Biomedical subjects

H Labelle

Publications and source records attributed to H Labelle.

At least 37 records · Page 2Linked to original sources

PubMed1998

[Morphometric characteristics of the scoliotic spine].

GOAL: Results from a morphometric investigation performed on a rare complete scoliotic specimen are presented. The aim of the study is to describe the vertebral body wedging. MATERIALS: The specimen used in the study presented a thoracic curve of 150 degrees Cobb angle with the apex at T8. The measures were made using 3D-computer graphics models. The wedging in the frontal and sagittal planes as well as the 3D wedging were measured. The height variation of the vertebral bodies was also measured. RESULTS: The wedging measures show that it increases progressively with the vertebral level to reach a maximum of 27 degrees at the apex. Perdriolle has found a linear relation between the vertebral body wedging and the Cobb angle. The relation predicts a wedging of 24 degrees for 150 degrees of Cobb angle. An inflection point was identified on the vertebral end plate on the convex side. These inflection points were described by Perdriolle as being on the concave side of the vertebra. CONCLUSION: Our measures follow the relation between the Cobb angle and the wedging of the vertebral body, even for very large Cobb angles. Furthermore, inflection points on the vertebral body were identified on the convex side as opposed to the concave side in the literature. This leads us to believe that the vertebral body wedging progressively affects the vertebral endplates.

Adult↗

PubMed1998

[A biomechanical study of new orthotic treatment approaches for the 3D correction of scoliosis].

Scoliosis is a complex deformity of the spine and rib cage often treated by the Boston brace. The goal of this research is to study the simulation of two new treatment approaches and to compare their results to the Boston brace. A personalized biomechanical model has been used to simulate the treatment on 20 scoliotic teenagers with double curvature. On the first treatment, different forces were applied at the thoracic apex level and the posterior displacement of the rib hump was locked. For the second treatment, an oblique force oriented 45 degrees with respect to the frontal plane was added at the lumbar apex. Following each simulation, geometrical and clinical measurements were calculated and compared to the initial geometry and the Boston brace treatment. Overall, the two new treatment modalities correct the thoracic Cobb angle in the frontal plane while maintaining the normal physiological curvatures in the sagittal plane, move the thoracic plane of maximum deformity towards the sagittal plane and reduce axial rotation and rib hump. In comparison, the Boston brace reduces the Cobb angles in the frontal as well as in the sagittal planes, moves the planes of maximum deformities towards the coronal plane and has no effect on axial rotation and rib hump. This biomechanical study shows force patterns that correct scoliosis more efficiently than the Boston brace. These new treatment approaches must be personalized for each patient and still require clinical evaluation.

Adolescent↗

PubMed1997

Relation between adolescent idiopathic scoliosis and morphologic somatotypes.

STUDY DESIGN: A prospective and controlled comparative study. OBJECTIVES: To verify the difference in morphologic appearance between a group of adolescents with progressive adolescent idiopathic scoliosis and a control group of normal adolescents. SUMMARY OF BACKGROUND DATA: In a previous retrospective study, the possibility of a relation between progressive adolescent idiopathic scoliosis and specific morphotypes was demonstrated. METHODS: Fifty-two adolescent girls with progressive adolescent idiopathic scoliosis were compared with an age-matched control group of 62 unaffected girls using a classification technique based on morphologic somatotypes. Morphotypes were evaluated with standardized pre-established criteria based on Sheldon's technique. RESULTS: Patients with progressive adolescent idiopathic scoliosis showed significantly less mesomorphism (mean value of 0.88 +/- 0.51) than control girls (mean value of 1.72 +/- 0.52). CONCLUSION: Adolescent girls with progressive adolescent idiopathic scoliosis have a morphologic somatotype that is different from the normal adolescent population. Subjects with progressive adolescent idiopathic scoliosis are significantly less mesomorphic than control girls. This observation may be of value as a predictive factor for early identification of subjects with adolescent idiopathic scoliosis at greater risk of progression.

