Herring classification: how useful is the initial radiograph?

The Herring lateral pillar classification has been shown to be a useful predictor of subsequent femoral head deformity in Perthes disease. The initial Herring classification, however, can often be misleading with regard to outcome, as further collapse can occur. The purpose of this study was to assess the predictability of the initial Herring classification. The radiographs of 253 patients (275 hips) conservatively treated were reviewed. The Herring grade was recorded on both the first and subsequent radiograph, and any change in grade was noted. Ninety-two hips required upgrading. The average duration of symptoms to the initial radiograph was 108 days compared with 204 days in the group showing no change. The predictability of the initial Herring classification is related to time from onset of symptoms. The greater the duration of symptoms, the more accurate the initial grading; 7 months is the average time at which one could expect no further collapse.