Novel computer-assisted fluoroscopy system for intraoperative guidance: feasibility study for distal locking of femoral nails.
OBJECTIVE
Orthopaedic procedures that use fluoroscopy require intraoperative mental navigation of the surgical tools in a three-dimensional space. Moreover, because of their reliance on real-time monitoring, such procedures are frequently associated with increased x-ray exposure. The goal of this study was to develop a computer-guided surgical navigation system based on fluoroscopic images that not only facilitates direction of surgical tools within anatomy, but also provides constant feedback without the need for radiologic updates. To evaluate the feasibility of the new technology, the authors used it on cases requiring distal locking of femoral nails.


METHODS
The hardware components of the system include an instrumented C-arm, optoelectronic position sensor, stereotactic tools, and custom-made software. Computer integration of these devices permitted C-arm alignment assistance and real-time navigation control without constant x-ray exposure. The nails were locked in a variety of media, including plastic femurs, dry human femoral specimens, human cadavers, and one clinical case. Unreamed femoral nail sizes ranged from 9/340 to 12/400. Radiographs were taken to confirm that screws were positioned correctly, and fluoroscopic time associated with the locking procedure was recorded.


RESULTS
All distal holes were locked successfully. In eight (11 percent) of seventy-six holes, the drill bit touched the canal of the locking hole, albeit with no damage to the nail and no clinical consequences. The fluoroscopy time per pair of screws was 1.67 seconds.


CONCLUSIONS
The developed system enables the physician to precisely navigate surgical instruments throughout the anatomy using just a few computer-calibrated radiographic images. The total radiation time per procedure can be significantly reduced because additional x-ray exposure is not required for tool navigation.
M. E. Müller Institute for Biomechanics, University of Bern, Switzerland.
M A
MA
Slomczykowski
R
R
Hofstetter
M
M
Sati
C
C
Krettek
L P
LP
Nolte
D001858:Bone Nails; D002102:Cadaver; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004867:Equipment Design; D004869:Equipment Safety; D005240:Feasibility Studies; D005265:Femoral Neck Fractures / Q000000981:diagnostic imaging* / Q000601:surgery*; D005471:Fluoroscopy / Q000379:methods*; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D016343:Monitoring, Intraoperative / Q000379:methods*; D012680:Sensitivity and Specificity