Adolescent↗

PubMed1997

Rib cage-spine coupling patterns involved in brace treatment of adolescent idiopathic scoliosis.

STUDY DESIGN: The three-dimensional (3-D) interrelations in the correction of the spine and rib cage produced by the Boston brace were analyzed in a group of adolescents with idiopathic scoliosis. OBJECTIVES: To investigate the coupling movements between the spine and rib cage initiated by brace wear (i.e., the displacements of the spine that take place in other directions than the ones generated by brace pressures on the thorax). SUMMARY OF BACKGROUND DATA: The effects of thoraco-lumbo-sacral orthosis in the frontal plane have been well documented, but they have never been studied in terms of 3-D coupled movements between the spine and rib cage. METHODS: The spine and rib cage of 36 adolescents with idiopathic scoliosis with and without their Boston brace were reconstructed in 3-D using a stereo-radiographic technique. Several geometric indices were evaluated on the trunk, and the relative motions of the spine and rib cage resulting from brace wearing were compared by means of Student t tests, Pearson correlation matrices, and linear regressions. RESULTS: Rib cage transverse plane translations resulting from brace pressures are related to those of the spine. Coupled movements between the spine and rib cage were found to alter substantially the expected 3-D correction of the trunk. Significant anterior displacements of the thorax were observed and were statistically associated with lateral displacements of the spine and with an increase of spinal thoracic curvatures in the frontal and sagittal planes. CONCLUSION: Brace loads are not applied in an optimal way to correct the 3-D deformities associated with thoracic idiopathic scoliosis. Loads applied on the posterior rib hump should be reequilibrated to reduce anterior displacement of the trunk.

Biomechanical Phenomena↗

PubMed1997

Morphometric evaluations of personalised 3D reconstructions and geometric models of the human spine.

In the past, several techniques have been developed to study and analyse the 3D characteristics of the human spine: multi-view radiographic or biplanar 3D reconstructions, CT-scan 3D reconstructions and geometric models. Extensive evaluations of three of these techniques that are routinely used at Sainte-Justine Hospital (Montréal, Canada) are presented. The accuracy of these methods is assessed by comparing them with precise measurements made with a coordinate measuring machine on 17 thoracic and lumbar vertebrae (T1-L5) extracted from a normal cadaveric spine specimen. Multi-view radiographic 3D reconstructions are evaluated for different combinations of X-ray views: lateral (LAT), postero-anterior with normal incidence (PA0 degree) and postero-anterior with 20 degrees angled down incidence (PA20 degrees). The following accuracies are found for these reconstructions obtained from different radiographic setups: 2.1 +/- 1.5 mm for the combination with PA0 degree-LAT views, and 5.6 +/- 4.5 mm for the PA0 degree-PA20 degrees stereopair. Higher errors are found in the postero-anterior direction, especially for the PA0 degree-PA20 degrees view combination. Pedicles are found to be the most precise landmarks. Accuracy for CT-scan 3D reconstructions is about 1.1 +/- 0.8 mm. As for a geometric model built using a multiview radiographic reconstruction based on six landmarks per vertebra, accuracies of about 2.6 +/- 2.4 mm for landmarks and 2.3 +/- 2.0 mm for morphometric parameters are found. The geometric model and 3D reconstruction techniques give accurate information, at low X-ray dose. The accuracy assessment of the techniques used to study the 3D characteristics of the human spine is important, because it allows better and more efficient quantitative evaluations of spinal dysfunctions and their treatments, as well as biomechanical modeling of the spine.

Evaluation Studies as Topic↗

PubMed1997

[Intra-observer variability of measurement of posture with three-dimensional digitization].

