Novel computer-assisted fluoroscopy system for intraoperative guidance: Feasibility study for distal locking of femoral nails

Objectives: Orthopaedic procedures that use fluoroscopy require intraoperat ive mental navigation of the surgical tools in a three-dimensional space. M oreover, 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 w ithin anatomy, but also provides constant feedback without the need for rad iologic updates. To evaluate the feasibility of the new technology, the aut hors used it on cases requiring distal locking of femoral nails. Methods: The hardware components of the system include an instrumented C-ar m, optoelectronic position sensor, stereotactic tools, and custom-made soft ware. Computer integration of these devices permitted C-arm alignment assis tance and realtime navigation control without constant x-ray exposure. The nails were locked in a variety of media, including plastic femurs, dry huma n femoral specimens, human cadavers, and one clinical case. Unreamed femora l nail sizes ranged from 9/340 to 12/400. Radiographs were taken to confirm that screws were positioned correctly, and fluoroscopic time associated wi th 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, al beit with no damage to the nail and no clinical consequences. The fluorosco py time per pair of screws was 1.67 seconds. Conclusions: The developed system enables the physician to precisely naviga te surgical instruments throughout the anatomy using just a few computer-ca librated radiographic images. The total radiation time per procedure can be significantly reduced because additional x-ray exposure is not required fo r tool navigation.