Biomedical subjects

J A de Guise

Publications and source records attributed to J A de Guise.

At least 19 recordsLinked to original sources

PubMed2006

Comparing three attachment systems used to determine knee kinematics during gait.

This work compared three attachment systems (AS) designed to minimize soft tissue artefacts in gait analysis measurements. The systems' displacement for different knee flexion angles and after 50 gait cycles was investigated using an EOS low dose biplanar X-ray system. Eighteen subjects (six per AS) were equipped with one AS and placed in five positions. Frontal and profile views were taken for each position. The bones' 3D model and the AS's position were obtained from stereoradiographic reconstructions. The AS's relative position to the underlying bone were computed and interpreted in the anatomical coordinate systems (CS). The AS appeared to be stable in the frontal and sagittal plane (under 1.5 degrees average displacement around the underlying bones) but unstable in the axial plane (over 6 degrees average displacement). The average translation along the femoral and tibial diaphysis was 4.5mm and 2.7 mm, respectively. Femoral system B translated significantly less along the diaphysis than the other AS. Concerning the axial rotation, system C appeared to present the most important displacement but there was no statistically significant difference. Systems A and B's rotation in the transverse plane correlated to the knee flexion angle. For the tibia, system B was more stable than systems A and C (p=0.04). On the whole, system B appeared to be the most stable system. This study highlights the fact that no system can limit displacement in the transverse plane.

Adult↗

PubMed2006

3D reconstruction of the pelvis from bi-planar radiography.

3D personalized models are more and more requested for clinical and biomechanical studies. Techniques based on bi-planar X-rays present the advantage of a low radiation dose for the patient. However, up to now, such techniques have shown limited accuracy in the case of pelvis reconstruction. This study proposes and validates a method providing accurate 3D personalized model of the pelvis from bi-planar X-rays. The algorithm is based on the fast computation of an initial solution followed by local deformations based on 2D anatomical points and contours that are digitized in both radiographs. Results were close to CT-scan reconstructions (mean difference 1.6 mm and differences under 4.3 mm for 95% of the points). Moreover, 3D morphometry of the pelvis could be obtained with an accuracy of 5%. This technique provides 3D patient specific model with a low radiation dose.

Aged↗

PubMed2006

Habituation to treadmill walking.

The use of a treadmill to evaluate gait patterns makes it possible to analyze many gait cycles and stride to stride variations. The objective of this study was to assess the time required for a subject to habituate to walking on a treadmill. The evolution of knee kinematics and spatio-temporal parameters were analyzed to measure habituation to walking on the treadmill. To obtain this information, data were recorded on 10 healthy subjects for about 45 minutes as they walked on a treadmill. A steady state was attained for knee kinematics and most spatio-temporal parameters at the time the treadmill had attained its maximal speed (approximately 30 seconds). However, 10 minutes were necessary for stride length to become reproducible. Time for habituation to walking on a treadmill must be considered when kinematics are evaluated during gait of healthy and disabled subjects. We have shown that, at least for young, healthy individuals who are non-naïve to walking on a treadmill, a 10-minute warm-up is enough before three-dimensional knee kinematics and spatio-temporal data can be recorded.

Adaptation, Physiological↗

PubMed2004

Three-dimensional X-ray absorptiometry (3D-XA): a method for reconstruction of human bones using a dual X-ray absorptiometry device.

Three-dimensional accurate evaluation of the geometry of the proximal femur may be helpful for hip fracture risk evaluation. The purpose of this study was to apply and validate a stereo-radiographic 3D reconstruction method of the proximal femur, using contours identification from biplanar DXA images. Twenty-five excised human proximal femurs were investigated using a standard DXA unit. Three-dimensional personalized models were reconstructed using a dedicated non-stereo corresponding contours (NSCC) algorithm. Three-dimensional CT-scan reconstructions obtained on a clinical CT-scan unit were defined as geometric references for the comparison protocol, in order to assess accuracy and reproducibility of the 3D stereo-radiographic reconstructions. The precision of a set of 3D geometric parameters (femoral-neck axis length, mid-neck cross-section area, neck-shaft angle), obtained from stereo-radiographic models was also evaluated. This study shows that the NSCC method may be applied to obtain 3D reconstruction from biplanar DXA acquisitions. Applied to the proximal femur, this method showed good accuracy as compared with high-resolution personalized CT-scan models (mean error = 0.8 mm). Moreover, precision study for the set of 3D parameters yielded coefficients of variation lower than 5%. This is the first study providing 3D geometric parameters from standard 2D DXA images using the NSCC method. It has good accuracy and reproducibility in the present study on cadaveric femurs. In vivo prospective studies are needed to evaluate its discriminating potential on hip fracture risk prediction.

