ordered because of the vague symptoms and help localize the problem to a particular bone or joint. If a three- phase study is done over the pelvis, there may be hyperemia at the hip, but a lack of activity at the physis. This prompts further investigation with radiographs or CT or MRI. The lack of activity is secondary to the diminished blood flow to the epiphysis. As the physis closes, blood vessels grow across it to supply the mature head. These vessels are injured because of the motion across the physis, and subsequent motion damages them further. Chronic slips may allow re-growth of vessels after each episode. In the acute slip there may be no activity at the epiphysis because there is no arterial flow. This sign has been linked to an increased incidence of later avascular necrosis (AVN) of the head.

CT is used in the occasional patient who has a slip and measurement of the degree of rotation is called for. The CT is done with only a few slices through the femoral neck. Abduction or oblique positioning of the patient is sometimes used but volumetric scans can be reconstructed into appropriate planes for measurements.

MRI is being used for early detection of slip and surveillance of the opposite hip. Originally patients underwent MRI of the pelvis because a diagnosis was uncertain. Very early acute slips and even a "pre-slip" appearance have been described. The test is preformed with standard water sensitive sequences and actual slips are easy to identify. The "pre-slip" state is characterized by high signal in the femoral neck and head on T2 and STIR (usually anteriorly and medially, though it can be seen throughout). Contrast can be given and dynamic MRI sequences performed to demonstrate areas of diminished flow. This technique is applied to determine a "viable" head, but several factors confound it. The acutely slipped epiphysis may be so edematous as to have delayed flow, but only small studies have been performed to confirm this method.A more promising use for MRI is to evaluate the opposite hip. As contralateral disease is so common, many surgeons will prophylactically pin the opposite side, even before symptoms. This is not as barbaric as it sounds because it settles the problem of any leg length discrepancy resulting from pinning only one side (which should be minor as the child is near the end of growth). Because MRI is able to find the pre-slip states, some surgeons will ask for an MR prior to the initial pinning to detect any signs of contralateral disease. Others may ask for an MRI with any contralateral symptoms, rather than prophylactically pinning the hip.

If a patient comes for ultrasound of the hip, it is usually because the diagnosis has not been made and an effusion is suspected. Hemarthrosis detected at ultrasound-guided hip aspiration should prompt further investigation to rule out SCFE in the adolescent patient. Some authors have explored ultrasound as a method of determining the age or stability of a slip2

In an adolescent with hip pain a frontal non-shielded radiograph of the pelvis should first be obtained. If SCFE is diagnosed no further radiographs are necessary. If the frontal view is negative, a frog-leg lateral view is recommended. MRI is considered to evaluate for early slip suspected based on radiographs or clinical suspicion and to evaluate the contralateral hip. In undifferentiated hip pain, hip ultrasound is useful as an adjunct to radiographs to evaluate for hip joint effusion.

Contemporary treatment is internal fixation, but past treatment methods included bed rest, spica or long-leg casts. Most of the time an orthopedic surgeon will fix the fracture in the position it presents, "pin it where it lays." The fixation is done with one or two percutaneous screws placed across the physis through the femoral neck. These compression screws close the physis and fix the fracture.

Some surgeons will reposition the head either if the slip is so severe that abduction is limited, or the head is devascularized and repositioning it into a more functional relationship will be of benefit. Moving a "viable" epiphysis puts it at great risk for AVN 1 7.

If the head is too rotated, motion at the hip will be compromised. In the acute setting if the epiphysis is mobile and very rotated repositioning can be done to prevent severe impingement. This is sometimes revered to as an unstable hip, and ultrasound has been used to identify motion and joint fluid. Often the unstable fragment will spontaneously reduce on the fracture table. Occasionally the child may require a later osteotomy to correct the deformity. Chondrolysis is also a risk following surgery even if the pins do not violate the epiphyseal cartilage. African American girls seem to have the highest incidence of this complication.

The incidence of failure is high and all slips are considered unstable until they are pinned.

There is a high risk of AVN after a slip regardless of treatment. Patients have a high incidence of subsequent arthritis. Because the consequences of a slip may be crippling, the radiologist and clinician must strongly consider this diagnosis in an adolescent with hip pain to avoid delay in treatment. For these reasons, patients with suspected SCFE are kept on crutches until the slip is confirmed or excluded through careful imaging, which can be performed within the next several days after presentation.