A new acute scaphoid fracture assessment method: a reliability study of the 'long axis' measurement.

BACKGROUND: The aim of this study was to assess the inter observer and intra observer reliability of acute scaphoid fracture classification methods including a novel 'long axis' measurement, a simple method which we have developed with the aim of improving agreement when describing acute fractures. METHODS: We identified sixty patients with acute scaphoid fractures at two centres who had been investigated with both plain radiographs and a CT (Computed Tomography) scan within 4 weeks of injury. The fractures were assessed by three observers at each centre using three commonly used classification systems and the 'long axis' method. RESULTS: Inter observer reliability: based on X-rays the 'long axis' measurement demonstrated substantial agreement (Intraclass Correlation Coefficient (ICC) =0.76) and was significantly more reliable than the Mayo (p < 0.01), the most reliable of the established classification systems with moderate levels of agreement (kappa = 0.56). Intra observer reliability: the long axis measurement demonstrated almost perfect agreement whether based on X-ray (ICC = 0.905) or CT (ICC = 0.900). CONCLUSIONS: This study describes a novel pragmatic 'long axis' method for the assessment of acute scaphoid fractures which demonstrates substantial inter and intra observer reliability. The 'long axis' measurement has clear potential benefits over traditional classification systems which should be explored in future clinical research.