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Incidence, Predictors and Fracture Mapping of (Occult) Posterior Malleolar Fractures Associated with Tibial Shaft Fractures.

OBJECTIVES
1) Evaluate the incidence of posterior malleolar fractures (PMF) in patients with tibial shaft fractures (TSF) using advanced imaging; 2) identify predictors for patients at risk for an (occult) PMF; and 3) describe PMF characteristics to guide "malleolus-first" fixation.


DESIGN
Retrospective diagnostic imaging study.


SETTING
Level-I trauma centre.


PATIENTS
One-hundred sixty-four patients treated with intramedullary nailing for TSFs that underwent low-dose postoperative computed tomography (CT)-scans to assess (mal)rotational alignment INTERVENTION:: Analysis of advanced imaging for presence of PMFs. Uni- and multivariate analyses to identify predictors. Qualitative analysis of PMFs by fracture mapping.


MAIN OUTCOME MEASURES
1) Incidence of PMFs in patients with TSFs as diagnosed on post-op CT-scans; 2) independent predictors for the presence of PMFs; and 3) PMF patterns.


RESULTS
One-in-five patients with a TSF has an associated PMF (22%), increasing to one-in-two in patients with simple spiral fractures (56%). In 25% these fractures were occult.Univariate analysis identified simple spiral and distal third TSFs, proximal third and spiral fibula fractures, and low energy trauma as predictors for PMFs. Multivariate analysis demonstrated that distal third and simple spiral TSFs were the only independent predictors.Haraguchi Type I is the pattern specific to PMFs associated with TSF.


CONCLUSIONS
Half of patients presenting with a simple spiral TSF have an associated PMF. In one in four these are occult.Additional preoperative CT-scan imaging may be considered in patients presenting with simple spiral distal third TSFs, despite negative lateral radiographs, so that PMFs can be identified and managed with "malleolus-first" fixation.


LEVEL OF EVIDENCE
Level-III diagnostic.