Legg-Calvé-Perthes: interobserver and intraobserver reliability of the modified Herring lateral pillar classification.

BACKGROUND

The purpose of our study was to independently assess the reliability of the modified Herring lateral pillar classification.

METHODS

Thirty-five standardized true anteroposterior radiographs of children in the fragmentation phase were independently assessed by 6 senior observers on 2 separate occasions (6 wk apart). The κ analysis was used to assess the interobserver and intraobserver agreement.

RESULTS

Intraobserver analysis revealed at best only moderate agreement for 2 observers. Three observers showed fair consistency, whereas 1 remaining observer showed poor consistency between repeated observations (P < 0.01). The highest scores for interobserver agreement varying between moderate to good could only be established between 2 observers. For the remaining observers results were just fair (P < 0.01).

CONCLUSIONS

This study highlights the lack of agreement between senior clinicians when applying the modified lateral pillar classification. The results from the Herring group were significantly better than ours, but utilized a weighted κ for analysis, which may have given artificially high scores. To our knowledge, this is the first time the modified lateral pillar classification has been independently tested for its reproducibility by a specialist pediatric orthopaedic unit.