Introduction: A previously published comparative study demonstrated that, although both ventral and dorsal surgery are effective at alleviating symptoms of cervical spondylotic myelopathy (CSM), ventral surgery is associated with superior overall health-related quality of life (HR-QoL) at one year. The purpose of this study was to determine if post-operative cervical sagittal balance might be an independent predictor of HR-QOL outcome following surgery for CSM.
Methods: A prospective, nonrandomized 4-center study enrolled 49 patients over 2 years. Patients with degenerative CSM and cervical spinal cord compression at 2 or more levels were eligible; a surgical equipoise panel of 14 spinal experts confirmed case eligibility. Outcome measures (mJOA scale, Oswestry NDI, SF-36 PCS, EQ-5D) were done preoperatively, at 3 months, 6 months, and 1 year postoperatively. Sagittal balance was measured on standing plain films preoperatively and at 1 year and was defined as the distance from a plumb line drawn at the midpoint of C2 to the plumb line at the midpoint of C7 (figure 1). Statistical analysis was performed with SAS v.9.3 (Cary, NC).
Results: The two cohorts were similar with respect to baseline characteristics except by gender and preoperative sagittal balance (table 1). Most patients experienced improvement in all outcome measures regardless of approach (table 2). Both preoperative and postoperative sagittal balance measurements were independent predictors of clinically significant improvement in SF-36 PCS scores (p=0.03 and p=0.02). The majority of patients with sagittal balance value >40mm did not improve from an overall HR-Qol perspective (SF-36 PCS) despite improvement in myelopathy (figure 2). Postoperative sagittal balance was inversely correlated with clinically significant improvement of SF-36 PCS scores in patients undergoing dorsal surgery but not ventral surgery (p=0.003 vs p=0.84).
Conclusions: Particularly for patients treated with dorsal surgery, cervical sagittal imbalance is an important predictor of poorer patient outcome following surgery for CSM.
Patient Care: By understanding how cervical sagittal balance affects patient outcomes following surgery for CSM, we can improve overall health-related quality of life by optimizing sagittal balance when treating patients with CSM.
Learning Objectives: (1) Patients with CSM treated with decompressive surgery may not experience improvements in HR-QOL outcomes despite improvement in symptoms of myelopathy
(2) Postoperative cervical sagittal imbalance is an independent negative predictor of improvement in SF-36 PCS scores
(3) Patients treated with dorsal surgery are more sensitive to the negative effect of poor sagittal imbalance on improvement in SF-36 PCS scores than patients treated with ventral surgery. Patients with poor cervical sagittal balance may benefit more from ventral decompression and fusion than from dorsal decompression.