A new technology using Mixed Reality Surgical Navigation with UCRT frame to assist pelvic fracture reduction and fixation
Description
Accurate reduction is a prerequisite for optimal screw placement. However, due to the complexity of the pelvic anatomical structure, the closed reduction process cannot be directly monitored. Consequently, the success of a closed reduction procedure relies on a certain degree of luck. Several reduction tools and techniques, including the Matta, Starr, and unlocking close reduction technique (UCRT) frames, have been developed to allow surgical navigation-assisted closed reduction to be performed. More recently, a new technology using mixed reality surgical navigation (MRSN) with UCRT frame has been developed that allows real-time monitoring of fracture fragment displacement to instruct pelvic fracture reduction. This new technology can also help determine the CS trajectory for fixation of the pelvic ring after good reduction.
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2.1 Preoperative preparation In a CT room, each patient was administered local anesthesia. A special set screw which connects to a reference frame with an infrared reflective tracker was firmly secured to the bilateral iliac crest. Subsequently, the pelvis and bilateral trackers were scanned with a CT machine. 2.2 Navigation calibration and registration of pelvic bone or surgical instruments High precision voxel model data which included both pelvis and infrared reflecting trackers were generated based on preoperative CT three-dimensional (3D) imaging. Under an optical tracking system, the pelvic bone or surgical instrument was calibrated and registered according to the voxel registration method. 2.3 Installation of pelvic UCRT frame A pelvic UCRT frame was connected to the operating table and a connecting rod was used to stabilize the spatial reduction construct for each pelvic fracture. 2.4 Navigation-assisted placement of auxiliary long screws for reduction Under guidance provided by the surgical navigation system, two Schanz screws are inserted. 2.5 MRSN-assisted fracture reduction The UCRT technique was performed as previously described16-18. Briefly, the normal hemipelvis was secured before the displaced injured hemipelvis was aligned and rotated to the target position. The latter was achieved through a pelvic symmetric reduction method based on structural symmetry of the pelvis. First, the position of the pelvis was adjusted and displacement of the pelvic fragments was subsequently observed in multi-dimensional views under the guidance of MRSN. Second, the right pelvic reduction target position was set by mirroring the left ilium at the perpendicular midline plane of the sacrum. Third, the right mirrored ilium was translated or rotated to the location of the fractured right ilium Subsequently, the reduction strategy was simplified with translation or rotation of ilium #5 to the position of #8 by controlling the long screw which grasped the pelvic bone and applying femoral supracondylar traction to the pelvis. In brief, the pelvic closed reduction procedure was simplified by reducing the bony landmarks, anterior superior iliac crest, pubic tubercle, and posterior superior iliac crest. Physical reduction of the pelvic fragments was projected into a 3D visualization system in real-time under the MRNS. The surgeon was also able to switch the viewpoint, zoom the field of vision, adjust the display mode of the pelvic fragments at any time, observe the gap/interpenetration of the broken end of the fracture, and ensure the accuracy of the reduction procedure under the mixed reality environment. 2.6 MRSN-assisted definitive fixation After achieving satisfactory reduction, confirmed by C-arm examination, a suitable CS was implanted to fix the fracture.
Institutions
- Chinese PLA General Hospital Department of Orthopaedics