Markus Weiten

Utility of the LevelCheck Algorithm for Decision Support in Vertebral Localization.

Study Design. An automatic radiographic labeling algorithm called “LevelCheck” was analyzed as a means of decision support for target localization in spine surgery. The potential clinical utility and scenarios in which LevelCheck is likely to be the most beneficial were assessed in a retrospective clinical data set (398 cases) in terms of expert consensus from a multi-reader study (three spine surgeons). Objective. The aim of this study was to evaluate the potential utility of the LevelCheck algorithm for vertebrae localization. Summary of Background Data. Three hundred ninety-eight intraoperative radiographs and 178 preoperative computed tomographic (CT) images for patients undergoing spine surgery in cervical, thoracic, lumbar regions. Methods. Vertebral labels annotated in preoperative CT image were overlaid on intraoperative radiographs via 3D-2D registration. Three spine surgeons assessed the radiographs and LevelCheck labeling according to a questionnaire evaluating performance, utility, and suitability to surgical workflow. Geometric accuracy and registration run time were measured for each case. Results. LevelCheck was judged to be helpful in 42.2% of the cases (168/398), to improve confidence in 30.6% of the cases (122/398), and in no case diminished performance (0/398), supporting its potential as an independent check and assistant to decision support in spine surgery. The clinical contexts for which the method was judged most likely to be beneficial included the following scenarios: images with a lack of conspicuous anatomical landmarks; level counting across long spine segments; vertebrae obscured by other anatomy (e.g., shoulders); poor radiographic image quality; and anatomical variations/abnormalities. The method demonstrated 100% geometric accuracy (i.e., overlaid labels within the correct vertebral level in all cases) and did not introduce ambiguity in image interpretation. Conclusion. LevelCheck is a potentially useful means of decision support in vertebral level localization in spine surgery. Level of Evidence: N/A

On the Accuracy of a Video-Based Drill-Guidance Solution for Orthopedic and Trauma Surgery: Preliminary Results

Over the last years, several methods have been proposed to guide the physician during reduction and fixation of bone fractures. Available solutions often use bulky instrumentation inside the operating room (OR). The latter ones usually consist of a stereo camera, placed outside the operative field, and optical markers directly attached to both the patient and the surgical instrumentation, held by the surgeon. Recently proposed techniques try to reduce the required additional instrumentation as well as the radiation exposure to both patient and physician. In this paper, we present the adaptation and the first implementation of our recently proposed video camera-based solution for screw fixation guidance. Based on the simulations conducted in our previous work, we mounted a small camera on a drill in order to recover its tip position and axis orientation w.r.t our custom-made drill sleeve with attached markers. Since drill-position accuracy is critical, we thoroughly evaluated the accuracy of our implementation. We used an optical tracking system for ground truth data collection. For this purpose, we built a custom plate reference system and attached reflective markers to both the instrument and the plate. Free drilling was then performed 19 times. The position of the drill axis was continuously recovered using both our video camera solution and the tracking system for comparison. The recorded data covered targeting, perforation of the surface bone by the drill bit and bone drilling. The orientation of the instrument axis and the position of the instrument tip were recovered with an accuracy of 1:60 +/- 1:22° and 2:03 +/- 1:36 mm respectively.

A Portable Intra-Operative Framework Applied to Distal Radius Fracture Surgery

Fractures of the distal radius account for about 15% of all extremity fractures. To date, open reduction and internal plate fixation is the standard operative treatment. During the procedure, only fluoroscopic images are available for the planning of the screw placement and the monitoring of the instrument trajectory. Complications arising from malpositioned screws can lead to revision surgery. With the aim of improving screw placement accuracy, we present a prototype framework for fully intra-operative guidance that simplifies the planning transfer. Planning is performed directly intra-operatively and expressed in terms of screw configuration w.r.t the used implant plate. Subsequently, guidance is provided solely by a combination of locally positioned markers and a small camera placed on the surgical instrument that allows real-time position feedback. We evaluated our framework on 34 plastic bones and 3 healthy forearm cadaver specimens. In total, 146 screws were placed. On bone phantoms, we achieved an accuracy of 1.02i¾?±i¾?0.57mm, 3.68i¾?±i¾?4.38i¾? and 1.77i¾?±i¾?1.38i¾? in the screw tip position and orientation azimuth and elevation respectively. On forearm specimens, we achieved a corresponding accuracy of 1.63i¾?±i¾?0.91mm, 5.85i¾?±i¾?4.93i¾? and 3.48i¾?±i¾?3.07i¾?. Our analysis shows that our framework has the potential for improving the accuracy of the screw placement compared to the state of the art.