Clinical Improvement Through Surgery for Adult Spinal Deformity: What Can Be Expected and Who Is Likely to Benefit Most?

Study design: Multicenter, prospective, nonconsecutive, surgical case series from the International Spine Study Group.

Objectives: To evaluate the extent of clinical improvement after surgery for adult spinal deformity (ASD) based on minimal clinically important difference (MCID) and baseline measures.

Summary of background data: For ASD, evaluation of surgical treatment success using clinical scores should take into account baseline disability and pain and the improvement defined relative to the MCID.

Methods: Inclusion criteria included operative patients (age >18 years) with baseline and 2-year SRS-22 scores. Normative values for the SRS scores were included and improvement for patients was expressed in number of MCIDs. At baseline, patients were classified by differences in activity and pain scores from normative values in four groups: "worst," "severe," "poor," and, "moderate." At 2 years after surgery, patients were classified into four groups based on their change in SRS score as follows: "no improvement or deterioration," "mediocre," "satisfactory," or "optimal." Distinction among curve types was also performed based on the SRS-Schwab ASD classification.

Results: A total of 223 patients (age = 55 ± 15 years) were included. At baseline, for 77% of the patients, the worst scores were in Activity or Pain. At baseline, the distribution was 36% "worst," 28% "severe," 19% "poor," and 17% "moderate." Patients with sagittal malalignment only were more likely to be in the "worst" state (54%). The overall distribution of improvement was as follows: 24% no improvement or deterioration, 17% mediocre, 25% satisfactory, and 33% optimal. Forty-one percent of baseline "moderate" patients achieved no improvement. Of the baseline "worst" patients, 20% achieved no improvement, and 36% and 19% achieved "satisfactory" and "optimal" improvement, respectively.

Conclusion: Overall, 24% of patients did not experience improvement after surgery. Patients with baseline severe disability were more likely to perceive improvement than patients with less disability.

Level of evidence: Level II.