Détermination rapide des paramètres caractéristiques des scolioses en vue frontale

ScolioMedIS: web-oriented information system for idiopathic scoliosis visualization and monitoring

Adolescent idiopathic scoliosis is the most common type of abnormal curvature observed in spine and it progresses rapidly during the puberty period. The most followed clinical way of assessing the spinal deformity is subjective by measuring the characteristic angles of spinal curve from a set of radiographic images. This paper presents a web-based information system (called ScolioMedIS) based on parameterized 3D anatomical models of the spine to quantitatively assess the deformity and to minimize the amount of radiation exposure by reducing the number of radiographs required. The main components of the system are 3D parametric solid model of spine, back surfaces, relevant clinical information and scoliosis ontology. The patient-specific spine model is regenerated from the parametric model and surface data using anatomical information extracted from radiographic images. The system is designed to take inherent advantage of Web for facilitating multi-center data collection and collaborative clinical decisions. The preliminary analysis of patient data showed promising results, which involve improved documentation standard, clinical decision knowledge base record, facilitated exchange and retrieval of medical data between institutions in multi-center clinical studies, 3D visualization of spinal deformity, and permanent monitoring of treatments.

RELATIONSHIP BETWEEN SAGITTAL SPINAL CURVES AND BACK SURFACE PROFILES OBTAINED WITH RADIOGRAPHS

The purpose of this article is to introduce a novel approach, by using coupled video and radiographic analysis of back surface and spinal curves in the sagittal plane to decrease the ionizing radiation exposure for subjects requiring long-term follow-up of their spinal deformity. This approach is specifically designed for the use in a clinical set-up for the follow-up of subjects with progressive spinal deformities. The subjects are radiographed with nine steel balls embedded in circular markers evenly distributed on the subject's back surface over the spinous processes of C7 to S1. A technique allows to draw the external back profile and the spinal curve. Patient-specific transfer functions are defined moving the back profile to the spinal curve. Sixteen adult volunteers were tested to validate the concepts proposed. For each of them, the values of transfer functions between radiographic back surface profile and corresponding spinal curve have been calculated. Each internal curve is correctly simulated when based upon the back profile. Our research is now focused on the prediction of the internal curve of patients from their back surface profile based on patient-specific transfer functions.

Geometric Structure of 3D Spinal Curves: Plane Regions and Connecting Zones

This paper presents a new study of the geometric structure of 3D spinal curves. The spine is considered as an heterogeneous beam, compound of vertebrae and intervertebral discs. The spine is modeled as a deformable wire along which vertebrae are beads rotating about the wire. 3D spinal curves are compound of plane regions connected together by zones of transition. The 3D spinal curve is uniquely flexed along the plane regions. The angular offsets between adjacent regions are concentrated at level of the middle zones of transition, so illustrating the heterogeneity of the spinal geometric structure. The plane regions along the 3D spinal curve must satisfy two criteria: (i) a criterion of minimum distance between the curve and the regional plane and (ii) a criterion controlling that the curve is continuously plane at the level of the region. The geometric structure of each 3D spinal curve is characterized by the sizes and orientations of regional planes, by the parameters representing flexed regions and by the sizes and functions of zones of transition. Spinal curves of asymptomatic subjects show three plane regions corresponding to spinal curvatures: lumbar, thoracic and cervical curvatures. In some scoliotic spines, four plane regions may be detected.

Beyond the classic correction system: a numerical nonrigid approach to the scoliosis brace

BACKGROUND CONTEXT

Adolescent idiopathic scoliosis (AIS) causes a spine and rib cage three-dimensional (3D) deformity previously treated by bracing. Whatever the manufacturing process, this rigid system acts biomechanically on the patient through the "three-point bending" mechanical principle. It applies corrective forces to a limited area and acts especially in the frontal plane. It seemed to us that a nonrigid system, called "Cbrace," with 3D action allowing distribution of forces could increase compliance and provide better long-term correction prospects.

PURPOSE

The aim of this study was to design a nonrigid brace by numerically testing in a finite-element model developed here.

STUDY DESIGN

A finite-element model has been developed to simulate brace effect on AIS right thoracic deformation of a 10-year-old patient.

METHODS

A two-step method was needed; first, the reliability of our model is evaluated, and then, the ability to use distributed forces to correct scoliosis deformation is tested. To obtain a 3D correction, several treatments are experimented, leading to a comparison test between the best combination to the "three-point bending" principle.

RESULTS

The numerical model developed here shows good qualitative answers for the treatment of brace forces. The first results demonstrate numerically that distributed forces may be of interest in brace treatment design. Overall force of 40 N above cartilage of the last nonfloating ribs associated to two posterior asymmetrical areas appears to be the best way to correct scoliosis deformation with nonrigid action.

CONCLUSION

The results show numerical efficacy of distributed forces to correct spinal deformities and raises the prospect that a new numerical brace, called "Cbrace," could be a starting point in the search for a nonrigid system.

Classification of pelvic and spinal postural patterns in upright position. Specific cases of scoliotic patients

The 3D analyses of spinal shapes and postural features give a great number of data. The global patient posture includes his pelvic morphology and tilting, and his pelvic and spinal balance. In some scoliotic spines, the spinal curve belongs to a unique plane. In other scoliotic patients, the spinal curve shows several plane regions. The spinal structures are modeled from parameters locating the structural planes and by values of maximum curvatures. Some parameters have been introduced for describing the postural patterns and the spinal deformities. For each tested patient, each major parameter has been characterized by an index of class.

Personalized models of bones based on radiographic photogrammetry

The radiographic photogrammetry is applied, for locating anatomical landmarks in space, from their two projected images. The goal of this paper is to define a personalized geometric model of bones, based uniquely on photogrammetric reconstructions. The personalized models of bones are obtained from two successive steps: their functional frameworks are first determined experimentally, then, the 3D bone representation results from modeling techniques. Each bone functional framework is issued from direct measurements upon two radiographic images. These images may be obtained using either perpendicular (spine and sacrum) or oblique incidences (pelvis and lower limb). Frameworks link together their functional axes and punctual landmarks. Each global bone volume is decomposed in several elementary components. Each volumic component is represented by simple geometric shapes. Volumic shapes are articulated to the patient's bone structure. The volumic personalization is obtained by best fitting the geometric model projections to their real images, using adjustable articulations. Examples are presented to illustrating the technique of personalization of bone volumes, directly issued from the treatment of only two radiographic images. The chosen techniques for treating data are then discussed. The 3D representation of bones completes, for clinical users, the information brought by radiographic images.