The standard approach of diagnosing and monitoring scoliosis involves using the Cobb angle from posteroanterior (PA) radiograph. This approach has two key limitations: 1) It involves exposing the patients to ionising radiation during a period of heightened radiosensitivity. 2) The 2D x-ray image is a projection image of a 3D deformity and the Cobb angle represents only lateral rotation. 3DUS would overcome both these limitations.

We developed a 3DUS system by combining motion capture technology, a conventional 2D ultrasound scanner and bespoke software. An ex vivo experiment and a pilot clinical study were carried out to demonstrate the system's ability in identifying vertebrae landmarks and quantifying the curvature. For the ex vivo validation, a spine phantom was created by 3D-printing a segmented abdo-pelvis CT scan. The spine phantom was then scanned using 3DUS and the level of agreement in the dimensions measured using 3DUS and CT was assessed. An 11 year old female with adolescent idiopathic scoliosis (AIS) was scanned with 3DUS. The SP co-ordinates were projected on a plane of best-fit to compare the curvature angle from 3DUS with the Cobb angle from the x-ray image.

The spinous (SP), transverse processes and the laminae demonstrated high echogenicity and were easily identifiable. The difference between the spine phantom inter-SP dimension measurements made in 3DUS and CT was <2.5%. The PA x-ray of the AIS patient revealed 47° (L4-T11) and 52° (T6-T11) curves. 3DUS was able to represent the deformity in 3D revealing complex curvatures in all planes. The curvature angle from derived from 3DUS for the L4-T11 and T6-T11 curves were 132° (48°) and 125° (55°) respectively.

The results of this pilot study demonstrate 3DUS as a promising tool for imaging spine curvature