Capital necrosis, metaphyseal cyst and subluxation in coxa plana.

Three specific elements associated with a poor prognosis in Legg-Calvé-Perthes disease, i.e., capital necrosis, metaphyseal cyst and subluxation, have been selected for study to determine the effect of each on the end result. A retrospective analysis was made of 337 children who received non-weight-bearing treatment. Half of the patients were treated in abduction splints, over a third with bed rest and traction and the remainder with a variety of routines including sling and crutches, wheelchair or bed rest alone. The group was treated as representing a common pool of therapy and was analyzed statistically in this overall manner. End results were graded by the Knud Mose method (concentric circle matching plus epiphyseal quotient determinations). Good and fair results were combined into an acceptable category while the poor results were considered unacceptable. Femoral capital necrosis was present either segmentally or totally. A classification was devised of three grades of partial epiphyseal involvement and one of total necrosis. The patients with total necorsis (Group IV) had a higher percentage of poor results than those with segmental involvement (Groups I, II and III). The lowest percentage of poor results correlated with the least involvement of the femoral head (Group III). Total head involvement occurred in the unacceptable group one and one half times as frequently as it did in the acceptable group. Metaphyseal cyst formation exhibited a close relationship to the fragmentation of the capital epiphysis. It is suggested that the metaphyseal lesion itself is part of the overall necrotic process and that the "cyst" is resorption associated with revascularization as healing is taking place. We noted twice the frequency of metaphyseal cysts in patients with poor results in comparison to that found in the acceptable group. Subluxation is defined as loss of acetabular centration of the femoral head due to upward and outward displacement. Increased distance between the medial margin of the metaphysis and the lateral limb of the "tear drop" figure is practically a universal finding on early roentgenograms and was not considered "subluxation" in this prognostic evluation. In the series under study there were three times as many subluxations in the poor result group as in the group with acceptable results. A prognostic profile revealing three of the above-listed features was associated with a poor result and should constitute an objective basis of evaluation of new forms of therapy.