Biomedical subjects

V Pomero

Publications and source records attributed to V Pomero.

7 recordsLinked to original sources

PubMed2004

A proprioception based regulation model to estimate the trunk muscle forces.

Evaluation of loads acting on the spine requires the knowledge of the muscular forces acting on it, but muscles redundancy necessitates developing a muscle forces attribution strategy. Optimisation, EMG, or hybrid models allow evaluating muscle force patterns, yielding a unique muscular arrangement or/and requiring EMG data collection. This paper presents a regulation model of the trunk muscles based on a proprioception hypothesis, which searches to avoid the spinal joint overloading. The model is also compared to other existing models for evaluation. Compared to an optimisation model, the proposed alternative muscle pattern yielded a significant spine postero-anterior shear decrease. Compared to a model based on combination of optimisation criteria, present model better fits muscle activation observed using EMG (38% improvement). Such results suggest that the proposed model, based on regulation of all spinal components, may be more relevant from a physiologic point of view.

Abdomen↗

PubMed2003

Variability of the spine and pelvis location with respect to the gravity line: a three-dimensional stereoradiographic study using a force platform.

Analyzing standing posture requires a precise measure of the orientation of the various body segments with respect to the gravitational vector. We studied the posture variability of 34 healthy upright standing subjects. Using a force platform combined with a powerful stereoradiographic technique, we acquired the spine and pelvis three-dimensional (3D) geometry and located it with respect to the gravity line. For our data set, the mean 3D distance between the geometrical center of each vertebral body and the gravity line was 28 mm with a standard deviation of 5.6 mm. The vertebrae location variability, defined as plus or minus twice the mean standard deviation, was +/-40 mm in the sagittal plane and +/-25 mm in the frontal plane. The line connecting the middle of the external acoustic meatus (center of both acoustic meati: CAM) to the middle of the bi-coxo-femoral axis (hip axis: HA) was almost vertical. Its mean distance to the gravity line was 30 mm. Our data show a left lateralization, with respect to the gravity line, of the "Head-Spine-Pelvis" segments. The mean distance was 7.6 mm (SD 1.6 mm). This might be due to uneven partitioning of the body mass on each side of the sagittal plane.

Adult↗

PubMed2003

Spinal penetration index: new three-dimensional quantified reference for lordoscoliosis and other spinal deformities.

We studied and conceptually analyzed a retrospective case series of patients with airway compression due to an anterior vertebral body protrusion. The goal was to describe the pathology, methods of management, and a new concept for quantifying deformity. Case reports have been published on this pathology, but there has been no case series to date. In this study 18 patients with ages ranging from 7.3 to 18.0 years had thoracic lordoscoliosis due to a variety of etiologies; most ( n = 10) had a neuromuscular disorder. Following treatment, which most commonly was anterior subtotal subperiosteal vertebral body resection followed by posterior instrumentation and arthrodesis, atelectasia disappeared and any abnormal blood gases normalized; however, the effect on vital capacity was variable. Based on computed tomographic studies, the concept of the deformity as an endothoracic vertebral hump was developed and quantified. Study of this series of patients with compression of the airway due to vertebral body protrusion into the thorax provided the opportunity to describe treatment, define a new concept (the spinal penetration index), and make general recommendations about the management of both the endothoracic hump and the exothoracic rib hump.

Adolescent↗

PubMed2002

[Thoracic scoliosis: exothoracic and endothoracic deformations and the spinal penetration index].

