General Session: MIS - Hall F
Presented by: N. Anand
N. Anand(1), B. Khandehroo(1), S. Kahwaty(1), C. Kong(1), E. Nomoto(1)
(1) Cedars Sinai Medical Center, Spine Center, Los Angeles, CA, United States
Introduction: CMIS techniques are gaining popularity for treating significant ASD. Nonetheless, deciding where the ideal upper instrumented vertebra (UIV) of a long-segment fusion should be, remains inconclusive. We conducted this study to determine the outcomes of Staged Thoraco-lumbar CMIS correction for ASD patients with marked Schwab sagittal modifier(++) where UIV was T10-L2.
Methods: This is a retrospective review of a prospectively collected database of 225 consecutive ASD patients who underwent staged CMIS correction from Jan.2007 to Oct.2015. Considering marked Schwab sagittal modifier (SVA>95mm or PI-LL>20 or PT>20), +3 levels fused and +2year follow-up included 31pts. In all patients, multilevel LLIF±L5-S1 ALIF were done in the first stage. The patients were ambulated after a standing radiograph obtained 2days later and further correction of alignment was planned for the second stage accordingly. 3days later MIS pedicle screws with aggressive rod contouring and derotation/translation was done. Indirect decompression of stenosis was documented by clinical relief of leg pain after the first stage. MIS TLIF was done at L5-S1 if an ALIF was not possible(Figure 1). Radiographic parameters(Cobb, SVA, PT,PI/LL mismatch) and VAS,SRS-22,ODI and SF-36 were evaluated preop and postoperatively.
Result: Mean age was 69yrs(52-85) with mean follow-up of 67months(24-120). Mean level fused was 6.7 levels(4-8). The Mean pre-op Cobb angle of 33.5o(11.3-61.5) was corrected to 11.8o(1.6-28.2)(p< .05). The mean pre-op SVA of 78.3mm(13.5-151) was corrected to 49.4mm(0-84.4) (p< .05). The mean pre-op PI/LL mismatch of 22.6 (3.9-36.4) corrected to 15.4 (1.2-28.5)(p< .05) and pre-op PT of 29.6(6-53) maintain at 29.7(9-53) at the last follow-up. Out of 31patients which were classified as marked(++) deformity, 18pts improved to Moderate(+) Schwab classification and 13pts to non pathologic(0) deformity at the last follow-up. PJK was identified in 5 of the 31pts(16.1%). However, only 2(6.4%) were symptomatic and underwent revision surgery (extension of the UIV to T2-T3) and 3patients have remained asymptomatic. The mean pre-op of VAS, ODI, SF-36 and SRS-22 were significantly improved at 6months, 1year and final FU visit(Table1). 9patients had total of 10 complications for a 32.2% incidence of major and minor complications and underwent revision surgery(Table 2).
Conclusion: There was significant improvement in functional outcomes with minimal incidence of PJK or revision surgery at 2years. Our study suggests that Staged CMIS allows us to reassess the sagittal balance based on the intervening xray following MIS lateral fusionALIF, we were able to limit the UIV to T10-L2 even in patients with severe sagittal imbalance. This gives pause to consider whether T2 to pelvis is needed routinely as a fusion construct for severe sagittally imbalanced patients.