RESUMO
PURPOSE: To assess the biomechanical effects and effectiveness of an interspinous spinal spacer (ISS) on the intradiscal pressure using in vitro biomechanical tests. MATERIALS AND METHODS: Six calf spine specimens (less than 2 weeks of age, L1-L5) were divided to two groups the intact and the surgery groups (n=3 each). For the surgery group, an ISS made from PMMA (Greek pi=12-mm) were inserted into the space between the spinous processes of L3-L4. The intradiscal pressures at the various regions of the annulus (anterior, posterior, and posterolateral locations) and the nucleus pulposus were measured using the four pressure transducers under pure compression (700 N) and extension loads (700 N+7.5 Nm). RESULTS: An increase in pressure was observed from neutral to extension at the posterior and posterolateral annulus. After inserting the ISS, the changes in pressure at the adjacent disc levels (L2-L3, L4-L5) were negligible regardless of the loading conditions (p>0.05). However, at the implanted level (L3-L4) statistically significant changes in the pressure were found under extension loading at the nucleus pulposus, posterior and posterolateral regions of the annulus with a pressure drop from 1.48 MPa, 1.42 MPa, 1.71 MPa to 1.11 MPa, 0.961 MPa, 1.08 MPa, at the respective locations (p<0.05). The relative percentage decrease were 25%, 31.7%, and 36.8%. CONCLUSION: On the implanted level, these results showed that the insertion of the ISS with PMMA can effectively reduce the intradiscal pressures by at least 25% quite uniformly over the intravertebral disc during extension. More effective reduction was observed at the posterolateral location. The pressure changes at the adjacent levels were negligible in contrast to the abnormal pressure changes that are frequently reported after conventional rigid fusion. This suggests that the likelihood of adjacent level degeneration after surgery can be minimized using the ISS insertion.
Assuntos
Polimetil Metacrilato , Estenose Espinal , Coluna Vertebral , Transdutores de PressãoRESUMO
The purpose of this study is to measure the standard volume of the ventricle of normal Koreans in their 20s and 40s and find out difference in the volume of the ventricle according to age and gender. We collected MR brain images from 118 people in their 20s (male 58, female 60)and 100 people in their 40s (male 41, female 59), so a total of 218 people.For each of sagittal, coronal and axial sections, the ventricular part was segmented using automatic and manual methods, and the volume was measured. In order to observe difference according to age and gender and to observe the interactive effect between age and gender, two-way ANOVA was carried out using age (2 levels)and gender (2 levels)as independent variables. The average volume of the ventricle of Koreans in their 20 s was 16.2 [cm3]and that of Koreans in their 40s was 23.1 [cm3].The average volume of the ventricle of male Koreans in their 20s and 40s was 21.9 [cm3]and that of female Koreans was 17.5 [cm3].The volume of the ventricle was significantly larger in Koreans in their 40s than those in their 20s, and in male Koreans than n female ones. Moreover, the increase of the volume of the ventricle with age was significantly larger in male Koreans than in female ones. According to the results of measuring the volume of the ventricle of normal Koreans in their 20s and 40s, the volume was significantly different according to age and gender, and the increase of the volume of the ventricle with age was significantly larger in men than in women.