ObjectiveTo explore the mechanical stability of the three-dimensional (3-D) external fixator for osteoporotic fracture so as to provide the biomechanical basis for clinical application. MethodsForty-five fresh frozen adult tibial specimens were selected to rapidly prepare the extracorporal tibia osteoporotic fracture models, and were randomly divided into 3 groups (n=15). Fractures were fixed with 3-D external fixators (3-D external fixators group), intramedullary nails (intramedullary nail group), and plate (plate group) respectively. Five specimens randomly from each group were used to do axial compression test, three-point bending test, and torsion test with microcomputer control electronic universal testing machine, then the mechanical parameters were calculated. ResultsIn the axial compression test, the displacement of 3-D external fixator group and intramedullary nail group were shorter than plate group, showing significant differences (P<0.05); but no significant difference was found between 3-D external fixator group and intramedullary nail group (P>0.05). In the three-point bending test and torsion test, the deflection and the torsional angle of 3-D external fixator group and intramedullary nail group were smaller than plate group, showing significant differences (P<0.05); but no significant difference was found between 3-D external fixator group and intramedullary nail group (P>0.05). ConclusionThe 3-D external fixator can fix fracture three-dimensionally from multiple plane and it can offer strong fixing. It is biomechanically demonstrated to be suitable for osteoporotic fracture.
ObjectiveTo compare the fixation strength of optimum placed pedicle screw (OS) with re-directionally correctly placed pedicle screw (RS) following a violation of lateral pedicle. MethodsThirty fresh lumbar vertebrae (L1-5) were obtained from 6 pigs weighing 95-105 kg, male or female. Each vertebra was instrumented with a monoaxial pedicle screw into each pedicle using two different techniques. On one side, a perfect screw path was created using direct visualization and fluoroscopy. A pedicle screw of 5 mm in diameter and 35 mm in length was placed with a digital torque driver (OS). On the other side, a lateral pedicle wall violation was created at the pedicle-vertebral body junction with a guide wire, a cannulated tap, and a pedicle probe. This path was then redirected into a correct position, developed, and instrumented with a 5-mm-diameter by 35-mm-long pedicle screw (RS). For each pedicle screw, the maximal torque, seating torque, screw loosening force, and post-loosening axial pullout were measured. Screw loosening and axial pullout were assessed using an MTS machine. ResultsMaximal insertion torque was (111.4±8.2) N·cm and (78.9±6.4) N·cm for OS and RS respectively, showing significant difference (Z=3.038, P=0.002). The seating torque was (86.3±7.7) N·cm and (59.7±5.3) N·cm for OS and RS respectively, showing significant difference (Z=2.802, P=0.005). The screw loosening force was (76.3±6.2) N and (53.0±5.8) N for OS and RS respectively, showing significant difference (Z=2.861, P=0.004). The post-loosening axial pullout force was (343.0±12.6) N and (287.0±10.5) N for OS and RS respectively, showing significant difference (Z=2.964, P=0.003). ConclusionCompared with OS, RS placement after a lateral wall violation shows significantly decreased maximal insertion torque, seating torque, screw loosening force, and post-loosening axial pullout. On this occasion, RS augmentation is a probable option for remediation.
Abstract: Objective To evaluate a new type of treatment that reduces calcification of glutaraldehydetreated bovine jugular venous conduit (BJVC). Methods Fresh bovine jugular veins were treated with glutaraldehyde, followed by Triton X-100 and epoxy chloropropane (EC+Tr group). We compared the group’s appearance, histology, shrinkage temperature, tensile strength, and elongation at break with those of a fresh group, and with a group treated with glutaraldehyde only (GA group). We then implanted the EC+Tr and GA group BJVCs subcutaneously into the backs of SD rats and left them for eight weeks (n=8). The morphologic properties and inflammatory response of the test specimens were evaluated by HE staining. The tissue calcium content was determined by atomic absorption spectrophotometer. Results The shrinkage temperature, tensile strength, and elongation at break of the EC+Tr group were significantly higher than those of the fresh group (86.15±0.92 ℃ vs. 69.94±0.92 ℃,t=35.239, P=0.000; 5.31±0.14 mPa vs.3.15±0.95 mPa,t=6.362, P=0.000; 265.11%±27.80% vs. 16521%±25.06%,t=7.550, P=0.000) and of the GA group (86.15±0.92 ℃ vs. 82.73±1.28 ℃, t=6.137, P=0.000; 5.31±0.14 mPa vs. 4.52±0.56 mPa,t=3.871, P=0.002; 265.11%±27.80% vs.237.85%±17.41%,t=2.351,P=0.034). The tissue structure of the subcutaneously implanted EC+Tr veins remained intact;degradation was slight and they contained few inflammatory cells. The calcium content of the EC+Tr group was lower than that of the GA group (51.22±2.69 μg/mg vs. 73.24±3.82 μg/mg, t=11.545，P=0.000). Conclusion Treatment with Triton X-100 and epoxy chloropropane modification with glutaraldehydetreated bovine jugular venous conduit was an effective way to prepare BJVC that avoided calcification.
