Three-Dimensional Heat Map: The OTA/AO Type 43C Pilon Fracture Lines Distribution

Abstract

Background: This study aimed to create three-dimensional heat map and study the characteristic of fracture lines and represented fragments of OTA/AO type 43C pilon fractures.

Methods: CT scan was performed in105 fractures diagnosed with OTA/AO type 43C pilon fractures between January 2017 and December 2022. Three-dimensional pilon fracture maps were created and converted into fracture heat maps. CT scan graphic parameters including the fracture line height, α angle, β angle, the ratio of the area and size of bone fragment represented by the fracture line to the total articular surface were measured.

Results: The study included 105 patients with 91 males and 14 females. The fractures included C1 (n=16), C2 (n=23), and C3 (n=66). There was no statistically different among the most parameters except in the fracture-line height of the anterior fracture line (p=0.03) and the sagittal fracture line (p=0.02) between C2 and C3 pilon fractures. The average size of the anterolateral fragment, occupied approximately 13.5% of the articular surface area, was (11.5±2.8) mm × (20.5±6.3) mm with the average height of 29.8 mm. The average size of the posterolateral fragment, occupied approximately 13.0% of the articular surface area, was (15.7±4.6) mm × (19.3±4.0) mm with the average height of 19.1 mm.

Conclusion: This study demonstrates that the articular surface fracture lines in the C type pilon fracture are formed by fixed main fracture lines. The understand of morphological and distribution characteristics of the fracture lines and size of fragments in OTA/AO type 43C pilon fractures would help the surgeons take suitable approach and fixation.

Keywords: classification; heat map; pilon fractures; three-dimensional reconstruction.

Figure 1

(A) Creating and reducing 3D fracture models using the Mimics 21.0 system; (B) Drawing fracture line on the standard right tibial model in 3-matic research; (C) Superimposing 3D fracture lines on standard 3D tibial models; (D) Abstracting the fracture lines through Photoshop; (E) Converting fracture lines map to heat map by using Python.

Figure 2

The angle α is defined that the angle between the sagittal fracture line and the ankle mortise line.

Figure 3

The angle β is defined that the angle between the fracture line of the transverse section and the line of the bilateral malleolus which was taken as the axis of the maximum tibiofibular notch connection.

Figure 4

In C1 pilon fracture, the metaphyseal fracture lines of the C1 pilon fractures encircled the distal tibia, and the simple articular fracture lines, including anterior fracture lines, the posterior fracture lines, the anterolateral fracture lines and the sagittal fracture lines, divided the distal tibia into two parts.

Figure 5

In C2 pilon fracture, fractures were simple joint fractures with multiple bone fragments in the metaphysis.The comminuted areas of the metaphyseal fractures were mainly concentrated in the anteromedial and the anterolateral distal tibia.

Figure 6

In C3 pilon fracture, the distal articular surface of the tibia was basically involved except the fracture line at the medial malleolus, the anterolateral articular plafond and the posterolateral articular plafond were sparsely distributed.

Figure 7

Selection of surgical approaches for type C pilon fractures. The approach for the SFLs can be determined by the surgeon’s experience, with three different approaches available. AFL, anterior fracture line; PFL, posterior fracture line; ALFL, anterolateral fracture line; SFL, sagittal fracture line; PLFL, posterolateral fracture line.