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Biomedical subjects

Hubert Labelle

Publications and source records attributed to Hubert Labelle.

At least 55 records · Page 3Linked to original sources
PubMed2003

Evaluation of a transpedicular drill guide for pedicle screw placement in the thoracic spine.

Insertion of pedicle screws in the thoracic spine is technically difficult and may lead to major complications. Although many computer-assisted systems have been developed to optimize pedicle screw insertion, these systems are expensive, not user-friendly and involve significant radiation from pre-operative computed tomographic (CT) scan imaging. This study describes and evaluates a transpedicular drill guide (TDG) designed to assist in the proper placement of pedicle screws in the thoracic spine. Pilot holes were made manually using the TDG in the thoracic spine (T1-T11) of three human cadavers before inserting 4.5-mm-diameter screws. CT scans followed by visual inspection of the spines were performed to evaluate the position of the screws. Five of 66 screws (7.6%) violated the pedicle wall: two (3.0%) medially and three (4.5%) laterally. The medial and lateral perforations were within 1 mm and 2 mm of the pedicle wall, respectively. The medial perforations were not at risk of causing neurological complications. No screw penetrated the superior or inferior pedicle wall. The TDG is easy to use and can decrease the incidence of misplaced thoracic pedicle screws. The TDG could be used as a complement to fluoroscopy in certain applications, especially for training surgeons.

Aged↗
PubMed2003

Electromyography of scoliotic patients treated with a brace.

When a brace is used to correct spinal deviation, patients may seek to ease the discomfort from the pressure exerted by the orthosis by actively recruiting specific trunk muscles. The effect of bracing on trunk electromyography (EMG) has been reported in only one study where a limited number of electrodes were placed mainly in the thoracic region. Our hypothesis was that a multi-electrode mapping of the activity of the thoracic, lumbar, and abdominal trunk muscles would provide a more representative picture of the muscular reaction in response to bracing. With a larger number of EMG measuring sites, the presence of any brace-induced trunk muscle activity should be detected. Therefore, EMG signals of 11 adolescent idiopathic scoliosis patients who had been undergoing Boston brace treatment for 0.7-3 years were collected during four isometric tasks to evaluate the response of trunk muscles in the minutes following the application of the brace. Twenty-two pairs of bipolar electrodes were used to measure the EMG signals of the main superficial trunk muscles during four isometric tasks. EMG signals of trunk muscles were compared in braced and unbraced conditions. Brace-induced increases in EMG activity were significant in 43% of the individual measurements and in three of the four tasks for the group mean values. Increases were greater in the lumbar area, especially on the convex side of the secondary (lumbar) curve. These results thus suggest that immediately following the application of the brace, significant muscular responses can be observed in some patients.

Abdominal Muscles↗
PubMed2003

Evidence of three-dimensional variability in scoliotic curves.

In the current study, 98 patients with idiopathic scoliosis were selected for analysis. The object of this study was to determine whether three-dimensional variability exists within each class of the King classification, and to evaluate the currently used King classification in its ability to categorize different scolioses adequately. Anteroposterior and lateral radiographs were digitized, and three-dimensional models were reconstructed for each spine. Several parameters were recorded for each individual: age, gender, four Cobb angles, (1) anteroposterior, (2) lateral, (3) maximum (Cobb angle at the plane of maximum deformity), and (4) minimum (Cobb angle at the plane of minimum deformity), and the orientation of the planes of maximum and minimum deformity. Most of the curves were kyphotic, but a small percentage in each class were hypokyphotic or lordotic. This was not seen in the analysis in which the individual King classes were compared. It was seen, however, when the authors reanalyzed the data after having pooled the subjects and reclassified them according to presence or absence of kyphosis. The King classification was shown to be inadequate for describing spinal deformities in three dimensions, because different variants of sagittal spine configurations were seen which can look identical on the anteroposterior view. Therefore, the need for a new three-dimensional classification, which takes this variability into account, is established.

