Radiological Diagnosis

SLIPPED CAPITAL FEMORAL EPIPHYSIS (DUE TO PSOAS ABSCESS)

The radiograph shows the femoral epiphysis within the pelvis cavity with subluxation of the femur and a soft tissue opacity over the hip.

Slippage of the capital femoral epiphysis is a well- recognized occurrence in children and adolescents. It occurs in boys between the ages of 10 and 17 years and in girls between the ages of 8 and 15 years [1]. In rare cases, a slipped epiphysis occurs in younger children and neonates who have had severe trauma or disorders such as malnutrition, developmental dysplasia of the hip, Legg-Calve-Perthes disease or tuberculosis [2].

Trauma is an important precipitating event in slipped epiphysis in infants and young children. Adolescent growth spurt is a well-recognized factor for slipped epiphysis [3]. Obesity increases the shearing stress on the growth plate and can lead to slippage of the epiphysis during usual activity [4].

The femoral head in the acetabulum is located in a posterior and medical direction with respect to the remainder of the femur. Although a postero-medio-inferior slippage of the capital femoral epiphysis is typical, other directions in which the epiphysis can move are anteriorly and superiorly or in a valgus orientation.

In our patient, caudal extension of a psoas abscess from the lower abdomen and pelvis was seen into the thigh. This communicated with the left hip joint cavity, which resulted in a free-floating epiphysis that migrated into the pelvic cavity. The abscess was drained and the sequestrated left femoral head was removed. The abscess fluid analysis was not positive for acid fast bacilli.

Psoas abscess arising in the muscle per se without a vertebral source is rare [5]. Over the past few decades, the incidence of pyogenic infections has increased because of a drop in the incidence of tuberculous spondylitis [6]. Psoas abscess leading to slipped capital femoral epiphysis is a rarity.