Cervical disc prostheses need a variable center of rotation for flexion / extension below disc level, plus a separate COR for lateral bending above disc level to more closely replicate in-vivo motion: MRI-based biomechanical in-vivo study.

Level C3/4: from ME-IE there is no significant difference for the x- and the y-coordinates (x: p = 0.251; y: p = 0.131); from IE-N a significant difference was found for the x-coordinates (x: p = 0.005) but not for the y-coordinates (y: p = 0.337); from N-IF a near-significant difference for the x-coordinates was found (x: p = 0.066) but not for the y-coordinates (y: p = 0.187); from IF-MF no significant difference was found both for the x- and y-coordinates (x: p = 0.949; y: p = 0.755).

also in 2,306 other papers