Adolescent↗
PubMed2003

Continuous curve registration as an intertrial gait variability reduction technique.

Timing in peak values shifts slightly between gait trials. When gait data are averaged, part of the standard deviation could be associated with this intertrial variability unless normalization is carried out beforehand. The objective of this study was to determine how continuous curve registration, an alignment technique, can reduce intersubject variability in gait data without altering the original curve characteristics. Gait data were obtained by means of a four-camera high-speed video system synchronized to a force plate. The data for 60 gait trials were collected from 20 young, healthy subjects. Curve registration was applied to hip angular displacement, net moment, and power curves generated in the sagittal plane. Following registration, the peak values increased by an average of 1.2% (0.11 +/- 0.26 degrees) for angular displacement, and by 11.2% (0.11 +/- 0.09 W/kg) for power, while there were no changes for moments. First and second derivatives of the unregistered and registered curves did not display significant differences, and the harmonics were barely affected. Continuous curve registration would thus be an appropriate technique for application prior to any statistical analysis using able-bodied gait patterns.

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

Relations between standing stability and body posture parameters in adolescent idiopathic scoliosis.

STUDY DESIGN: A retrospective study of standing imbalance and body posture in 71 able-bodied girls and subjects with adolescent idiopathic scoliosis was conducted. OBJECTIVE: To test the hypothesis that postural parameters are related to standing stability parameters. SUMMARY OF BACKGROUND DATA: Spinal deformity not only modifies the shape of the trunk, but also changes the relations between body segments affecting posture in scoliotic children. These postural adaptations to the scoliotic curve progression could be linked in part to increased body sway in upright standing. This has not yet been related to specific postural parameters involving the head, trunk, and pelvis in nontreated idiopathic scoliosis. METHODS: The head, trunk, and pelvis orientations of each subject were measured by a Flock of Bird system. An AMTI force platform was used to assess quiet standing stability and to monitor the position and displacement of the center of pressure (COP). The center of mass (COM) excursion was estimated from a biomechanical model using force plate information only. Analyses of variance (ANOVAS) were performed to determine the statistical differences between the scoliotic and nonscoliotic subjects, and backward stepwise multiple regression analyses were performed to identify any correlation between measures of quiet standing stability and body postural parameters RESULTS: The scoliotic group was characterized by a decrease in standing stability. There was an increase in the sway areas measured by the variations of the COP and COM. From the backward stepwise multiple regression analysis, it appears that for the able-bodied girls, the body posture parameters were correlated only with the mean anteroposterior center of pressure (COP(AP)) position. For the scoliotic group, the sway areas and the mean position of the centers of pressure and the COP(AP)-COM(AP) were correlated significantly with body posture parameters. The higher COP-COM differences for the scoliotic group were attributed to a greater neuromuscular demand to maintain standing balance. The coefficients of correlation of the multiple regression analyses ranged from 0.64 to 0.85 for the nonscoliotic group and from 0.55 to 0.72 for the scoliotic group. CONCLUSIONS: The use of backward stepwise multiple correlations highlighted the interaction between several body parameters and their relation to standing stability in both able-bodied girls and scoliotic subjects. The scoliotic group displayed a much larger number of correlations between standing stability and body posture parameters than the nonscoliotic group. Standing imbalance was related to altered body posture parameters measured in the frontal and horizontal planes only. Although the correlation coefficients were relatively high, factors other than body posture parameters appeared related to standing imbalance in adolescent idiopathic scoliosis. These findings support the concept of either a primary or a secondary dysfunction in the postural regulation system of scoliotic subjects.

Adolescent↗
PubMed2002

The effect of the Relton-Hall operative frame on trunk deformity in adolescent idiopathic scoliosis.

