Biomedical subjects

Jacques de Guise

Publications and source records attributed to Jacques de Guise.

7 recordsLinked to original sources

PubMed2005

A reproducible method for studying three-dimensional knee kinematics.

The methods used in movement analysis often rely on the definition of joint coordinate systems permitting three-dimensional (3D) kinematics. The first aim of this research project was to present a functional and postural method (FP method) to define a bone-embedded anatomical frame (BAF) on the femur and tibia, and, subsequently, a knee joint coordinate system. The repeatability of the proposed method was also assessed. Using FP method to define the BAFs, 4 kinematic parameters (flexion/extension, abduction/adduction, tibial internal/external rotation, and antero-posterior translation) were computed for 15 subjects walking on a treadmill. The repeatability for all four kinematic parameters was then assessed, using intra- and inter-observer settings. After pooling the results for all observers, the mean repeatability value ranged between 0.4 degrees and 0.8 degrees for rotation angles and between 0.8 and 2.2 mm for translation.

Adolescent↗

PubMed2004

Vertebral wedging characteristic changes in scoliotic spines.

STUDY DESIGN: A morphometric analysis of vertebral wedging in vertebrae from scoliotic specimens. OBJECTIVE: To quantify the vertebral body changes in 30 anatomic specimens affected by a scoliotic deformity. SUMMARY OF BACKGROUND DATA: Only a few studies have evaluated the exact changes occurring at the level of the vertebral body in scoliotic spines. Most are observational studies of rare scoliotic specimens presenting major curvatures. The orientation of vertebral wedging is important for the planning of corrective surgery, performing vertebral osteotomy, and the evaluation of possible growth modulation. MATERIALS AND METHODS: Thirty scoliotic specimens with curves presenting various degrees of severity were studied using a three-dimensional digitizing protocol developed to create a precise three-dimensional reconstruction of the vertebrae. Every scoliotic specimen was then matched with a normal specimen, and comparisons were made on the vertebral body parameters both for thoracic and lumbar vertebrae. Analysis of variance and t test calculations were performed to identify significant differences with P = 0.05. RESULTS: A total of 471 vertebrae from scoliotic spines and 510 vertebrae from normal specimens were measured. Vertebral wedging increased progressively towards the apex of the curve and was maximal at the apex. Vertebral wedging was more prominent in the frontal plane, and there was minimal wedging in the sagittal plane. Vertebral heights were significantly different at T3 and T4 for the upper adjacent curve and at T6-T8 for a typical right thoracic curve, with smaller heights located on the concavity of the curve. No changes were observed on the convexity of the curve. CONCLUSION: Vertebral wedging is an essential component of the scoliotic deformity. The present study provides critical information for corrective surgery and vertebral osteotomy, as vertebral wedging occurs primarily in the frontal plane. Accurate knowledge of this deformity should also provide new insight into corrective surgical strategies aiming at growth modulation and more efficient surgical correction.

Disease Progression↗

PubMed2004

Thoracic pedicle morphometry in vertebrae from scoliotic spines.

STUDY DESIGN: A morphometric analysis of thoracic pedicles in vertebrae from scoliotic specimens. OBJECTIVE: The objective of this study was to quantify the changes occurring in thoracic pedicles affected by a scoliotic deformity. SUMMARY OF BACKGROUND DATA: There exists a lot of controversy in the literature concerning the shape and size of thoracic pedicles in idiopathic scoliosis. In recent years, thoracic pedicle screws are being used more frequently in corrective spine surgery, but few studies have evaluated the morphology of scoliotic thoracic pedicles. MATERIAL AND METHOD: Thirty scoliotic specimens with curves presenting various degrees of severity were studied using a three-dimensional digitizing protocol developed to create a precise three-dimensional reconstruction of the vertebrae. Twenty-two parameters describing specifically the pedicles were then calculated for each vertebra from these reconstructions. Every scoliotic specimen was then matched with a normal specimen to provide for a representative control group and comparisons were made on pedicle width, length, height, surface, and orientation. RESULTS: A total of 683 thoracic vertebrae were measured (325 scoliotic and 358 normal vertebrae). Pedicles located on the concavity of typical right thoracic curves were found to be significantly thinner than their normal counterparts with a maximal mean difference of 1.37 mm at T8. The pedicles on the concavity of the high thoracic compensatory curve were also found to be significantly diminished with a maximal mean difference of 1.68 mm at T4. Mean left pedicle width at T8 (concavity) and mean right pedicle width at T4 (concavity) were found to be 4.08 mm and 2.60 mm, respectively. Pedicle length was found to be slightly increased, and pedicle height was found to be slightly decreased in pedicles from scoliotic spines with no preference for concavity or convexity. Pedicle orientation and inclination were unchanged with respect to each corresponding vertebral body. CONCLUSION: These results are of critical importance for clinicians performing spinal corrective surgery in patients with AIS. Pedicle width is significantly diminished on the concavity of scoliotic curves. Our results advocate caution in the use of pedicle screws in the thoracic spine especially on the concave side of the curve.

