Both navigation and instrumented bone referencing use unreliable intraoperative landmark identification or fixed referencing rules which don't reflect patient specific variability. PSI, however, lacks the flexibility to adapt to soft tissue factors not known during preoperative planning, in addition to suffering error from guide fit. A novel method of recreating surgical cut planes that combines preoperative image based identification of landmarks and planning with intraoperative adjustability is under development. This method uses an intraoperative 3D scan of the bone in conjunction with a preoperative CT scan to achieve the desired cuts and so avoids issues of intraoperative identification of landmarks. During TKA surgery, a reference device is placed on the exposed femur. The device is used to position a target block which is pinned to the bone (see Figure 1). The condyles and target block are then scanned, the process taking a second to complete. This 3D scan is filtered to remove extraneous bodies and noise leaving only the bony geometry and target block (see Figure 2). The scan is then reconciled to the known bone geometry taken from preoperative CT scans. A cutting block is then fixed to the target block with a reference array visible to the camera attached. Pre-planned cut planes on a computer model of the bone are compared to the position and configuration of the distal cutting guide. Software guides the surgeon in real-time on the necessary configuration changes required to align the cutting block. The cut is performed on the distal femur, the cutting guide removed from the target-block, and a second scan performed. The software repeats the filtering and alignment processes and provides the surgeon with data on how closely the performed cut matches the alignment planned.Introduction
Method