A new system based on 3D digitization with magnetic fields has been developed by our research team. The focus of this study was to evaluate the intratester reproducibility of this technique of measurement. Twenty key morphological parameters were used twice to digitize the fourty five female subjects aged 7 to 23 years. The results of variance analysis (ANOVA) for repeated measures showed no statistically significant difference between the two series of measurements for the twenty angles studied. In 56% of the measurements, the difference of the means was less than 1 degree, the greatest being 1.82 degrees. These results confirm the reliability of this new technique of postural evaluation when the measurements are taken by the same tester. Therefore, 3D digitization with magnetic fields could be an interesting alternative to X-Rays for the evaluation of scoliosis.

Adolescent↗

PubMed1997

[In vitro evaluation of computer-assisted pedicle screw system].

GOAL: The goal of this study is to evaluate influence on the accuracy of pedicle hole positions when a surgeon uses a computer assisted system. STUDY DESIGN: This comparative study was undertaken using dry thoraco-lumbar specimens in order to measure the position of drilled holes with and without computer assistance in the hands of an experienced surgeon as well as with a resident in training. METHODS: Pedicle holes were drilled from D1 to L5 in identical dry thoraco- lumbar specimens. For half of the specimens a computer assisted pedicle screw installation system was used. Holes having been drilled for all specimens, we then measured the maximum distance between the axis of the drilled holes and the pedicle cortices All distances less or equal to 2 mm were classified as safe while all bigger distances were classified as unsafe for pedicle screw installation. RESULTS: Nine specimens were drilled for a total of 306 holes, 170 of them with computer assistance. We have observed a 95% success rate with the computer assisted holes compared to a 62% success rate using conventional methods (p < 0.001). No difference was found between the results of an experienced surgeon and the results of a resident in training while using the computer assistance system. All holes drilled from D12 to L5 were found to be in optimal position, completely within the pedicles. CONCLUSION: These results suggest that this computer assisted pedicle screw installation system could improve the accuracy of pedicle screw placement and enhance the safety of the procedure. Moreover, the computer system could become a valuable teaching tool for the training spine surgeons.

Bone Screws↗

PubMed1997

[Evaluation of peroperative measurement system in the follow-up of vertebral displacements].

A computer assisted surgery system has been developed to quantify the vertebral displacements induced by the Cotrel-Dubousset instrumentation and to visualize in 3-D the spine at different per-operative steps. This spinal surgery is realized to correct idiopathic scoliosis. Per-operative measurements are obtained by using a magnetic digitizer. Five points per thoracic vertebra and six points per lumbar vertebra are digitized. The method proposed estimates the location of the digitized points on a computer graphics 3-D model of vertebrae by a point-to-surface matching algorithm. The 3-D models are constructed before the surgery using multiplanar radiographic reconstruction technique (2 or 3 views) and geometric modeling methods. Computer tools permit the 3-D visualization of the spine peroperatively and the evaluation of clinical indices such as Cobb angles and vertebral rotations. The system includes 3 principal error sources: 2) reconstruction error; 2) digitizer error (digitizer precision) and 3) point-to-surface matching error. In order to validate the overall system, measurements have been simulated for 2 vertebrae and 2 digitizers of different precision, taking onto account the reconstruction error. For 5 and 6 digitized points per vertebra, the matching algorithm gives a RMS error of respectively 3.0 and 2.0 mm.

Biomechanical Phenomena↗

PubMed1997

[Computer graphic analysis of the three dimensional deformities of scoliotic vertebrae].

GOAL: A computer graphics method that permits the reconstruction, visualization and measure of the vertebral deformities of the scoliotic spine is presented. MATERIALS: Medical imaging techniques utilizing computerized tomography is at the foundation of the reconstruction technique. The studied morphometric parameters are: 1) vertebral body wedging, 2) transverse and spinous process orientation and dimensions and 3) bilateral variation of pedicular dimensions. RESULTS: The reconstructed specimen showed the usefulness of this technique for visualizing and measuring vertebral deformities. Preliminary results seem to be in agreement with the literature concerning the deformities of scoliotic vertebrae. CONCLUSION: This tool will be useful in morphometric investigations for the evaluation of the deformations of scoliotic vertebrae.

