Is the diagnosis of 5th metatarsal fracture subtype consistent? An inter-observer reliability study
J. Chapman, Z. Choudhary, S. Gupta, G. Airey, L. Mason
Introduction: Treatment pathways of 5th metatarsal fractures are commonly directed based on fracture classification, with Jones types for example, requiring closer observation and possibly more aggressive management.
Primary objective: To investigate the reliability of assessment of subtypes of 5th metatarsal fractures by different observers.
Methods: Patients were identified from our prospectively collected database. We included all patient referred to our virtual fracture clinic with a suspected or confirmed 5th metatarsal fracture. Plain AP radiographs were reviewed by two observers, who were initially trained on the 5th metatarsal classification identification. Zones were defined as Zone 1.1, 1.2, 1.3, 2, 3, diaphyseal shaft (DS), distal metaphysis (DM) and head. An inter-observer reliability analysis using Cohen’s Kappa coefficient was carried out, and degree of observer agreement described using Landis & Koch’s description. All data was analysed using IBM SPSS v.27.
Results: 878 patients were identified. The two observers had moderate agreement when identifying fractures in all zones, apart from metatarsal head fractures, which scored substantial agreement (K=.614). Zones 1.1 (K=.582), 2 (K=.536), 3 (K=.601) and DS (K=.544) all tended towards but did not achieve substantial agreement. Whilst DS fractures achieved moderate agreement, there was an apparent difficulty with distal DS, resulting in a lot of cross over with DM (DS 210 vs 109; DM 76 vs 161). Slight agreement with the next highest adjacent zone was found when injuries were thought to be in zones 1.2, 1.3 and 2 (K=0.17, 0.115 and 0.152 respectively).
Conclusions: Reliability of sub-categorising 5th metatarsal fractures using standardised instructions conveys moderate to substantial agreement in most cases. If the region of the fracture is going to be used in an algorithm to guide a management plan and clinical follow up during a virtual clinic review, defining fractures of zones 1-3 needs careful consideration.
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