Scoliosis Surgical Risk Calculator

Written and reviewed for scientific and factual accuracy by Dr. Austin Jelcick, PhD and Dr. Matthew Janzen, DC. Last reviewed/edited on October 28, 2020. First published December 14, 2019.

What This Calculator Does

There are two major questions everyone asks about their child’s scoliosis curve: will the curve get worse, and will the curve get worse enough that it requires surgery. Based on the most current research, you can estimate the likelihood that your child’s curve will progress to the point that it requires surgery by using the scoliosis surgical risk calculator below. Risk for surgery depends on the type of scoliosis curve, so be sure to select the matching curve type. This calculator is designed for growing children and teens (skeletally immature), and considers a Cobb angle of 45 degrees or more to require surgery.

What’s your Cobb angle? Enter it below

Choose your Cobb angle
What’s your Sander’s score? Enter it below

Choose your Sander’s score
What’s your curve type? Enter it below

Choose your curve type

Your Risk of Surgery

Once you calculate your surgical risk it will be displayed here.

What Is a Sander’s Score?

A Sander’s score is a measure of how skeletally mature (or immature) a child is. Skeletal maturity lets us know how much growing a child has left to do, which is important because we know scoliosis gets worse with growth, especially during growth spurts. Unlike the Risser scale which looks at the pelvis, the Sander’s score determines a child or teen’s skeletal age by looking at an x-ray of the hand. Ultimately, the younger the child, the less skeletally mature they are, and the bigger the scoliosis surgical risk.

Don’t know your Sander’s score? We can help!

The Sander’s score is a scale from zero (0) to eight (8), with 0 representing a completely skeletally immature child while 8 represents a skeletal maturity. To give a better idea of when a child will reach each Sander’s level, a Sander’s scale of 1 represents a child before they have reached their adolescent growth spurt, while a Sander’s scale of 2 represents a child who has started their adolescent growth spurt, but has not reached the fastest rate of growth yet. A Sander’s of 8 is equivalent of a Risser 5, where growth has finished and the child has reached skeletal maturity.

What Is a Cobb Angle?

The Cobb angle is the technical or medical term for the angle of the scoliosis curve. In addition to Cobb angle, a curve is also described as right or left depending on where the convex part of the curve is. This angle is measured using a x-ray or MRI of the spine, and one which is taken looking from the rear of the patient (as opposed to the front). This is commonly referred to as a posteroanterior radiograph or MRI; posterior meaning rear, anterior meaning front, and posteroanterior meaning the image is taken from back to front.

To measure the Cobb angle of a scoliosis curve, the physician will find the vertebrae which is the most tilted above the apex of the curve. The physician will then find the vertebrae which is the most tilted below the apex. The angle between the top of the top vertebrae and the bottom of the bottom vertebrae is the Cobb angle. This is calculated by drawing perpendicular lines which can be a bit confusing, but you can learn more about the math behind the Cobb angle on Wikipedia. Just as skeletal immaturity is associated with a higher risk, the bigger the Cobb angle is, the greater the scoliosis surgical risk is.

What Is This Calculator Based On?

This surgical risk calculator is based on scientific research published by Dr. Dolan and Dr. Weinstein, et. al. from the University of Iowa in 2019. You may recognize Dr. Weinstein’s name as he is a well known and respected figure in the world of scoliosis care and research and is a pediatric orthopedic surgeon specializing in spinal deformities and problems with the hip. The ground breaking BRAIST study which found bracing to be an effective treatment for scoliosis was also published by Dr. Weinstein and his group.

By looking at 115 patients with scoliosis who were untreated, a number of possible predictive factors were analyzed including the age of the patient, their gender, the type of their curve, their Cobb angle, and skeletal maturity. Ultimately, a mathematical model was developed that looked at skeletal maturity (via the Sander’s scale), Cobb angle, and the type of curve. Our calculator has been updated to include all curve types described by the scientific publication; simply selecting the matching curve type will adjust the calculation accordingly.

Just as the conclusions of the paper stated, we hope that this calculator for estimating the likelihood of surgery if a curve is left untreated will help you and others to make better, more informed treatment decisions. Now instead of merely wondering and hoping that a curve won’t get worse and require surgery, you can calculate the risk of a curve worsening using rigorous scientific data from real cases of untreated scoliosis.


1.  Dolan, Lori A.; Weinstein, Stuart L.; Abel, Mark F.; Bosch, Patrick P.; Dobbs, Matthew B.; Farber, Tyler O. et al. (2019): Bracing in Adolescent Idiopathic Scoliosis Trial (BrAIST). Development and Validation of a Prognostic Model in Untreated Adolescent Idiopathic Scoliosis Using the Simplified Skeletal Maturity System. In Spine deformity 7 (6), 890-898.e4.

2.  Sanders, James O.; Khoury, Joseph G.; Kishan, Shyam; Browne, Richard H.; Mooney, James F.; Arnold, Kali D. et al. (2008): Predicting scoliosis progression from skeletal maturity. A simplified classification during adolescence. In The Journal of bone and joint surgery. American volume 90 (3), pp. 540–553.