Fig. 1.

We calculated the cervical ROM at each level between flexion and extension positions. For example, when we registered at C2 and inserted the CPS into the C2 pedicle, we defined the ROM as 0°. When we inserted it into another pedicle, we added the ROM at each level. For example, with single-time multilevel registration at C2 we calculated the total ROM as follows: ROM of C2/3 with insertion at C3; C2/3 + C3/4 with insertion at C4; C2/3 + C3/4 + C4/5 with insertion at C5