PURPOSE OF THE STUDY: We reviewed retrospectively our patients with thoracic lordoscoliosis and conducted a conceptual analysis of the patients with airway compression and atelectasia due to anterior protrusion of the vertebral bodies in order to describe the pathological conditions involved and the management methods used. Our goal was to develop a new concept for quantifying thoracic deformation. The individual cases discussed here have been reported earlier, but this is the first series analysis to date. MATERIAL AND METHODS: Eighteen patients, aged 7.3 to 18 years, with thoracic lordoscoliosis due to a variety of causes, mostly neuromuscular disorders (12 cases), are described. Most patients were treated by anterior subtotal periosteal resection of the vertebral body followed by posterior instrumentation and arthrodesis. RESULTS: Atelectasia disappeared with a normalization of blood gases but the effect was variable on vital capacity. The analysis of the CT studies led to the concept of spinal deformity as an endothoracic deformation resulting from protrusion of the vertebral body into the thorax, the endothoracic vertebral hump. This concept was developed and quantified leading to the definition of a new index: the spinal penetration index. The spinal penetration index was obtained by tracing a line tangent to the posterior curve of the concave and convex ribs on each CT slice to determine a relationship between the real thoracic surface and theoretical thoracic surface measured with this tangent and the circumference of the thoracic cage. The index was expressed as a percent of the endothoracic surface occupied by the protruding veterbral body and the associated ribs. Calculated for each successive CT slice for the entire height of the thorax yielded a spinal penetration index quantifying the thoracic volume occupied by the spine. For the control population, we used CT series of the thorax obtained to search for pulmonary metastases in patients with malignant tumors. This gave a theoretical volume of 8 to 10% occupied by the spine in normal subjects. In our patients with lordoscoliotic deformations we obtained real volumes of 15, 20 and even 50%. DISCUSSION: The spinal penetration index is an important morphological index of thoracic anatomy that measures the real volume of the functional thoracic cavities and which must be differentiated from vital capacity which measures both volume and function. This index can be used for pre- post-operative comparisons and constitutes a first step in 3-D assessment of thoracic spine deformations. It can also be used to classify spinal deformations and to make general recommendations concerning the management of both endothoracic humps and exothoracic rib humps.

Adolescent↗

PubMed2002

Muscular modelling: relationship between postural default and spine overloading.

The objectives of the study are to describe and use a muscular model to compare spinal loads and muscles recruitments between an unbalanced subject (patient) and a normal volunteer. Data collection was performed and imputed into the muscular model: from sagittal X-rays, together with plantar foot pressure measurements, external loads for the L3/L4 level were calculated. Using MRI of the thoraco-lumbar region and muscular testing, a personalized muscular model was constructed. The main results are as follow: external loads for the unbalanced subject were higher because of the postural default, especially for flexion moment. Running the model, simulations showed a higher erector spinae group activation for the patient. This induced a significant difference in joint compression. Setting the maximum admissible stress of the extensor muscles of the patient to an equivalent level as the one found for the volunteer to maintain the posture, a second simulation was performed. Joint compression was reduced, but postero-anterior shear and flexion moment increased drastically. The model suggests that either the muscular system needed a stronger activation, yielding a higher joint compression and probably a muscle fatigue in such an activation level, or the spinal loads increased to a higher and probably dangerous level.

Humans↗

PubMed2002

Geometric and postural analysis of mild idiopathic scoliotic patients.

Understanding the aggravation process of mild idiopathic scoliosis is still a challenge. The aim of this study is to investigate the spine and pelvis configuration with regard to gravity line using 3D reconstruction coupled with foot pressure measurements. The distance between each vertebral center and the gravity line is calculated in order to observe the global equilibrium of spine. A protocol has been set and used for 10 mild idiopathic scoliotic patients. 34 asymptomatic volunteers who were previously observed with the same protocol were used as reference for biomechanical comparisons. The first results showed differences between scoliotic and asymptomatic subjects and also among scoliotic patients. The proposed protocol should allow clinicians to follow up scoliotic patients with an innovative and efficient tool.

Adolescent↗

PubMed2001

Computer-assisted assessment of spinal sagittal plane radiographs.

The sagittal shape of the spine, particularly its sagittal balance, currently is being extensively investigated. The major purpose of this study is to examine the measurement repeatability of SpineView software, which calculates 13 independent variables, to shorten and facilitate the measurement of lateral spinal radiographs; another purpose is to collect physiological data for nonpathologic spines, which can be used as a reference in future research. This article also presents two new parameters and discusses their possible role in forthcoming investigations. The interobserver repeatability study shows that most of the variables are more repeatable (less than +/-1.5 degrees ) when the operator is experienced. A less (+/-6.5 degrees ) repeatable measurement is T4-T12 kyphosis, which may be because of the poor contrast generally observed on radiographs of the upper thoracic vertebrae. The intraobserver repeatability study also demonstrates that subjective failures do not influence the results significantly, but the quality of the radiographs may have significant effect on long-term repeatability. The mean values were generally different between male and female subjects, and significant differences between the two sexes were only noticed for pelvic thickness and global spinal inclination. Normal range values and correlations between some pelvic and spinal parameters were similar to data found in the literature. The results of the current study provide evidence that the SpineView software is useful for experimental investigation of sagittal spinal alignment.

Adult↗