Retrospective Study With Patients Treated With STALIF® C or M and Ti or FLX Implants for 1 and 2 Levels

Inclusion Criteria: * Diagnosed with up to a Grade1 spondylolisthesis or retrolisthesis or degenerative disc disease of the cervical or lumbar spine at time of surgery. * 2 levels, between: * C: C2-T1 (neck) * M: L2-S1 (low back) * Skeletally mature at the time of surgery with clinical and radiological evidence of degenerative disc disease of the cervical or lumbar spine. Exclusion Criteria: * Subject who had surgery with the STALIF devices at more than 2-levels. * In the Investigator's opinion, the subject diagnosed with a disease or condition, which precludes the possibility of healing at the time of surgery