ABSTRACT
BACKGROUND: Lumbar disc herniation is a common clinical disease, and its pathological basis is disc degeneration. Long-term mechanical load is considered to be an important cause of lumbar disc degeneration. Because the occurrence of lumbar disc herniation is strongly associated with its mechanical state, it is necessary to further study the stress/strain behavior in the lumbar disc to provide inspiration for preventing lumbar disc herniation. OBJECTIVE: To analyze the effect of fatigue loading on mechanical properties of the whole and different regions of the intervertebral disc. METHODS: The freshly slaughtered sheep lumbar intervertebral discs L1-L2, L3-L4, and L5-L6 were obtained and made into experimental samples. The experimental samples were fixed on the experimental platform through the upper and lower vertebrae, and a quasi-static compression-cyclic loading compression-quasi-static compression experiment was performed. The L3-L4 motion segment was cut parallel to the sagittal plane, and the non-contact digital image correlation technique was used to record the internal deformation of the lumbar disc during compression. RESULTS AND CONCLUSION: (1) The results showed that all lumbar intervertebral discs exhibited non-linear load-displacement and stress-strain characteristics. (2) Effect of fatigue loading: The Young’s modulus of the lumbar intervertebral disc increased significantly after fatigue loading. (3) Impact of segment changes: The Young’s modulus changed with segment changes as follows: L5-L6 segments < L3-L4 segments < L1-L2 segments. (3) Effect of loading rate: Comparing the mechanical properties under the compression rate of 0.01 mm/s and 0.1 mm/s, it could be seen that with the increase of the compression rate, the Young’s modulus of the intervertebral disc increased significantly. (5) Internal displacement distribution: Fatigue loading had a significant effect on the internal displacement distribution of the lumbar disc under compression. Before fatigue loading, the axial displacement in upper afferent fiber was largest, and the radial displacement in inner afferent fiber was slightly smaller than that in outer afferent fiber. After fatigue loading, the axial displacement in upper afferent fiber was smallest, and the radial displacement in inner afferent fiber was significantly smaller than in outer afferent fiber. (6) The research work in this article has important theoretical guiding significance for preventing lumbar disc herniation in daily life.
ABSTRACT
Objective To describe the MR imaging features and pathologic findings of hepatic angiomyolipoma (HAML), and to evaluate the utility of MR imaging in diagnosis of this tumor. Methods The MR imaging features of eight patients with HAMLs confirmed pathologically were analyzed retrospectively and correlated with pathologic findings. Results Eight patients had a solitary hepatic mass, five (mixed type HAML) of which were diagnosed correctly, and two (1 myomatous type HAML and 1 angiomatous type HAML) of which were diagnosed as hepatic adenoma and focal nodular hyperplasia, and one (mixed type HAML) with hemorrhage and multiple cystic change was mistaken for malignant tumor. Six cases of mixed type HAML exhibited heterogeneously high signal intensity on T 1 and T 2WI. The high signal intensity on T 1WI in five cases disappeared completely after using fat saturation, and most part of the high signal intensity in one case disappeared and some of the high signal intensity remained unchanged after using fat saturation, and multiple cystic change within this mass was detected. One myomatous type HAML and one angiomatous type HAML showed hypointensity on T 1WI and hyperintensity on T 2WI. Multiphase dynamic Gd DTPA enhanced MR scanning was performed in six patients and all those masses showed strong enhancement during arterial phase, and four of which showed moderate enhancement and two slight enhancement during portal venous and delayed phase. Pseudocapsule detected in five cases showed slight enhancement on portal venous and (or) delayed phase. Conclusion MR imaging can reveal the characteristic findings of mixed type HAML and accurate preoperative diagnosis can be made.
ABSTRACT
Objective To study X-ray and CT findings of retroperitoneal fibrosis and their value for diagnosis of this disease.Methods X-ray and CT findings and clinical data of 5 cases confirmed with retroperitoneal fibrosis by clinicopathology were retrospectively analysed in combination with literature review.Results X-ray and CT manifestations of retroperitoneal fibrosis included diffuse mass at retroperitoneum,the neighboring organs were enveloped by masses,and one or bilateral renal pelvis and the ureter expansion.Conclusion X-ray and CT have vital clinical significance in diagnosing the retroperitoneal fibrosis.