Absorptiometry, Photon↗

PubMed2004

Validation of the relative 3D orientation of vertebrae reconstructed by bi-planar radiography.

The three dimensional (3D) reconstruction of the spine can be obtained by stereoradiographic techniques. To be safely used on a routine clinics basis, stereoradiography must provide both accurate vertebral shape and coherent position. Although the accuracy of the reconstructed morphology of the vertebrae is well documented, only few authors studied the accuracy of the vertebral orientation. Therefore, this paper focuses on the evaluation of the orientation accuracy of the reconstructed vertebrae (obtained by non-stereo corresponding point technique) considering either a 178 point vertebral model or a 6 point vertebral model (previously proposed in the literature). Five dried vertebrae were fixed on holders containing four markers each. The 3D reconstruction of both vertebrae and markers were obtained by stereoradiographic techniques. Using least square method matching from one position to another, the relative orientation was computed for the vertebral models (6 or 178 points) and the four markers. These vertebral and holder orientations were compared (considering the holder's one as reference). The repeatability of these relative orientations (vertebrae and holders) was also evaluated. The mean (RMS) orientation error of 178 point vertebral model was 0.6 degrees (0.8 degrees ), for lateral rotation, 0.7 degrees (1.0 degrees ) for sagittal rotation and 1.4 degrees (1.9 degrees ) for axial rotation. The intra-observer repeatability was 0.5 degrees (0.7 degrees ) for lateral rotation, 0.7 degrees (0.8 degrees ) for sagittal rotation and 0.9 degrees (1.2 degrees ) for axial rotation. The orientation was found more accurate and precise when using the 178 point vertebral model than when using the basic 6 point vertebral model. The relative orientation (in post-operative follow-up with respect to the pre-operative examination) of the vertebrae of one scoliotic patient was performed as an example of clinical application. The stereoradiographic method is a reliable 3D quantitative tool to assess the spine deformity, that can be used in clinics for the follow-up of scoliotic patients.

Adult↗

PubMed2004

A 3D generic inverse dynamic method using wrench notation and quaternion algebra.

In the literature, conventional 3D inverse dynamic models are limited in three aspects related to inverse dynamic notation, body segment parameters and kinematic formalism. First, conventional notation yields separate computations of the forces and moments with successive coordinate system transformations. Secondly, the way conventional body segment parameters are defined is based on the assumption that the inertia tensor is principal and the centre of mass is located between the proximal and distal ends. Thirdly, the conventional kinematic formalism uses Euler or Cardanic angles that are sequence-dependent and suffer from singularities. In order to overcome these limitations, this paper presents a new generic method for inverse dynamics. This generic method is based on wrench notation for inverse dynamics, a general definition of body segment parameters and quaternion algebra for the kinematic formalism.

Acceleration↗

PubMed2003

Computer based method for the three-dimensional kinematic analysis of combined posterior cruciate ligament and postero-lateral complex reconstructions on cadaver knees.

The aim of this study is to evaluate the effect of combined posterior cruciate ligament (PCL) and postero-lateral corner (PLC) reconstruction on laxity and three-dimensional kinematics of cadaver knees. We performed anatomical double bundle PCL reconstruction, and functional one bundle 'over-the-bottom' PCL reconstruction combined with one type of PLC reconstruction, running from the postero-lateral tibia to an isometric point near the lateral epicondyle of the femur. Our results showed that combined reconstruction was necessary to restore rotatory laxity. PLC reconstruction, according to the technique described, invariably created a shift towards internal rotation of the kinematic curves, compared to the intact knee.

