Is the diagnosis of 5th metatarsal fracture subtype consistent? An inter-observer reliability study

J. Chapman, Z. Choudhary, S. Gupta, G. Airey, L. Mason

¹Liverpool University Hospitals NHS Foundation Trust, Liverpool Trauma and Orthopaedics Service, Liverpool, United Kingdom

²University of Liverpool, School of Medicine, Liverpool, United Kingdom

Introduction: Treatment pathways of 5^th 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 5^th 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 5^th metatarsal fracture. Plain AP radiographs were reviewed by two observers, who were initially trained on the 5^th 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 5^th 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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