Slipped Capital Femoral Epiphysis

Diagnostic imaging in SCFE

Radiography and magnetic resonance imaging are used to confirm the diagnosis.

The standard anteroposterior view (Anteroposterior view) may be uninformative: changes on it are sometimes barely noticeable and manifest only as a slight widening of the growth plate. To avoid missing the pathology, a Lauenstein projection radiograph (the so-called frog-leg lateral view, Frog leg lateral) must be performed. It is in this position that head slippage is visualized most clearly.

In doubtful cases or when an early process is suspected, MRI becomes the method of choice, capable of detecting epiphyseolysis even before overt radiographic signs appear.

Radiometric parameters

Assessment of the degree of displacement is based on two main geometric indicators.

The first indicator is Klein's line (Klein line). It is drawn on an anteroposterior radiograph by drawing a tangent along the superior edge of the femoral neck. In a healthy joint, this line should intersect approximately the outer (lateral) 1/6 part of the epiphysis. If the patient develops SCFE, Klein's line either misses the epiphysis entirely or cuts off a significantly smaller fragment from it.

The second criterion is the slip angle (Slip angle). It is measured on a radiograph in the Lauenstein projection. This angle is formed by the intersection of two lines: the first is perpendicular to the plane of the growth plate, and the second is parallel to the longitudinal axis of the femoral diaphysis. Depending on the magnitude of the angle, three severity grades of SCFE are distinguished:

• Mild (Mild): displacement angle less than 30°;
• Moderate (Moderate): angle from 31° to 50°;
• Severe (Severe): angle exceeding 51°.

Important note: although the angle value reflects the anatomical severity of the pathology, it does not act as the sole determining factor when choosing the treatment regimen.

Femoral Dysplasia and Coxa Vara

The concept of Femoral Dysplasia includes a wide range of conditions. Mild forms include idiopathic varus deformity, moderate forms include proximal defects, and in the most severe cases, the patient develops only the distal femoral condyles.

Idiopathic Coxa Vara (Idiopathic Coxa Vara) is a pathology whose essence boils down to a decrease in the neck-shaft angle. A striking radiographic sign of this condition is the Fairbank triangle (Fairbank triangle) — a separate bone fragment visualized near the lower part of the femoral neck. The prognosis of the disease directly depends on the degree of deformity: if the neck-shaft angle drops below 100 degrees, the process will steadily progress without surgical intervention.

Proximal Focal Femoral Deficiency

Proximal Focal Femoral Deficiency, PFFD (Proximal Focal Femoral Deficiency, PFFD) is characterized by agenesis of the proximal femur of varying severity. Bilateral involvement is diagnosed in only 10% of patients. It has been proven that the severity of this pathology correlates closely with the degree of acetabular dysplasia.

To systematize defects, the Aitken classification (Aitken classification) is used, dividing PFFD into four groups (A, B, C, and D). Group membership is determined by the following factors:

1. Presence or complete absence of the femoral head.
2. Preservation of the connection between the head and the proximal end of the bone.
3. Morphological features of the acetabulum.
4. Severity of femoral shortening.

PFFD is often combined with other malformations: lower leg shortening, fibula aplasia or hypoplasia, as well as the absence or underdevelopment of cruciate ligaments.

Radiography is sufficient to assess the degree of bone aplasia. However, in young children, MRI or arthrography is required to visualize unossified cartilage tissue. In addition, knee MRI is necessary for a precise evaluation of the cruciate ligaments.

Tibial Vara

Tibial Vara (Tibia Vara and Tibial Bowing) is an O-shaped outward curvature of the legs. The pathological curve can form directly at the knee joint level or affect the proximal tibia. The deformity can be either unilateral or bilateral.

Class and exam questions

What else to study on this topic

• Criteria for groups A, B, C, and D in the Aitken classification
• Features of performing MRI and arthrography in young children
• Correlation between PFFD and acetabular dysplasia
• Associated anomalies in PFFD: pathology of the fibula and knee ligaments

Other Topics in "Pediatric Diagnostic Radiology"

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