Aged↗

PubMed2003

Reliability of a quantification imaging system using magnetic resonance images to measure cartilage thickness and volume in human normal and osteoarthritic knees.

OBJECTIVE: The aim of this study was to evaluate the reliability of a software tool that assesses knee cartilage volumes using magnetic resonance (MR) images. The objectives were to assess measurement reliability by: (1) determining the differences between readings of the same image made by the same reader 2 weeks apart (test-retest reliability), (2) determining the differences between the readings of the same image made by different readers (between-reader agreement), and (3) determining the differences between the cartilage volume readings obtained from two MR images of the same knee image acquired a few hours apart (patient positioning reliability). METHODS: Forty-eight MR examinations of the knee from normal subjects, patients with different stages of symptomatic knee osteoarthritis (OA), and a subset of duplicate images were independently and blindly quantified by three readers using the imaging system. The following cartilage areas were analyzed to compute volumes: global cartilage, medial and lateral compartments, and medial and lateral femoral condyles. RESULTS: Between-reader agreement of measurements was excellent, as shown by intra-class correlation (ICC) coefficients ranging from 0.958 to 0.997 for global cartilage (P<0.0001), 0.974 to 0.998 for the compartments (P<0.0001), and 0.943 to 0.999 for the condyles(P<0.0001). Test-retest reliability of within-reader data was also excellent, with Pearson correlation coefficients ranging from 0.978 to 0.999 (P<0.0001). Patient positioning reliability was also excellent, with Pearson correlation coefficients ranging from 0.978 to 0.999 (P<0.0001). CONCLUSIONS: The results of this study establish the reliability of this MR imaging system. Test-retest reliability, between-reader agreement, and patient positioning reliability were all extremely high. This study represents a first step in the overall validation of an imaging system designed to follow progression of human knee OA.

Adult↗

PubMed2003

A biplanar reconstruction method based on 2D and 3D contours: application to the distal femur.

A three-dimensional (3D) reconstruction algorithm based on contours identification from biplanar radiographs is presented. It requires, as technical prerequisites, a method to calibrate the biplanar radiographic environment and a surface generic object (anatomic atlas model) representing the structure to be reconstructed. The reconstruction steps consist of: the definition of anatomical regions, the identification of 2D contours associated to these regions, the calculation of 3D contours and projection onto the radiographs, the associations between points of the X-rays contours and points of the projected 3D contours, the optimization of the initial solution and the optimized object deformation to minimize the distance between X-rays contours and projected 3D contours. The evaluation was performed on 8 distal femurs comparing the 3D models obtained to CT-scan reconstructions. Mean error for each distal femur was 1 mm.

Algorithms↗

PubMed2003

Assessment of the 3-d reconstruction and high-resolution geometrical modeling of the human skeletal trunk from 2-D radiographic images.

This paper presents an in vivo validation of a method for the three-dimensional (3-D) high-resolution modeling of the human spine, rib cage, and pelvis for the study of spinal deformities. The method uses an adaptation of a standard close-range photogrammetry method called direct linear transformation to reconstruct the 3-D coordinates of anatomical landmarks from three radiographic images of the subject's trunk. It then deforms in 3-D 1-mm-resolution anatomical primitives (reference bones) obtained by serial computed tomography-scan reconstruction of a dry specimen. The free-form deformation is calculated using dual kriging equations. In vivo validation of this method on 40 scoliotic vertebrae gives an overall accuracy of 3.3 +/- 3.8 mm, making it an adequate tool for clinical studies and mechanical analysis purposes.

Humans↗

PubMed2002

Computer-based method for the 3-D kinematic analysis of posterior cruciate ligament and postero-lateral corner lesions.

Posterior cruciate ligament (PCL) rupture, whether or not combined with postero-lateral corner (PLC) tears, are more often diagnosed today thanks to improved imaging techniques. However, due to the lack of reliable instrumentation to quantitatively evaluate the knee, much is still unknown about the function of these ligamentous structures. The aim of this paper is to present results on the effect of progressive resection of the PCL and PLC on knee laxity and 3-D knee kinematics. The results show that 3-D movement analysis is important and complements laxity measurements by helping to interpret the complex alteration of knee function.

