Purpose Medial femoral neck fractures are common, and closed reduction and internal fixation by three cannulated screws is an accepted method for the surgical treatment.Computer navigation for screw placement may reduce fluoroscopy time, the number of guidewire passes and optimise screw placement. Methods In the context of a sawbone study, a computerassisted planning and navigation system based on 3D-imaging for guidewire placement in the femoral neck was tested to improve screw placement. Three screws were inserted into 12, intact, femoral sawbones using the conventional technique and into 12, intact, femoral sawbones guided by the computer-based navigation system. Guidewire and subsequent screw placement in the femoral neck were evaluated. Results Use of the navigation system resulted in a significant reduction of the number of drilling attempts (p≤0.05) and achieved optimised accuracy of implant placement by attaining significantly better screw parallelism (p≤0.05) and significantly enlarged neck-width coverage by the three screws (p≤0.0001). Computer assistance significantly increased the number of fluoroscopic images (p≤0.001) and the operation time (p≤0.0001).Conclusions Three-dimensional computer-assisted navigation improves accuracy of cannulated screw placement in femoral neck while increasing the number of fluoroscopic images and operation time. Additional studies including fractured sawbones and cadaver models with the goal of reducing operation time are indispensable before introduction of this navigation system into clinical practice.

Metal-on-metal hip resurfacing arthroplasties represent an alternative to total hip arthroplasties for young and active patients, enabling the preservation of intact femoral bone and therefore improving the prognosis for future hip joint replacements. Follow-up studies have shown that the main reasons for early implant failure are mal-orientation of the implant stem in relation to the femoral neck axis, and notching of the femoral neck during femoral head preparation, as well as by exposed cancellous bone after implantation. A computer-assisted planning and navigation system for the implantation of femoral hip resurfacing implants has been developed which supports the surgeon during intraoperative fluoroscopy-based planning and navigation of implant positioning. This paper presents the results of a cadaver study performed to evaluate the system's functionality and accuracy.

BIOMEDICAL PAPEREvaluation of a fluoroscopy-based navigation system enabling a virtual radiation-free preview of X-ray images for placement of cannulated hip screws. A cadaver study Abstract Accurate placement of cannulated screws is essential to ensure fixation of medial femoral neck fractures. The conventional technique may require multiple guide wire passes, and relies heavily on fluoroscopy. A computer-assisted planning and navigation system based on 2D fluoroscopy for guide wire placement in the femoral neck has been developed to improve screw placement. The planning process was supported by a tool that enables a virtual radiation-free preview of X-ray images. This is called ''zero-dose C-arm navigation''. For the evaluation of the system, six formalin-fixed cadaveric fullbody specimens (12 femurs) were used. The evaluation demonstrated the feasibility of fluoroscopically navigated guide wire and implant placement. Use of the novel system resulted in a significant reduction in the number of fluoroscopic images and drilling attempts while achieving optimized accuracy by attaining better screw parallelism and enlarged neckwidth coverage. Operation time was significantly longer in the navigation assisted group. The system has yielded promising initial results; however, additional studies using fractured bone models and with extension of the navigation process to track two bone fragments must be performed before integration of this navigation system into the clinical workflow is possible, and these studies should focus on reducing the operation time.

Metal-on-metal hip resurfacing arthroplasties represent an alternative to total hip arthroplasties for young and active patients, enabling the preservation of intact femoral bone and therefore improving the prognosis for future hip joint replacements. Follow-up studies have shown that the main reasons for early implant failure are mal-orientation of the implant stem in relation to the femoral neck axis, and notching of the femoral neck during femoral head preparation, as well as by exposed cancellous bone after implantation. A computer-assisted planning and navigation system for the implantation of femoral hip resurfacing implants has been developed which supports the surgeon during intraoperative fluoroscopy-based planning and navigation of implant positioning. This paper presents the results of a cadaver study performed to evaluate the system's functionality and accuracy.