Computer Graphics↗

PubMed1996

Three-dimensional effect of the Boston brace on the thoracic spine and rib cage.

STUDY DESIGN: Three-dimensional reconstructions of the spine and rib cage were done and compared just before and 1 month after initiation of treatment with a Boston brace in a group of adolescents with idiopathic scoliosis. OBJECTIVES: To document the immediate changes in shape of the thoracic spine and rib cage induced by the original Boston brace design. SUMMARY OF BACKGROUND DATA: The effect of the Boston brace has been well documented in the frontal plane but is poorly understood in the other planes of deformity. METHODS: Three-dimensional reconstructions were obtained with and without the brace using a stereoradiographic technique in a group of 40 adolescents with idiopathic scoliosis. Several geometric indices of the spine and rib cage were compared using Student t tests. RESULTS: The brace produced significant curve correction of the spinal deformity in the frontal plane at the expense of a significant reduction of thoracic kyphosis in the sagittal plane, as well as in the plane of minimum deformity. No significant effect on rotation of the thoracic apical vertebra, on the rib hump, or on frontal balance could be documented, but changes were noted in the sagittal orientation of the rib cage and in the sagittal balance of the spine. CONCLUSIONS: The original Boston brace does not completely correct the three-dimensional deformities associated with thoracic idiopathic scoliosis, although it reduces Cobb angles in the frontal plane.

Adolescent↗

PubMed1996

[Computer assisted pedicle screw installation. Our first 3 cases].

Pedicle screw fixation is sometimes a difficult surgical procedure relying on anatomical landmarks that may be modified by vertebral asymmetries. A significant incidence of cortex penetration and neuro-vascular complications have been documented. Our study evaluates the usefulness of a computer-aided pedicle installation system and analyses the results for our first 3 clinical cases. The system was used for 3 adolescent patients with idiopathic scoliosis undergoing surgical correction and instrumentation. In all cases, selected vertebrae were reconstructed in 3D pre-operatively. At surgery, the surgeon compared the computer-suggested pedicle location to his own opinion. After pedicular hole drilling was done in the usual fashion, hole positions were confirmed per-operatively with the computer software. Post-operatively, software hole positions were measured and compared to the actual screw axis using CT-Scans. Three dimensional models produced for all selected vertebrae allowed visualization of asymmetrical deformations of the scoliotic vertebrae. All pedicles were correctly detected by the software. Pedicular hole measurements agreed with the actual screws positions on post-op CT-Scans. The computerized surgical assistant can be of value in a clinical situation. These initial results warrant a large scale trial in order to establish accuracy and reliability.

Adolescent↗

PubMed1996

[3-D evaluation of posture in normal and scoliotic adolescents].

We have developed a new clinical evaluation of the human posture based on 3D digitization with magnetic fields. This 3D postural evaluation displays the relative position of the head, the shoulders and the pelvis. The main purpose is to identify key morphological parameters in order to demonstrate significant differences between 2 groups of subjects. Nineteen adolescent control subjects and 22 patients with AIS have been evaluated. The t-tests showed significant statistical differences between the 2 groups for every measurements studied. The 2 most significant were tilt of the shoulders in the postero-anterior plane and the angle of the shoulder-blades vs the shoulders in the transverse plane (p < 0.0005). These results support the value of the 3D postural evaluation as a clinical tool for the evaluation of AIS. This technique is non-invasive and could be used for the clinical follow-up in order to evaluate the postural evolution in scoliotic patients.

Adolescent↗

PubMed1996

[Dorso-lumbal pain and idiopathic scoliosis in adolescence].

