Do patients with high ASA classes have sustained benefit 5 years after surgery for grade 2 spondylolisthesis? A Spine CORe™ analysis of QOD data

OBJECTIVE: The aim of this study was to assess whether the severity of systemic illness affects outcomes following surgery for grade 2 spondylolisthesis by using prospectively collected data from the Quality Outcomes Database (QOD) spondylolisthesis database. METHODS: This retrospective analysis of patients who underwent surgery for grade 2 degenerative lumbar spondylolisthesis used a prospective national longitudinal registry of data collected from 14 sites. The American Society of Anesthesiologists (ASA) physical classification system was used to assess systemic illness and compare patients categorized as ASA classes I and II with patients categorized as ASA classes III and IV. Baseline demographics, comorbidities, and clinical variables were collected for comparison. Primary outcomes were Oswestry Disability Index (ODI) and EQ-5D scores 3, 12, 24, and 60 months after surgery, and multiple linear regression was used to determine whether ASA class significantly predicted postoperative change in patient-reported outcome measures. RESULTS: Of the 328 patients in the grade 2 spondylolisthesis QOD cohort, 172 (52.4%) were categized as having a low ASA class (ASA class I or II) and 156 (47.6%) with a high ASA class (ASA class III or IV). There was a > 80% follow-up rate 5 years after surgery. Compared with patients in the low ASA class group, those in the high ASA class group were older (mean age 64.1 [SD 10.1] years vs 57.3 [SD 13.2] years, p < 0.001), had a higher BMI (mean 31.9 [SD 7.2] vs 28.8 [SD 5.9], p < 0.001), and had higher rates of comorbidities (diabetes, coronary artery disease, chronic obstructive pulmonary disease, and chronic kidney disease). The hospital length of stay and readmission rate did not differ significantly between the two groups. At baseline, ODI scores were significantly higher in the high ASA class group (mean 23.8 [SD 7.2] vs 21.5 [SD 8.3], p = 0.01), but there was not a significant difference in the ODI score 3, 12, 24, and 60 months after surgery. There were no significant differences in the mean EQ-5D score between the two groups at all time points. Multiple linear regression showed that ASA class was not a significant predictor of change in the ODI or EQ-5D score from baseline to 60 months postoperatively. CONCLUSIONS: Patients with higher systemic illness, categorized as ASA classes III or IV, had a higher baseline ODI score compared with those with low ASA classes (I or II), but had similar ODI scores 3, 12, 24, and 60 months postoperatively. There were no significant differences in the length of stay or readmission rate between groups. These findings suggest that patients with high ASA classes benefit from surgery for grade 2 spondylolisthesis and experience significant improvements in disability status.