Validation of a Redundant Robotic Manipulator for Shoulder in Vitro Biomechanical Testing.

Abstract

Cadaveric joint simulators are commonly used to explore native and pathological joint function as well as to test medical devices. Recently, robotic manipulators have been proposed as a new gold standard for in vitro biomechanical testing as they offer higher possibilities than Universal Testing Machines in terms of degrees of freedom (DOF). However, current protocols remain conducted in extra-corporal conditions by fixing one segment of a diarthrodial joint while mobilising the other segment. Moreover, induced motions are commonly not specimen-specific and do not respect related joint kinematic constraints and physiologic boundaries. In this study, using a 7 DOF redundant robotic manipulator, an intra-corporal condition protocol was defined. This protocol allows 1) the analysis of the shoulder girdle full kinematic chain, 2) the replication of specimen-specific humerus motions initially induced by an operator. On the 10 shoulders tested, the robotic manipulator was able to perform requested end-effector motions with a reliability of 0.28 ± 0.57 mm and 0.15 ± 0.25°, and a fidelity of 0.27 ± 0.56 mm and 0.22 ± 0.28°. This protocol will be used in the future to explore joint function as well as to test medical devices, on the shoulder girdle and potentially other joints.