Classification of Joints Used in Steerable Instruments for Minimally Invasive Surgery—A Review of the State of the Art

Abstract

This review article provides a comprehensive overview and classification of the joint types used in the steerable tips of minimally invasive surgical instruments. The review was carried out with the objective to pinpoint the essence of the joints' fundamental mechanical design and to provide a qualitative comparison of their strengths and weaknesses with respect to a number of straightforward criteria. Besides researching the ASME scientific literature, the entire Espacenet patent database was searched using the keywords endo* or lapar* or surg* in title and steer* or articu* or deflect* in title or abstract. The extensive scope of the patent results was further limited to World (WO), United States (US), and European (EP) patents only as well as to the period of the last decade, 2003–2013, with a few exceptions predating this period. Overall, more than 840 patents were reviewed and categorized on the basis of the joints' mechanical design and supplemented with the scientific papers. A number of joint categories and subcategories were identified. At the fundamental level the joints can be differentiated as planar and spatial, where the spatial are further split as perpendicular mirrored and revolved. Based on the means of establishing rotational motion, the joint types can be discriminated as rolling, sliding, the combination of rolling and sliding, and bending. Lastly, the rolling and sliding categories can be further split with regard to the phenomenon or feature used for transferring the rotational motion, i.e., friction, teeth, belts, curved features, and hinges. In general, the most favored joint types were identified as the sliding and the bending joint categories overall. Nevertheless, it was recognized that no single fundamental joint type can be considered as ideal and that novel and preferably more superior joint configurations can be generated by combining several fundamental categories together.