Reliability of manual measurement of Cobb angle for patients with idiopathic scoliosis

Abstract

Objective To analyze the reliability of manual measurement of Cobb angle of the patients with idiopathic scoliosis.Methods Fifty three patients with idiopathic scoliosis had full-length standing posteroanterior and lateral radiographs were measured by four orthopedic surgeons independently.Coronal measures included Cobb angles of the three main curves.Sagittal parameters included T2-T5 and T5-T12 regional thoracic kyphosis,T10-L2 thoracolumbar junction sagittal curvature,T12-L2lumbar lordosis.The measurements were redone 2 weeks later.Inter-observer and intra-observer reliability for each parameter were assessed using intraclass correlation coefficient(ICC)method.Results Of the 53 patients,36 patients'proximal thoracic Cobb angles(PT),53 patients'main thoracic Cobb angles(MT),41 patients'thoracolumbar/lumbar Cobb angles,and all patients' T2-5.T5-12,T10-L2 and T12-L1 Cobb angles were measured.Main curves Cobb angles were 54.4(range,22 to 167).In the coronal Cobb angle measurements,the proximal thoracic curves measurements showed fair to good interobserver reliability(γ=0.592-0.714)and fair to good intraobserver reproducibility(γ=0.538-0.735);the main thoracic curves measurements showed good to excellent interobserver reliability(γ=0.881-0.942)and excellent intraobserver reproducibility(γ=0.919-0.964),while thoracolumbar/lumbar curves demonstrated fair to excellent interobserver reliability(γ=0.649-0.915)and good to excellent intraobserver reproducibility(γ=0.875-0.930).In the sagittal Cobb angle measurements,T2-5 curves demonstrated worst reliability and validity,low to fair interobserver reliability(γ=0.373-0.662)and intraobserver reproducibility(γ=0.433-0.527).T5-12,T10-L2 and T12-L1 curves demonstrated good to excellent interobserver reliability(γ=0.787-0.909;0.857-0.964;0.889-0.983).T5-12 curves demonstrated good to excellent intraobserver reproducibility(γ=0.873-0.943).T10-L2 and T12-L1 curves demonstrated excellent intraobserver reproducibility(γ=0.915-0.968;0.937-0.981).Conclusions The majority of the radiographic parameters for idiopathic scoliosis assessment demonstrate good or excellent reliability for manual measurement. Key words: Scoliosis; Kyphosis; Reliability and validity