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 effectiveness and biomechanical analysis of 3 fixation methods of screw anterior-posterior fixation (SAPF), screw posterior-anterior fixation (SPAF), and buttress plate fixation (BPF) in treatment of posterior Pilon fractures. Methods Fifteen fresh-frozen skeleto-ligamentous lower leg specimens were harvested to establish the models of posterior Pilon fracture, and then fracture was fixed with BPF (n=5), SAPF (n=5), and SPAF (n=5). Vertical force was loaded to internal fixation failure in a speed of 1 cm/minute with servohydraulic testing machine. The instantaneous loads of 1 mm and 2 mm steps and the failure modes were recorded. Between May 2008 and December 2011, 56 patients with posterior Pilon fracture were treated with SAPF (SAPF group) in 11 cases, or SPAF (SPAF group) in 26 cases, or BPF (BPF group) in 19 cases. There was no significant difference in age, gender, injury cause, side, disease duration, and complications among groups (P gt; 0.05). Clinical and radiographic examinations were used to assess the reduction and healing of fracture; the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score and the visual analogue scale (VAS) were used to evaluate the functional outcomes. Results No breaking or bending was observed in all specimens, fixation failure was caused by cancellous bone compression. The instantaneous loads of 1 mm and 2 mm steps were the largest in BPF group, larger in SPAF group, and smallest in SAPF group, showing significant differences among 3 groups (P lt; 0.05). A total of 47 cases were followed up 16-54 months (9 in SAPF group, 22 in SPAF group, and 16 in BPF group), with a mean time of 35.2 months. Fixation failure was found in 2 cases of SAPF group; the other cases obtain bony union within 3 to 4 months (mean, 3.2 months) with no fixation failure. The AOFAS score was significantly lower in SAPF group than in SPAF and BPF groups (P lt; 0.05), but no significant difference was found between SPAF and BPF groups (P gt; 0.05). The VAS score was significantly higher in SAPF group than in SPAF and BPF groups (P lt; 0.05), but no significant difference was found between SPAF and BPF groups (P gt; 0.05). Conclusion SAPF could not reach enough fixation strength for the posterior Pilon fracture; both SPAF and BPF could reach rigid fixation, and have good effectiveness. And from the biomechanical points, BPF could reach better fixation strength than screw fixations.
