Arthrography as an aid to diagnosis, prognosis and therapy in Legg-Calvé-Perthes' disease.

Measurements of head diameter and acetabulum-head quotient (AHQ) were made on the plain radiographs and corresponding arthrograms of 37 consecutive patients with unilateral Legg-Calvé-Perthes' Disease (L.C.P.D.). Although on plain radiographs the affected osseous femoral capital epiphysis was slightly larger (22) the same size (9) or smaller (6) than that on the normal side, on arthrography the osteochondral head was much larger in 34 and the same size in 3 instances. In 35 cases the arthrograms revealed flattening of the osteochondral head. The AHQ computed from the arthrograms was almost invariably less than that computed from the plain radiographs. Thus the AHQ computed on arthrograms more realistically assessed the almost invariably poor head coverage in L.C.P.D. This, together with signs of flattening, diagnoses the severity of the disease process and helps to differentiate the "head at risk" which requires treatment. During arthrography the degree of abduction-medial rotation of the leg necessary for containment of the flattened protruding head within the acetabulum can be determined, allowing accurate therapy to be planned, be it operative or orthotic.