Objective To explore the characters of intra-stress distribution in cervical spine during cervical rotatory manipulation(CRM).Methods A 3D finite element model of C3/4～C6/7 was set up through software systems handling normal C3～C7 CT images.The decomposed mechanic parameters of CRM were analyzed by the finite element system.The changes of intra-stress distribution in model were displayed simultaneously during simulating manipulation.Results The size and region of stress suffered cervical model gradually decreased,and then increased gradually during pulling manipulation.The regions of stress concentration were mainly in C3/4 zygapophyseak joints.With increased thrust in C4 spinous process turning to the left,left bottom and root of C4 spinous process,combination area in left bottom and vertebral of pedicle C4 spinous process appeared stress concentration in turn,with the greatest stress of 9.627 kpa.In the process of cervical spine turning and right rotating about 40°,bilateral C3～C6 zygapophyseak joints,C4～C6 vertebral arch,the root of C4～C6 spinous process and the lateral side of C4～C6 vertebral body appeared stress concentration in turn,with the greatest stress of 363.6kpa in right of C3/4 zygapophyseak joints.The size and the region of stress suffered model reduced quickly at the stage of quickly returning to neutral position.Conclusions Cervical spine has its unique characters of intra-stress distribution under the CRM.Zygapophyseak joints suffer the major stress during the cervical spine movement.Model suffered the greatest stress under right rotation with 40°,but it did not injure the normal structrue of cervical spine.
To evaluate the effect of a new internal fixation system utilizing vertebral pedicle screw in fixing unstable lumbar spine in vitro.Twelve lumbar spine specimens (L(2 to 5)) obtained from fresh human cadavers were randomly divided into 2 equal groups, namely groups A and B. All intact specimens were subjected to nondestructive testing in 6 loading modalities on a universal testing machine, before complete L(2 to 5) instability was produced by means of a wedge fracture induced by resection of the posterior ligamentous structures. Specimens in group A were fixed with the new internal fixation system, and group B with SOCON pedicle screw. The same nondestructive testing was repeated to determine the structural stability of the spine after fixation in both groups.The injured spines fixed with implants in both groups were significantly more stable than the intact specimens in all modes of tests (P < 0.05), especially in flexion and extension tests, in which a stability increase by 62.8% for flexion and 63.9% for extension was recorded in group A, and 54.9% for flexion and 51.0% for extension in group B. The two fixation systems exhibited similar effect in stabilizing the injured lumbar in all the 6 loading modalities (P < 0.05).This internal fixation system with vertebral pedicle screw is capable of providing biomechanical stability for unstable lumbar spine.
To evaluate the effect of bending and rotation on the lumbar facet joints under load-bearing conditions.Eight lumbar-sacral spines (L1-S1) taken from fresh young adult cadavers were placed on the MTS system. The forces of the two facet joints of the L4-5 motion segments were measured using pressure sensitive films. The specimens were measured in erection, bending and rotation postures.In erection posture the L4-5 facet joints could support 31.16+/-7.15 N of 400 N which was axial compressing load. In bending 15 degree posture the forces of each side of the L4-5 facet joints were equal, and were found to have no marked effect on the force in erection. Yeat only opposite facet joints could endure force in rotation, but the force was 7 times that in erection.Both sides of lumbar facet joints could support load in bending position but only the opposite could endure load in rotation.
A finite element model was used to compare the biomechanical properties of a novel anterior transpedicular screw artificial vertebral body system (AVBS) with a conventional anterior screw plate system (ASPS) for fixation in the lower cervical spine. A model of the intact cervical spine (C3–C7) was established. AVBS or ASPS constructs were implanted between C4 and C6. The models were loaded in three-dimensional (3D) motion. The Von Mises stress distribution in the internal fixators was evaluated, as well as the range of motion (ROM) and facet joint force. The models were generated and analyzed by mimics, geomagic studio, and ansys software. The intact model of the lower cervical spine consisted of 286,382 elements. The model was validated against previously reported cadaveric experimental data. In the ASPS model, stress was concentrated at the connection between the screw and plate and the connection between the titanium mesh and adjacent vertebral body. In the AVBS model, stress was evenly distributed. Compared to the intact cervical spine model, the ROM of the whole specimen after fixation with both constructs is decreased by approximately 3 deg. ROM of adjacent segments is increased by approximately 5 deg. Facet joint force of the ASPS and AVBS models was higher than those of the intact cervical spine model, especially in extension and lateral bending. AVBS fixation represents a novel reconstruction approach for the lower cervical spine. AVBS provides better stability and lower risk for internal fixator failure compared with traditional ASPS fixation.