Aged↗

PubMed2002

Comparison of two methods for reconstruction of the posterior cruciate ligament using a computer based method: quantitative evaluation of laxity, three-dimensional kinematics and ligament deformation measurement in cadaver knees.

The aim of this paper is to present a biomechanical comparison of two different methods for reconstruction of the posterior cruciate ligament in cadaver knees. We used an original computer-based method allowing precise calculation of three-dimensional (3D) knee kinematic parameters as well as the estimation of combined graft deformation (elongation-flexion-torsion). After isolated posterior cruciate ligament (PCL) dissection, double bundle and 'over-the-bottom' methods were performed successively on each knee using synthetic polyester ligaments. The effect of pre-tensioning was tested with the 'over-the-bottom' method. antero-posterior (A-P) and rotational laxity as well as 3D kinematics were recorded and analysed. Our computer based method allowed us to show that both reconstruction methods were equivalent in restoring A-P and rotational laxity as well as kinematic curves. Combined deformation of the prostheses was equivalent for both ligaments.

Aged↗

PubMed2002

3D biplanar statistical reconstruction of scoliotic vertebrae.

A new 3D reconstruction method of scoliotic vertebrae of a spine, using two calibrated conventional radiographic images (postero-anterior and lateral), and a global prior knowledge on the geometrical structure of each vertebra is presented. This geometrical knowledge is efficiently captured by a statistical deformable template integrating a set of admissible deformations, expressed by the first modes of variation in the Karhunen-Loeve expansion of the pathological deformations observed on a representative scoliotic vertebra population. The proposed reconstruction method consists in fitting the projections of this deformable template with the preliminary segmented contours of the corresponding vertebra on the two radiographic views. The 3D reconstruction problem is stated as the minimization of a cost function for each vertebra and solved with a gradient descent technique. The reconstruction of the spine is then made vertebra by vertebra. The proposed method allows also to efficiently obtain an accurate 3D reconstruction of each scoliotic vertebra and, consequently, it allows also to get an accurate knowledge of the 3D structure of the whole scoliotic spine. This reconstruction method is in final phase of validation.

Artificial Intelligence↗

PubMed2002

3D detailed reconstruction of vertebrae with low dose digital stereoradiography.

As scoliosis requires a global and local 3D examination of the spine in standing position, stereoradiography appears as one of the most adequate 3D imaging tool for it diagnosis. Our purpose was to increase the geometry definition of the stereoradiographic reconstruction to obtain morpho-realistic models and to validate them using 41 dry vertebrae. Our results propose 2000 points 3D personalised models without any loss of accuracy in comparison to previous studies.

Algorithms↗

PubMed2002

Pre and post 3D modeling of scoliotic patients operated with in situ contouring technique.

A three-dimensional segmental analysis was performed on the stereoradiographic reconstructions of ten right thoracic scoliotic patients. From the quantitative model of the spine and pelvis, the vertebral and intervertebral orientations were computed pre and post operatively. These orientations allow to determine the apical and junctional zones of the high thoracic, thoracic and lumbar curves. The apical zone corresponds to the maximum of vertebral axial rotation. Pre operatively, the tendency was T7 for the thoracic transverse apex with 20 AE of axial rotation. The junctional zone corresponds to the maximum of vertebral lateral rotation and the maximum of intervertebral axial rotation. The tendency was T5 and T12 for the junctional vertebrae of the thoracic curve with, at both levels, 30 AE of vertebral lateral rotation and 10 AE of intervertebral axial rotation. The surgical correction obtained by in situ contouring technique was evaluated through these 3D orientations. The vertebral axial rotation at the high thoracic, thoracic and lumbar apex was corrected with respectively 52%, 60% and 60%.

Adolescent↗

PubMed2001

Analysis of pressure distribution at the body-seat interface in able-bodied and paraplegic subjects using a deformable active contour algorithm.

