The Relationship Between Improvements in Myelopathy and Sagittal Realignment in Cervical Deformity Surgery Outcomes
Authors: Passias Peter Gust , Horn Samantha R. , Bortz Cole A. , Ramachandran Subaraman , Burton Douglas C. , Protopsaltis Themistocles , Lafage Renaud , Lafage Virginie , Diebo Bassel G. , Poorman Gregory W. , Segreto Frank A. , Smith Justin S. , Ames Christopher , Shaffrey Christopher I. , Kim Han Jo , Neuman Brian , Daniels Alan H. , Soroceanu Alexandra , Klineberg Eric 
Published: February 2018

Study Design.
Retrospective review.

Objective.
Determine whether alignment or myelopathy improvement drives patient outcomes after cervical deformity (CD) corrective surgery.

Summary of Background Data.
CD correction involves radiographic malalignment correction and procedures to improve motor function and pain. It is unknown whether alignment or myelopathy improvement drives patient outcomes.

Methods.
Inclusion: Patients with CD with baseline/1-year radiographic and outcome scores. Cervical alignment improvement was defined by improvement in Ames CD modifiers. modified Japanese Orthopaedic Association (mJOA) improvement was defined as mild [15–17], moderate [12–14], severe [<12]. Patient groups included those who only improved in alignment, those who only improved in mJOA, those who improved in both, and those who did not improve. Changes in quality-of-life scores (neck disability index [NDI], EuroQuol-5 dimensions [EQ-5D], mJOA) were evaluated between groups.

Results.
A total of 70 patients (62 yr, 51% F) were included. Overall preoperative mJOA score was 13.04 ± 2.35. At baseline, 21 (30%) patients had mild myelopathy, 33 (47%) moderate, and 16 (23%) severe. Out of 70 patients 30 (44%) improved in mJOA and 13 (18.6%) met 1-year mJOA minimal clinically important difference. Distribution of improvement groups: 16/70 (23%) alignment-only improvement, 13 (19%) myelopathy-only improvement, 18 (26%) alignment and myelopathy improvement, and 23 (33%) no improvement. EQ-5D improved in 11 of 16 (69%) alignment-only patients, 11 of 18 (61%) myelopathy/alignment improvement, 13 of 13 (100%) myelopathy-only, and 10 of 23 (44%) no myelopathy/alignment improvement. There were no differences in decompression, baseline alignment, mJOA, EQ-5D, or NDI between groups. Patients who improved only in myelopathy showed significant differences in baseline-1Y EQ-5D (baseline: 0.74, 1 yr:0.83, P < 0.001). One-year C2-S1 sagittal vertical axis (SVA; mJOA r = −0.424, P = 0.002; EQ-5D r = −0.261, P = 0.050; NDI r = 0.321, P = 0.015) and C7-S1 SVA (mJOA r = −0.494, P < 0.001; EQ-5D r = −0.284, P = 0.031; NDI r = 0.334, P = 0.010) were correlated with improvement in health-related qualities of life.

Conclusion.
After CD-corrective surgery, improvements in myelopathy symptoms and functional score were associated with superior 1-year patient-reported outcomes. Although there were no relationships between cervical-specific sagittal parameters and patient outcomes, global parameters of C2-S1 SVA and C7-S1 SVA showed significant correlations with overall 1-year mJOA, EQ-5D, and NDI. These results highlight myelopathy improvement as a key driver of patient-reported outcomes, and confirm the importance of sagittal alignment in patients with CD.

Level of Evidence: 3