Current immobilization techniques of the cervical spine are associated with complications including pressure ulcers, discomfort, and elevated intracranial pressures with limited access to the thorax and airway. In this study, a newly developed craniothoracic immobilizer (Pharaoh mattress) for critical care patients with cervical injury was tested for its restriction of cervical movement, peak interface pressures, comfort, and radiolucency, and compared with headblocks strapped to a spineboard. Cervical movement was measured by roentgen stereophotogrammetric analysis in 5 fresh frozen cadavers. Peak interface and discomfort pressures were measured in 10 healthy volunteers. Radiographic absorption was calculated by measuring the total emission radiation with and without immobilizer. The Pharaoh mattress caused a mean restriction of 59% (SD: 15) flexion-extension, 77% (SD: 14) lateral bending, and 93% (SD: 3) rotation, compared with the unrestricted situation. No significant differences in restriction of cervical movement were found between headblocks strapped to a spineboard and the Pharaoh mattress. The mean peak pressures on the Pharaoh mattress were significantly lower than on the spineboard. Healthy volunteers gave significantly lower numeric discomfort scores on the Pharaoh mattress than on the spineboard. The Pharaoh mattress absorbed more x-rays than the spineboard. The Pharaoh mattress provides similar restriction of cervical movement compared with headblocks strapped to a spineboard but with lower interface pressures and increased comfort. This new mattress could be useful for immobilization of the cervical spine in critical care patients with mechanically instable spinal fractures.
Purpose Navigation has been suggested to guide complex benign bone tumor curettage procedures, but the contribution of navigation to the accuracy of curettage has never been quantified. We explored the accuracy of navigated curettage in a cadaveric observational pilot study, comparing navigated to freehand curettage, performed independently by an expert and a novice user. Methods The expert performed curettage on 20 cadaveric bones prepared with a paraffin wax mixture tumor, 10 freehand and 10 navigated. We re-used 12 bones for the novice experiments, 6 freehand and 6 navigated. Tumor and curettage cavity volumes were segmented on pre- and post-cone-beam CT scans. Accuracy was quantified using the Dice Similarity Coefficient (DSC), and with remaining tumor volume, bone curettage volume, maximal remaining width and procedure times compared between navigation and freehand groups for both users. Results There were little differences in curettage accuracy between a navigated (DSC 0.59[0.17]) and freehand (DSC 0.64[0.10]) approach for an expert user, but there were for a novice user with DSC 0.67(0.14) and 0.83(0.06), respectively. All navigated and freehand procedures had some amount of remaining tumor, generally located in a few isolated spots with means of 2.2(2.6) cm3 (mean 20% of the tumor volume) and 1.5(1.4) cm3 (18%), respectively, for the expert and more diffusely spaced with means of 5.1(2.8) cm3 (33%) and 3.0(2.2) cm3 (17%), respectively, for the novice. Conclusions In an explorative study on 20 cadaveric bone tumor models, navigated curettage in its current setup was not more accurate than freehand curettage. The amount of remaining tumor, however, confirms that curettage could be further improved. The novice user was less accurate using navigation than freehand, which could be explained by the learning curve. Furthermore, the expert used a different surgical approach than the novice, focusing more on removing the entire tumor than sparing surrounding bone.
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