The prone operative position affects the geometry of the scoliotic spine. However, the literature provides little information concerning the effect of operative position on the scoliotic trunk geometry. This study compared the trunk deformity of 31 adolescent idiopathic scoliosis patients in two standardized positions: standing and prone on a Relton-Hall frame. The geometry of the trunk was assessed using 11 magnetic sensors placed on anatomical landmarks. Eight geometric indices of the trunk were compared using paired Student t-tests (alpha=0.01). The transverse rotation of shoulders, the coronal rotation of shoulders, the lateral shift of C7 with respect to S1, and the thoracic and lumbar angles of trunk rotation assessed in the operative position did not show any significant change compared to the standing position. Therefore, operative positioning using the Relton-Hall frame did not lead to an overall reduction in the scoliotic trunk deformity. Modifications to the Relton-Hall frame are required for optimal presurgical correction of the scoliotic trunk deformity.

Adolescent↗
PubMed2002

Is Cobb angle progression a good indicator in adolescent idiopathic scoliosis?

STUDY DESIGN: A retrospective follow-up study of spine geometry after posterior instrumentation and fusion for adolescent idiopathic scoliosis (AIS). OBJECTIVES: To evaluate 1) if Cobb angle progression is a reliable indicator of the crankshaft phenomenon; 2) if significant growth of the spine can occur after surgery without the development of a crankshaft phenomenon? SUMMARY OF BACKGROUND DATA: Anterior fusion of the spine is often recommended for skeletally immature scoliotic patients to avoid the risk of a crankshaft phenomenon, a long-term loss of curve correction caused by residual growth of the spine combined with the constraints of a posterior fusion. The crankshaft phenomenon is usually assessed indirectly by documenting progression of the Cobb angle on frontal radiographs. Thus far, no study has directly measured the three-dimensional growth of the spine after surgery in AIS. METHODS: Cobb angle, spine length and spine height were obtained from three-dimensional radiographic reconstructions of the spine in 48 adolescent scoliotic patients undergoing posterior instrumentation and fusion. Measurements were done before surgery, after surgery and at skeletal maturity. A significant growth of the spine was defined as a > or = 10 mm increase in spine length, while a significant curve progression was defined as a > or = 10 degrees increase in Cobb angle at skeletal maturity. RESULTS: In the majority of patients (56%), there was no significant change in spinal length or in Cobb angle measurements at an average 2.4 years post surgery. A crankshaft phenomenon was detected in 6 patients (12%) for which significant increases both in spinal length and Cobb angle measurement were found. Significant curve progression without any change in spine length was noted in 9 patients (19%) while an increase in spine length with no evidence of curve progression was present in 6 patients at last follow-up. CONCLUSION: Spinal growth as indicated by an increase in spinal length can be measured in a significant proportion of adolescents with idiopathic scoliosis after posterior instrumentation and fusion. Some of these study participants will develop a crankshaft phenomenon but Cobb angle progression is not a reliable indicator of this complication, since it may occur without any detectable growth of the spine.

Adolescent↗
PubMed2002

Indices of torso asymmetry related to spinal deformity in scoliosis.

OBJECTIVE: To develop indices that quantify 360 degrees torso surface asymmetry sufficiently well to estimate the Cobb angle of scoliotic spinal deformity within the clinically important 5-10 degrees range. DESIGN: Prospective study in 48 consecutive adolescent scoliosis patients (Cobb angles 10-71 degrees ). BACKGROUND: Scoliotic surface asymmetry has been quantified on the back surface by indices such as back surface rotation (BSR) and curvature of the spinous process line and torso centroid line, though with limited success in spinal deformity estimation. Quantification of 360 degrees torso shape may enhance surface-spine correlation and permit reduced use of harmful X-rays in scoliosis. METHODS: For each patient a 3D torso surface model was generated concurrently with postero-anterior X-rays. We computed indices describing principal axis orientation, back surface rotation, and asymmetry of the torso centroid line, left and right half-areas and the spinous process line. We calculated correlations of each index to the Cobb angle and used stepwise regression to estimate the Cobb angle. RESULTS: Several torso asymmetry indices correlated well to the Cobb angle (r up to 0.8). The Cobb angle was best estimated by age, rib hump and left-right variation in torso width in unbraced patients and by centroid lateral deviation in braced patients. A regression model estimated the Cobb angle from torso indices within 5 degrees in 65% of patients and 10 degrees in 88% (r=0.91, standard error=6.1 degrees ). CONCLUSION: Consideration of 360 degrees torso surface data yielded indices that correlated well to the Cobb angle and estimated the Cobb angle within 10 degrees in 88% of cases. RELEVANCE: The torso asymmetry indices developed here show a strong surface-spine relation in scoliosis, encouraging development of a model to detect scoliosis magnitude and progression from the surface shape with minimal X-ray radiation.

