Does Cobb Angle Correlate with Self-Reported Outcomes of Patients Undergoing Adolescent Idiopathic Scoliosis (AIS) Reconstruction?

Presented at SMISS Annual Forum 2014
By Matthew Geck MD
With Devender Singh PhD, Dana Hawthorne MPAS, PA-C, Eeric Truumees MD,

Disclosures: Matthew Geck MD A; Pfizer. D; Stock options: Diffusion. Devender Singh PhD None, Dana Hawthorne MPAS, PA-C None, Eeric Truumees MD A; Pfizer, Stryker. F; Stryker.,

Introduction:
Cobb Angle is widely used to quantify the magnitude of spinal deformity. Clinicians use this tool to track the degree of scoliosis correction following surgical interventions. This study investigates the correlation between Cobb angles and self-reported outcomes of patients undergoing AIS reconstruction using MIS technique.

Aims/Objectives:
We investigated the degree of correlation between Cobb angles and self-reported outcomes of patients undergoing minimally invasive surgical (MIS) stabilization of adolescent idiopathic scoliosis (AIS).

Methods:
28 consecutive patients undergoing MIS correction of AIS were prospectively studied. Age, Body mass index (BMI), Lenke curve, preoperative (pre-op) and postoperative (post-op) Cobb angles, Scoliosis Research Society-22r (SRS-22r), Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) were evaluated. Mean (standard deviations) were calculated. Surgical technique was uniform in all patients using two or three para-midline incisions. At different pre-op and post-op time periods, linear regressions were conducted in which the Cobb angle was the independent variable and outcome scores were the dependent variables.

Results:
Mean patient age was 16 years (11- 47 years). Mean BMI was found to be 20.4 (±2.9) Curves were classified as: 13 Lenke 1A, 8 Lenke 1B, 2 Lenke 1C; 5 Lenke 5C. Mean flexibility index of main curve was 56.46% (±11.53%). Pre-op VAS and ODI were weakly correlated with pre-op Cobb Angles with r2=0.036 and 0.110, respectively. At 2 weeks, 6 months, 1 year and 2 years post-op, the correlation between post-op Cobb angles and VAS gradually improved from weak to moderate with r2 =0.003, 0.007, 0.086 and 0.405, respectively. Similarly, post-op Cobb angles and ODI at 2 weeks, 6 months, 1 year and 2 years follow-ups were consistently correlated weakly with r2 =0.118, 0.112, 0.091 and 0.118, respectively. SRS-22r and post-op Cobb angles at 1 and 2 years follow-ups were weakly correlated with r2 =0.028 and 0.035, respectively.

Conclusions:
Our cohort’s data indicate that Cobb angle and self-reported patient outcomes are weakly correlated. There is no gold standard to measure the surgical outcomes in MIS; rather clinicians should rely on combination of tools varying from radiographic evaluations, patient reported outcome measures to their own clinical judgments.