Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P78. Likelihood of reaching minimal clinically important difference in adult spinal deformity surgery: a comparison of patients from North America and Japan.

BACKGROUND CONTEXT As anchors for defining minimum clinical important difference (MCID) thresholds are determined by individual values, we sought to evaluate if MCID thresholds can be affected by cultural differences. PURPOSE The purpose of this study was to compare the MCID threshold and the proportion of adult spinal deformity (ASD) patients achieving SRS-22R MCID in North America (NA) versus Japan (Jp). STUDY DESIGN/SETTING Retrospective review of prospectively collected data. PATIENT SAMPLE Two hundred-eight cases [NA; 148 cases (male 16, female 132, average 59.8years old), Jp; 60 cases (male 4, female 56, average 65.5years old)] who followed for at least more than 2years after corrective fixation surgery for ASD patients with coronal Cobb angle of over 30° and over 40years old. OUTCOME MEASURES SRS22R MCID thresholds. METHODS There were 148 cases from NA (132 females, mean age=59.8 years) and 60 cases from Jp (56 females, mean age=65.5 years) with at least 2-year follow-up after corrective spine surgery for ASD. Except for self-image, published Jp MCID values are higher (function=0.90, pain=0.85 and self-image=1.05, subtotal=1.05) than the published NA MCID values (function=0.60, pain=0.40, self-image=1.23, subtotal=0.43). RESULTS There was statistically significant improvement in all domain scores at 2-year follow-up compared to baseline in both cohorts. Except for mental health (NA:0.32, Jp:0.72, p=.005), the mean improvement from baseline to 2 years was similar between the North American and Japanese cohorts. Except for self-image (NA:57%, Jp:58%, p=.877), the proportion of patients achieving MCID was higher in North America for function (NA:51%, Jp:30%, p=.006), pain (NA:80%, Jp:47%, p<.001), and subtotal (NA:72%, Jp:35%, p<.001). CONCLUSIONS Despite similar improvements in SRS22R domain scores from baseline to 2years postop, the proportion of patients reaching SRS22R MCID for function, pain and subtotal after ASD surgery are higher in a North American cohort compared to a Japanese cohort. This may imply that patients in North America and Japan may regard the value of these changes differently. [ABSTRACT FROM AUTHOR]