Biomechanical in vitro study.To determine whether the peak pull-out force (PPF) of cervical anterior transpedicular screw (ATPS) fixed in osteoporotic vertebrae positively influence screw stability or not before and after fatigue.Multilevel cervical spine procedures with osteoporosis can challenge the stability of current screw-and-plate systems. A second surgical posterior approach is coupled with potential risks of increased morbidity and complications. Hence, anterior cervical instrumentation that increases primary construct stability, while avoiding the need for posterior augmentation, would be valuable.Sixty formalin-fixed vertebrae at different levels were randomly selected. The vertebrae were divided into healthy controls (groups A1, A2), osteoporotic controls (B1, B2), healthy ATPS groups (C1, C2), osteoporotic ATPS groups (D1, D2), and osteoporotic restoration controls (E1, E2). The procedure of ATPS insertion was simulated with 2 pilot holes being drilled on each side of 20 vertebral bodies that were implanted with either vertebral screw or polymethylmethacrylate. Each side randomly received either instant PPF or PPF beyond fatigue (2.5 Hz; 20,000 times).The prefatigue PPFs were significantly higher than the postfatigue PPFs in all groups (group A: 366.06 ± 58.78 vs. 248.93 ± 57.21 N; group B: 275.58 ± 23.18 vs. 142.79 ± 44.78 N; group C: 635.99 ± 185.28 vs. 542.57 ± 136.58 N; group D: 519.22 ± 122.12 vs. 393.16 ± 192.07 N, and group E: 431.78 ± 75.77 vs. 325.74 ± 95.10 N). The postfatigue PPFs were reduced by 32.00% (group A), 48.19% (group B), 14.69% (group C), 24.28% (group D), and 24.72% (group E). The acute and postfatigue PPFs of both control groups were significantly lower than that of ATPS groups (P < 0.05). The cyclic osteoporosis ATPS group achieved the same PPF compared with the vertebral restoration screw group.The findings of this study suggest that instant PPF and fatigue resistance capability of an ATPS fixation were significantly better than other control groups, especially in the osteoporotic vertebrae.
Renal dysfunction greatly influences decision-making for emergency percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI). This observational study investigated renal function changes and risk factors for renal injury in patients with AMI with reduced estimated glomerular filtration rate (eGFR) who underwent emergency PCI. The study included 85 patients with AMI with decreased eGFR who underwent emergency PCI, categorized into stage 2, 3, and 4 chronic kidney disease groups. Baseline data, laboratory indicators, coronary characteristics, and serum creatinine concentration were monitored at multiple time points. Renal injury was defined using two criteria: an increase in serum creatinine level by 0.3 mg/dL or a 50% increase from baseline. During the 1-year follow-up, renal injury incidence varied from 1.18% to 15.29%. The pattern showed an increasing trend in the 1st week after PCI, peaking at 1 week, followed by a decrease at 3 months, and another increase at one year. Low basal eGFR, high contrast agent dosage, and diabetes were associated with renal injury according to logistic regression analysis. The eGFR cutoff value of 35.475 mL/minute·1.73 m2 had a sensitivity of 83.05% and specificity of 57.69% for predicting renal injury based on receiver operating characteristic curve analysis. In summary, patients with AMI with basal eGFR lower than 35.475 mL/minute·1.73 m2 have a higher risk of renal injury after PCI. These findings emphasize the importance of assessing renal function and considering associated risk factors when deciding on emergency PCI for AMI with reduced eGFR.
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