Background: The fifth metacarpal fractures are the most common in all of hand fractures. To our knowledge, the classification of the fifth distal metacarpal bone fractures has not been studied.

Aims: The aim of this study was to describe a new classification system based on x-ray and to evaluate its reliability and reproducibility.

Material and methods: A total of 166 fifth distal metacarpal fractures were identified for classification and recorded. Two orthopedic surgeons reviewed and categorized them according to a newly designed classification. twice 1 month apart. Reliabilities of intra- and inter-observer were calculated with Spearman's rho correlation coefficient.

Results: Mean values of inter and intra-observer reliability were excellent (p = 0.85) and substantial (p = 0.70), respectively. In 166 patients (163 males and 3 females), concerning the percentage of the distribution of fracture types, the most common type was Type I accounted for 81 (48.8%) followed by Type II 70 (42.2%), Type III 11 (6.6%), and Type IV 4 (2.4%). Type Ia was the most prevalent among all groups.

Conclusion: This study represented a unique classification system for fractures of the distal part of the fifth metacarpal bone. Categorization in radiographs might provide ideas regarding the prognosis and clinical outcomes of fracture patterns. Therefore, this study could guide future investigations to determine the first-line treatment of fifth distal metacarpal fracture patterns using this classification and help form a common language among surgeons concerning their treatment options.