Head-at-risk signs in Legg-Calvé-Perthes disease: poor inter- and intra-observer reliability.

BACKGROUND: The head-at-risk signs are used as prognostic indicators in Legg-Calvé-Perthes disease. These signs have been assessed only once regarding inter-observer reliability, however. Intra-observer reliability seems not to have been studied to date. METHOD: 76 anteroposterior pelvic radiographs of unilateral Legg-Calvé-Perthes disease were assessed by 5 observers on 2 occasions, in order to assess the inter- and intra-observer reliability in identifying head-at-risk signs. The observers included 1 consultant pediatric orthopaedic surgeon, 1 consultant radiologist, 2 specialist registrars and 1 senior house officer. Inter- and intra-observer reliabilities were assessed using the kappa coefficient. RESULTS: The intra-observer reliability was good for lateral subluxation and metaphyseal cystic changes, moderate for lateral calcification, and fair for Gage's sign and horizontal growth plate. The inter-observer reliability was moderate for lateral subluxation, fair for lateral calcification and metaphyseal cystic changes, and slight for Gage's sign and horizontal growth plate. INTERPRETATION: There was considerable variation in the diagnosis of the head-at-risk signs between observers. This makes the classification difficult to use in clinical practice.

The reliability and validity of assessment of sagittal plane deviations in children who have spastic diplegia.

OBJECTIVE: To assess the reliability and validity of a newly described classification of sagittal plane alignment in spastic diplegic gait. DESIGN: Twenty split-screen videos of children with spastic diplegia, Gross Motor Function Classification System levels I to III, were viewed on 2 occasions, 6 weeks apart, by 5 raters. The sagittal plane alignments of the right and left lower limbs in gait were classified separately as true equinus, jump knee, apparent equinus, or crouch, based on the published classification. A fifth category, nonclassifiable, was used if classification was not possible. We then used sagittal plane kinematic data to confirm the classification for each subject and these were compared with rater classification scores, which used the video information only. SETTING: Tertiary-level children's hospital. PARTICIPANTS: Three pediatric orthopedic surgeons and 2 pediatric orthopedic residents. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Gait classification scores derived from visual observation were compared among and within raters. The gait classification scores derived from visual observation were compared with the scores derived from sagittal plane kinematic data to assess validity. RESULTS: A moderate correlation was found among the 5 raters within each session, with an interrater weighted kappa score of .45 in session 1 and .49 in session 2. The intrarater, weighted kappa scores showed a moderate to substantial level of agreement between sessions, ranging from .50 to .68. The classification scores of individual raters had moderate validity when compared with classifications derived from the sagittal plane kinematic data. However, there was a substantial level of agreement between the consensus opinion and the classification obtained using the kinematic data as well as the video recordings (weighted kappa=0.8). CONCLUSIONS: This classification has only moderate reliability and validity when a single experienced rater views the 2-dimensional gait videos. However, the consensus opinion derived from the scores of 5 raters considerably improves the validity of the assessment.