Comparison of sagittal vertical axis and decompression on the clinical outcome of cervical spondylotic myelopathy.

Objective: Decompression and cervical balance are major goals in the surgical treatment of cervical spondylotic myelopathy (CSM). Cervical balance is assumed to be a key factor for neurological recovery and pain reduction. Surgical reduction of C2-7 sagittal vertical axis (SVA) correlates with clinical improvement. However, it remains unclear, how much or even if correction is necessary for clinical improvement as long as surgery results in successful decompression. We aim to evaluate the role of radiological cervical balance parameter on the short-term course of CSM.

Methods: This is a retrospective study with prospectively collected data of 90 patients. The authors identified 45 patients suffering from CSM that underwent decompressive surgery and instrumentation and showed an increased C2-7 sagittal vertical axis (SVA) after surgery. 45 consecutive patients with a decreased C2-7 SVA were selected as a control group.

Results: Surgery improved the clinical outcome of both groups significantly. No differences could be seen comparing neck pain and neurological improvement between both groups. An increased C2-7 SVA did not correlate with an inferior clinical outcome. T1-slope correlated with the Cobb-angle.

Conclusions: Decompression and stabilization appear to be key elements of surgical treatment of CSM. In short terms, clinical improvement does not appear to affect patients negatively who show a larger C2-7 SVA after surgery. Optimal C2-7 SVA and necessity for a specific C2-7 correction is unclear. The term "balance" remains a complex entity without clear definition.