A new classification system for distal clavicle fractures: based on fracture location and ligament integrity

Although various classification systems have been introduced for the description of distal clavicle fractures, there is no consensus on the best classification system that is helpful in determining treatment and prognosis. The objective of this study was to establish a new classification system for distal clavicle fractures and to verify the reliability of the new classification system by evaluating the inter- and intraobserver agreement.

A total of 1075 consecutive patients with distal clavicle fractures were selected from five university-affiliated hospitals between 2012 and 2022. The distal fragment size (DFS), the coracoclavicular distance (CCD) and the acromioclavicular distance (ACD) were measured on anteroposterior radiographs of each acromioclavicular joint. Twenty independent investigators evaluated 1075 radiographs of distal clavicle fractures, completing the fracture typing according to the new classification system and selecting a treatment choice for each case. This procedure was repeated 3 months later. Fleiss κ values were calculated to estimate the inter- and intraobserver agreement.

The new classification categorizes distal clavicle fractures into three types based on the relationship between fracture location and ligament footprints. Type I fractures occur distal to the coracoclavicular (CC) ligaments with or without ligament injury. Type II fractures occur CC ligament attachment regions with ligament injury Type III fractures occur proximal to the CC ligaments without ligament injury. Several subtypes (types IA, IB, IC, ID, IIA, IIB, IIC, IID, and IIE) were further introduced according to fracture displacement and ligament integrity. The inter- and intraobserver reliability of our new classification system was substantial (κ = 0.622 vs. 0.678). Inter- and intraobserver reliability for treatment choice was perfect (κ = 0.846 vs. 0.882).

The new classification system which takes into account fracture location and ligament integrity brought few disputes in category division and treatment selection.