The minimum clinically important difference in SRS-22R total score, appearance, activity and pain domains after surgical treatment of adult spinal deformity

Study Design. Longitudinal cohort. Objective. To establish minimum clinically important difference (MCID) threshold values for Scoliosis Research Society-22R (SRS-22R) domains in patients with adult spinal deformity undergoing surgical correction. Summary of Background Data. The SRS-22R has been shown to be reliable, valid and responsive to change in patients with adult spinal deformity undergoing surgery. The MCID quantifies a threshold of improvement that is clinically relevant to the patient. Methods. Patients in a prospective database who completed the SRS-22R preoperatively and the SRS-30 1 year postoperatively were identified. Answers to the last 8 questions of the SRS-30 were used as anchors to determine MCID for the pain, appearance and activity domains, subscore, and total score using receiver-operating-characteristic curve analysis. Calculations of MCID using distribution-based methods were also done. Results. A total of 1321 patients were included in the analysis; 83% were females and 10% were smokers. Mean age was 53 years. Mean body mass index was 26.3 kg/m². Mean preoperative SRS-22R appearance score was 2.50 improving to 3.62 at 1 year postoperatively (P < 0.001). Mean preoperative SRS-22R activity score was 2.96 and it improved to 3.33 at 1 year postoperatively (P < 0.001). Mean preoperative SRS-22R pain score was 2.73 improving to 3.60 at 1 year postoperatively (P < 0.001). Mean preoperative total score was 2.93 and it improved to 3.65 at 1 year postoperatively (P < 0.001). There was a statistically significant difference in domain scores among the responses to the anchors (P < 0.001). The different calculation methods yielded MCID values of 0.19 to 1.23 for appearance, 0.23 to 0.60 for activity, 0.24 to 0.57 for pain, 0.16 to 0.43 for subscore, and 0.17 to 0.71 for total score. Conclusion. When combined with previous reports, the results of this study in a population with adult spinal deformity undergoing surgical treatment show MCID for SRS-22 scores can be estimated as 0.4. This corresponds to a change of 1 interval in 2 of the 5 questions for a single domain.