Current knowledge on the association between back pain and idiopathic scoliosis is often contradictory. The presence, localisation and importance of pain was evaluated for a cohort of 426 adolescents with AIS. Patients were recruited from a scoliosis clinic in a pediatric hospital. A questionnaire and an analogue visual scale graduated from 0 (no pain) to 100 (maximal pain) were used in order to verify more precisely, the importance of the association between AIS and back pain. Chisquare, linear regression and Student T-test were used for statistical analysis. 239 patients with right thoracic and left lumbar curves (RTLL) had a prevalence of pain of 54%. The mean of maximum pain intensity was 49 mm +/- 20. No relation was found between the severity of the scoliosis and back pain. The two groups (with and without pain) were comparable. Cobb angles were about the same for the thoracic and lumbar regions, as well as kyphosis and lordosis, weight, height and age. Risser sign, sex, brace and pelvic tilt were the only variables associated with pain (p < 0.0001). Association between AIS and pain is more frequent than generally reported. Pain appears to be more related with pelvic tilt than severity of the scoliosis.

Adolescent↗

PubMed1996

[A study of biomechanical coupling between spine and rib cage in the treatment by orthosis of scoliosis].

Orthoses are widely used to treat scoliotic deformities of the trunk, but the way the corrective forces are transmitted from the thorax to the spine remains not well understood, and several undesired effects such as the reduction of sagittal curvatures or weak derotations are often reported. A biomechanical finite element model of the trunk was used to investigate the hypothesis that there exist coupling mechanisms between the scoliotic spine and rib cage which may explain incomplete and unexpected results obtained by orthotic treatments. Forces of 40 N were applied on the rib hump and on the lateral side of the thorax, and their individual effects were evaluated in 3-D on the spine and thorax using several geometrical indices (transverse plane translations, axial, sagittal and frontal rotations, Cobb angles). These biomechanical simulations demonstrated the existence of coupled motions between the spine and rib cage subjected to orthotic loads. It showed that reduction of physiological sagittal curvatures (up to 30%) are possibly related to anterior orthotic loads applied on the rib hump. These loads also contribute to increase lateral shift of the spine (up to 7 mm) as well as scoliotic frontal curvatures (up to 4 degrees). Based on the results found in this study, a simple and more optimal approach to treat scoliotic deformities was proposed and consisted to apply loads laterally on the convex side and on the anterior thorax opposite to the rib hump, with a system that mechanically constrains the posterior rib hump to move backward. It was simulated on 4 scoliotic patients presenting thoracic curves between 22 degrees and 54 degrees to evaluate its practicability and it was found that derotation of the trunk (between 7 degrees and 13 degrees) and reduction of frontal curvatures (up to 4 degrees) could be done without reducing physiological sagittal curvatures. More simulations on different scoliotic configurations are necessary to find the most optimal combination of forces to produce a real 3-D correction of scoliotic deformities.

Biomechanical Phenomena↗

PubMed1995

Comparison between preoperative and postoperative three-dimensional reconstructions of idiopathic scoliosis with the Cotrel-Dubousset procedure.

STUDY DESIGN: Pre- and postoperative three-dimensional reconstructions of the spine and rib cage were done and compared in a group of adolescents with idiopathic scoliosis. OBJECTIVE: Changes in the shape of the thoracic spine and rib cage induced by the Cotrel-Dubousset instrumentation and procedure were documented. SUMMARY OF BACKGROUND DATA: Although many authors have reported significant curve improvement in the frontal plane, attempts to document derotation of the spine have shown only limited correction of apical vertebral rotation. METHODS: Three-dimensional reconstructions were obtained pre- and postoperatively using a stereoradiographic technique in a group of 37 adolescents with idiopathic scoliosis. Several geometrical indices of the spine and rib cage were compared using Student t tests. RESULTS: The curve correction averaged 50% in the frontal plane and 24% in the plane of maximum curvature, while normal thoracic kyphosis was maintained in the sagittal plane. The orientation of the plane of maximum curvature was shifted very significantly toward the sagittal plane, indicating en bloc movement of the thoracic spine and three-dimensional correction of the deformity. A small but significant change in vertebral axial rotation and rib hump was found and improvement in the overall orientation of the ribs was documented. CONCLUSIONS: The Cotrel-Dubousset instrumentation and procedure are effective in producing three-dimensional improvement of the thoracic spine by en bloc relocation of the instrumented spine rather than by vertebral axial derotation.

