Purpose of the study: Percutaneous osteosynthesis of scaphoid fractures remains a difficult technique which requires a long learning curve. Complications remain a problem, even in experienced hands of specialized surgeons. The purpose of this work was to study the potential contribution of fluoroscopic navigation for precutaneous screwing of the carpal scaphoid.
Material and methods: Right and left arm anatomic specimens from ten subjects were sectioned at the elbow level. Both wrists from each subject were prepared and each of the scaphoids was fixed by percutaneous screwing using regular fluoroscopic guidance for one and the other with fluoroscopic navigation. The regular fluoro-scopic guidance technique was used for the first wrist, selected randomly. Fluoroscopic navigation was used for the other side to achieve strict fixation of the wrist in the ideal screwing position using a stable radiotranspar-ent and flexible device. Using a calibraton grid displayed on the fluoroscope screen the system software corrected for distortions of the fluoroscope image. Reflecting patches on the surgical instruments were recognized by the 3D optical localization system. This enabled a real time screen display of instrument movement. Resolution was sufficient to align the screw with the scaphoid axis and calculate the length of the screw.
The resolution of the reformated digital images enabled real time screen display of instrument movement at a resolution which enabled pin insertion in the scaphoid axis. The length of the perforated screw inserted percutaneously over the pin was measured on the screen.
Results and discussion: Unlike the regular screwing method and excepting the image acquisition time which can be achieved without exposing the operator, exposure time to radiation was zero with fluoroscopic navigation. The duration of the operation was longer with navigation because the instruments had to be calibrated and because a learning curve is required. The quality of the screw fixation assessed on plain x-rays, computed tomography, and photographs of the entire scaphoid then sectional along the major axis after removal was similar between the two methods.
Conclusion: In conclusion, fluoroscopic navigation is a reliable technique which protects both the operator and the patient from radiation exposure. The technique remains to be standardized to shorten the learning curve, improve the navigation software, and develop a calibrated instrumentation before it can be used in routine clinical practice.
