Objective To evaluate the biomechanicalproperties and structuralcharacteristics of various composites of partially decalcified allogenic bone matrix gelatin and bone cement at different ratios. Methods According to Urist method, partially decalcified allogenic bone matrix gelatin was prepared and mixedwith bone cement at different ratios of 0, 400, 500, and 600mg/g. Then the comparisons of these composites were performed in microstructure, ultimate compression strength and ultimate bending strength properties. Results The electronic microscope showed that the bone particles and bone cement were distributed evenly in the composite, irregularly connecting by multiple points; with the increase ofbone particles and decrease of bone cement in the composite, there were more and more natural crevices, varying from 100 μm to 400 μm in width, in the biomaterials. Of all the composites with the ratios of 0, 400,500, and 600 mg/g, the measurements of ultimate compression strength were (71.7±2.0) MPa, (46.9±3.3) MPa, (39.8±4.1) MPa, and (32.2±3.4) MPa, respectively; and the measurements ofultimate bending strength were (65.0±3.4) MPa, (38.2±4.0) MPa, (33.1±4.3) MPa and (25.3±4.6) MPa, respectively. Conclusion The compositeof partially decalcified allogenic bone matrix gelatin and bone cement has a good biomechanical property and could be easily fabricated and re-shaped, which make it available to be used clinically as an idea bone graft biomaterial.
Objective To analyze the biomechanical changes of the adjacent cervical facet joints when the angled cervical prosthesis is replaced. Methods A total of 400 northwestern people were involved, with an age of 40 years or older.The cervical vertebra lateral X-ray films were taken, and the cervical angles were measured by professional computer aided design software, then the cervical intervertebral disc prosthesis with 10° angle was designed. The finite element models of C4，5and C4-6 segments with intact cervical discs were developed; the C4，5 disc was replaced by the cervical prosthesis with 0° and 10° angle respectively; and then all models were subjected to axial loading, flexion/extension, lateral bending, and torsion loading conditions; the stress effects on adjacent facet joints after replacement were observed by comparing with that of the intact model. Results The cervical angles were (9.97 ± 3.64)° in C3，4, (9.95 ± 4.34)° in C4，5, (8.59 ± 3.75)° in C5，6, and (8.49 ± 3.39)° in C6，7, showing no significant difference between C3，4 and C4，5, C5，6 and C6，7 (P gt; 0.05) and showing significant differences between the other cervical angles (P lt; 0.05). When C4，5 model was axially loaded, no significant difference in equivalent shearing stress were observed in intact, 0°, and 10° groups; at flexion/extension loading, the stress was biggest in intact group, and was smallest in 10° group; at lateral bending, the stress got the high rank in intact group, and was minimum in 10° group; at torsion loading, the stress state of 10° group approached to the intact one condition. When C4-6 model was loaded, the facet joint stress of the replaced segment (C4，5) decreased significantly at axial loading, flexion/extension, and lateral bending; while no obvious decrease was observed at torsion loading; the stress of the adjacent inferior disc (C5，6) decreased significantly at axial loadingand lateral bending condition, while less decrease was observed at torsion loading, no significant change at flexion/extension condition, it approached to that of the intact one. Conclusion The finite element analysis reveals that the biomechanical properties of 10° designed prosthesis is approximate to that of the intact cervical disc, thus the 10° designed prosthesis can meet the requirements of biomechanical function reconstruction of the cervical spine.
Objective To compare the biological and biomechanical characteristics of decellularized bovine jugular venous tissue-engineered valved conduit scaffolds with that of fresh bovine jugular veins. Methods Fortyeight fresh bovine jugular veins were divided into control group and experimental group with random number table method, 24 veins in each group. There were fresh bovine jugular veins in control group, decellularized bovine jugular veins in experimental group. The veins of experimental group were treated with sodium deoxyeholate plus Triton-X-100 to decellularize the cells in valves and vessel walls. The thickness, water absorption rate, water maintenance rate, destroying strength, stretch rate of valves and vessel walls in two groups were detected. Results The endothelial cell and fibroblast of valves and vessel walls in experimental group were completely decellularized, no cell fragments were retained within the matrix scaffold; collagen fiber and elastin fiber had been preserved with intact structure and wavily arrayed; deoxyribonucleic acid content of valves and vessel walls in experimental group were decreased by 97.58%, 97.25% compared with that of control group. The thickness, water absorption rate and water maintenance rate of valves and vessel walls in experimental group were lightly increased than those of control group, but there were no significant differences between them （P 〉 0. 05）. There were no significant differences in destroying strength and stretch rate of valves and vessel walls between two groups （P〉0. 05）. Conclusion Decellularized bovine jugular vein scaffold has stable biological and biomechanical characteristics and it may be ideal natural fibrous matrix for developing the tissue-engineered valved conduit by host recellularization.