Adolescent↗

PubMed1995

Peroperative three-dimensional correction of idiopathic scoliosis with the Cotrel-Dubousset procedure.

STUDY DESIGN: A peroperative measurement technique based on magnetic fields was used to document the thoracic and lumbar vertebral changes induced by derotation of the concave rod during corrective surgery of idiopathic scoliotic deformities with Cotrel-Dubousset instrumentation. OBJECTIVES: Objective was to accurately document the immediate changes induced by the derotation maneuver to gain a better understanding of its effect on curve correction during a surgical procedure. SUMMARY OF BACKGROUND DATA: Accurate peroperative documentation of these three-dimensional changes was very limited, and the exact contribution of the derotation maneuver in the entire process of correction of a scoliotic deformity was still poorly understood. METHODS: A digitizer using magnetic fields was used to record the three-dimensional orientation and x, y, and z coordinates of the tip of every spinous process exposed at surgery before and after derotation of the concave rod in a group of 22 female patients with idiopathic scoliosis. RESULTS: A significant improvement of the scoliotic deformity was noted in the frontal plane, and improvement of thoracic hypokyphosis and lumbar hypolordosis in the sagittal plane was seen. Vertebral axial rotation remained unchanged. CONCLUSIONS: The derotation maneuver is effective in achieving three-dimensional correction of idiopathic scoliosis, but vertebral axial derotation is not an important component of this correction.

Adolescent↗

PubMed1995

Computer-assisted pedicle screw fixation. A feasibility study.

STUDY DESIGN: We evaluated a computer-assisted surgical tool for inserting pedicle screws. OBJECTIVES: This study reviewed the feasibility, usefulness, and accuracy of the proposed tool. SUMMARY OF BACKGROUND DATA: Reviews documented neurovascular damage caused by screw misplacement. Currently, screw hole position is assessed by radiologic means and curette palpation. METHODS: Three sheep vertebrae and one artificial object were reconstructed three-dimensionally from computed tomography scan slices. At surgery, the surgeon's movements were displayed relative to the three-dimensional vertebrae on a computer screen. The tool was used to detect pedicles and to verify the position of drilled holes. In our laboratory, we calculated the system's accuracy by taking measurements on the artificial object. RESULTS: All pedicles were identified with the computer. Five of the six drilled hole positions were correctly represented. An accuracy of 4.5 mm +/- 1.1 mm RMS (root of the mean squared) and 1.6 degrees +/- 1.2 degrees were calculated. CONCLUSIONS: Results suggested the proposed system could be useful for pedicle detection and assessing the intravertebral location of a drilled hole. The proposed system could be used for many different orthopedic procedures where structures are hidden from the surgeon's view.

Animals↗

PubMed1995

Variability of geometric measurements from three-dimensional reconstructions of scoliotic spines and rib cages.

Three-dimensional (3-D) reconstructions of the spine are being used with increasing frequency to describe scoliotic deformities, but the reproducibility of most of these techniques and the implication for the reliability of measurements made on the reconstructions has not been reported. How reliable are these reconstructions, and can a clinician interpret with confidence the results of studies based on such mathematical models? A reproducibility study of various computerised measurements obtained from 3-D reconstructions of the spine and rib cage for five subjects with adolescent idiopathic scoliosis was done to evaluate the errors associated with repeated measurements and compare them with inter- and intraobserver errors reported for similar commonly used clinical measurements. The mean variation for the Cobb angle differed according to the plane of computation from 0.6 degrees in the frontal plane to 6.7 degrees in the sagittal plane; vertebral axial rotation varied from 2.3 degrees to 5.9 degrees according to the vertebral level, and rib hump measurements displayed an average variation of 1.4 degrees. All these variations are below or within the error levels reported for equivalent 2-D measurements used by clinicians, which suggests that this 3-D model of idiopathic scoliosis may be used with confidence for clinical evaluations.

Child↗