Aurélien Courvoisier

3D reconstruction of rib cage geometry from biplanar radiographs using a statistical parametric model approach

Rib cage 3D reconstruction is an important prerequisite for thoracic spine modelling, particularly for studies of the deformed thorax in adolescent idiopathic scoliosis. This study proposes a new method for rib cage 3D reconstruction from biplanar radiographs, using a statistical parametric model approach. Simplified parametric models were defined at the hierarchical levels of rib cage surface, rib midline and rib surface, and applied on a database of 86 trunks. The resulting parameter database served to train statistical models which were used to quickly provide a first estimate of the reconstruction from identifications on both radiographs. This solution was then refined by manual adjustments in order to improve the matching between model and image. Accuracy was assessed by comparison with 29 rib cages from CT scans in terms of geometrical parameter differences and in terms of line-to-line error distance between the rib midlines. Intra and inter-observer reproducibility was determined for 20 scoliotic patients. The first estimate (mean reconstruction time of 2 min 30 s) was sufficient to extract the main rib cage global parameters with a 95% confidence interval lower than 7%, 8%, 2% and 4° for rib cage volume, antero-posterior and lateral maximal diameters and maximal rib hump, respectively. The mean error distance was 5.4 mm (max 35 mm) down to 3.6 mm (max 24 mm) after the manual adjustment step (3 min 30 s). The proposed method will improve developments of rib cage finite element modelling and evaluation of clinical outcomes.

Evaluation of a Three-Dimensional Reconstruction Method of the Rib Cage of Mild Scoliotic Patients

STUDY DESIGN Validation study. OBJECTIVE To evaluate a method of 3-dimensional (3D) reconstruction of the rib cage in a population of scoliotic patients. SUMMARY OF BACKGROUND DATA Evaluation of the thoracic cage clinical parameters would be helpful in the management of spinal deformities. METHODS Biplanar X-rays were performed using the EOS system and the rib cage was reconstructed using a previously developed semi-automated method. Thoracic parameters were calculated from the 3D reconstructions: volume, frontal and sagittal diameters, 3D spinal penetration index (SPI), thoracic index, and rib hump. To test accuracy, the authors constructed biplanar projections from 3 computed tomography scans and then used these projected X-rays as material for stereoradiographic reconstructions. The models were then compared with volumetric objects reconstructed from these 3 computed tomography scans. To test intra-observer and interobserver reproducibility, 22 chests (mean Cobb angle, 28° [range, 17° to 45°]) were reconstructed twice by 3 operators. The 95% confidence interval was calculated for the study parameters. RESULTS The mean signed point to surface distance was -1.6 mm. Interobserver reproducibility was 9 mm for maximum anteroposterior and lateral diameters, <0.8% for SPI, 5° for rib hump, .02 for thoracic index, and 450 cm3 for volume. CONCLUSIONS The results of the reproducibility study were satisfactory. The 95% confidence interval was <6% for the transverse diameters and <10% for volume and SPI. The reported method of 3D reconstruction of the rib cage provides accurate and reproducible determinations of the investigated thoracic parameters in scoliotic patients.

The change on vertebral axial rotation after posterior instrumentation of idiopathic scoliosis

PurposeAgreement between the correction objectives and the instrumentation strategies remains controversial in idiopathic scoliosis. Most studies have focus on the frontal and sagittal plane. The goal of this study was to evaluate the change on vertebral axial rotation after posterior instrumentation in fused and unfused segments.MethodsFourteen patients operated on for idiopathic scoliosis were prospectively included. Fusion and instrumentation were done by posterior approach. All patients had a pre-operative and a 10-day post-operative radiological evaluation with the EOS system. Axial orientation of the vertebrae with special interest to the apical, junctional, and unfused areas was obtained thanks to the reconstruction software.ResultsMean apical vertebra axial rotation statistically decreased from 21° pre-operatively to 13° post-operatively. But, there were no statistically significant differences between pre-operative and post-operative mean axial intervertebral rotations in the main curve and axial rotation of the non-instrumented lower counter curve.Conclusions3D analysis of the spine in standing position is a great advancement for post-operative analysis of adolescent idiopathic scoliosis (AIS) corrections. This study confirmed that actual instrumentations are able to achieve “en bloc” 3D correction of the spine but not intervertebral axial rotation correction.

A New Paradigm for the Management of Thoracolumbar Pediatric Spine Traumas.

