Introduction of the Biokinemetric Triangle - a New Surrogate Parameter for Analysis of Spinal Range of Motion

Background: In preparation for a cervical device study (CDS) we developed a software-based surrogate model in order to analyze pre- and postoperative segmental range-of-motion (ROM) and help determine the optimal height of cervical implants. Besides eliminating surgeon's bias during intraoperative device-height choice, this software-based approach to spinal implantation surgery aims to reduce postoperative neck pain. In this study we evaluated the feasibility of using this surrogate model to determine changes in pre- and postoperative segmental motion characteristics independent of surgeon-related bias of device-height choice. Methods: The software's surrogate model is based on videofluoroscopic movement recordings in addition to conventional radiographs recorded during standardized movements. Software-based evaluation of segment-specific range-of-motion (ROM) characteristics was based on the newly introduced surrogate parameter "biokinemetric triangle". Depending on changes of the triangles surface area during pre- and post-operative analysis, segment-specific ROM were determined and evaluated with regards to surgery-related ROM changes. Structural pattern recognition was employed to examine whether biokinemetric triangle based ROM analysis is able to discriminate between different implants. Results: The surrogate parameter biokinemetric triangle software plug-in allows detection of implant-specific functional alterations of segmental movement characteristics (p<0.05). It is a valuable follow-up parameter for the investigation of changes in the segmental motion characteristics after device implantation. Conclusions: Biokinemetric triangle analysis displays segmental motion characteristics and detects segmental changes after device implantation in CDS. Common range of motion (ROM) analysis based on angular observations requires complete movement execution in order to make significant comparisons, whereas the triangle-based analysis allows movement characterization independent of complete execution.