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 investigate the feasibility of fabricating an oriented scaffold combined with chondrogenic-induced bone marrow mesenchymal stem cells (BMSCs) for enhancement of the biomechanical property of tissue engineered cartilage in vivo. Methods Temperature gradient-guided thermal-induced phase separation was used to fabricate an oriented cartilage extracellular matrix-derived scaffold composed of microtubules arranged in parallel in vertical section. No-oriented scaffold was fabricated by simple freeze-drying. Mechanical property of oriented and non-oriented scaffold was determined by measurement of compressive modulus. Oriented and non-oriented scaffolds were seeded with chondrogenic-induced BMSCs, which were obtained from the New Zealand white rabbits. Proliferation, morphological characteristics, and the distribution of the cells on the scaffolds were analyzed by MTT assay and scanning electron microscope. Then cell-scaffold composites were implanted subcutaneously in the dorsa of nude mice. At 2 and 4 weeks after implantation, the samples were harvested for evaluating biochemical, histological, and biomechanical properties. Results The compressive modulus of oriented scaffold was significantly higher than that of non-oriented scaffold (t=201.099, P=0.000). The cell proliferation on the oriented scaffold was significantly higher than that on the non-oriented scaffold from 3 to 9 days (P lt; 0.05). At 4 weeks, collagen type II immunohistochemical staining, safranin O staining, and toluidine blue staining showed positive results in all samples, but negative for collagen type I. There were numerous parallel giant bundles of densely packed collagen fibers with chondrocyte-like cells on the oriented-structure constructs. Total DNA, glycosaminoglycan (GAG), and collagen contents increased with time, and no significant difference was found between 2 groups (P gt; 0.05). The compressive modulus of the oriented tissue engineered cartilage was significantly higher than that of the non-oriented tissue engineered cartilage at 2 and 4 weeks after implantation (P lt; 0.05). Total DNA, GAG, collagen contents, and compressive modulus in the 2 tissue engineered cartilages were significantly lower than those in normal cartilage (P lt; 0.05). Conclusion Oriented extracellular matrix-derived scaffold can enhance the biomechanical property of tissue engineered cartilage and thus it represents a promising approach to cartilage tissue engineering.
Objective To investigate the biomechanical properties of porous bioactive bone cement (PBC) in vivo and to observe the degradation of PBC and new bone formation histologically. Methods According to the weight percentage (W/ W, %) of polymethylmethacrylate (PMMA) to bioglass to chitosan, 3 kinds of PBS powders were obtained: PBC I (50 ︰ 40 ︰ 10), PBC II (40 ︰ 50 ︰ 10), and PBC III (30 ︰ 60 ︰ 10). The bilateral femoral condylar defect model (4 mm in diameter and 10 mm in depth) was established in 32 10-month-old New Zealand white rabbits (male or female, weighing 4.0-4.5 kg), which were randomly divided into 4 groups (n=8); pure PMMA (group A), PBC I (group B), PBC II (group C), and PBC III (group D) were implanted in the bilateral femoral condylar defects, respectively. Gross observation were done after operation. X-ray films were taken after 1 week. At 3 and 6 months after operation, the bone cement specimens were harvested for mechanical test and histological examination. Four kinds of unplanted cement were also used for biomechanical test as control. Results All rabbits survived to the end of experiment. The X-ray films revealed the location of bone cement was at the right position after 1 week. Before implantation, at 3 months and 6 months after operation, the compressive strength and elastic modulus of groups C and D decreased significantly when compared with those of group A (P lt; 0.05), but no significant difference was found between groups C and D (P gt; 0.05); the compressive strength at each time point and elastic modulus at 3 and 6 months of group B decreased significantly when compared with those of group A (P lt; 0.05). Before implantation and at 3 months after operation, the compressive strength and elastic modulus of groups C and D decreased significantly when compared with those of group B (P lt; 0.05); at 6 months after operation, the compressive strength of group C and the elastic modulus of group D were significantly lower than those of group B (P lt; 0.05). The compressive strength and elastic modulus at 3 and 6 months after operation significantly decreased when compared with those before implantation in groups B, C, and D (P lt; 0.05), but no significant difference was found in group A (P lt; 0.05). At 3 months after operation, histological observation showed that a fibrous tissue layer formed between the PMMA cement and bone in group A, while chitosan particles degraded with different levels in groups B, C, and D, especially in group D. At 6 months after operation, chitosan particles partly degraded in groups B, C, and D with an amount of new bone ingrowth, and groups C and D was better than group B in bone growth; group A had no obvious change. Quantitative analysis results showed that the bone tissue percentage was gradually increased in the group A to group D, and the bone tissue percentage at 6 months after operation was significantly higher than that at 3 months within the group. Conclusion According to the weight percentage (W/W, %) of PMMA to bioglass to chitosan, PBCs made by the composition of 40 ︰ 50 ︰ 10 and 30 ︰ 60 ︰ 10 have better biocompatibility and biomechanical properties than PMMA cement, it may reduce the fracture risk of the adjacent vertebrae after vertebroplasty.
