THE GLOBAL TILT: EVALUATION OF A PARAMETER CONSIDERING THE GLOBAL SPINOPELVIC ALIGNMENT.

PURPOSE: Regarding the close interaction between the spinal balance and the pelvis orientation no parameter is routinely used to describe and to evaluate the global spinopelvic balance, taking into account simultaneously the spinal part and the pelvic part of the global alignment. The global tilt was described to analyze malalignment, considering spinal and pelvic imbalance together. From a geometrical point of view, the global tilt is the sum of the C7 vertical tilt and the pelvic tilt. The aim of this study is to evaluate the global tilt by analyzing its correlation with spinal malalignment. METHODS: A cohort of patients who underwent a lumbar pedicle subtraction osteotomy (PSO) for major sagittal malalignment was realized. All patients had preoperative and postoperative full spine EOS radiographies to measure spinopelvic parameters. The lack of lordosis was calculated after prediction of theoretical lumbar lordosis. Correlation analysis between different spinopelvic parameters, including the global tilt, was performed for preoperative and postoperative values. RESULTS: Thirty-one consecutive patients were included. All parameters were correlated with spinal malalignment but the global tilt was the most correlated parameter in preoperative (r = 0.71) and in postoperative (r = 0.78). When spinal and pelvic parameters were analyzed separately, 19% of patients presented mismatches between spine and pelvis. CONCLUSION: This study highlights the interest of a global parameter evaluating the spinal balance and the pelvic balance together. The global tilt appeared to be the most correlated parameter in this study with spinal malalignment and could be used for the interpretation of clinical series in spine surgery.

[Physiological aging spine]. / Vieillissement physiologique de la colonne vertébrale.

Physiological aging spine. The process of physiological aging or senescence of the spine begins in the first decade of life and then accelerates from the third. It is essentially fundamentally linked to a phenomenon of entropy that inexorably alters the machinery of all the cells of the body, to which are added random pathologies. Senescence is thus responsible for so-called degenerative multisystem alterations so that the term «degenerative disc disease¼, is too restrictive and inappropriate. All the connective structures of the column are involved (intervertebral discs, articular joints and vertebral bone) but also muscle, vascular and neural components. In addition, there are neurological abnorma¬lities in the cerebral cortex and cerebellum that regulate the functioning of the verte¬bral column. The sum of the functional and tissue alterations modifies mechanical behavior both in the vertebrae (osteoporosis often complicated by fractures and de¬formities) than that of the intervertebral mobile segments, responsible for disc rupture, spondylolisthesis or degenerative deformities sometimes complicated by radicular or myelopathic abnormalities depending on the levels concerned. The impact of degene¬rative lesions in the spine is, however, highly variable from one subject to another depending on genetics, lifestyle, and for low back pain, the psychosocial context.

Vieillissement physiologique de la colonne vertébrale. Le processus de vieillissement physiologique ou sénescence de la colonne vertébrale débute dès la première décennie de la vie puis s'accélère à partir de la troisième. Il est pour l'essentiel fondamentalement lié à un phénomène d'entropie qui altère inexo¬rablement la machinerie de toutes les cellules de l'organisme auquel s'ajoutent les pathologies aléatoires que chacun peut développer. La sénescence est ainsi responsable d'altérations multitissulaires dites dégénératives si bien que le terme de « degenerative disc disease ¼, trop restrictif, est inapproprié. Toutes les structures conjonctives de la colonne sont plus ou moins concernées (disques intervertébraux, jointures interfacet¬taires et os des vertèbres ) mais aussi les composants musculaires, vasculaires et nerveux. De plus, s'y ajoutent des anomalies neurologiques au niveau des centres nerveux médullaires et cérébraux qui régulent le fonctionnement de la colonne. La somme des altérations tissulaires et fonctionnelles modifie le comportement mécanique tant au niveau des vertèbres (ostéoporose souvent compliquée de fractures et de déformations) qu'au niveau des segments mobiles intervertébraux, responsable de ruptures discales, de spondylolisthésis ou de déformations dégénératives parfois com¬pliqués de radiculalgies ou de myélopathies selon les niveaux concernés. Le retentis¬sement des lésions dégénératives de la colonne est cependant très variable d'un sujet à un autre en fonction de la génétique, du mode de vie, et, pour la lombalgie, du contexte psychosocial.

