ObjectiveTo completely establish a three-dimensional (3D) simulation model of degenerative lumbar scoliosis (DLS) with the whole lumbar segments, then to analyze the biomechanical changes of the scoliosis segments by finite element analysis.MethodsA case of DLS patient was selected with L1-5 segments of CT scanning data, which was imported into MIMICS 15, SolidWorks, Hyper-Mesh software to establish a 3D simulation model, and ANSYS 15 was used to analyze the model. At the same time, different material properties and boundary loading conditions were assigned to various structures to simulate the actual human body conditions.ResultsThe 3D model built a total of 856 154 units and 232 850 nodes, including the reconstruction of fine vertebral bodies, intervertebral disc tissue, structure of various ligaments and joint cartilages. Under the load and torque, the range of whole lumbar segments was decreased, in the stress distribution on the four discs: the L2/3 intervertebral disc stress value (3.320 MPa) > L 4/5 intervertebral disc stress value (0.783 MPa) > L 3/4 intervertebral disc stress value (0.551 MPa) > L 1/2 intervertebral disc stress value (0.462 MPa). The stress distribution of the vertebral body showed that, L5 vertebral stress (34.0 MPa) > L 4 (33.6 MPa) >L 3 (30.0 MPa) > L 1 (23.3 MPa) > L 2 (22.4 MPa).ConclusionThe range of motion of the six degrees of freedom of the lumbar spine in DLS is decreased, the local stress distribution of the lumbar spine is abnormal, and the abnormal stress changes of the apical vertebral body and the top intervertebral disc may be the biomechanical basis for the occurrence or progression of DLS.
ObjectiveTo summarize and analyze the characteristics of L1-L4 vertebrae and hip bone mineral density (BMD) in patients with degenerative lumbar scoliosis under dual energy X-ray absorptiometry (DEXA). MethodsWe collected all the preoperative total spine frontal and lateral X-ray images and DEXA examination results of patients with degenerative lumbar scoliosis who were hospitalized in the Department of Orthopedic Surgery in West China Hospital between August 2013 and August 2014. SPSS 21.0 was used to analyze patients’ age, height and body weight; BMD of each vertebra of L1-L4 vertebrae and L1-L4 vertebrae as a whole, and the T score; BMD of left femoral neck, Ward triangle, greater trochanter, and femoral shaft, and the general BMD of femoral neck, and the T score. ResultsThirty-eight patients with an average age of (67.4±8.2) years were enrolled in this study. DEXA examination results showed that 23.7% (9/38) and 28.9% (11/38) of the patients were osteoporotic in the spine and the hip, respectively; the examination results of total lumbar vertebrae and total femoral neck bones were concordant in 60.5% (23/38) of the patients. For lumbar vertebrae, the BMD from high to low was listed as: L4 vertebra, L3 vertebra, total L1-L4 vertebrae, L2 vertebra, and L1 vertebra. The BMD of L4 vertebra was significantly higher than that of L1 vertebra, and the BMD of lumbar vertebrae from L1 to L4 in turn presented a step-like increasing trend. For hip bones, the BMD from high to low was listed as: femoral shaft, total femoral neck area, femoral neck, greater trochanter, and Ward triangle. The BMD of the femoral shaft was significantly higher than that of Ward triangle. In the whole DEXA examination, the BMD of total L1-L4 lumbar vertebrae and its T score were higher than the BMD of left femoral neck area and its T score, respectively. ConclusionsDegenerative changes of the lumbar spine may lead to misinterpretation of BMD measurements and cause underdiagnosis of osteoporosis with DEXA. Routine reporting of spine BMD at L1 can add valuable information for reassessment and monitoring. The BMD of hip is less affected by osteoarthritis, osteophytes than the lumbar spine, and thus, it will be more meaningful in diagnosing and monitoring of the disease.