THE EFFECT OF DISC DEGENERATION ON ANTERIOR SHEAR FLEXIBILITY IN THE LUMBAR SPINE
Notice bibliographique
Résumé
Summary Statement Spinal flexibility in bending and axial torque has been shown to exhibit very modest changes with advancing disc degeneration. This study is the first to address the possible relationship in pure anterior shear and no clear relationship was observed. Introduction Disc degeneration (DD) is a risk factor for low back pain. Stable or unstable spine segments may be treated with an isolated decompression or instrumented stabilization, respectively. The effect of DD on spinal flexibility has been addressed by several groups in bending but not in shear; a highly relevant load direction in the lumbar spine is anterior shear. The objective of our study was to determine the effect of DD on anterior translation and specimen stiffness under shear loading in an in vitro model of degenerative spondylolisthesis. Methods Magnetic resonance images were obtained for human cadaveric lumbar FSUs (N=30). Disc degeneration was assessed with the Pfirrmann five-point grading scale. Three surgeons independently graded the discs and the grade common to at least two of the surgeons was assigned to that specimen. Each specimen was then tested in three sequential states: intact, facet destabilization, and disc destabilization, with the latter two states representing the clinical scenario of degenerative lumbar spondylolisthesis. The specimens were loaded with a constant 300 N axial compressive force, representing body weight, combined with a cyclic anterior shear force (5–250 N). Vertebral translation was tracked with an optoelectronic motion capture system. Kruskal-Wallis ANOVA and multiple comparison Dunn9s tests were performed to determine the effect of DD on anterior translation and specimen stiffness. Results There was only one specimen with disc grade V, and it was grouped with specimens with disc grade IV for the statistical analyses. DD had no effect on anterior translation or specimen stiffness for the intact and disc destabilization conditions. In the facet destabilization condition, specimens with disc grade II translated more than those with disc grades IV and V (p=0.03). Stiffness increased with DD in the facet destabilization condition (ANOVA p=0.04; Dunn9s test was not significant). However, we re-analyzed the data with each surgeon9s disc grades and found no significant differences in any of the specimen conditions for all three surgeons. Discussion In the original data analysis, the translation results showed a trend to reduced anterior translation in shear with advancing degeneration only in the facet destabilization condition. These results suggest that shear stiffness of an intact specimen is not affected by overall degeneration, except in the case where the facets are not competent to resist load. In the subsequent data analyses, no significant effects were found. These findings indicate the sensitivity of the analyses to the assignment of disc grade. There are numerous disc grading scales reported in the literature and it is not clear which scale best defines disc degeneration. We are continuing to assess our methods to determine the most appropriate method of defining disc degeneration by disc grade.
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Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
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