Objectives The transient breath holding sign (TBHS) is a clinical sign often associated with magnetic resonance imaging (MRI) spine traumatic lesions. The aims of this study were to prospectively evaluate the TBHS in the detection of thoracolumbar lesions in a large cohort of children and to establish a comprehensive strategy on the use of MRI in spine traumas in children. Study Design All conscious 5- to 16-year-old patients admitted for a spine trauma in our institution were prospectively included in the study. All patients were asked for the TBHS and underwent a full spine MRI. Sensitivity and specificity of the TBHS were derived from the confusion matrix. All MRI lesions were analyzed and classified. Results One hundred ninety-eight patients were included. The sensitivity of the TBHS was 92%, the specificity was 83%, the positive predictive value was 83%, and the negative predictive value was 91%. The x-rays missed 67% of the vertebrae injured in the MRI. The MRI lesions consisted in an upper end plate injury, in the sagittal plane only, in 90% of the cases. The vertebral canal and the spinal cord were never injured. Conclusions This study confirms that the TBHS is a relevant clinical tool that should be added in the routine questionnaire after any trauma at admission. Magnetic resonance imaging should be restricted to patients with a TBHS positive at admission. A single T2 Short T1 Inversion Recovery (STIR) sagittal sequence seems sufficient to make the diagnosis and could replace the use of standard x-rays in pediatric spine traumas.

Osteochondrosis of the medial malleolar epiphysis: A case report and review of the literature

Highlights • Presentation and management of medial malleolar osteochondrosis based on our• experience and a complete literature review.• All ossification centres are predisposed to develop osteochondrosis: we report a rare case of this painful condition.• The first review of all described cases of medial malleolar osteochondrosis.• In a pediatric ankle pain medial malleolar osteochondrosis should be considered in the differential diagnosis.• A complete clinical and radiological description of a rare case of medial malleolar osteochondrosis.

A thoracic spinal bone giant cell tumor in a skeletally immature girl. A case report and literature review

PurposeGiant cell tumors (GCT) are benign primary bone tumors, locally aggressive, affecting in long bones in young adults during the third decade. It is rare to experience this lesion in skeletally immature patients. GCT are related to a risk of local recurrence and malignant transformation.MethodWe report a rare case of a giant cell tumor of the thoracic spine in a skeletally immature girl presenting with a painful right scoliosis.ResultsMRI, CT scan, and bone scintigraphy were discordant and the percutaneous biopsy non-contributive.ConclusionA marginal “en bloc” resection was performed and revealed the GCT. Based on a literature review, the diagnosis and the surgical management of this case are discussed.

Vertebroplasty for vertebral hemangioma in children: a report of two cases with 2-year follow-up

PurposeTo describe two cases of a dorsal vertebral hemangioma diagnosed in a 12- and 14-year-old child successfully treated with vertebroplasty.MethodCases reports.ResultsTwo cases of aggressive vertebral hemangiomas were diagnosed and treated in two independent institutions. Percutaneous vertebroplasty was then decided. Bipedicular vertebroplasty was performed under general anesthesia, under biplanar fluoroscopic guidance. The injection of acrylic cement filled the entire vertebral body without significant leakage. At last follow-up, the clinical and radiographic outcome was very good. In one patient, last control radiographs showed a gap between the end plates and the cement, spinal growth seemed to have resumed.ConclusionVertebral hemangioma is rare in pediatric patients, and its diagnosis requires meticulous and regular clinical examinations and a combination of imaging studies, particularly an MRI and a CT scan, which can assess the aggressiveness of the lesion. Vertebroplasty seems to be an effective and safe treatment of this benign tumor in children with stable outcome at 2-year follow-up. Spinal growth may resume despite the aggressiveness of both the tumor and the treatment.

Congenital lumbar kyphosis with skin ulceration and osteomyelitis in a myelomeningocele child: a case report

IntroductionKyphosis is a frequent problem in children with spina bifida, and this deformity may cause different complications as respiratory insufficiency, bowel dysfunction, and skin ulcers.Case reportWe report on a 13-year-old myelomeningocele male with a lumbar kyphoscoliosis associated to a septic skin ulceration that resulted in an acute sepsis. An X-ray revealed a kyphosis of 110° and a scoliosis of 25° between T9 and L5. The wound and blood cultures showed Staphylococcus aureus colonization, and an appropriate antibiotic therapy was started. An MRI showed a wedged vertebra at T12, a laminae defects from T8 to the sacrum, and a spondylitis at T12-L1. Ulcer resection and kyphectomy from T12 to L3 were performed “en bloc,” and the spine was instrumented fromT7 to S1. After the surgery, the kyphosis was corrected to 10°, and the scoliosis was corrected to 0°. At an 18-month follow-up, a solid bony fusion was obtained, and no recurrence of skin ulcer was reported.ConclusionAntibiotherapy associated to one-step “en-bloc” surgical debridement and kyphectomy should be considered as a valid option to eradicate the infection and to correct the spine deformity in kyphosis due to myelomeningocele associated to septic skin ulcer and spondylitis.