Objective To establish a rapid, simple, and economic method to prepare osteoporosis (OP) in vitro model. Methods Eighty pairs of fresh goat femur were collected from 18-month-old female goats and were randomly divided into 4 groups (20 pairs in each group). The femur was immersed decalcifying solution (18% EDTA) for 1-5 days (group B), 6-10 days (group C), and 11-15 days (group D), while group A had no treatment as control. Four pairs of femur were taken out every day. Quantitative computed tomography was used to scan the medial and lateral femoral condyles, and the bone mineral density (BMD) was calculated. Electronic universal testing machine was used to do three-point bending test and compress and tensile ultimate strenght test, and the mechanical parameters for femur were calculated. Results With demineralized time passing, BMD of the medial and lateral femoral condyles were downtrend in groups A, B, C, and D, showing significant differences among 4 groups (P lt; 0.05); BMD of the lateral femoral condyle was significantly higher than that of the medial femoral condyle in each group (P lt; 0.05). The three-point bending test showed that broken load, ultimate strength, and elastic modulus of groups A and B were significantly higher than those of groups C and D (P lt; 0.05); but no significant difference was found between groups A and B, and between groups C and D (P gt; 0.05). Compress and tensile ultimate strength test showed that the compress and tensile ultimate strengths were significantly higher in group A than in groups C and D (P lt; 0.05), and in group B than in group D (P lt; 0.05), but no significant difference was found between groups A and B, between groups B and C, and between groups C and D (P gt; 0.05). Conclusion The 18% EDTA immersing for 6-15 days is a fast, simple, economical method to prepare an OP in vitro model of goat femur.
Objective To evaluate the biomechanical effect of a self-made iliac screw plate on the stability of lumbo-iliac fixation construct before and after fatigue loading. Methods Twelve fresh lumbo-pelvic specimens from donated adult cadavers with formalin embalm were used in the study. According to whether use the iliac screw plate or not, the specimens were randomly assigned into group A (with iliac screw plate, n=6) and group B (without iliac screw plate, n=6). The bone mineral density (BMD) of L1-4 was measured using dual-energy radiograph absorptiometry. The pedicle screw and iliac screw fixation were given at L3-5, and bilateral facetectomy and diskectomy at L5, S1 level were performed to prepare the model of the intervertebral destabilization. The biomechanical testing was conducted on a material testing machine under 0-600 N compression and — 7-7 N · m torsion loading modes for the initial compressive stiffness and torsional stiffness evaluation. And then 20 000 cyclic compressive loading of 40-400 N was given to the specimen, the stiffness evaluation was repeated. Then the maximum pull-out strength of screws at every level was measured and compared. Gross observation and radiological observation were performed during experiment. Results The BMD values of groups A and B were (1.15 ± 0.13) g/cm2 and (1.12 ± 0.11) g/ cm2 respectively, showing no significant difference between 2 groups (t=0.428, P=0.678). All pedicle screws and iliac screws were inserted in good position; no loosening or breaking of screw was observed during loading. After fatigue loading, the incidence of halo ring around the iliac screws of groups A and B was 16.7% (1/6) and 50.0% (3/6), respectively. The compressive stiffness and torsional stiffness after fatigue loading were significantly lower than those in initial state in groups A and B (P lt; 0.05); there was no significant difference in compressive stiffness and torsional stiffness between groups A and B before fatigue loading (P gt; 0.05). However, group A had higher compressive stiffness than group B (t=2.664, P=0.024) after fatigue loading, and there was no significant difference in torsional stiffness between 2 groups (t=0.410, P=0.690). No significant difference was found in screw pull-out strength of pedicle screws at L3, L4, and L5 levels between groups A and B (P gt; 0.05); however, the pull-out strength of the iliac screws in group A was significantly higher than that in group B (t=3.398, P=0.007). In groups A and B, the pull-out strength of L3 screw was significantly lower than that of L4 and L5 screws (P lt; 0.05). In group A, pull-out strength of the iliac screws was significantly higher than that of L3, L4, and L5 screws (P lt; 0.05); in group B, the pull-out strength of iliac screws was significantly lower than that of L4 and L5 screws (P lt; 0.05). Conclusion In the lumbo-iliac reconstruction, the use of iliac screw plate could resist iliac screw loosening, therefore, it has the potential to increase the stability of lumbo-iliac fixation construct.