Development of a vertebral endplate 3-D reconstruction technique.

The increase of low back problems has stimulated the development of different analysis and evaluation techniques. Among these methods, the direct linear transformation (DLT) technique is commonly used to reconstruct the spine in three dimensions by means of its known image coordinates on radiographs. Despite its efficiency and precision, general reconstruction of some standard anatomical landmarks (7-11) does not give all the necessary data for a detailed analysis of the intrinsic geometrical characteristics of lumbar vertebrae. Thus, in order to obtain such geometrical information a three-dimensional (3-D) reconstruction vertebral endplate contour technique has been developed. This technique involves 1) iterative optimization and reconstruction processes of the vertebral endplate centroid and 2) 3-D reconstruction of vertebral endplate contour. Validation based on mathematical simulations demonstrated that two or three iterations are necessary to correct (within 2 mm) the endplate centroid position for simulated error higher than 10 mm. Other validations based on 3-D reconstructions of a chamfered tube and a dry vertebra contours of known dimensions have given mean errors of 2 mm. Application on a healthy subject demonstrated the potential of this 3-D reconstruction technique. Finally, 3-D data obtained on vertebral endplates would allow the development of new clinical measurements that could be used to evaluate the lumbar spine geometrical behavior and orthoses biomechanical effects.

Application of a stereoradiographic method for the study of intervertebral motion.

A technique of three-dimensional reconstruction along with a method of adjusting anatomic landmarks were used to evaluate movements of the lumbar vertebrae of living subjects. Altogether, 16 subjects took part in the experiment. Each subject was radiographed in an upright standing position, and in each of the following positions: flexion, extension, axial rotation, and lateral bending. The results of the three-dimensional reconstruction procedures and the correction of anatomic landmarks show an adequate level of accuracy for experimentation with living subjects. The mean relative displacements of lumbar vertebrae in rotation are 10 degrees of flexion, 3 degrees of extension, 5 degrees of lateral bending, and 1 degree of axial rotation.

Combined single stage anterior and posterior osteotomy for correction of iatrogenic lumbar kyphosis.

Fifty-four patients were treated by a standardized single stage anterior opening wedge and a posterior closing extension wedge osteotomy for back pain associated with postoperative loss of lumbar lordosis (iatrogenic flat back syndrome). Presenting complaints were fatigue, pain and a stooped posture. Etiological factors were, in descending order of frequency, distraction instrumentation with the lower end at the L5 or S1 vertebra, thoracolumbar junction kyphosis greater than 15 degrees, especially if associated with a hypokyphotic thoracic spine, and degenerative changes above and below a previous fusion. Kostuik-Harrington instrumentation was used anteriorly for the opening wedge and Dwyer cables and screws together with a midline plate were used posteriorly for the closing extension osteotomy. Malunion occurred in three patients, one requiring recorrection. Pain relief occurred in 48 (90%). Neurological complications occurred in two patients, one with permanent deficient. Follow-up averaged 4 years. Average preosteotomy lordosis L1-S1 was 21.5 degrees and was restored to 49 degrees (equal to the lordosis before the initial surgery) for an average correction of 29 degrees, (range 24 degrees to 63 degrees). Prevention of this complication can be accomplished by maintaining normal lordosis at the time of initial surgery.

Degeneration of the human lumbar spine ligaments. An ultrastructural study.

The fine structural alterations in human lumbar spine ligaments were studied in tissue samples obtained from 8 young patients operated upon for idiopathic scoliosis and from 10 adult patients operated upon for herniated discs. The ultrastructure of the scoliotic ligaments was found to be normal. The majority of cells encountered were the fibroblastic-like cells. The collagen-proteoglycans interaction was similar to that described in other normal soft tissues. However, two forms of degenerative changes were demonstrated in posterior ligaments of patients with herniated discs. Metaplasia of ligamentous tissue into fibrocartilage was a common finding. The fibroblasts were replaced by chondrocytes. A few cells which had suffered necrosis were found. Alterations in the collagen-proteoglycans arrangement were also evidenced. This form of degeneration resembled that commonly associated with wear and tear phenomena. A second form of degeneration due to ageing was found to coexist with the aforementioned alterations.

Three-dimensional evaluation of lumbar orthosis effects on spinal behavior.

The effects of the lumbosacral Lumbostab orthosis on intervertebral mobility, spinal geometry, and the geometrical deformations of discs have been investigated with a three-dimensional (3-D) reconstruction technique of the lumbar spine. Positions studied are neutral standing, maximal flexion, extension, left lateral bending, and left axial rotation. Results from this preliminary study indicate that the orthosis has a tendency to reduce vertebral mobility and discal deformations mainly at the upper segments (L1-L3), while it seems to increase vertebral displacements and discal deformations at the lower levels.

Surgical treatment of post-traumatic kyphosis: a report of 16 cases.

Thoracic and lumbar spine fractures may lead to symptomatic progressive kyphosis for which surgery remains a controversial treatment. Sixteen patients with kyphosis were treated surgically at the Sacré-Coeur Hospital in Montreal between 1979 and 1985. The mean follow-up was 38 months. Initially, treatment of the fractures varied. On average the post-traumatic kyphosis was surgically corrected 34 months later. The corrective procedure consisted of staged anterior and posterior fusion with instrumentation (six patients), posterior fusion with instrumentation (five), staged anterior fusion, posterior osteotomy and fusion with instrumentation (four), posterior osteotomy and fusion with Harrington instrumentation (one). Anterior decompression was also performed in 5 of the 10 patients who had anterior fusion. There was no major perioperative complication. Pain was relieved in 13 patients and 9 of 11 had substantial neurologic improvement. Two patients had nonunion of posterior grafts, but these united after revision. The mean loss of correction in the early postoperative period was 3.5 degrees. The authors conclude that surgical treatment of post-traumatic symptomatic progressive kyphosis is effective and safe.

[Study of the microscopic structure of the posterior ligaments of the lumbar spine]. / Etude de la structure microscopique des ligaments postérieurs du rachis lombaire.

Biopsies of supraspinous ligaments (SSL), interspinous ligaments (ISL) and ligamenta flava (LF), removed at operation from 12 patients aged from 17 to 77 years, were examined by light microscopy, scanning electron microscopy and transmission electron microscopy. The structure of normal ligaments was first established, and then a comparison between normal and pathological ligaments was made. It was found that the SSL and ISL were composed of collagen, while the LF contained predominantly elastic fibres. In normal ligaments, a helical arrangement of the collagen fibrils was found. The fascicles were characterized by a regular waviness. Proteoglycan filaments were demonstrated in the three types of ligaments, forming a regular interfibrillar linking between adjacent collagen fibrils. Degenerative changes were found in most of the ligaments obtained from patients with disc herniation. On light microscopy, metaplasia into fibrocartilage and calcification was commonly seen. Ultrastructurally, the flattened fibroblasts were replaced by chondrocytic cells, and an accumulation of proteoglycans with a random arrangement and a cellular necrosis was encountered. The relevance of these degenerative changes to the mechanical properties and to low back pain is discussed.