This study aimed to quantify the effect of different current clinical treatments on intervertebral disc degeneration in the cervical spine. It aimed to understand the effect of implant stiffness on range of motion and adjacent intervertebral disc stress. It produced a validated finite element model and simulated healthy, degenerated, total disc replacement and spinal fusion at the C4-C5 level. The results showed that spinal fusion at the C4-C5 level produced decreased range of motion and increased stresses to clinically unacceptable levels. Total disc replacements performed better, however, the results suggest that implants should be designed with modulus values between 20–30 MPa in order to restore range of motion and limit IVD stresses.