THE ASSOCIATION BETWEEN SUBJECTIVE AND OBJECTIVE OUTCOMES IN POSTERIOR INSTRUMENTED SCOLIOSIS CORRECTION

Abstract

Background: Surgery in adolescent idiopathic scoliosis is done mainly for cosmesis and outcomes are reported in terms of radiological measurements (Cobb angle), outcome questionnaires (SRS-22) and back surface measurements (Scoliometer & Quantec). Previous studies have shown correlations between SRS-22 and objective radiological and back surface measures at a point in time (Asher et al 2003 & 2004).

Aim: of the study was to evaluate the association between subjective and objective outcomes in posterior instrumented scoliosis correction.

Patients and Methods: 43 patients with late-onset thoracic idiopathic scoliosis were included in the study with 39 girls and 4 boys with a mean age 13.2 years. Mean pre-operative Cobb angle was 71o. The objective assessment of back surface was done using a scoliometer and the POTSI & Suzuki Hump Sum scores. The subjective assessment was done using the Scoliosis Research Society (SRS)-22 score. The assessments were done pre-operatively and then post-operatively at 8-weeks and one year.

Results: The average percentage improvement in various outcomes after surgery was as follows: Cobb angle (71%), Maximum Angle of Trunk Inclination (Max. ATI) (52 % at 8 weeks and 39 % at 1 year), POTSI (57%), Hump Sum (24%), SRS-Total (14%), SRS-self image (14%). Pre-operatively, there were good inter-correlations (r= 0.4–0.7) between the objective measures (Max. ATI, POTSI and Hump Sum). Significant correlation was found between SRS-22 total versus Cobb angle (p-0.001, r=0.41). No significant correlation was found between the SRS-22 (total & domains) versus the Max. ATI, POTSI or the Hump Sum scores. Post-operatively, good correlation (r=0.6) was again found between the objective measures (Max. ATI, POTSI and Hump Sum) of back surface measurements (absolute and percentage). No significant correlation was found between SRS-22 (domains & total) versus Cobb angle correction, Max. ATI, POTSI, or Hump Sum.

Conclusion: In this study SRS-22 was found to be responsive to change with surgery, especially the self-image/appearance domain. However the SRS-22 score after surgery and the change in this score did not correlate with the change in objective measures of back surface deformity after surgery.