Computational modeling of lumbar disc degeneration before and after spinal fusion.

BACKGROUND: Advancing age and degeneration frequently lead to low back pain, which is the most prevalent musculoskeletal disorder worldwide. Degenerative changes in intervertebral discs and musculo-ligamentous incapacity to compensate sagittal imbalance are typically amongst the sources of instability, with spinal fusion techniques being the main treatment options to relieve pain. The aims of this work were to: (i) assess the link between ligament degeneration and spinal instability by determining the role of each ligament per movement, (ii) evaluate the impact of disc height reduction in degenerative changes, and (iii) unveil the most advantageous type of posterior fixation in Oblique Lumbar Interbody Fusion to prevent adjacent disc degeneration. METHODS: Two L3-L5 finite element models were developed, being the first in healthy condition and the second having reduced L4-L5 height. Different degrees of degeneration were tested, combined with different fixation configurations for Oblique Lumbar Interbody Fusion. FINDINGS: Facet capsular ligament and anterior longitudinal ligament were the most influential ligaments for spinal stability, particularly with increasing degeneration and disc height reduction. Pre-existent degeneration had lower influence than the fusion procedure for the risk of adjacent disc degeneration, being the highest stability and minimal degeneration achieved with bilateral fixation. Right unilateral fixation was more suited to reduce disc stress than left unilateral fixation. INTERPRETATION: Bilateral fixation is the best option to stabilize the spinal segment, but unilateral right fixation may suffice. This has direct implications for clinical practice, and the extension to a population-based study will allow for more efficient fusion surgeries.

[A radiological assessment of the nasopharynx in healthy children from the Madrid area]. / Evaluación radiológica de la nasofaringe en niños sanos de nuestro medio.

OBJECTIVE: The objective of this study was to assess the adenoid size of each pediatric age group in our media and to compare the subjective visual assessment with a confronted measurement, the Fujioka's adenoidal-nasopharyngeal (AN) ratio. These data would allow the composition of a map, a guide for pediatricians useful in predicting the degree of upper airway obstruction, the role of adenoids in the etiology of serious otitis media and/or in selecting patients for adenoidectomy. PATIENTS AND METHODS: We studied 1,033 radiographs of the nasopharynx taken in the emergency room of children between 5 months and 15 years of age that did not have any otorhinolaryngological (ENT) pathology. These individuals had no history of ear, nose or throat disease and the ENT evaluation was done in order to discard any ENT pathology. The subjective review and the AN ratios were calculated by experienced observers, tabulated and statistically analyzed. RESULTS: Only 692 infants and children passed the careful selection. The differences in mean values among the ages were statistically significant (p < 0.001). The mean AN ratio reached its highest value (0.575) at 5 years of age. The AN ratio as an indicator of adenoid size was comparable to the visually estimated classifications of adenoid size (p < 0.0001). In addition, 85% of the radiographs selected were in the group normal to slightly enlarged (AN = 0.48). CONCLUSIONS: The distribution of the mean AN ratios for age groups in healthy children shows a line which we could use as a standard, or guideline, to compare the AN ratio of any infant or child with any pathology related to the adenoids.