Analysis of sagittal profile of spine using 3D ultrasound imaging: a phantom study and preliminary subject test

ABSTRACT

Radiographic Cobb’s angle is the gold standard for evaluation of spinal curvature, however, X-ray is ionising. In contrast, ultrasound is non-ionising and inexpensive. However, no study has reported the reliability and accuracy of ultrasound on sagittal curvature analysis. Ultrasound and X-ray scanning were conducted on 16 sets of spine phantoms with different deformities. Intra-rater and inter-rater reliability, correlations, mean absolute differences (MAD) and linear regression of ultrasound spinous process angles (USSPA), X-ray spinous process angles (XSPA) and X-ray Cobb’s angles (XCA) together with the intra-operator reliability of USSPA were investigated. In addition, USSPA and XCA of five AIS subjects were obtained using the ultrasound system. In the phantom study, excellent intra-rater and inter-rater reproducibility for the three angles and excellent intra-operator reproducibility for USSPA were demonstrated. Good to moderate or better correlations were obtained among the angles. All three angles indicated positive linear relationships with MAD ≤ 6.0°. The results of the preliminary study demonstrated a high intra-reliability for the ultrasound measurements. The measured difference between the USSPA and XCA methods was 6.3° ± 5.4°. The results showed that ultrasound is feasible for measuring sagittal curvature and has the potential for monitoring the curve progression and evaluating sagittal spinal profiles.

KEYWORDS:

• Spine
• sagittal balance
• Cobb’s angle
• 3D ultrasound imaging
• spinous process

Acknowledgments

The authors would like to thank Ms Sally Ding for her kind help for editing the manuscript.

Additional information

Funding

This work was supported by the University–Industry collaboration Programme under the Innovation and Technology Fund [UIM/213]; General Research Fund by University Grants Committee [PolyU152220/14E,PolyU5332/07E].

Notes on contributors

Timothy Tin-Yan Lee

Timothy Tin-Yan Lee is a Ph.D. student of the Department of Biomedical Engineering from The Hong Kong Polytechnic University.

James Chung-Wai Cheung

James Chung-Wai Cheung is a senior scientific officer of the Department of Biomedical Engineering from The Hong Kong Polytechnic University.

Siu-Yu Law

Siu-Yu Law was a B.Eng. student of the Department of Biomedical Engineering from The Hong Kong Polytechnic University during the preparation of the manuscript.

Michael Kai Tsun To

Michael Kai Tsun To is a clinical associate professor in the Department of Orthopaedics and Traumatology from the University of Hong Kong.

Jason Pui Yin Cheung

Jason Pui Yin Cheung is a clinical associate professor in the Department of Orthopaedics and Traumatology from the University of Hong Kong.

Yong-Ping Zheng

Yong-Ping Zheng is a professor and the head of the Department of Biomedical Engineering from The Hong Kong Polytechnic University.