Intraoperative Imaging and Navigation

Prior to its introduction to orthopedic surgery, intraoperative computer guidance systems were used primarily in neurological surgery, assisting in the identification of the precise location of brain tumors. Since that time, intraoperative imaging and navigation has found utility across many surgical disciplines, from craniofacial surgery to orthopedic surgery. Once introduced into orthopedic surgery, several avenues of potential application were explored, including total joint arthroplasty, spine surgery, trauma, and tumor surgery. Early investigations of computer navigation found a natural home in total hip replacement surgery, given the importance of accuracy and reproducibility of appropriate anteversion and abduction of the acetabular components [1]. Likewise, in total knee replacement, computer navigation saw early adoption in an attempt to improve coronal alignment, precision of mechanical axis realignment, and femoral component positioning [2, 3]. In the subspecialty of spine surgery, computer navigation has found a home in ensuring the accuracy of screw placement correctly within the pedicles [4]. Indeed, the accuracy of screw placement within the pedicles has been shown to improve when navigation is employed. In one study, 95% of screws placed under navigation guidance were found on postoperative imaging to be appropriately placed, as compared to only 85% of screws being appropriately placed using conventional methods [4]. In an associated analysis, subsequent rates of return to the operating room for screw revision were lower for a computer-assisted pedicle placement group when compared to a non-navigated approach [5]. In orthopedic trauma surgery, navigation has been particularly useful in the assistance of percutaneous sacroiliac screw insertion, especially in the consideration of patients with abnormal sacral morphology [6]. However, despite these advantages and utilizations across these subspecialties of orthopedic surgery, intraoperative imaging and navigation have not been without attendant complications, disappointments, and controversies. For example, routine utilization of navigation in primary arthroplasty has been limited due to its associations with periprosthetic fracture, increased cost, and increased surgical time [7, 8]. Furthermore, the increased precision afforded by computer navigation during arthroplasty may not translate to a significant clinical benefit. While it has been shown that considerable component malalignment leads to increased risk of revision arthroplasty surgery, no study to date has clearly demonstrated consistent, improved clinical outcomes with the use of navigation for arthroplasty versus traditional surgical technique [2, 9, 10]. That is, the improved precision of a few degrees of component rotation or tilt that computer navigation may provide does not change the outcome of a well-performed arthroplasty surgery done under the care of a skilled orthopedic surgeon. As another example of the limitations of computer navigation in surgery, in the realm of trauma surgery, specific difficulties relative to fractures, such as the mobility of the fracture fragments and the inability to register several bone fragments in their relationship to each other, have limited the reliable use of navigation. Finally, although utilization rates of navigation spine surgery are higher than an arthroplasty and trauma, navigation is still not considered by some surgeons to bring enough clinical benefit to have enjoyed universal adoption and use. The primary issue again hinges on limited evidence of improved clinical outcomes when compared to non-navigated surgery.