Impact of Sacroiliac Interosseous Ligament Tension and Laxity on the Biomechanics of the Lumbar Spine: A Finite Element Study.

OBJECTIVE: To investigate the influence of sacroiliac interosseous ligament tension and laxity on the biomechanics of the lumbar spine. METHODS: A static analysis of a three-dimensional finite element model of the Lumbar-Pelvic is conducted to verify the model's effectiveness. Adjusting the sacroiliac ligament's elasticity modulus under a 10Nm lumbar flexion/extension moment, it simulates ligament tension/laxity to calculate vertebrae displacements, intervertebral disc stress and deformation, nucleus pulposus pressure, facet joint force, and ligament stress. RESULTS: With the elastic modulus of the sacroiliac ligament changing by +50%, -50%, and -90%, the angular displacement of vertebra 3 in forward flexion changes by +1.64%, -4.84%, and -42.3%, and the line displacements change by +5.7%, -16.4%, and -144.9%, respectively; and the angular displacements in backward extension change by +0.2%, -0.6%, -5.9% and the line displacements change by +5.5%, -14.3%, and -125.8%. However, the angular displacement and center distance between adjacent vertebrae do not change, leading to no change in the maximum stress of the intervertebral disc and the maximum pressure in the nucleus pulposus. Flexion and extension directly affect the deformation and stress magnitude and distribution in the lumbar spine. CONCLUSIONS: While sacroiliac interosseous ligament laxity and tension have little effect on disc deformation and stress, and nucleus pulposus pressure, they reduce the stability of the lumbar-sacral vertebrae. In a forward flexion state, the lumbar ligaments bear a large load and are prone to laxity, thereby increasing the risk of lumbar injury.

Finite element analysis of the cervical spine: dynamic characteristics and material property sensitivity study.

The study aimed to investigate the dynamic characteristics of the cervical spine and determine the effect of the material properties of the cervical spinal components on it. A finite element model of the head-cervical spine was developed based on CT scan data, and the first six orders of modes (e.g. flexion-extension, lateral bending, and vertical, etc.) were verified by experimental and simulation studies. The material sensitivity study was conducted by varying elasticity modulus of cervical hard tissues (cortical bone, cancellous bone, endplates, and posterior elements) and soft tissues (intervertebral disc and ligaments). The results showed that increasing the elastic modulus of ligaments by 4 times increased the natural frequency by 77%, while increasing that of cancellous bone by 4 times only increased the natural frequency by 6%. In the axial mode, the cervical spine had not only axial deformation but also anterior-posterior deformation, with the largest deformation located at the intervertebral disc C6-C7. Decreasing the elastic modulus of a component in soft tissues by 80% increased modal displacement by up to 62%. The material properties of the intervertebral discs and ligaments had opposite effects on the modal displacement and deformation of the cervical spine. Low cervical discs were more susceptible to injury in a vertical vibration environment. Cervical spine dynamics were more sensitive to soft tissue material properties than to hard tissue material properties. Disc degeneration could reduce the range of vibratory motion of the cervical spine, thereby reducing the ability of the cervical spine to cushion head impacts.

Comparison of clinical effects of total spondylectomy with different procedures in treating lumbar metastatic tumor / 中国骨伤

<p><b>OBJECTIVE</b>To compare the therapeutic effects of debris spondylectomy, piecemeal spondylectomy, total en bloc spomdylectomy in treating lumbar metastatic tumors.</p><p><b>METHODS</b>The clinical data of 20 patients with lumbar metastatic tumors treated from January 2008 to October 2013 were retrospectively reviewed. There were 8 males and 12 females, aged from 35 to 65 years old with an average of (49.50 ± 9.97) years. All patients had single solitary metastases. Four cases were in L1,5 cases in L2,4 cases in L3,4 cases in L4, and 3 cases in L5. According to the type of Tomita, type II had in 4 cases, type III in 6 cases, type IV in 6 cases, type V in 4 cases. Tokuhashi score was 12.50 ± 1.97. All patients complained with back or leg pain, VAS score was 8.13 ± 0.85. Among patients, 7 cases were treated with debris spondylectomy (group A), 7 cases with piecemeal spondylectomy (group B), 6 cases with total en bloc spondylectomy (group C). Statistical analysis was used to compare the three groups with respect to surgical trauma (including operative time, transoperative bleeding, and intraoperative blood transfusion), clinical symptoms (by VAS score at 1 week after operation), surgical procedures conditions (by AP and lateral X-rays), and long-term results (by recurrence and death information).</p><p><b>RESULTS</b>All patients were followed up from 6 to 36 months with an average of (16.50 ± 7.88) months. Operative time for debris spondylectomy was (6.14 ± 0.68) h, intraoperative bleeding was (3 457.14 ± 399.40) ml, and intraoperative blood transfusion was (2 771.43 ± 423.14) ml. Operative time for piece-meal spondylectomy was (4.93 ± 0.61) h, intraoperative bleeding was (1 942.86 ± 378.51) ml, and intraoperative blood transfusion was (1 500.00 ± 336.65) ml. Operative time for total en bloc spondylectomy was(4.17 ± 0.67) h, intraoperative bleeding was (1 341.67 ± 361.13) ml, and intraoperative blood transfusion was (916.67 ± 321.66) ml. There was significant differences in operative time, intraoperative blood loss, and intraoperative blood transfusion between three groups (P < 0.05). In terms of these factors, total en bloc spondylectomy had the best outcome followed by piecemeal spondylectomy. All pains had released, VAS score decreased obviously at 1 week after operation (P < 0.05), and there was no significant differences between three groups (P > 0.05). Surgical effects were well with these methods according to the evaluation of AP and lateral X-rays . At final follow-up, group A had 4 recurrences (2 with breast cancer, 1 with prostate cancer,and 1 with thyroid cancer) and 3 deaths (2 with lung cancer and 1 with thyroid cancer); group B had 2 recurrences (1 with breast cancer and 1 with prostate cancer) and 3 deaths (1 with lung cancer, 1 with breast cancer and 1 with kidney cancer);group C had no recurrences and 2 deaths for lung cancer. There was significant differences in recurrence and death between three groups (P < 0.05). In terms of these factors, total en bloc spondylectomy had the best outcome in three methods.</p><p><b>CONCLUSION</b>Three kinds of operation method can relieve pain, improve nerve function, increase the spinal stability, control the local lesions, improve the patient's quality of life in treating lumbar metastatic tumors, but total en bloc spendylectomy, respect to operative time, transoperative bleeding, intraoperative blood transfusion, tumor recurrence and death is clearly superior to other two methods.</p>