Subcapital correction osteotomy in slipped capital femoral epiphysis by means of surgical hip dislocation.

OBJECTIVE: The aim of treatment of slipped capital femoral epiphysis is an anatomically aligned epiphysis with normal blood supply. This result can be achieved by open subcapital reorientation of the epiphysis or by a wedge osteotomy of the femoral neck. Other procedures have, so far, not gained optimal control over the risk of avascular necrosis.

INDICATIONS: Acute epiphyseolysis. Chronic epiphyseolysis for which trimming of the metaphyseal overhang to permit free flexion and internal rotation without impingement would leave less than two thirds of the femoral neck diameter intact.

CONTRAINDICATIONS: Ankylosis of the hip joint at an advanced stage. Destruction of the femoral head.

SURGICAL TECHNIQUE: The blood supply to the epiphysis from the medial femoral circumflex artery can be preserved by surgical hip dislocation and a soft-tissue flap derived subperiosteally from the retinaculum and external rotators. This soft-tissue flap permits not only the detachment of the epiphysis, but also complete callus resection from the femoral neck without causing tension in the retinaculum. Dislocation of the femoral head ensures its manual protection during curettage of the epiphyseal plate and, ultimately, allows anatomic reduction under visual control of the retinaculum. With the head dislocated there is less risk to the integrity of the retinaculum due to unintentional manipulation of the leg than there would be, if the head remained in the socket.

RESULTS: From 1996 to 2005, 30 hips with a diagnosis of slipped capital femoral epiphysis were treated according to the technique described. The average follow-up time was 55 months (24-96 months). Femoral head necrosis did not occur. Distribution across sexes was well balanced. Girls were 12 years old at the time of the operation and boys were 14 years old on average. Posterior displacement was measured at 30-70 degrees. In six hips there was a so-called acute on chronic slip. Two hips required revision due to screw failure, a difficulty that was addressed by the introduction of fully threaded wires. One hip had to be revised because the fully threaded wire bent. After reoperation, shortening of maximum 1 cm was seen in these three cases. In one patient with ectopic bone formation at the anteroinferior femoral neck, internal rotation in flexion is reduced by half.