Effect of a Percutaneous Screw Guide on Screw Placement for Posterior Talar Fractures

Abstract

AIM: This study aimed to evaluate the hypothesis that the utilization of percutaneous screw guides enhances the precision of screw placement in the surgical fixation of talar fractures. 

METHODS: Computed tomography (CT) scans of ankle joints were obtained from 40 healthy adults and 10 cadaveric specimens between April 2019 and August 2020 at Ningbo No. 6 Hospital. The acquired CT data were imported into  Materialise Interactive Medical Image Control System (MIMICS) software for processing. Three-dimensional (3D) digital models of the ankle joints were reconstructed, and relevant anatomical parameters were measured. A percutaneous screw guide (PSG) was designed and fabricated to facilitate accurate screw placement in the posterior talar process. Ten eligible cadaveric ankle joints were selected for further analysis and their 3D models were reconstructed using the MIMICS software. Screw trajectory parameters were then measured and analyzed based on these cadaveric models, forming the model group for comparative analyses. Ten cadaveric specimens were utilized in this study, equally divided into two groups: a guider group (n = 5) and a free-hand group (n = 5). In the guider group, talar posterior process screws were inserted using percutaneous screw guidance. In the free-hand group, screws were inserted into the talar posterior process without guidance. Post-operative CT scans were performed on all specimens. The following parameters were quantitatively compared between the two groups: screw trajectories, entry point distances in specimens with preselected screws, entry point distance trajectories in the 3D model, operation time, frequency of fluoroscopic imaging, and number of drilling attempts. 

RESULTS: Following the generation of the 3D models from 10 cadavers, a virtual screw was digitally inserted into each model. In the model group, the preselected screw trajectory was oriented towards the medial aspect of the talar neck base, with a cephalad inclination angle (CIA) of 3.1° ± 1.5° in the transverse~plane and a medial diverge angle (MDA) of 12.0° ± 1.4° in the coronal plane. The CIA and MDA of the screw trajectory in the guider group were 2.1° ± 1.7° and 11.2° ± 1.6°, respectively, whereas the CIA and MDA in the free-hand group were 6.0° ± 2.2° and 18.8° ± 1.6°, respectively. Statistical analysis revealed significant differences in both CIA and MDA between the two groups (p < 0.05). Furthermore, the guider group yielded superior outcomes in terms of entry point distance, operation time, fluoroscopic exposure time, and number of drilling attempts compared to the free-hand group (p < 0.05). 

CONCLUSIONS: Percutaneous screw guidance can improve the accuracy and safety of the posterior process of the talar screws, which can be feasible for percutaneous fixation. Further studies are required to confirm the efficacy and clinical outcomes of percutaneous screw guidance.