Adolescent↗
PubMed2002

Comparison of Cobb angles measured manually, calculated from 3-D spinal reconstruction, and estimated from torso asymmetry.

While scoliotic spinal deformity is traditionally measured by the Cobb angle, we seek to estimate scoliosis severity from the torso surface without X-ray radiation. Here, we measured the Cobb angle in three ways: by protractor from postero-anterior X-ray, by computer from a 3-D digitized model of the vertebral body line, and by neural-network estimation from indices of torso surface asymmetry. The estimates of the Cobb angle by computer and by neural network were equally accurate in 153 records from 52 patients (standard deviation of 6 degrees from the Cobb angle, r=0.93), showing that torso asymmetry reliably predicted spinal deformity. Further improvements in predictive accuracy may require estimation of other 3-D indices of spinal deformity besides the Cobb angle with its wide measurement variability.

Adolescent↗
PubMed2002

Genetic algorithm-neural network estimation of cobb angle from torso asymmetry in scoliosis.

Scoliosis severity, measured by the Cobb angle, was estimated by artificial neural network from indices of torso surface asymmetry using a genetic algorithm to select the optimal set of input torso indices. Estimates of the Cobb angle were accurate within 5 degrees in two-thirds, and within 10 degrees in six-sevenths, of a test set of 115 scans of 48 scoliosis patients, showing promise for future longitudinal studies to detect scoliosis progression without use of X-rays.

Abdomen↗
PubMed2002

Three-dimensional imaging for the surgical treatment of idiopathic scoliosis in adolescents.

Scoliosis is not simply a lateral deviation of the spine but is a complex deformity of the entire trunk. Recent advances in 3-dimensional (3-D) imaging have improved our understanding of the 3-D nature of adolescent idiopathic scoliosis (AIS) and have resulted in the development of a new generation of spinal instrumentation. Stereophotogrammetry, computed tomography, magnetic resonance imaging and surface topography all have their specific 3-D applications and relevance in the clinical management of AIS. In the near future, novel 3-D imaging applications will provide tools to guide the surgeon in the planning, performance and evaluation of increasingly sophisticated and less invasive surgical procedures, thus improving the outcome of surgical treatment for AIS.

Adolescent↗
PubMed2002

Relationships between strap tension, interface pressures and spine correction in brace treatment of scoliosis.

The Boston brace has been shown to efficiently prevent scoliosis curve progression. However, it rarely achieves complete 3-D correction; its adjustment being often empirical and its biomechanical modes of action still remaining poorly understood. This study investigates the in-brace spinal shape (correction) in relationship with the patient's out-of-brace deformation, and the adjustment parameters of the brace, namely the strap tensions and the equivalent forces calculated at the patient-brace interface. Many of the observed relationships illustrate the fact that the in-brace spinal shape is strongly related to the characteristics of the patient's out-of-brace deformation. The pattern of pressure distribution as described by the equivalent forces computed in the thoracic, lumbar, pelvic and sternal regions has important effect on the in-brace Cobb angles, lumbar lordosis, frontal and sagittal imbalances and the apical axial rotations. The complex role of the strap tension on the correction has not been explained and needs further investigation. This project has the potential to give insight into the biomechanical effects of brace treatment by providing a statistical model leading to more rational and personalized brace adjustments.

