Assistant Professor of Neurological Surgery (in Orthopaedic Surgery) Columbia University Medical Center New York, New York, United States
Introduction: We sought to identify specific factors that lead to delayed deterioration after circumferential minimally invasive surgery (cMIS) for adult spinal deformity (ASD).
Methods: This was a bispective analysis of a multicenter ASD database. Patients undergoing cMIS for ASD with 2-year follow-up were included. Characteristics were compared for cohorts with the same or improved ODI (unchanged) or worse ODI (worse) between 1 (1Y) and 2 years (2Y) postoperatively. Clinically significant ODI worsening was defined as ΔODI >2.5 standard deviations. Outcome measures included 2-year ODI, NRS Back Pain, NRS Leg Pain, EQ-5D, EQ-5D VAS, SF-36 PCS, SF-36 MCS, and SRS-22r Total Score. Radiographic parameters included CVA, maximum coronal Cobb angle (CC), fractional curve cobb angle (FC), SVA, PI-LL, and PT.
Results: Of 85 patients prospectively enrolled, 67 met inclusion criteria: 36 patients (53.7%) were Unchanged and 31 patients (46.3%) were Worse—only 2 (3.0%) had significant ODI worsening. The two cohorts had similar baseline clinical, radiographic, and surgical characteristics (p>0.05). Despite starting with similar 1Y clinical outcomes (p>0.05) and superior 1YODI (22.7 vs. 30.9, p=0.027), Worse ultimately had higher 2YODI (38.0 vs. 21.0, p< 0.001), 2YNRS Back Pain (5.1 vs. 3.4, p=0.012), and 2YLeg Pain (3.4 vs. 2.2, p=0.045). Starting at 6 weeks, CVA was greater for Worse (36.3 vs. 22.8 mm, p=0.010) and this was sustained through 2Y (30.0 vs. 20.4 mm, p=0.038). This was associated with a 2Y elevation in FC for Worse (9.6 vs. 5.5º, p=0.023). There was no association between delayed deterioration and SVA, PI-LL, PT, and max CC (p>0.05). Reoperation and complication rates did not differ (p>0.05).
Conclusion : Following cMIS for ASD, coronal malalignment at 6 weeks is associated with delayed ODI deterioration between 1 and 2 years. An association between sagittal parameters and delayed deterioration was not observed.
