Spine Surgeon NYU School of Medicine New Canaan, CT, US
Introduction: Seemingly, there should be a point at which degeneration across multiple levels results in malalignment and sagittal correction tremendously improves clinical outcomes following fusion of cervical deformity(ACD). We sought to determine baseline thresholds in cervical parameters that, when exceeded, more often meet ideal clinical outcomes with sagittal correction.
Methods: ACD patients with two-year(2Y) data included. Parameters assessed: C2 slope(C2S), C2-C7 Lordosis, C2-C7 SVA(cSVA), T1 Slope(T1S), TS-CL. Outcomes: Virk et al Good Clinical Outcome(GCO):[Meeting 2 of 3: 1)an NDI>20 or meeting MCID,2) mJOA >=14,3) an NRS-Neck<=5 or improved by 2 or more points]. Binary logistic regression assessed each baseline parameter to determine if correction was more likely needed to achieve GCO. Conditional inference tree(CIT) run machine learning analysis generated baseline thresholds for each parameter, above which, correction was more often seen when achieving GCO. Multivariable logistic regression controlling for age, baseline deformity and disability identified associations between thresholds and meeting GCO.
Results: Included: 105 ACD patients. There were 54% of patients achieving GCO. Correction was necessitated when baseline C2S was above 20°(OR: 6.8, [1.6-28.9];p=.01) and when baseline C2-C7 Lordosis was below 10°(OR: 16, [2.4-107.5];p=.004). Patients presenting with a cSVA above 20 mm more often achieved clinical success when corrected(74.2% vs. 0.0%,p < .001). TS-CL more likely required correction to reach GCO when above 26° at baseline(OR: 7.0, [1.7-29.1];p=.007). When assessing patients above both the cSVA and C2S threshold versus the remaining cohort, these patients more likely met GCO when corrected in either parameter(OR: 22.5, [3.3-52.0];p=.001).
Conclusion : Our study highlighted the importance of correction and the threshold at which it dramatically impacts clinical success. These new thresholds delineate patients obtaining superior benefit for sagittal correction and may better increase the utility gained from surgical intervention for cervical deformity.
