Fig. 2From: 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 studyDetermination of the COR. a graphically illustrates the determination of the COR; b shows the respective mathematical algorithm [23,24,25]Back to article page