In this paper, a semi-automatic method for segmenting pressure distribution image-based data at the body-seat interface is presented. The purpose of this work was to estimate the surface and the load supported by the ischial tuberosity (IT) region. The proposed method involves three steps: (1) detecting the IT region using a pressure-distribution image gradient; (2) estimating the contour of the IT region by an iterative active contour algorithm and finally (3) estimating the percentage of the surface and the weight-bearing of the IT region in a group of able-bodied (AB) and spinal-cord injury (SCI) subjects. It was found in this study that the weight bearing on the IT for the spinal-cord injured group is distributed on half the surface in comparison with the AB group or the powered wheelchair users groups. The findings of this study provide insights concerning pressure distribution in sitting for the paraplegic and able-bodied.

Adult↗

PubMed2000

A three-dimensional radiographic comparison of Cotrel-Dubousset and Colorado instrumentations for the correction of idiopathic scoliosis.

STUDY DESIGN: A prospective clinical study comparing two instrumentation systems for the correction of idiopathic scoliosis. OBJECTIVES: To measure the short-term three-dimensional changes in the shape of the spine after corrective surgery and compare the Cotrel-Dubousset instrumentation to the more recent Colorado instrumentation to determine whether one system provides better three-dimensional correction. SUMMARY OF BACKGROUND DATA: Adequate three-dimensional correction of scoliotic deformities has been reported with the Cortrel-Dubousset instrumentation system. During the past decade, a new generation of more versatile and user-friendly spinal implants has appeared, but there are no reports available to indicate whether similar or better correction can be obtained with these newer systems. METHODS: The three-dimensional geometry of the thoracic and lumbar spine was documented in the standing position using a three-dimensional reconstruction technique based on multiplanar radiography in 67 adolescents with idiopathic scoliosis undergoing correction by a posterior approach. Changes in spinal shape were measured 3 days before and 1 month after the surgery in 31 patients with Cotrel-Dubousset instrumentation and 36 patients with Colorado instrumentation. RESULTS: In both groups, adequate three-dimensional correction of the scoliotic deformities was documented for thoracic and lumbar curves, with significant changes in the frontal plane, in the plane of maximum curvature, and in its orientation. When comparing both groups, better correction was obtained in the frontal plane with the Colorado instrumentation (65% vs. 48% with Cotrel-Dubousset), a finding that may be explained by the significantly greater proportion of pedicle screws used in this group. CONCLUSION: Both instrumentation techniques achieve an effective and comparable three-dimensional correction of the scoliotic deformities.

Adolescent↗

PubMed1999

Intraoperative comparison of two instrumentation techniques for the correction of adolescent idiopathic scoliosis. Rod rotation and translation.

STUDY DESIGN: A prospective and controlled comparative study of two instrumentation techniques used for the correction of adolescent idiopathic scoliosis. OBJECTIVE: To measure the three-dimensional intraoperative correction obtained with a rotation maneuver as compared with that obtained with a translation maneuver of the first instrumentation rod inserted to determine the difference, if any, in the two techniques for achieving three-dimensional correction. SUMMARY OF BACKGROUND DATA: Adequate three-dimensional correction of scoliotic deformities has been reported with the Cotrel-Dubousset instrumentation using the rod-rotation maneuver. More recently, however, authors of studies with newer instrumentation systems have claimed that better correction can be obtained using a translation technique. So far, no report has clearly demonstrated the three-dimensional changes obtained with this more recent instrumentation technique. METHODS: The changes in position of thoracic and lumbar vertebrae exposed during surgery were documented using a three-dimensional magnetic digitizer in 70 adolescents with idiopathic scoliosis undergoing correction by a posterior approach. Vertebral positions were measured intraoperatively before and after the surgical maneuver in 39 patients with the Cotrel-Dubousset instrumentation (rod rotation) and in 31 patients with the Colorado instrumentation (translation). RESULTS: In both groups, adequate three-dimensional correction of the scoliotic deformities was documented, with significant changes in the frontal and sagittal planes and in the orientation of the plane of maximum deformity for thoracic and lumbar curves. On the other hand, no significant differences were documented between the two procedures except in the frontal plane where a tendency for greater correction was observed for thoracic curves with the translation technique. CONCLUSIONS: The two instrumentation techniques are equally able to achieve a comparable and effective three-dimensional correction of the scoliotic deformities. The use of either a rotation maneuver or a translation technique during surgery does not result in any significant measurable difference in three-dimensional correction.

Adolescent↗