RADIOLOGICAL MEASUREMENT OF FEMORAL-HEAD POSITION IN LEGG-CALVE-PERTHES DISEASE

Purpose: Since the establishment of the principle of weight-bearing me thods of treatment in Legg-Calve-Perthes disease (LCPD), lateral displ acement of the femoral head has become an important prognostic factor. Material and Methods: In order to establish reliable boundary lines b etween orthotopic and subluxated hip, the migration percentage (MP) an d the medial joint space (MJS) were determined retrospectively: a) on 166 normal hip radiographs; b) on bilateral arthrograms and radiograph s from 37 patients with unilateral LCPD. Results and Conclusion: The m ean upper normal values for MP and MJS on normal radiographs were 20.8 and 11.5 respectively. On arthrograms, the corresponding values were 31 and 5.7. The MP is easy to determine on both radiographs and arthro grams, and is recommended for detecting and measuring subluxation in c ases with LCPD. MJS is of no advantage for detecting containment in LC PD but may be used in other diseases such as coxitis simplex.