gms | German Medical Science

Objectives/Interrogation: Create customized 3-D printed apparatus for percutaneous retrograde screw fixation of scaphoid fractures (the Fixation Approaches to Scaphoid Trauma, FAST, Procedure) is more accurate, faster, and has less radiation exposure to the surgical team than fluoroscopy-guided percutaneous fixation. We describe in this presentation our process development of this guide.

Methods: We devised a complete system that allows the surgeon to define an optimal insertion point and trajectory on 3D renditions of CT data, and then to construct a guide to position a k-wire in the desired trajectory in cadaver arms. After defining the intended insertion point and trajectory, a 3D printer is programmed to produce the components that perfectly guides a K-wire into the intended position. We developed 4 different models during the process.

With this system, we conducted experiments in which orthopedic residents placed casts outfitted with special openings (windows) designed to accommodate the k-wire guides on 7 cadaver arms. Following casting, pre-op CTs were acquired and treatment planning to define the k-wire trajectory was done. Custom guiding inserts were designed based on 3D models of the skeleton and stereolithography (STL) files suitable for 3D printing were produced and made into guide blocks. Finally, the residents placed the blocks into the windows and inserted the k-wires in place. Post-op CTs were used to verify the correct placement of the k-wires and we were able to confirm correct position in all 14 cases.

We had the same 7 residents perform standard percutaneous pinning utilizing a mini c-arm.

Results and Conclusions: We first developed an optimal model. We then tested this with resident surgeons. We found that:

• FAST is Faster (30 seconds versus 21 minutes)
• FAST is More Accurate (all within central axis of the scaphoid)
• FAST has no radiation exposure to the surgeon
• FAST Procedure planned trajectory courses along the exact planned path (Figure 1)

The FAST Procedure is a faster, more accurate, and more reliable way to perform percutaneous pinning for orthopaedic residents. We present the steps that we took to produce this technique.