Can we predict size, Haraguchi type and preoperative displacement of posterior malleolar fractures in association with tibial shaft fractures?

Purpose To (1) determine if any injury characteristics or radiographic parameters of tibial shaft fractures (TSFs) could predict posterior malleolar fracture (PMF) size, and (2) identify characteristics of PMFs that were fixed versus those that were not in a cohort of ipsilateral TSFs that underwent intramedullary nailing. Methods A cross-sectional radiographic study was performed at a single academic institution. Demographic and radiographic parameters of TSFs were recorded, including fracture obliquity angle (FOA) and distance from distal extent of fracture to plafond (DFP). Using CT, the PMFs were evaluated for Haraguchi classification, size measurements, and preoperative displacement. Multivariate regression analysis was used to identify independent predictors of PMF Harachuchi classification, size parameters, and preoperative displacement. Univariate differences between PMF that were fixed and not fixed were identified. Results 47 (50%) PMF underwent surgical fixation with 47 treated conservatively. There were no demographic differences between groups. Multivariate linear regression demonstrated increasing DFP and high energy injury mechanism as independent variables correlated with plafond surface area involvement, PMF height and width on sagittal CT cuts. Increasing DFP alone was correlated with PMF width on axial CT cuts and extent > 50% into incisura. Haraguchi type II fractures were associated with high energy injury mechanism (OR = 4.2 [95% CI = 1.3-14.5]; p = 0.02). Odds of Haraguchi type 3 fractures increased 9% per increased year of age (OR = 1.09 [95% CI = 1.04-1.16]; p = 0.006) and decreased 13% per 1% increase in relative DFP (OR = 0.87 [95% CI = 0.75-0.98]; p = 0.04). Conclusions An increasing DFP of TSFs and high energy injury mechanism were independent predictors of PMF size, and high energy injury mechanism was also correlated with Haraguchi type II fracture patterns. Increasing age and decreasing DFP of TSFs predict Haraguchi type III PMF patterns. These radiographic parameters should prompt surgeons to plan for fixation in scenarios in which CT scan is not available.