Objective To investigate the stability and the stress distributions of L3-5 fused with three different approaches (interbody, posterolateral and circumferential fusions) and to investigate degeneration of thesegment adjacent to the fused functional spinal unit. Methods A detailed L3-5 three-dimensional nonlinear finite element model of a normal man aged 32 was established and validated. Based on the model, the destabilized model, the interbody, posterolateral and circumferential fusions models of L4-5 were established. After the loadings were placed on all the models, we recorded the angular motions of the fused segment and the Von Mises stress of the adjacent intervertebral disc. Results The circumferential fusion was most stable than the others, and the interbody fusion was more stable than the posterolateral fusion. The maximal Von Mises stress of the adjacent L3,4 intervertebral disc in all the models was ranked descendingly as flexion,lateral bending,torsion and extension. For the three kinds of fusions, the stress increment of the L3,4 intervertebral disc was ranked ascendingly as interbody fusion,posterolateral fusion and circumferential fusion. Conclusion After destabilization of the L4,5 segment, the stability of the circumferential fusionis better than that of the others, particularly under the flexional or extensional loading. The stability of the interbody fusion is better than that of the posterolateral fusion, except for under the flexional loading. The feasibility of adjacent segment degeneration can be ranked descendingly as: circumferential fusion,posterolateral fusion and interbody fusion.
Accurately evaluating the local biomechanics of arterial wall is crucial for diagnosing and treating arterial diseases. Indentation measurement can be used to evaluate the local mechanical properties of the artery. However, the effects of the indenter’s geometric structure and the analysis theory on measurement results remain uncertain. In this paper, four kinds of indenters were used to measure the pulmonary aorta, the proximal thoracic aorta and the distal thoracic aorta in pigs, and the arterial elastic modulus was calculated by Sneddon and Sirghi theory to explore the influence of the indenter geometry and analysis theory on the measured elastic modulus. The results showed that the arterial elastic modulus measured by cylindrical indenter was lower than that measured by spherical indenter. In addition, compared with the calculated results of Sirghi theory, the Sneddon theory, which does not take adhesion forces in account, resulted in slightly larger elastic modulus values. In conclusion, this study provides parametric support for effective measurement of arterial local mechanical properties by millimeter indentation technique.
Objective To explore changes in the height and width of the cervical intervertebral foramina of C6,7 before and after the C5,6 discetomy, the replacement or the anterior intervertebral fusion so as to provide the theoretical basis for the clinical practice. Methods Eleven fresh cervical spinal specimenswere obtained from young adult cadavers. The specimens of C5,6 were divided into the integrity group, the discectomy group, the artificial disc replacement group, and the intervertebral fusion group. The range of variety (ROV) of the C6,7 intervertebral foramen dimensions (height, width) before and after the loading tests (0.75, 1.50 Nm) were measured in the 4 groups. Results The C6,7 intervetebral foramen height and width increased significantly during flexion (Plt;0.01) but decreased significantly during extension (Plt;0.01). There was a significantdifference between the two test conditions in each of the 4 groups (Plt;0.01). However, in the two test conditions there was no significant difference in ROV of the C6,7 intervetebral foramen height and width during flexion and extension betweenthe integrity group, the discectomy, and the artificial disc replacement group（Pgt;0.05）, but a significant difference in the above changes existed in the intervertebral fusion group when compared with the other 3 groups (Plt;0.05). In the same group and under the same conditions, the ROV of the C6,7 intervetebral foramen height and width was significantly different in the two test conditions (Plt;0.01). Conclusion The results have indicated thatartificial disc replacement can meet the requirements of the normal cervical vitodynamics. The adjacent inferior cervical intervetebral foramen increases during flexion but decreases during extension. The intervertebral fusion is probably one of the causes for the cervical degeneration or the accelerated degeneration and for the cervical spondylotic radiculopathy and the brachial plexus compression.
