Introducing the forearm fracture index to define the diametaphyseal junction zone through clinical evaluation in a cohort of 366 diametaphyseal radius fractures

Background: Unstable diametaphyseal radius fractures (DMRFs) can be prone to complications, and treatment strategies are heterogeneous. Studies are difficult to interpret as definitions of the diametaphyseal junction zone (DMJZ) are impractical for clinical use, imprecise, or prone to error.

Methods: We introduce the forearm fracture index (FFI) to define DMRFs in radiographs and ultrasound. The FFI is calculated by the ratio of the fracture's distance to the distal radius growth plate over the width of the radius growth plate. The higher the FFI, the more proximal the fracture is. We define DMRFs to have an FFI between 1 and 2. All DMRFs treated at our institution between 2010 and 2020 were identified, and demographic data, fracture characteristics, and therapeutic strategies were assessed retrospectively. Comparative sub-analysis was performed between DMRFs(-) as defined in previous publications (Lieber in Unfallchirurg 114:292-299, 2011) and DMRFs( +) that were more proximal but still met our criteria.

Results: 516 DMRFs were identified, representing 13.0% of all screened radius fractures. Excluding buckle fractures and patients lost to follow-up, 366 DMRFs were eligible for further analysis. Conservatively managed DMRFs were more distal than those managed operatively, represented by a lower FFI (1.28 vs. 1.34, p = 0.0051). 21 (5.7%) of all DMRFs were identified as DMRFs( +). These were significantly more dislocated and necessitated surgery more often than DMRFs(-) (52.4 vs. 24.6%, p = 0.009).

Conclusions: The FFI may be a good tool to identify and describe DMRFs. It can help guiding treatment decisions and make future studies on this entity more comparable.

Level of evidence: Study of Diagnostic Test, Level II.