Radiographic classifications in Perthes disease

Abstract

Background and purposeDifferent radiographic classifications have been proposed for prediction of outcome in Perthes disease. We assessed whether the modified lateral pillar classification would provide more reliable interobserver agreement and prognostic value compared with the original lateral pillar classification and the Catterall classification.Patients and methods42 patients (38 boys) with Perthes disease were included in the interobserver study. Their mean age at diagnosis was 6.5 (3–11) years. 5 observers classified the radiographs in 2 separate sessions according to the Catterall classification, the original and the modified lateral pillar classifications. Interobserver agreement was analysed using weighted kappa statistics. We assessed the associations between the classifications and femoral head sphericity at 5-year follow-up in 37 non-operatively treated patients in a crosstable analysis (Gamma statistics for ordinal variables, γ).ResultsThe original lateral pillar and Catterall classifications showed moderate interobserver agreement (kappa 0.49 and 0.43, respectively) while the modified lateral pillar classification had fair agreement (kappa 0.40). The original lateral pillar classification was strongly associated with the 5-year radiographic outcome, with a mean γ correlation coefficient of 0.75 (95% CI: 0.61–0.95) among the 5 observers. The modified lateral pillar and Catterall classifications showed moderate associations (mean γ correlation coefficient 0.55 [95% CI: 0.38–0.66] and 0.64 [95% CI: 0.57–0.72], respectively).InterpretationThe Catterall classification and the original lateral pillar classification had sufficient interobserver agreement and association to late radiographic outcome to be suitable for clinical use. Adding the borderline B/C group did not increase the interobserver agreement or prognostic value of the original lateral pillar classification.

Reliability of the modified lateral pillar classification for Legg Calvé Perthes disease performed by a large group of international paediatric orthopaedic surgeons

“…Reports of inter-observer reliability for this classification have been variable, ranging from fair to good. [2][3][4][5] Salter and Thompson 6 utilized the subchondral fracture line seen in the initial stage of disease to classify femoral head involvement. One practical limitation of this classification is that not all patients demonstrate this sign, making it applicable only to a subset of patients.…”

“…Herring reported agreement 78% of the time between observers and an inter-observer kappa value of 0.52. 7 Subsequent studies have shown better correlation of the LPC with radiographic outcome than the Catterall classification, 2,8 and moderate to good inter-observer and intra-observer reliability of the LPC. 2,3,[8][9][10] Due to difficulties finding consensus in classifying a specific group of hips that were more severe than typical Group B hips and less severe than most Group C hips, Herring described a modification of the LPC (mLPC) in 2004, adding a B/C border group.…”

“…7 Subsequent studies have shown better correlation of the LPC with radiographic outcome than the Catterall classification, 2,8 and moderate to good inter-observer and intra-observer reliability of the LPC. 2,3,[8][9][10] Due to difficulties finding consensus in classifying a specific group of hips that were more severe than typical Group B hips and less severe than most Group C hips, Herring described a modification of the LPC (mLPC) in 2004, adding a B/C border group. 11 The B/C group was defined as hips with any of the following radiographic findings: 1) very narrow lateral pillar maintaining > 50% height, 2) lateral pillar with very little ossification but > 50% original height, or 3) lateral pillar is depressed relative to central pillar but maintaining 50% of the original height.…”

“…Herring reported good inter-observer agreement of the mLPC with a modified weighted kappa of 0.71, 11 but subsequent reports of inter-observer agreement have not been able to reproduce this level of agreement, finding only fair reliability (weighted kappa values of 0.39-0.40). 2,12 Additionally, previous studies of reliability of the mLPC have pre-selected the fragmentation radiographs for rating and have included only a small group of observers (five to six). 2,12 This does not reproduce the clinical environment in which surgeons with a wide variety of experience sort through serial radiographs, selecting the appropriate radiograph for assigning the mLPC in order to assess severity and predict prognosis.…”

Degenerative hip disorders in children

“…Среди методов диагностики БЛКП используют рентгенографию (стандартные, специальные укладки) -так называемый «золотой стандарт». Благодаря этому методу удается оценить степень тяжести поражения костных компонентов сустава, возможные факторы риска, определить лечебную тактику [35]. Однако метод не позволяет диагностировать нарушения на стадии первоначальных изменений.…”