Clinical evaluation of a lumbar interspinous dynamic stabilization device (the Wallis system) with a 13-year mean follow-up.

The authors determined current health status of patients who had been included in a long-term survivorship analysis of a lumbar dynamic stabilizer. Among 133 living patients, 107 (average age at surgery, 44.2 +/- 9.9 years) completed health questionnaires. All patients had initially been scheduled for decompression and fusion for canal stenosis, herniated disc, or both. In 20 patients, the implant was removed, and fusion was performed. The other 87 still had the dynamic stabilizer. Satisfaction, Oswestry disability index, visual analog scales for back and leg pain, short-form (SF-36) quality-of-life physical composite score, physical function, and social function were significantly better (p < or = 0.05) in the patients who still had the dynamic stabilization device. SF-36 scores of the fused subgroup were no worse than those reported elsewhere in patients who had primary pedicle-screw enhanced lumbar fusion. This anatomy-sparing device provided a good 13-year clinical outcome and obviated arthrodesis in 80% of patients.

Long-term actuarial survivorship analysis of an interspinous stabilization system.

In 1986, an interspinous dynamic stabilization system (the prototype of the current Wallis implant) was designed to stiffen unstable operated degenerate lumbar segments with a hard interspinous blocker to limit extension and a tension band around the spinous processes to secure the implant and limit flexion. Restoring physiological mechanical conditions to the treated level(s) while preserving some intervertebral mobility was intended to treat low-back pain related to degenerative instability without increasing stress forces in the adjacent segments. The procedure was easily reversible. If low back pain persisted or recurred, the device was removed and stability was achieved using fusion. The intermediate-term results were promising, but the long-term safety and efficacy of this dynamic interspinous stabilization device has not been previously documented. We retrospectively reviewed the hospital files of all the patients (n = 241) who had this dynamic stabilization system implanted between 1987 and 1995, contacting as many as possible to determine the actuarial survivorship of the system. In this manner, 142 of the 241 patients (58.9%) were contacted by telephone. The endpoints used for the survivorship analysis were 'any subsequent lumbar operation' and 'implant removal'. At 14 years follow-up, values of actuarial survivorship with 95% confidence interval were 75.9 +/- 8.3 and 81.3 +/- 6.8% for the endpoints 'any subsequent lumbar operation' and 'implant removal', respectively. There was no difference in survivorship of multiple-level implants with respect to single-level devices. Although the conclusions of the present study must be tempered by the 41% attrition rate, these findings support the long-term safety of this system, and possibly long-term protective action against adjacent-level degeneration by motion preservation. Outcomes at least equivalent to those of fusion were observed without the primary drawbacks of fusion.

New interspinous implant evaluation using an in vitro biomechanical study combined with a finite-element analysis.

STUDY DESIGN: A combined in vitro and finite-element analysis was completed to assess the biomechanical effect of a new interspinous implant on the lumbar spine. OBJECTIVE: The aim was to investigate the effect of an interspinous implant on the biomechanical behavior of a vertebral segment. METHODS: An in vitro study on L3-L5 segments from fresh human cadavers was conducted combined with a 3-dimensional finite-element analysis. Intact, injured, and instrumented states of L4-L5 were compared loaded in flexion-extension, lateral-bending, and torsion. The evaluated implant is an interspinous spacer fixed to the spine by 2 polyester braids looped around the proximal and distal spinous. RESULTS: The effect of the implant appeared mainly in flexion-extension: experimental results showed reduced range of motion of the instrumented spine regarding the injured and intact one; and finite-element analysis indicated a decrease of disc stresses and increase of loads transmitted to the spinous processes. CONCLUSION: In this in vitro and finite-element analysis, the role of the new interspinous implant appeared to reduce motion without suppressing it and to lower stress in the disc fibers and anulus matrix. Further in vivo investigations are necessary to draw definitive conclusions.