Segmental instability in cervical spondylotic myelopathy with severe disc degeneration

Study Design. A retrospective study was conducted. Objective. To investigate relationships between severe disc degeneration (SDD) and segmental instability in cervical spondylotic myelopathy (CSM) and to discuss surgical treatment for CSM with severe disc degeneration. Summary of Background Data. Information on relationships between segmental instability and spinal cord compression in CSM with severe disc degeneration is scarce. Methods. Radiographs and magnetic resonance images of patients with CSM with (n = 42) and without (n = 75) SDD were reviewed retrospectively. Cervical instability and spinal cord compression factors were analyzed. Outcomes of anterior cervical decompression and fusion (ACDF) and expansive laminoplasty (ELAP) were evaluated in medical records of follow-up clinics. Results. Segmental instability was found in 71.4% of patients with SDD and 22.7% of patients without SDD. Spinal cord compression was found at the intervertebral space of SDD and upper adjacent disc space. The recovery rate of ACDF and ELAP was 60.8% and 57.1%, respectively. Conclusion. The upper adjacent vertebra above SDD has inclination of segmental instability. There is static spinal cord compression in intervertebral spaces of SDD and dynamic compression in upper adjacent intervertebral spaces. Multilevel anterior cervical decompression and fusion or expansive laminoplasty should be used for surgical treatment.