ObjectiveTo investigate the biomechanical properties of artificial ligament in the treatment of injuries to distal tibiofibular syndesmosis so as to provide a scientific basis for clinical application. MethodsSixteen fresh ankle specimens were harvested from 8 normal fresh-frozen cadavers. The initial tests were performed on 16 intact specimens (group A) and then the distal tibiofibular syndesmosis injury models were made (group B); the distal tibiofibular syndesmosis was fixed with artificial ligament in 8 specimens (group C) and with cannulated lag screw in the other 8 specimens (group D). The pros and cons of different fixation methods were analyzed by displacement, stress shielding effect, the strength and stiffness of ankle joints, the contact area of tibiotalar articular surface and the contact stress. ResultsUnder the physiological loading or combined with external rotation moment, the displacement of group C was significantly lower than that of groups B and D (P < 0.05), but no significant difference was found between groups A and C (P > 0.05); and there were significant differences among groups A, B, and D (P < 0.05). The rates of stress shielding in the tibia and fibula of group C were significantly lower than those of group D (t=-71.288, P=0.000;t=-97.283, P=0.000). The stress strength in tibia of group C was significantly higher than that of groups A and D (P < 0.05), but no significant difference was found between groups A and D (P > 0.05). Group C had the highest stress strength in fibula, followed by group A, group D had the lowest; differences were significant among 3 groups (P < 0.05). There was no significant difference in shear strength among groups A, C, and D (P > 0.05). The axial stiffness in tibia of group D was significantly lower than that of groups A and C (P < 0.05), but no significant difference was found between groups A and C (P > 0.05). The axial stiffness in fibula of group C was significantly higher than that of groups A and D (P < 0.05), but no significant difference was found between groups A and D (P > 0.05). Group C had the highest shear stiffness in tibia and fibula, followed by group D, group A had the lowest; differences were significant among 3 groups (P < 0.05). In groups A, C, and D, the contact area of tibiotalar articular surface gradually reduced, and the contact stress gradually increased, and differences were significant among 3 groups (P < 0.05). ConclusionFixation of distal tibiofibular syndesmosis injury with artificial ligament can better meet the physiological functions of the distal tibiofibular syndesmosis and has lower stress shielding, better stress distribution. Hopefully, it can reduce the complications of the distal tibiofibular syndesmosis injuries and become a better treatment choice.
Objective To investigate the effect of repeated freezing and thawing combining nuclease treatment on the decellularization of bovine tendons, and the morphology, structure, biochemical compositions, and mechanical properties of the decellularized tendons. Methods A total of 48 fresh 1-day-old bovine Achilles tendons were randomly divided into 3 groups (n=16): fresh normal tendons (group A), repeated freezing and thawing for 5 times (liquid nitrogen refrigeration/37℃ thawing, group B), and repeated freezing and thawing combining nuclease processing for 24 hours (group C). In each group, 2 tendons were used for scanning electron microscope (SEM), 3 tendons for histological and immunohistochemical observations, 3 tendons for DNA content detection, and 8 tendons for biomechanical testing. Results SEM observation indicated the intact, aligned, and densely packed collagen fibers with no disruption in groups A and B, and the slightly loose collagen fibers with little disruption in group C. The alcian blue staining, sirius red staining, and immunohistochemical staining showed that the most of glycosaminoglycan, collagen type I, collagen type III, and fibronectin in group C were retained after decellularization treatment. HE and DAPI staining showed that the cell nuclei between the collagen fibers were clearly visible in groups A and B; however, the cell nuclei between collagen fibers almost were invisible with a few residual nuclei on the endotendineum in group C. DNA quantitative detection confirmed that DNA content in group C [(0.05 ± 0.02) μg/mg] was significantly lower than those in group A [(0.24 ± 0.12) μg/mg] and group B [(0.16 ± 0.07) μg/mg] (P lt; 0.05). Biomechanical testing showed that the values of tensile strength, failure strain, stiffness, and elastic modulus were different among 3 groups, but no significant difference was found (P gt; 0.05). Conclusion Repeated freezing and thawing combining nuclease processing can effectively remove the component of cells, and simultaneously retain the original collagen fibrous structure, morphology, most of the extracellular matrix compositions, and mechanical properties of the bovine tendons.
