Reliability of radiological classifications used in Legg–Calve–Perthes disease

Abstract

Radiological assessment is a valuable tool in the assessment, management and prognostication of Perthes disease. Radiological assessment, however, is not an easy task and all classification systems used in Perthes disease have some degree of interrater and intrarater variabilities. In the past, there were some isolated studies to find the reliability of the classifications used in Perthes disease. In this study, we comprehensively studied three most commonly used radiological classifications (Salter-Thompson, lateral pillar and Catterall). We had 44 patients' radiographs (anteroposterior and lateral) taken in the fragmentation stage, and two experienced observers assessed and classified the radiographs on two separate occasions. In this study, we found that the average interrater reliability of the Salter-Thompson, lateral pillar and Catterall classifications was 0.163 (0.08-0.236), 0.722 (0.581-0.824) and 0.433 (0.280-0.546), respectively. The intrarater reliability was 0.313 and 0.699 for the Salter-Thompson, 0.707 and 0.658 for the lateral pillar and 0.38 and 0.577 for the Catterall classifications. Further, we tried to determine the possible reason for the low reliability associated with the Catterall classification. We think that the quantitative method of lateral pillar has better intrarater and interrater reliabilities than other classification systems, and the reliability of the Catterall classification can be significantly improved if some radiological parameters such as metaphyseal reaction and identification of the junction of involved to uninvolved region can be optimized.

Changes in the lateral pillar classification in Perthes' disease

“…The LP classification clearly predicted the radiological outcome, and it seems to be reliable [6][7][8][9][10]. However, our study showed that the changes in the LP grades might differ depending on the subsequent treatment method as well as with the extent of epiphyseal involvement.…”

“…A number of radiological classifications including the Catterall classification [3], the Salter-Thompson classification [4], and the lateral pillar (LP) classification [5], have so far been reported. The LP classification based on the height of the LP of the involved epiphysis at the fragmentation stage clearly predicted the radiological outcome, and it has been reported to be reliable [6][7][8][9][10]. This classification has thus been widely used in clinical practice, but it usually assesses patients at the fragmentation stage of disease, rather than at the initial examination.…”

Prognostic Value of Modified Lateral Pillar Classification in Legg-Calvé-Perthes Disease

“…Accordingly, there have also been many studies on LCPD treatment methods based on these classification systems. In some studies, a lateral pillar classification is described as a good indicator of the prognosis of LCPD and has better prognostic efficacy than the Catterall classification 12,13). There is no consensus regarding the association between the onset age and the disease.…”

What Is the Usefulness of the Fragmentation Pattern of the Femoral Head in Managing Legg-Calvé-Perthes Disease?

“…Moreover, the fragmentation patterns of the capital femoral epiphysis are quite variable, leading some physicians to suspect that certain patterns of fragmentation are likely to have satisfactory final outcomes while others (in the same lateral pillar class) often lead to unsatisfactory outcomes even in younger patients. Although many authors3,6,7,8,9,10) have found better interobserver agreement with the lateral pillar classification than with the Catterall classification, little attention has been given to the pattern of fragmentation, which varies with the location and the amount of necrosis of the epiphysis.…”