Measurement of the sustentaculum tali range and biomechanical screw analysis based on the space shape of the calcaneal trabeculae.

Background: The sustentaculum tali (ST) plays an important role in the surgical treatment of calcaneal fracture. However, there is a lack of relevant literature report on the true extent of the distance process. The introduction of the 'space shape of the trabeculae within the calcaneus allowed the ST range to be defined with reference to the trabecula topographic trend. Here, we investigated the biomechanical properties of two common ST screws after implantation by applying the finite element method (FEM).

Methods: Dicom imaging data of the calcaneus ST was obtained by computed tomography (CT)scanning techniques and a spatial three-dimensional (3D) coordinate system was established to measure the extent of the ST. The continuation range was identified according to the trend of the trabecula bone and then superimposed to form a new ST range. Next, by structural design and FEM, we performed biomechanical tests on the two type of ST screws: the 'pressure type (transverse group)' test for vertical fracture lines and the 'tension type (oblique group) of the center' test.

Results: Based on space shape of the trabeculae within the calcaneus, the spatial extent of the ST was redefined. According to FEM calculations, the load bearing capacity of the transverse group was better than that of the oblique group by 15.15% when the screws were implanted in the peak area. Furthermore, the load bearing capacity of the oblique group was better than that of the transverse group by 14.13% and 5.59% when the screws were implanted in the lumbar and valley regions.

Conclusions: Based on the space shape of the trabeculae within the calcaneus, the range of the ST is expanded. The best mechanical properties of two different screws were implanted in the peak area. The load-bearing capacity gradually reduced when implanted in the lumbar and valley regions. However, the waist area and valley area can still meet the requirements for structural strength and stability, and also provide a good fixation effect.

Level of evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.