Traumatic rotatory displacement of the lower cervical spine.

The authors describe the classification for traumatic rotary injuries of the cervical spine. The classification is based on a review of 306 severe lower cervical spine injuries observed in 255 patients between 1980 and 1994. Traumatic rotatory displacements (TRD) represented 39% of the 306 severe injuries. Three different lesions were observed: unilateral facet fractures, fracture-separation of the articular pillars, and unilateral facet dislocations.

[Percutaneous osteosynthesis of pelvic fractures with CT control]. / Ostéosynthése percutanée des fractures du bassin sous contrôle tomodensitométrique.

Pelvis fractures, most often multiple, are frequently unstable. Orthopedic treatment is hardly bearable (traction in bed sometimes up to 45 days), the open reduction and internal fixation (ORIF) is heavy. Percutaneous fluoroscopy guided fixation lacks precision in depth. Percutaneous screw fixation with CT scan control answers these drawbacks and represents a quick solution, with few hazard when performed by a trained team and allows a very early resumption of standing.

[Triple and quadruple images in scan of fractures of the articular processes of the lower cervical spine]. / "Triple et quadruple images" au scanner des fractures des apophyses articulaires du rachis cervical inférieur.

The authors describe the triple and quadruple image aspects of the articular pillar, which are encountered respectively in one-sided uni- and biarticular fractures of the lower cervical spine, and they have analysed these images' specificity from a retrospective study. This study concerned 52 cases out of a group of 220 patients hospitalised between 1979 and 1992, with an injury of the lower cervical spine and who underwent a CT-scan examination in addition to the conventional radiographic check-up. Among a total of 70 lesions, 14 uniarticular and 4 biarticular one-sided fractures were recorded. All presented these characteristic aspects, formed by the separated fragment of the articular process; the unseparated component of the process and, concerning the triple image the intact process, or concerning the quadruple image the fragments of the second fractured process. An only case of a transisthmian fracture associated with a fracture of the lower articular process showed a similar aspect, which underlines the high specificity of these images.

Pull-out strength of sacral implants using Cotrel-Dubousset fixation devices.

Our aim was to determine the bone structure of the sacrum and the optimum location in the sacrum for the insertion of lumbosacral screws in osteosynthesis. Anatomical tests were performed on mortuary specimens at the Medical School in Nice, France, on frozen sections of sacrum and in computed tomographic (CT) sections with 3-dimensional reconstruction. Density assessment of different structures from the first and second sacral vertebrae (S1, S2) was performed and expressed in Hounsfield units. The ala and the lateral part of S1 contained yellow marrow forming a fatty mass bounded by the cortex of the sacroiliac joint at the linea terminalis and by the cancellous bone in the pedicles and the body of S1 and S2. These studies were undertaken prior to the experimental tests. The experimental tests were made using Cotrel-Dubousset instrumentation to determine the pull-out strength of sacral screws with a 7-mm diameter by assessing pull-out strengths of paired screws arranged either unilaterally with one screw in S1 and one in S2 or symmetrically to the left and right in S1. The devices demonstrating the best pull-out strength were the "corporopedicular" screw in S1 and the caudal lateral oblique screw in S1 passing through the sacroiliac joint. The paired screws with the best pull-out strength were those which included a corporopedicular screw in S1.

Anatomic and experimental basis for the insertion of a screw at the first sacral vertebra.

The authors present the anatomic and experimental basis of an original technique for screwing at the first sacral level employed in lumbosacral fusion. The anatomic studies were based on specimens from the anatomy museum, frozen sections of the sacrum and CT examinations with three-dimensional reconstruction and assessment of the density of the different structures of S1 in Hounsfield units (HU). The findings were that the ala and lateral portions of S1 contain yellow marrow forming what amounts to a fatty sphere bounded by the cortical bone of the sacroiliac joint, the linea terminalis and the spongy bone of the pedicles and of the body of S1. The experimental study was made by avulsion of sacral screws (system of Cotrel Dubousset), each of 7mm diameter. No screw perforated the sacral cortex. Three directions were tested. The insertion of a screw through the pedicle and body of S1 is advised, with the point of insertion below and lateral to the articular process of S1 and an oblique course forward and inward at an angle of 10 degrees to the sagittal plane. This internal obliquity is limited by the posterior prominence of the iliac ala.

[Osteosynthesis of the spine using Cotrel-Dubousset instrumentation. Contribution of x-ray computed tomography with 3D reconstruction]. / Ostéosynthèse du rachis par matériel de Cotrel-Dubousset (C-D). Apport du scanner avec reconstruction 3D.

3D reconstruction is of a great interest in the study of the osteosynthesis of the spine by C-D material, where MRI is impossible and CT usually artifacted. The results obtained by 3D reconstruction allow visualization of osseous, extra osseous (disks, ligaments...) and metallic structures.