General Session: MIS-1
Presented by: N. Anand - View Audio/Video Presentation (Members Only)
N. Anand(1), B. Khandehroo(1), J. Cohen(1), R. Cohen(1), E. Baron(1), S. Kahwaty(1)
(1) Cedars-Sinai Medical Center, Spine Center, Los Angeles, CA, United States
Introduction: Recent studies have confirmed sagittal balance to be an important outcome parameter in surgical correction of adult spinal deformity (ASD). However, there is little data to show whether clinical outcomes are poor in all cases where the target sagittal vertical alignment (SVA) value was not achieved especially in patients who had CMIS correction of ASD. We assessed whether the clinical outcome was poor for patients who had not achieve target SVA (SVA less than 50mm) after cMIS correction of ASD.
Methods: A prospective registry of patients who underwent CMIS corrective surgery for ASD (Cobb>20 or SVA>50mm or PI/LL mismatch> 10) was queried. 153patients including 95 female and 58 male (mean age: 63 years, range 21-85 years) met the inclusion criterion of fusion of 3 or more levels and minimum 1year follow-up for this study (1-7yrs). Radiographic parameters were evaluated on lateral standing 36” X-rays. They included Cobb angle, Sagittal vertical alignment (SVA: C7 plumb line relative to S1) and PI-LL mismatch preoperatively and at final follow-up. Clinical outcomes were evaluated by Oswestry Disability Index questionnaire preoperatively and at 6 month, 1year and final follow-up (average 4 years).
Results: Out of 153 patients, 107 patients had post-op SVA< 50mm and 46 patients had post-op SVA>50mm. These 46 patients had mean age of 64 years (range 21-85). The pre-op SVA of 97.3mm (64.9-180) corrected to 72.5mm (51.6-113.9) postoperatively. The pre-op Cobb angle of 29.8 degrees (8.7-60.3) improved to 11 degrees (1.6-28.2) postoperatively. The mean pre-op PI-LL mismatch of 18 degrees (1-54) improved to 11.2 degrees (0-28) postoperatively. The mean pre-op ODI of 48 (14-80,SD 19) was changed to 40 (6-64) at 6months, to 29.4 (0-71) at 1year and to 27.3(0-60) at final follow-up after surgery. At the final follow-up (>1 year FU), of the 46 patients with post-op SVA>50mm, 22 had ODI of 0-20 (minimal disability), 17 had ODI of 21-40 (moderate disability) and 7 patients had ODI of 40-60 (severe disability).
Discussion: Global Sagittal Alignment is considered as a key radiographic parameter for post-op disability in patients with ASD. However, our study suggests that only 15% have significant disability with a post-op SVA > 5cm. Our data would suggest that elderly patients may continue to do well in spite of not so optimal sagittal balance. The study also gives us pause to consider whether muscle preservation with CMIS surgery may help limit the disability. Length of follow-up, single center and the small sample size may be major limitations in this study and further multi-center studies are required.