3D reconstruction of adolescent scoliotic trunk shape from biplanar X-rays: a feasibility study

ABSTRACT

Adolescent idiopathic scoliosis (AIS) is a 3D deformity of the spine detectable by trunk asymmetry. As a decision-aid tool, body scanners can assess non-invasively the external shape of the trunk. If AIS is diagnosed, additional 3D reconstructions of the spine, rib cage and pelvis are useful to plan a treatment such as bracing. Body scanners cannot currently guarantee reliable bones reconstruction but low-dose biplanar X-rays (BXR) is a relevant alternative. Recently, 3D body shape reconstruction of asymptomatic subjects from BXR was also proved to be accurate. To prevent AIS patients from multiple examinations, we investigated the feasibility of trunk shape reconstruction from BXR. The proposed method relied on the 3D reconstructions of the spine, rib cage and pelvis on which a statistical shape model was fitted. Additional 10 radio-opaque markers could also be considered yielding automatic deformations of the model. Finally, few manual adjustments were performed. This method was evaluated on 15 scoliotic subjects (13.7 ± 1.3 years, Cobb = 23.3° ± 8.5°). Using a larger set of markers, signed marker-to-surface differences were computed and appeared unbiased. Reproducibility on mesh nodes distribution was lower than 7mm. This study is a first step toward computer-aided brace design with a single examination.

KEYWORDS:

• 3D reconstruction
• trunk
• body-shape
• scoliosis
• biplanar X-rays

Acknowledgments

The authors deeply thank the ParisTech BiomecAM chair program on subject-specific musculoskeletal modelling and the PROTEOR group (Saint-Apollinaire, France) for their financial support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Laurent Gajny

Laurent Gajny is assistant professor in applied mathematics at Arts et Métiers ParisTech. His research interests are in numerical analysis and geometric modelling applied to the 3D reconstruction of the human body from medical images.

Léopold Robichon

Léopold Robichon is an engineer graduated from the Master on BioMedical Engineering held in Paris, France (biomechanics track).

Eleonora Pinto

Eleonora Pinto is an engineer graduated from the Master on BioMedical Engineering in Paris (biomechanics track). Her research focuses on the modelling of adolescent idiopathic scoliosis.

Thibault Hernandez

Thibault Hernandez is a surgeon in the Department of Paediatric Orthopaedics at the Armand Trousseau Hospital – APHP – Paris, France. He also graduated from the Master on BioMedical Engineering in Paris.

Raphaël Vialle

Raphaël Vialle (MD, PhD) is Professor of Infantile Surgery at the Sorbonne University. He is the Head of Department of Paediatric Orthopaedics at the Armand Trousseau Hospital – APHP – Paris. Prof. Raphaël VIALLE is the co-founder and co-header of the University-Hospital Department for Musculoskeletal Diseases Innovating Therapies (MAMUTH-DHU).

Wafa Skalli

Wafa Skalli is a professor in biomechanics at Arts et Métiers ParisTech. She is founder and scientific director of the Institut de Biomécanique Humaine Georges Charpak in Arts et Métiers ParisTech, and holder of the BiomecAM ParisTech chair on subject-specific musculoskeletal modelling. She is particularly involved in biomechanics and modelling of the spine, with a strong link to experimental and clinical approach.