Responsiveness of Image Perception Outcome Scales After Surgical Treatment of Idiopathic Scoliosis: A Comparison Between the Trunk Appearance Perception Scale (TAPS) and Scoliosis Research Society-22 (SRS-22) Questionnaire

Study design: Retrospective study of prospectively collected longitudinal data.

Objectives: To analyze the Trunk Appearance Perception Scale's (TAPS's) responsiveness to surgical treatment of idiopathic scoliosis (IS).

Summary of background data: TAPS is a drawing-based instrument to assess trunk deformity in IS. It shows appropriate metric properties, such as internal consistency and discriminant validity. However, no data on responsiveness to surgical treatment is available.

Methods: A total of 109 patients (85.3% females) with IS were included (mean age at surgery 18 years). In all the cases, surgery consisted of posterior spine fusion and instrumentation. The magnitude of the largest curve (MLC) was 63.8° before surgery and 26.3° (correction 58.3%) at a mean follow-up of 20.8 months. Internal and external responsiveness were analyzed on the basis of effect size (ES), standardized response mean (SRM), minimum detectable change (MDC), and correlation between percentage of MLC correction and outcome measure change. Data for TAPS were compared to those of SRS-22 Image domain.

Results: TAPS showed somewhat larger internal responsiveness (ES 1.96, SRM 1.73, 86.2% of patients exceeding MDC) than SRS-22 Image scale (ES 1.44, SRM 1.29, 73.4% of patients exceeding MDC). No correlation was found between the percentage of MLC correction and baseline to follow-up change in TAPS or SRS-22 Image scores.

Conclusion: The TAPS instrument shows adequate responsiveness to surgical treatment of idiopathic scoliosis and is somewhat larger than SRS-22 Image domain data. The lack of correlation between radiologic correction and clinical improvement indicates that the two outcomes must be independently collected. These data on responsiveness complete the TAPS validation process. TAPS is a valid, reliable, and responsive instrument to evaluate the outcome of surgical treatment of idiopathic scoliosis.

Level of evidence: Level IV.