Objective To evaluate the effect of polymethylmethacrylate (PMMA) augmentation on cervical stabil ity after anterior cervical interbody fusion (ACIF) before and after fatigue. Methods Twelve porcine cervical spines (C3-7) were subjected to testing angular displacement parameters, including the range of motion (ROM), neutral zone (NZ), and elastic zone (EZ), in nondestructive flexion and extension, right/left lateral bending, and left/right rotation on Motion Analysis motion capture system and MTS-858 servo-hydraul ic testing machine. Intact cervical spines served as control group (group A); oneleveldiscectomy and fusion was performed with anterior plate fixation based on group A as group B; flexion and extension,left/right lateral bending (5 000 cycles) fatigue testing based on group B as group C; the augmentation screw channel was used based on group C as group D; and flexion and extension, left/right lateral bending fatigue testing were performed based on group D as group E. Results The ROM, NZ, and EZ in group A were significantly different from those in other groups (P lt; 0.05) at flexion/extension, left/right bending, and left/right rotation. The ROM, NZ, and EZ in group B were significantly smaller than those in group C (P lt; 0.05) in flexion/extension, left/right bending, and left/right rotation, but there was no significant difference when compared with group D (P gt; 0.05). The ROM and NZ in flexion/extension and the EZ in flexion in group B were significant smaller than those in group E (P lt; 0.05), but there was no significant difference in the other indexes (P gt; 0.05). The ROM, NZ, and EZ in group C in flexion and extension, left/right lateral bending, and left/right rotation were significantly higher than those in groups D and E (P lt; 0.05). The ROM and NZ in flexion and extension and left/right lateral bending, and the ROM in left/right rotation, and the EZ in flexion and extension, right bending, and left/right rotation in group D were significantly smaller than those in group E (P lt; 0.05), but there was no significant difference in the other indexes (P gt; 0.05). Conclusion PMMA augmentation can significantly increase the instant cervical stabil ity and provide a biomechanics basis in cervical anterior plate fixation.
Objective To determine the change in humeral head anterosuperior migration after releasing the coracoacromial l igament in shoulders from cadavers with simulated intact or irreparable teared rotator cuff, to provide biomechanical basis for preserving the coracoacromial l igament or not during hemiarthroplasty. Methods Twelve freshfrozen cadaveric glenohumeral joints of adult preserving the scapula, upper 2/3 of the humerus, articular capsule and the coracoacromial l igament, were divided into 2 groups. The suprascapularis was preserved in group A (6 shoulders) and excised in group B (6 shoulders). Positioning the joint in a combination of 30° extension, 0° abduction and 30° external rotation, and imposing a 50 N axial compressive load to the humeral shaft, the anterosuperior displacement of the humeral head weremeasured before and after excising the coracoacromial l igament. Results In group A, the displacement of the humeral head was (5.96 ± 0.77）mm with intact coracoacromial l igament and (6.83 ± 0.84）mm after transecting the l igament. In group B, the displacement of the humeral head was (8.07 ± 2.46）mm with intact coracoacromial l igament and (9.92 ± 3.29）mm after transecting the coracoacromial l igament. So the mean increase of anterosuperior migration of the humeral head was (0.88 ± 0.34) mm (P lt; 0.01) in group A, and (1.85 ± 0.99) mm (P lt; 0.01) in group B, which was greater than the former (P lt; 0.05). Conclusion The coracoacromial l igament restrained anterosuperior translation of the humeral head, especially for patients with rotator cuff deficiency, so it should be preserved as far as possible during hemiarthroplasty.