Page 25 - Slipped Capital Femoral Epiphysis Pathogenetic and Clinical aspects

described by Song et al. [130]: On the AP radiograph of the pelvis, a decrease in acetabulo-trochanteric distance is found on the affected side compared to the
normal side in 76 % of all cases.
The frog lateral radiograph of the femoral head makes it easier to diagnose SCFE.
The Southwick classification can be made on the frog lateral (See radiological 2 classification) [18]. In fact there is not a pure AP or lateral deformity, but an oblique
plane deformity in SCFE. To evaluate this deformity accurately one can measure the degree of slip on an AP radiograph, and the axial deformity on a CT or MRI scan and calculate the real oblique plane from these angles [24].
In preslip or an early slip, the radiograph can be normal. Bonescintigraphy and MRI can be used for diagnosis in early SCFE. On the MRI one can detect a widening of the physis with bone oedema on the metaphysis, joint effusion and synovitis [50, 139]. Also, in an acute slip, the bonescintigraphy and the MRI can detect early avascular necrosis by impairment of the vascular supply to the femoral head due to the position of the metaphysis relative to the head or alternatively, due to the instability of the head [50, 113, 139].
In a later stage of SCFE femoro-acetabular impingement can occur (see FAI). Impingement by prominence at the femoral head-neck junction on the anterior acetabular rim may cause early osteoarthritis. Nőtzli et al. [93] developed a method to measure the aspherity of the femoral head and the cam-type deformity by the alpha angle: an angle between a line from the centre of the femoral head through the middle of the femoral neck and a line through a point where the contour of the femoral head-neck junction exceeds the radius of the femoral head .
In conclusion, SCFE is difficult to diagnose due to unfamiliarity with the diagnosis by healthcare providers and due to a challenging presentation of complaints. Traditionally the diagnosis is made on a radiograph of the pelvis. The AP view might be subtle to see a mild slip, a lateral radiograph of the proximal femur makes it easier. Different ways of investigating SCFE with radiographs, CT and MRI are discussed. Bonescintigraphy can be useful in diagnosis AVN pre and post operatively.
Classification.
Several classification methods exist based on clinical radiological features.
SCFE can be classified based on history according to the time of complaints of the patient in: preslip, acute, acute on chronic or chronic [10, 69]. The preslip occurs prior to the actual slipping through the physis. The patient provides a history of an episodic limp and limb weakness associated with pain in the groin, anterior
Slipped Capital Femoral Epiphysis
23