Morphologic characteristics of the posterior malleolus fragment: a 3-D computer tomography based study.

OBJECTIVES

The objective of this study was to evaluate the morphological characteristics of the posterior malleolus fragment (PMF) based on 3-D computed tomography scans, and evaluated the variability in different types of injuries (ankle fracture, spiral tibial shaft fracture and pilon fracture).

METHODS

A retrospective analysis of 3-D computed tomography data of PMF from June 2011 to February 2012 was conducted in a level 1 trauma centre. The cross angle (α), fragment length ratio (FLR), fragment area ratio (FAR), sagittal angle (θ), and fragment height (FH) were measured as morphologic assessments in the Picture Archiving and Communication System (PACS).

RESULTS

Based on the definition of the PMF, 144 cases were brought into this study. And the PMF was described with a mean α of 25.0°, a mean FAR of 17.66 %, a mean θ of 16.1° and a mean FH of 23.06 mm. Besides, this study showed a significant difference on FAR amongst the three injuries with the FAR was 30.31 % (P < 0.05) in pilon fracture group. Respectively, although the mean θ (16.1°) indicated a vertical fracture pattern, yet no significant difference was shown amongst the three groups.

CONCLUSIONS

Although the PMFs appear to be highly variable, most of the PMFs were located on the posterolateral of the distal tibia, and showed features with vertical nature. The information obtained from this study will be helpful for fracture models in a future biomechanical study and for determining appropriate surgical approaches.