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Objective To compare the rigidity at upper thoracic spine among the anterior transpedicular screw-plate system (ATPSPS),posterior transpedicle screw-rod system (PTPSRS) and anterior vertebral body screw-plate system (AVBSPS).Methods Twelve embalmed cadaver specimens were divided into three groups.The specimens in each group were randomly allocated to use the above 3 different internal fixation devices for conducting fixation.The stiffness of each specimen on the directions of axial compression,flexion and extension,and left and right lateral bending was detected under original status.All specimens conducted the simulated corpectomy of T2 (damage status).Then the rigidity on various directions was re-detected on the damage status.The corresponding internal fixation system was selected for conducting the install and fixation according to the grouping results.The intra-group and inter-group rigiditieson different directions were compared amongoriginal status,damage status and after internal fixation.Results The rigidities on different directions under original and damage statushad no statistical difference among various groups (P＜0.05).After conducting fixation in each group,the rigidity after fixation on different directions had statistically significant difference among groups(P＜0.05).The stiffness of anterior flexion in the ATPSPS group was greater than that in the other two groups (P＜0.05).The rigidity of axial compression and extension in the PTPSRS group was greater than that in the other two groups,the difference among groups was statistically significant (P＜0.05).The stiffness of lateral bending in the AVBSPS group was smaller than that in the other two groups,the difference was significant (P＜0.05),but the difference between the other two groups had no statistical significance (P＞0.05).Conclusion The rigidity of ATPSPS in all directions is higher than that of AVBSPS.The anterior flexion rigidity is greater than PTPSRS,and the axial compression and extension rigidity are less than PTPSRS,but the lateral bending rigidity is equivalent to PTPSRS.
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BACKGROUND:The aim of spinal mobilization and spinal manipulation is to correct vertebral subluxation. However, facet joint pressures are not clear during these two therapies. OBJECTIVE:To compare human lumbar facet joint pressures during simulated high-velocity, low-amplitude spinal manipulationversuslow-velocity, low-amplitude spinal mobilization. METHODS:Totaly 12 adult fresh lumbar spinal specimens (T12-S2) were divided into two groups randomly. Parameters of simulated spinal mobilization (n=6): preload angle 15° (speed 3°/s), maximum angle 20° (speed 1°/s), with 9 N horizontal force to L5 spinous process. Parameters of simulated spinal manipulation (n=6): preload angle 15° (speed 3°/s), impulse angle 20° (impulse speed 33°/s), with 22 N horizontal force to L5 spinous process. Pressures of bilateral L4-5/L5-S1 facet joints were measured with Tekscan system. RESULTS AND CONCLUSION:(1) During two spinal manipulative therapies (rotation to the right and then back to the neutral position), pressures of right facet joints decreased first and then increased gradualy, while pressures of left facet joints changed oppositely. (2) Pressures of right facet joints were similar regardless of manipulation type (P > 0.05). The maximum pressure of left facet joints was larger during manipulation than that during mobilization (P 0.05). Both ascending and descending speeds of the left facet joints were larger during manipulation than that during mobilization (P < 0.01). (4) During two spinal manipulative therapies, pressures of ipsilateral facet joints decreased first and then increased, while pressures of contralateral facet joints increased first and then decreased. Joint pressure after treatment restored to that before treatment. (5) Impulse speed and magnitude of pressures of facet joints during manipulation were larger than that during mobilization. Facet joints are more possible to be injured during manipulation than that during mobilization. During manipulation, we should pay attention to the speed and intensity of the impact.
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BACKGROUND:For severe thoracolumbar compression fracture (>1/3 compression), ideal therapeutic method is minimal y invasive internal fixation, which has good biomechanical functions. Moreover, bone graft is reliable. Injured vertebra reduction and bone graft stability achieved. Motor unit of spinal column and normal physiological function were retained, resulting in lessening nearby segmental degeneration. OBJECTIVE:To discuss the design of single vertebrae internal fixation system and evaluate its biomechanical performance which apply to treat thoracolumbar compression fracture by endoscope. METHODS:A brand-new single vertebrae internal fixation system was designed in accordance with data of anatomic measurement of adult thoracolumbar vertebra. Six fresh adult corpse specimens were prepared to produce models of L 1 compression fracture, and assigned to control group, fracture injury group, single vertebrae internal fixation system group, AF reduction internal fixation group and anterior plate internal fixation group.Three-dimensional movement range experiments were conducted separately. RESULTS AND CONCLUSION:The biomechanical comparison showed that there was no significant difference in three-dimensional range of motion among single vertebrae internal fixation system group (anteflexion, left and right lateroflexion), AF reduction internal fixation group and anterior plate internal fixation group (P>0.05). However, range of motion significantly increased at backward extension, left and right rotation (P<0.05). Results suggested that the design of single vertebrae internal fixation system was novel and the system had good biomechanical performance at anteflexion, left and right lateroflexion. However, it needs to be improved in which lacks of stability of extension and rotation.
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BACKGROUND: Interlocking intramedullary nails(SliN)is frequently used to treat femoral fracture.Routine pulling and compression and postoperative motorization are important for fracture healing.To improve fracture healing rate has been focused using various factors.OBJECTIVE: To explore the biomechanical performance of static SliN in fixation of femoral fracture,and the effect on fracture healing.METHODS: A total of 8 pairs of femurs from adult cadavers immersed in formalin were used to prepare models of midpiece transverse fracture.The fracture was respectively fixed using static SliN,TiNi shape-memory sawtooth-arm embracing internal fixator(TiNi SMA),and dynamic compression plate(DCP).The anti-compression,anti-bending,and anti-torsion rigidity were measured,and the stress shielding rate was calculated.RESULTS AND CONCLUSION: SliN was similar to DCP group in anti-compression rigidity and anti-bending rigidity(P > 0.05),but the anti-torsion was lower than DCP group(P<0.05).Compared with TiNi SMA group,SliN displayed greater anti-compression rigidity and anti-bending rigidity(P<0.05),but similar anti-torsion(P > 0.05).SliN was similar to DCP group in stress shielding rate(P>0.05),but significantly greater than TiNi SMA group(P<0.01).The biomechanics of SliN was stable,but the stress shielding rate was high.Changing static interlocking into dynamic interlocking in time is necessary in clinic to promote fracture healing.