Adolescent↗
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

Intraoperative tracking of the trunk during posterior instrumentation of the scoliotic spine: a feasibility study.

Scoliosis involves spine and trunk deformities. However, during posterior instrumentation of the scoliotic spine, only the exposed spine is currently seen or tracked using navigation systems. A technique for intraoperative tracking of the trunk was developed in order to optimize the surgical correction of the scoliotic trunk deformity. The feasibility of this technique was assessed by comparing the trunk geometry between 19 normal and 21 scoliotic subjects, using an experimental set-up simulating the position adopted during posterior scoliosis surgery. Eleven magnetic sensors placed on anatomical landmarks of the trunk were used to compute nine geometric indices. The geometric indices were closer to zero for normal subjects. Therefore, indices approaching zero during the surgical manoeuvres would indicate a reduction of the trunk asymmetry. Only three of the nine indices were significantly different between normal and scoliotic subjects. This result indicates that the positioning of the subjects on the Relton-Hall frame tends to "normalize" the trunk geometry since the standing position gives more significant differences between normal and scoliotic subjects. The real-time quantification of the trunk geometry during surgical correction of scoliosis may allow the surgeon to improve the correction of both spinal and trunk deformities or to optimize the positioning of the patients on the operating table.

Adolescent↗
PubMed2002

Prediction of spinal deformity in scoliosis from geometric torsion.

The shape of a curved line that passes through thoracic and lumbar vertebrae is often used to study spinal deformity with measurements in "auxiliary" planes that are not truly three-dimensional (3D). Here we propose a new index, the geometric torsion, which could uniquely describe the spinal deformity. In this study we assessed whether geometric torsion could be effectively used. to predict spinal deformity with the aid of multiple linear regression. Anatomical landmarks were obtained from multi-view radiographic reconstruction and used to generate 3D model of the spine and rib cage of 28 patients. Fourier series best fitted to the vertebral centroids approximated the spinal shape. For each patient, spinal deformity indices were computed. Torsion was calculated and 20 derived parameters were recorded. Torsion inputs were used in a multiple linear regression model for prediction of key spinal indices. The primary clinical Cobb angle (mainly thoracic) was predicted well, with r=0.89 using all 20 inputs of torsion or r=0.83 using just two. Torsion was also well related to the orientation of plane of maximal deformity (r=0.87). Torsion was less accurate but still significant in predicting maximal vertebral axial rotation (r=0.77). This preliminary study showed promising results for the use of geometric torsion as an alternative 3D index of spinal deformity.

Adolescent↗
PubMed2002

Relation between the pelvis and the sagittal profile in adolescent idiopathic scoliosis: the influence of curve type.

Previous studies have shown a correlation between pelvic parameters and the lumbar lordosis in normal subjects and in scoliotic adults. This study investigates the relationship between pelvic and spinal geometries in the sagittal plane for adolescent idiopathic scoliosis (AIS) patients having various curve types. The study group was composed of 129 AIS patients classified according to their curve type: King I, King II, King III or lumbar curve. The SpineView software (Surgiview, France) was used to compute five parameters on sagittal x-rays: thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI). The TK was significantly lower for King I, II and III curves as compared to the lumbar curves. The LL tended to be higher for patients having a major lumbar scoliotic (King I and lumbar) curve, although not significantly. No significant change between the groups was observed for the SS, PT and PI. The PI was significantly correlated to the LL, SS and PT for all groups. The SS was strongly related to the LL in all cases. However, no relationship was found between the TK and the LL in any group. This study showed that the TK mostly depends on the thoracic scoliotic curve and therefore on the shape and orientation of the vertebrae, which explains that many King I, II and III patients are hypokyphotic. Conversely, the LL is mainly influenced by the pelvic configuration. Since the pelvic parameters are similar for all groups, these parameters are not likely to be important in the development of a specific type of scoliotic curve.

Adolescent↗