Inter-Rater Reliability of Classifications for Fifth Metatarsal Base Fractures

Abstract

Category: Trauma; Midfoot/Forefoot; Sports Introduction/Purpose: Fractures of the fifth metatarsal base have been a source of confusion since their original description by Jones in 1902. The term Jones' fracture has been used indiscriminately leading to further confusion. Zone classifications have been described but never evaluated for their reliability. The most recent classification, metaphyseal versus metaphyseal-diaphyseal is unknown to most surgeons. The purpose of this study was to evaluate the inter-rater reliability of American Orthopaedic Foot & Ankle Society (AOFAS) members classifying fractures of the base of the fifth metatarsal. Methods: A survey was emailed to members of the AOFAS including radiographs of 18 fifth metatarsal base fractures. Demographic information was collected in addition to evaluation of the 18 sets of radiographs using three classification systems. Surgeons were asked if the fracture is a Jones' fracture, zone of the fracture and if the fracture was metaphyseal or metaphyseal- diaphyseal. A total of 223 surgeons with an average experience of 14 years in practice (range: fellow - 50 years) completed the initial survey for inter-rater reliability. Additionally, each surgeon was asked which zones or zone junctions they consider a Jones' fracture. Reliability was tested using Fleiss' Kappa scores. Results: Inter-rater agreement for use of the term Jones' fracture was moderate (kappa 0.533, 95% confidence interval (CI) [0.530, 0.535]). The zone classification had an inter-rater agreement was moderate (kappa 0.537, 95% CI [0.535, 0.539]). Inter- rater agreement for metaphyseal versus metaphyseal-diaphyseal was substantial (kappa 0.705, 95% CI [0.702, 0.708]). Results of surgeon definition of a Jones' fracture is seen in Figure 1. Conclusion: This is the largest study of its kind looking at inter-rater reliability of an orthopaedic classification with 223 raters. The terminology regarding the classification of fifth metatarsal base fractures remains confusing and inconsistent. The term Jones' fracture has little meaning in terms of communicating these injuries as there is only moderate agreement when surveying surgeons and it is defined differently by most. The zone classification has similar reliability as the Jones' fracture. The terms metaphyseal and metaphyseal-diaphyseal was the most reliable means to describe these fractures.