Fracture pattern analysis of fractures to the diaphysis of the fifth metatarsal

Background: Fractures to the fifth's metatarsal (MT-V) diaphysis are common. These are inconsistently referred to as diaphyseal-, shaft-, or Dancer's fractures. A comprehensive analysis of the MT-V fracture morphology is missing. The aim was to qualitatively and quantitatively analyze fracture patterns of MT-V diaphyseal fractures. Hypothesis: Fractures to the shaft of the fifth metatarsal feature specific fracture morphologies. Materials and methods: Retrospective, radiologic database study. Included were all acute, isolated MT-V shaft fractures (including the proximal [Lawrence and Botte (L&B) III] and distal meta-diaphysis). Demographics and fracture characteristics were assessed. Each proximal fracture line was drawn, scaled, and a qualitative and quantitative fracture line analysis was conducted. The quantitative fracture line analysis aimed at identifying dens clusters with arbitrary shape using the DBSCAN algorithm. Data are presented as mean +/- standard deviation. Results: Out of 704 eligible MT-V fractures, 156 met the inclusion criteria. Patient's mean age was 46 +/- 19 years and 94% suffered a low energy trauma. Qualitative and quantitative fracture line analysis revealed three distinct fracture patterns. The proximal (30%) and distal (5%) meta-diaphyseal clusters showed a predominant transverse fracture pattern. The vast majority of diaphyseal fractures (56%) were spiral/oblique fractures, progressing from the proximal lateral meta-diaphyseal region in an oblique course at 61 +/- 9(degrees) to the medial distal diaphyseal cortex. Seven percent of diaphyseal fractures showed a transverse fracture pattern. Discussion: Based on a qualitative and quantitative analysis of all MT-V shaft fractures, three distinct fracture clusters were identified with homogeneous fracture patterns. MT-V shaft fractures should therefore be classified as proximal meta-diaphyseal (L&B Type III), diaphyseal (oblique or transverse) and distal meta-diaphyseal.