Charles-Hilaire Rivard

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 surgeons 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 systems 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°± 1.2° were calculated. Conclusions Results suggested the proposed system could be useful for pedicle detection and assessing the intravertebral location of drilled hole. The proposed system could be used for many different orthopedic procedures where structures are hidden from the surgeons view.

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

STUDY DESIGN An experiment was conducted to investigate the effect of wearing a weight lifting belt on the endurance and fatigue characteristics of the extensor muscles of the spine. OBJECTIVE To evaluate the effectiveness of back belts in preserving the endurance characteristics of the spinal musculature. SUMMARY OF BACKGROUND DATA Previous studies have investigated the use of back belts in increasing intra-abdominal pressure and thus increasing the stabilization of the spine. Other studies have looked at the association of low back disability and wearing back belts. No study has examined the relationship between wearing back belts and measures of spinal muscle fatigue and endurance. METHODS Thirteen male industrial workers performed a lifting and lowering task from the floor to a 76.2 cm height at 4.3 min-1 2 days a week for 4 weeks. The load was psychophysically determined and averaged 28.1 kg for a total of 28.9 metric tons moved in 4 hours. Subjects lifted for 1, 2, 3, and 4 hours, respectively, for the first 4 days of the experiment. These were considered training days. During the last 4 days, subjects lifted for 4 hours per day; 2 days with a back belt, and 2 days without a back belt. Maximum isokinetic endurance of the extensors was measured for 50 repetitions (5 sets of 10 repetitions) at the end of 4 hours of lifting. Median frequencies of the electromyographic signal from six locations over the back extensors were measured for 30 seconds at 80% of maximum isometric voluntary contraction after 4 hours of lifting. RESULTS There were no significant differences in maximum isokinetic endurance, or in the slope of median frequency, between lifting with a back belt and lifting without a back belt. Similarly, a modified Borg scale and a postexperiment survey question were unable to distinguish between wearing a back belt and not wearing a back belt. CONCLUSION There were no significant differences in maximum isokinetic endurance and electromyographic spectral parameters of the back extensor muscles as a result of wearing a back belt during heavy lifting and lowering tasks.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.

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 Cotrel–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.

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.

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 Sheldons 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.

Acute systematic and variable postural adaptations induced by an orthopaedic shoe lift in control subjects

Abstract A small leg length inequality, either true or functional, can be implicated in the pathogenesis of numerous spinal disorders. The correction of a leg length inequality with the goal of treating a spinal pathology is often achieved with the use of a shoe lift. Little research has focused on the impact of this correction on the three-dimensional (3D) postural organisation. The goal of this study is to quantify in control subjects the 3D postural changes to the pelvis, trunk, scapular belt and head, induced by a shoe lift. The postural geometry of 20 female subjects (x– = 22, σ = 1.2) was evaluated using a motion analysis system for three randomised conditions: control, and right and left shoe lift. Acute postural adaptations were noted for all subjects, principally manifested through the tilt of the pelvis, asymmetric version of the left and right iliac bones, and a lateral shift of the pelvis and scapular belt. The difference in the version of the right and left iliac bones was positively associated with the pelvic tilt. Postural adaptations were noted to vary between subjects for rotation and postero-anterior shift of the pelvis and scapular belt. No notable differences between conditions were noted in the estimation of kyphosis and lordosis. The observed systematic and variable postural adaptations noted in the presence of a shoe lift reflects the unique constraints of the musculoskeletal system. This suggests that the global impact of a shoe lift on a patient’s posture should also be considered during treatment. This study provides a basis for comparison of future research involving pathological populations.

Cell-based screening test for idiopathic scoliosis using cellular dielectric spectroscopy.

Study Design. A cell-based assay was developed to identify asymptomatic children at risk of developing idiopathic scoliosis (IS) and to stratify IS patients at an earlier stage in order to better predict their clinical outcome. Clinical validation of this assay was performed by testing IS patients at different stages, healthy control subjects, and asymptomatic offspring, born from at least one scoliotic parent, who are considered at risk of developing this disorder. Objective. Our goal was to develop and validate a clinical test for IS using cellular dielectric spectroscopy (CDS) and peripheral blood mononuclear cells (PBMCs). Summary of Background Data. We have previously demonstrated the occurrence of a melatonin signaling dysfunction in osteoblasts obtained from severely affected IS patients using a cAMP assay. This led us to stratify IS patients into 3 functional subgroups. Methods. A group of 44 patients with IS was compared with 42 healthy control subjects and 31 asymptomatic at-risk children. PBMCs were obtained after centrifugation on a Ficoll-gradient. Melatonin signal transduction was measured by CDS in the presence of varying concentrations of melatonin or iodomelatonin. Results. Osteoblasts from distinct functional subgroups were retested using CDS, allowing their classification into the same functional subgroups with both ligands as initially demonstrated using a cAMP assay. Clinical data obtained with CDS and PBMCs showed 100% specificity and 100% sensitivity because melatonin signaling impairment was observed only in IS patients and not in healthy controls. Assessment of the risk of developing a scoliosis in asymptomatic children was determined by CDS in 33% of asymptomatic children at risk, which was confirmed clinically within 24 months. Conclusion. This cell-based assay can serve as a presymptomatic screening test to identify asymptomatic children at risk of developing IS and may be used to improve stratification of patients, which in turn allow clinicians to predict their clinical outcome. Moreover, this functional blood test is advantageous because it can be performed without prior knowledge of specifically mutated genes causing IS.

