Craniotomy size determines the neurosurgeon - microscope interaction: A proof-of-concept study.

[PURPOSE] Our study aimed to compare the differences in quantitative parameters, describing the processes of neurosurgeons' interaction with a microscope when performing traditional and minimally invasive approaches.

[METHODS] We designed a prospective observational study to assess the quantitative parameters of neurosurgeon-microscope interactions. Eighteen patients with intracranial tumors were enrolled in the research. All cases were divided into 2 groups: patients with deep-seated tumors, which were operated on with craniotomy apertures of standard sizes - 3 to 4.5 cm (standard craniotomy SC group) and patients with deep-seated tumors operated on with minimally invasive burr hole approaches with a diameter of 1.4 cm (BH group). Three video cameras were used to register and analyze surgeon-operating microscope interactions. The interaction of the neurosurgeon with the microscope was described by the following parameters: microscope repositioning; time of work at low, medium, and high magnification; and the number of changes in focal length. All the interaction parameters were measured per minute of the microsurgical operation stage.

[RESULTS] Nine parameters significantly differed (p value < 0.05) between groups: "total time needed for all microscope positioning adjustments", "number of microscope positioning adjustments per minute","average duration of one microscope position adjustment","operating time at high magnification", "operating time at low magnification","proportion of operating time at high magnification", "proportion of operating time at low magnification", "total time for interaction between neurosurgeon and microscope", "proportion of total time for interaction". Significant P values withstood Benjamini-Hochberg's adjustment for all variables.

[CONCLUSION] The results of the study provide the grounds to postulate that there is a direct and significant relationship between the size of the craniotomy and the frequency of microscope repositioning, as well as the degree of intraoperative microscope magnification.