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Computer Assisted Cobb Angle Measurements: A novel algorithm

Dean N. Papaliodis, MD,1 Pierino G. Bonanni, PhD,2 Timothy T. Roberts, MD,3 Khalid Hesham, MD,1 Nicholas Richardson, MD,1 Robert A. Cheney, MD,4 James P. Lawrence, MD, MBA,5 Allen L. Carl, MD,6 William F. Lavelle, MD7

1Department of Orthopaedics, Albany Medical Center, Albany, NY, 2GE Global Research, Niskayuna, NY, 3Cleveland Clinic Center for Spine Health, Cleveland, OH, 4Bone & Joint/ Capital Region Orthopaedics, Albany, NY, 5Bone & Joint/ Capital Region Orthopaedics, Albany, NY, 6Department of Neurology, Albany Medical Center, Albany, NY, 7Department of Orthopedics, SUNY Upstate Medical University, Syracuse, NY

Abstract

Background

The standard for evaluating scoliosis is PA radiographs using Cobb angle to measure curve magnitude. Newer PACS systems allow easier Cobb angle calculations, but have not improved inter/intra observer precision of measurement. Cobb angle and its progression are important to determine treatment; therefore, angle variability is not optimal. This study seeks to demonstrate that a performance equivalent to that achieved in the manual method is possible using a novel computer algorithm with limited user input. The authors compared Cobb angles from pre-determined spinal levels in the average attending score versus the computer assisted approach.

Methods

Retrospective analysis of PA radiographs from 58 patients previously evaluated for scoliosis was collected. Pre-designated spinal levels (e.g., T2-T10) were assigned for different curves and calculated by Cobb method. Four spine surgeons evaluated these Cobb angles. Their average scores were measured and compared to formulated values using the novel computer-based algorithm. Literature reports inter-observer reliability is 6.3-7.2degrees. Limits of accuracy were set at 5 degrees of average orthopedic surgeons’ score.

Results

The computer-based algorithm calculated Cobb angles within 5 degrees of orthopedic surgeons’ average with a standard deviation of 3.2 degrees. This result was based on a 95% confidence interval with p values <0.001. The computer algorithm was plotted against average angle determined by the surgeons, with individual determinations and linear regression (r2 =0.90). The average difference between surgeons’ measures and computer algorithm was 0.4 degrees(SD= 3.2degrees, n=79). There was a tendency for the computer algorithm program to overestimate the angle at larger angles, but difference was small with r2 = 0.09.

Conclusions

Our study showed the novel computer based algorithm was an efficient and reliable method to assess scoliotic curvature in the coronal plane with the possibility of expediting clinic visits, ensuring reliability of calculation and decreasing patient exposure to radiation. Level of Evidence: III.

Page Start: 
167
keywords: 
Cobb angle, computer algorithm, Scoliosis, scoliotic curvature
Volume 11 Issue 3
Page End: 
172
doi: 
10.14444/4021