Pelvis morphology, trunk posture and standing imbalance and their relations to the Cobb angle in moderate and severe untreated AIS.

Adolescent idiopathic scoliosis (AIS) is the most common form of scoliosis and usually affects young girls. Studies mostly describe the differences between scoliotic and non-scoliotic girls and focus primarily on a single set of parameters derived from spinal and pelvis morphology, posture or standing imbalance. No study addressed all these three biomechanical aspects simultaneously in pre-braced AIS girls of different scoliosis severity but with similar curve type and their interaction with scoliosis progression. The first objective of this study was to test if there are differences in these parameters between pre-braced AIS girls with a right thoracic scoliosis of moderate (less than 27°) and severe (more than 27°) deformity. The second objective was to identify which of these parameters are related to the Cobb angle progression either individually or in combination of thereof. Forty-five scoliotic girls, randomly selected by an orthopedic surgeon from the hospital scoliosis clinic, participated in this study. Parameters related to pelvis morphology, pelvis orientation, trunk posture and quiet standing balance were measured. Generally moderate pre-brace idiopathic scoliosis patients displayed lower values than the severe group characterized by a Cobb angle greater than 27°. Only pelvis morphology and trunk posture were statistically different between the groups while pelvis orientation and standing imbalance were similar in both groups. Statistically significant Pearson coefficients of correlation between individual parameters and Cobb angle ranged between 0.32 and 0.53. Collectively trunk posture, pelvis morphology and standing balance parameters are correlated with Cobb angle at 0.82. The results suggest that spinal deformity progression is not only a question of trunk morphology distortion by itself but is also related to pelvis asymmetrical bone growth and standing neuromuscular imbalance.

Relationship between gibbosity and Cobb angle during treatment of idiopathic scoliosis with the SpineCor brace.

Abstract The objective of this study was to quantify the relationship between gibbosity and spinal deformation expressed by the angle of Cobb before and during treatment with a brace for different classes of idiopathic scoliosis patients. As part of the standard treatment with the Dynamic Corrective Brace (SpineCor), 89 idiopathic scoliosis patients underwent an initial radiological examination and gibbosity measurement with a scoliometer wearing and not wearing the brace. The 89 patients were classified in relation to the apex of the scoliosis curves: thoracic (n = 29); thoracolumbar (n = 40); lumbar (n = 7) and double (n = 13). With the dynamic corrective brace, the patients showed a mean decrease of 8.3° for the major Cobb angle, and a mean decrease of 2.3° for their gibbosity. There was a significant positive relationship between gibbosity and Cobb angle with and without the brace for the thoracic and thoracolumbar curves. A linear regression analysis identified a small mean estimation error for the thoracic curves (7.4° no-brace; 2.7° with brace) and thoracolumbar curves (5.2° no-brace; 5.3° with brace), indicating a predictive potential of the scoliometer. The measure of gibbosity with the scoliometer provides a fairly reliable estimation of Cobb angle at the initial clinical examination of a scoliosis patient. However, when initial Cobb angle and gibbosity are considered, the measure of gibbosity when wearing a brace provides the clinician with a highly reliable estimation of the Cobb angle while in a brace. This relationship also exists for the follow-up with a brace, permitting a judgement of the patient’s evolution under the treatment with SpineCor.

Iliac crest orientation and geometry in able-bodied and non-treated adolescent idiopathic scoliosis girls with moderate and severe spinal deformity

PurposeTo identify pelvic rotation and/or distortion in able-bodied and untreated AIS girls with moderate and severe scoliosis and verify association of pelvic morphological changes with Cobb angle increase.MethodsThe 3D coordinates of nine anatomic bony landmarks were identified to estimate pelvic orientation using a Flock of Birds system. The distances between the first sacral vertebral body (S1) and each of the eight iliac spine landmarks in all three planes were calculated to identify pelvic distortion. Analysis of variance was used to assess pelvic orientation and determine pelvic distortion. Pearson coefficients of correlation were used to identify any relationships between Cobb angle and pelvic morphological parameters.ResultsPelvic orientation was similar in able-bodied and scoliotic girls regardless of the severity of the spinal deformity. Significant differences were observed in pelvic morphology between AIS with severe untreated scoliosis and those with a moderate scoliosis for the right anterosuperior iliac spines (ASIS), the tip of the superior iliac crest (TSIC) and the widest tip of the iliac crest (WTIC) widths from S1. Statistically significant correlations were observed between the Cobb angles and the iliac crest distances measured from S1.ConclusionsDifferences in iliac spine geometries occurred in the transverse plane correlating to Cobb angles which suggest altered bone growth in AIS girls. Such findings could indicate right thoracic spinal deformity as a result of pelvic torsion.