Establishing a central zone in scaphoid surgery: a computational approach

Abstract

Purpose Scaphoid fractures are commonly fixed with headless cannulated screws positioned centrally in the scaphoid. Judgement of central placement of the screw may be difficult. We generated a central zone using computer analysis of 3D reconstructions of computed tomography (CT) images. As long as the screw axis is completely contained within this central zone, the screw would be considered as centrally placed. Methods Thirty cases of 3D CT reconstructions of normal scaphoids in a computerised operation planning and simulation system (Vxwork software) were obtained. The central zone was established after some distance shrinkage of the original scaphoid surface reconstruction model using the function "erode" in the software. The shape of the central zone was evaluated, and the width of the central zone in the proximal pole, waist portion and distal pole was measured. We also established the long axis of the scaphoid to see whether it stays in the central zone. Results All central zones could be divided into distal, waist and proximal portions according to the corresponding irregular shape of the scaphoid. As the geometry of the central zone was so irregular and its width very narrow, it was possible to completely contain the screw axis either in the proximal portion alone, waist alone or distal central zone alone. Conclusions Establishing the central zone of scaphoid 3D CT images provided a baseline for discussion of central placement of a scaphoid screw. The geometry of the scaphoid central zone determined that the screw could hardly be inserted through entire scaphoid central area during surgery.

Determining the optimal radiologic wrist and forearm position to visualize screw protrusion in scaphoid fixation

“…17 Guo et al in 2014 showed that the central zones of the three scaphoid segments (proximal, waist and distal) are not continuous due to the irregular anatomy of the scaphoid bone and that it might not be possible to insert a screw that passes through the central zones of all three segments. 18 Quan et al in 2017 acknowledged the possibility of iatrogenic perforation of the scaphoid cortex especially if the screws appear close to the scaphoid cortex. 7 We are not aware of any publications describing the thickness of the articular cartilage surrounding the scaphoid.…”

Three-Dimensional Printed Targeting Device for Scaphoid Fracture Fixation

“…3,4,9 However, due to variations in scaphoid anatomy and fracture morphology, central third placement may not be ideal in all patients. 26 Our software allows the surgeon to make adjustments to ensure the screw is contained entirely within the scaphoid bone. Thus, preprocedure planning for the targeting device group was aimed at maximizing K-wire length within the scaphoid, but this came at the expense of some K-wire trajectories traveling outside the central axis.…”

“…Thus, preprocedure planning for the targeting device group was aimed at maximizing K-wire length within the scaphoid, but this came at the expense of some K-wire trajectories traveling outside the central axis. Guo et al 26 examined 30 scaphoid CT reconstructions and determined that the central zone could be defined within the proximal, waist, or distal portions of the scaphoid, but a single screw could rarely be inserted through the central zone of all three portions concurrently. Still, we reported the number of K-wires placed within the central third to allow comparison of accuracy between the two groups.…”

Scaphoid screw fixation perpendicular to the fracture plane: Comparing volar and dorsal approaches

“…1). As there is no clear definition of the scaphoid center due to the curved, irregular geometry [16], we calculated the centroids of the proximal and distal poles in transverse cross-sections at 25% and 75% length and defined the scaphoid center as the point halfway these centroids.…”