Catterall and Herring classifications in assessing Perthes disease - inter- and intra-observer study.

Area of Science:

• Orthopedics
• Radiology
• Pediatric Orthopedics

Background:

• Perthes disease classification is crucial for treatment planning.
• Existing classification systems, Catterall and Herring, require evaluation for accuracy.
• Inter-observer validity and intra-observer reliability are key metrics for diagnostic tool assessment.

Purpose of the Study:

• To compare the inter-observer validity and intra-observer reliability of the Catterall and Herring classification systems.
• To identify which system is more effective in assessing pathological changes in Perthes disease.
• To analyze the influence of observer experience and patient age on classification accuracy.

Main Methods:

• Retrospective analysis of 63 hip X-rays from 58 patients with Perthes disease.
• Assessment by three orthopedic specialists with varying experience levels.
• Statistical analysis using weighted kappa coefficient and percentage of agreement.

Main Results:

• The Herring system exhibited higher inter-observer validity and intra-observer reliability overall compared to the Catterall system.
• Classification accuracy varied by observer experience, with less agreement between residents and senior physicians.
• The Herring system showed greater validity in older children (>6 years), while Catterall was more reliable in younger children.
• Most classification difficulties occurred between Catterall groups II and III.

Conclusions:

• The Herring classification system is recommended over the Catterall system for assessing Perthes disease due to its superior validity and reliability.
• The findings highlight the need for standardized training and potentially revised classification criteria, especially for differentiating Catterall groups II and III.
• Age is a significant factor influencing the reliability of these classification systems.