Toronto orthosis for Legg-Perthes disease.

Abstract

1 Prosthetic Research and Training Unit, Ontario Crippled Children's Centre, 350 Rumsey Road, Toronto 17, Canada. The treatment of Legg-Perthes disease has been given considerable attention at the Hospital for Sick Children in Toronto during the last few years. It is now known that certain types of Legg-Perthes disease have a good prognosis regardless of the type of treatment used, whereas other types tend to have a poor prognosis. Proper prescription of treatment must, therefore, recognize this difference in prognosis. Attempts have been made to assess the outcome of the disease on the basis of age at onset and the degree of involvement of the ossific nucleus of the femoral head. In children who develop Legg-Perthes disease prior to the age of five years, the prognosis tends to be better than in a child who develops the condition at an older age. This difference is probably related to the total mass of bone that has to be reossified, since it has been noted that in a smaller femoral head the time for reossification is often shorter, being in the vicinity of 12 to 18 months compared to several years for an older child. The degree of involvement also plays a most important part, and attempts have been made here to differentiate between cases where the entire femoral head is involved, with avascular necrosis of the entire ossific nucleus, and those where merely a portion is involved. The partialhead-type of Legg-Perthes disease carries a much better prognosis and is less liable to deformity, since a part of the femoral head remains uninvolved. If there is any tendency towards the formation of a metaphyseal cyst, the possibility of a poor long-term result is increased. The stage at which the patient is first seen is of the utmost importance. If the child is seen early in the course of the disease, before joint deformity has occurred, proper management, if instituted quickly, can often result in a congruous joint. If, however, there is already considerable flattening and subluxation when the child is first seen, then the result, of course, cannot be as good. If the entire process of re-ossification has already occurred by the time the child is first seen, the golden opportunity has passed, and at this stage only secondary reconstructive procedures can be carried out, with even less satisfactory results. Certain selected cases are suitable for innominate osteotomy, in which the femoral head is covered and seated just as if the hip were held in abduction and internal rotation. At present, innominate osteotomy is restricted to the child who carries an unusually bad prognosis; that is, a child over the age of six years with total involvement of the femoral head. In addition, an arthrogram must be made to be certain that a significant joint deformity is not already present. If a deformity is present, innominate osteotomy is contraindicated. In addition, prior to the use of an innominate osteotomy, full joint movement must be obtained, which sometimes will require traction or soft tissue release of contracted structures, such as the psoas tendon. In the very young child with only a part of the head of the femur involved, often