Adult↗

PubMed2002

Morphometric analysis of anatomic scoliotic specimens.

STUDY DESIGN: Morphometric analysis of anatomic scoliotic specimens. OBJECTIVE: The objective of this study was to identify a typical deformation pattern for thoracic and lumbar vertebrae in idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Idiopathic scoliosis is a three-dimensional deformity affecting the orientation and position of the spine in space. The regional deformity has been studied extensively, but most of the knowledge we currently have regarding the local deformity is the result of isolated observations made on rare scoliotic specimens with severe deformities. MATERIALS AND METHODS: Thirty scoliotic specimens from two major osteologic sources were studied using a three-dimensional digitizing protocol developed by our research group creating a precise three-dimensional reconstruction of the vertebrae. Parameters were then calculated for each vertebra from these reconstructions. Every scoliotic specimen was then matched with a normal specimen to provide for a representative control group. RESULTS: A total of 984 vertebrae (472 scoliotic and 512 normal vertebrae) were measured, creating the largest database of normal and scoliotic vertebral specimens. A characteristic deformity pattern was identified consisting of progressive vertebral wedging, decreased pedicle width on the concave side of the curve, and articular facet surface varying greatly with all findings increasingly more important toward the apex of the curve and as curve severity increased. All findings were statistically significant with P< 0.05. CONCLUSION: These results are of critical importance for the understanding of the local and regional deformity and in understanding curve progression. Our results also advocate caution in the use of pedicle screws in the thoracic spine, especially on the concave side of the curve.

Biometry↗

PubMed2002

Morphometric analysis of one anatomic scoliotic specimen.

Idiopathic scoliosis is a 3-D deformation affecting the position of the spine in space. The regional deformity has been studied extensively but the local changes have not been widely investigated and this being mainly due to the rarity of anatomical specimens. The objective of this study was to identify a deformation pattern for idiopathic scoliosis. We thus studied one complete scoliotic specimen using a digitizing protocol developed by our research group. The anatomical specimen was selected from the Hamann-Todd Osteology Collection at the Cleveland Natural History Museum, which contains over 1,300 skeletons. We were also able to match this scoliotic specimen with one normal specimen for age, sex, race, height and weight. Each vertebra was measured by taking approximately 200 points on each surface. Parameters for each vertebra were then calculated from these sets of points. Each scoliotic vertebra was then compared with a corresponding normal vertebra of the matched specimen. We present the first findings of these measurements, which show pedicle and posterior elements changes that are thought to be secondary to the scoliotic deformation.

Humans↗

PubMed2002

Semi-automation of the 3D reconstruction of the spine using wavelets and splines.

We propose a wavelet multi-resolution analysis to localize specific features in both lateral and frontal radiographs. This analysis allows an elegant spectral investigation that leads simultaneously to image de-noising and edge extraction. It is combined with an a priori knowledge of the spine's morphology and a 3D spline curve characterization of its global shape. Actual work deals with identifying the contours of the vertebral bodies and the localization of vertebrae's endplates. However, this information could also lead to the selection of a 3D statistical model of the spine suited for the studied deformation. Working with retro-projections of the model, we aim at creating edge models for each vertebra that will be used to geometrically match the wavelet's edges. The manual feature identification could then be replaced in the reconstruction of the 3D representation of the spine.

Algorithms↗

PubMedDate not supplied

3D/2D registration and segmentation of scoliotic vertebrae using statistical models.

We propose a new 3D/2D registration method for vertebrae of the scoliotic spine, using two conventional radiographic views (postero-anterior and lateral), and a priori global knowledge of the geometric structure of each vertebra. This geometric knowledge is efficiently captured by a statistical deformable template integrating a set of admissible deformations, expressed by the first modes of variation in Karhunen-Loeve expansion, of the pathological deformations observed on a representative scoliotic vertebra population. The proposed registration method consists of fitting the projections of this deformable template with the preliminary segmented contours of the corresponding vertebra on the two radiographic views. The 3D/2D registration problem is stated as the minimization of a cost function for each vertebra and solved with a gradient descent technique. Registration of the spine is then done vertebra by vertebra. The proposed method efficiently provides accurate 3D reconstruction of each scoliotic vertebra and, consequently, it also provides accurate knowledge of the 3D structure of the whole scoliotic spine. This registration method has been successfully tested on several biplanar radiographic images and validated on 57 scoliotic vertebrae. The validation results reported in this paper demonstrate that the proposed statistical scheme performs better than other conventional 3D reconstruction methods.

Humans↗