Reliability of Fifth Metatarsal Base Fracture Classifications and Current Management

Classification of fifth metatarsal base fractures has been a source of confusion since originally described by Jones in 1902. Zone classifications have been described but never evaluated for reliability. The most recent classification, metaphyseal vs meta-diaphyseal, may be unknown to many surgeons. The purpose of this study was to evaluate reliability of American Orthopaedic Foot & Ankle Society (AOFAS) members classifying fifth metatarsal base fractures and current management of these fractures.

A survey was emailed to AOFAS members including radiographs of 18 fifth metatarsal base fractures. Demographic information was collected in addition to evaluation of the radiographs. Interrater reliability was assessed for each measurement: presence of Jones fracture, zone classification, and metaphyseal vs metaphyseal-diaphyseal, using Fleiss kappa. After 3 weeks, a second email was sent to the members asking to retake the survey to evaluate intrarater reliability. Respondents were asked which region is a Jones fracture, which classification is used, if symptomatic zone 2 and 3 fractures are treated similarly, and what fractures are operative in healthy symptomatic acute fractures.

A total of 223 AOFAS members, with a median time in practice of 12 years (range 0-50), completed the initial survey. Eighty members (36%) repeated the survey for intrarater comparison. Interrater reliability was moderate for Jones and zone classification but substantial for the 2-zone metaphyseal/meta-diaphyseal classification. The median intrarater kappa was 0.78, 0.75, and 0.78 for Jones, zone, and metaphyseal/meta-diaphyseal respectively. Seventy percent of respondents treat zones 2 and 3 similarly, and approximately 60% consider an acute symptomatic fracture identified as Jones, zone 2 or zone 3 operative.

A 2-zone system may be the best available classification for fifth metatarsal base fractures given high interrater reliability and 70% of AOFAS members treat zones 2 and 3 in similar fashion.

Level III, diagnostic study.