Teaching Case

A 13-year-old boy was submitted to pelvis X-ray and MR due to left hip pain during sport activity and at rest.

A 13-year-old male came to our attention for a left hip pain since 2-3 months. His symptoms have begun two years before, when the patient complained about a light knee pain during sport activities and at rest. The clinical hypothesis was that the young patient was affected by epiphysiolysis. The patient underwent X-ray film and MRI of the pelvis to confirm the diagnosis. The pelvis radiographic exam, using the frog-lateral position, pointed out a pathologic angle between the head and the neck of left femur, which was not found at the right-sided hip. This pathological angle is a sign of initial sliding of proximal epiphysis of the femur, as regards as epiphysis plate. MRI confirmed the presence of epiphysis leak, detecting two areas of high-signal with T2-weighted coronal scans with fat suppression technique. These areas of increase signal are significant for the bone marrow edema of the left-sided femur proximal epiphysis, at the both side of the growth plate, associated to the presence of slight joint fluid effusion. The chondral ossification nucleus of the left femoral head showed normal signal on T1-weighted images, excluding an avascular necrosis (AVN).

The epiphysiolysis is a pediatric disease of the femur head. The left-sided hip is more frequently interested in boys between 9 and 15 year while the girls usually have both side affected. The pathogenesis is not defined but there could be many factors involved as endocrine diseases, overweight, mechanical stress or congenital hip dysplasia. The capital femoral epiphysis is biomechanics unstable. Hence, the head of the femur slowly slides to the midline, in the lower part and posteriorly, causing a progressive malformation of the head and the neck of the femur. If the epiphysiolysis recovers itself spontaneously, the child develops condrolysis, hip arthrosis, coxa vara and avascular necrosis (AVN). The clinical onset is often insidious. The hip pain (50%) with a halting walk is the main symptom. In 25% of cases the patient refers knee or leg pain. In the clinical examination the limb is shorter, adducted, rotated internal and in flexion; moreover, the patient is not able to keep the femur in external rotation and abduction. The X-ray film detects the pathological Klein line: the tangent of the femur neck does not cross the lateral epiphysis, forming a pathological angle between the epiphysis and the diaphysis (head-shaft angle). The Capner sign is not evident in the affected hip on x-ray film. Furthermore, if the patient is affected by a chronic disease, the x-ray film could show a remodeling of the femur neck (Hernendon sign). MRI could be useful to confirm the radiographic findings and to obtain a more reliable evaluation of the pathological condition. MRI could show the bone marrow edema, the synovitis, the joint fluid effusion and it is very important mostly in the detection of epiphysiolysis’s complications such as condrolysis and AVN. In our case the x-ray film was diagnostic, detecting the described pathological angle; in order to complete the diagnosis, the patient underwent MRI that showed the edema of the slipped capital femoral epiphysis, especially on coronal scan. MRI is not needed to make the diagnosis since the radiograph is sufficient but is useful to detect earlier controlateral epiphysiolysis and complications. Therefore, the diagnostic x-ray exam confirmed the clinical hypothesis of epiphysiolysis and using MRI the complications of this pathology could be excluded. Surgery is the main treatment for epiphysiolysis. If there is an acute slip, it possible to reduce it in narcosis and than to keep the epiphysis in the correct position using metallic screw. If the femur head is acutely slipped more than ½ of its diameter, the correct treatment could be the osteotomy, keeping the slipped femur epiphysis in a correct position. The other-sided healthy hip could undergo a preventive surgical treatment, considering that this is often a bilateral disease and the other hip could be affected in a second time. Surgical reposition is not performed in chronic epiphysiolysis.