Background: In general, stiffness-related functional disability (SRFD) is expected to increase as longer fusion length, but there have been no studies on factors affecting SRFD besides fusion length.
Objective: To identify the factors affecting SRFD after long segmental fusion in patients with adult spinal deformity (ASD).
Methods: We retrospectively reviewed the patients who underwent ≥4-segment fusion including sacrum for ASD. The severity of SRFD was evaluated using the Specific Functional Disability Index (SFDI) consisting of 12 items with 4 categories as follows: sitting on the floor, sanitation activity, lower body activity, and moving activity. Each category contains 3 items which was given a maximum of 4 points. The presumed factors affecting SFDI were analyzed.
Results: A total of 148 patients were included in the study with their mean age of 67.3 years. The mean fusion length was 6.4 segments. The mean score of each SFDI category was highest in sitting on the floor (9.9), followed by lower body activities (7.6), sanitation activities (6.0), and moving activities (5.9). The total sum was 29.3 points. In multivariate analysis, total sum of SFDI was significantly higher in female sex, patients with higher American Society of Anesthesiology grade, and longer fusion length. However, the sagittal parameters did not show a significant correlation with SRFD, except pelvic incidence-lumbar lordosis which correlated with only one category (lower body activities).
Conclusion: This study showed that female sex, higher American Society of Anesthesiology grades, and longer fusion length influenced SRFD after long segmental fusion for ASD. Sagittal parameters related to the degree of deformity correction did not significantly affect SRFD.
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