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 role of glenoid osseous structure on anterior stabil ity of shoulder so as to provide the biomechanical basis for cl inical treatment. Methods Ten fresh shoulder joint-bone specimens were collected from10 adult males cadavers donated voluntarily, including 4 left sides and 6 right sides. The displacements of the specimens were measured at 0° and 90° abduction of shoulder joint by giving 50 N posterior-anterior load under the conditions as follows: intact shoulder joint, glenoid l ip defect, 10% of osseous defect, 20% of osseous defect, and repairing osseous defect. Results For intact shoulder joint, glenoid l i p defect, 10% of osseous defect, 20% of osseous defect, and repairing osseous defect, the displacements were (10.73 ± 2.93), (11.43 ± 3.98), (13.58 ± 4.86), (18.53 ± 3.07), and (12.77 ± 3.13) mm, respectively at 0° abduction of shoulder joint; the displacements were (8.41 ± 2.10), (8.55 ± 2.28), (9.06 ± 2.67), (12.49 ± 2.32), and (8.55 ± 2.15) mm, respectively at 90° abduction of shoulder joint. There was no significant difference between intact shoulder joint and others (P gt; 0.05) except between intact shoulder joint and 20% of osseous defect (P lt; 0.05). Conclusion When shoulder glenoid l ip defects or the glenoid osseous defect is less than 20%, the shoulder stabil ity does not decrease obviously, indicating articular l igament complex is not damaged or is repaired. When glenoid osseous defect is more than 20% , the shoulder stabil ity decreases obviously even if articular l igament complex is not damaged or is repaired. Simultaneous repair of glenoid osseous defect andarticular l igament complex can recover the anterior stabil ity of the shoulder.
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 determine whether the number of distal locking bolts have an impact on the biomechanical feature of locking intramedullary nails. Methods Twenty locking nails tested were divided into two groups randomly. One distal locking screw was used in first group (single bolt group); and two were used in the other group (double bolts group). After being fixed in the model, compressive and torsional strength of the interlocking nail were measured in each group. Results The average maximum strength of double bolts group and single bolt group was 2 160 N and 1 880 N respectively in compression tests(P＜0.05). In torsion tests, the average maximum torsional moment of double bolts group and single bolt group was 55.8 Nm and 55.5 Nm respectively(P＞0.05), the average maximum torsional angle indouble bolts group and single bolt group was 58.3° and 58.0° respectively(P＞0.05). Conclusion Single distal bolt used in interlocking nail system can meet clinical request, though the whole biomechanical behavior isnot better than that of double bolts. One distal bolt is enough for the stable fracture types and double bolts should be used in the serious fracture types.
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 explore the biomechanical stabil ity of dynamic sleeve three-wing screw for treatment of femoral neck fracture and to provide theoretical basis for choosing dynamic sleeve three-wing screw in cl inical appl ication. Methods Nine human cadaveric femurs were selected and divided randomly into 3 groups (n=3), excluding deformities, fractures, and other lesions. The central neck of the specimens were sawn with hand saw respectively at Pauwels angles of 30, 50, and 70°. All cut ends were fixed with dynamic sleeve three-wing screw. Instron-8874 servohydraul ic mechanical testing machine was used to fixed the specimens which simulated uni ped standing, at the rate of 10 mm/minute and l inear load 0-1 200 N at 11 key points. The strain values of princi pal pressure side and princi pal tension side under different loads were measured. Results There was a peak at 6th point in the 1 200 N load. The strain values at Pauwels angles of 30, 50, and 70° were (—1 657 ± 171), (—1 879 ± 146), and (—2 147 ± 136) με; showing significant differences (P lt; 0.01). The strain values of princi pal pressure side and princi pal tension side of the femoral neck became higher with the increasing Pauwels angle under the same load, showing significant differences (P lt; 0.01). The strain values became higher with the increasing load under the same Pauwels angle (P lt; 0.01). Conclusion Dynamic sleeve three-wing screw has good biomechanical stabil ity for treatment of femoral neck fracture. It explains theoretically that the fracture is more unstable with the increasing Pauwels angle．
Objective To investigate the influence of collagen on the biomechanics strength of tissue engineering tendon. Methods All of 75 nude mice were madethe defect models of calcaneous tendons, and were divided into 5 groups randomly. Five different materials including human hair, carbon fibre (CF), polyglycolic acid (PGA), human hair and PGA, and CF and PGA with exogenous collagen were cocultured with exogenous tenocytes to construct the tissue engineering tendons.These tendons were implanted to repair defect of calcaneous tendons of right hind limb in nude mice as experimental groups, while the materials without collagenwere implanted to repair the contralateral calcaneous tendons as control groups. In the 2nd, 4th, 6th, 8th and 12th weeks after implantation, the biomechanicalcharacteristics of the tissue engineering tendon was measured, meanwhile, the changes of the biomechanics strength were observed and compared. Results From the 2nd week to the 4th week after implantation, the experimental groups were ber than the control groups in biomechanics, there was statistically significantdifference (Plt;0.05). From the 6th to 12th weeks, there was no statisticallysignificant difference between the experiment and control groups (Pgt;0.05). Positivecorrelation existed between time and intensity, there was statistically significant difference (Plt;0.05). The strength of materials was good in human hair,followed by CF, and PGA was poor. Conclusion Exogenous collagen can enhance the mechanics strength of tissue engineering tendon, and is of a certain effect on affected limb rehabilitation in early repair stages.
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 an optimal method for SD rat skeletal muscle decellularization. Methods Sixteen SD rats (male and female) weighing 180-200 g were used. Thirty-six skeletal muscle bundles obtained from 10 rats were randomly divided into 3 groups: normal group (group A, n=4) received non-decellularization; time group (group T, n=16) andconcentration group (group C, n=16) underwent decellularization using hypotonic-detergent method. Concentration of sodium dodecyl sulfate (SDS) was 1.0% for T group, which was subdivided into groups T1, T2, T3 and T4 (n=4 per subgroup) according to different processing durations (24, 48, 72 and 96 hours). Group C was treated for 48 hours and subdivided into groups C1, C2, C3 and C4 (n=4 per subgroup) according to different SDS concentrations (0.5%, 1.0%, 1.5% and 2.0%). The muscle bundles of each group underwent HE staining observation and hydroxyproline content detection in order to get the optimal decellularization condition. Seven of 14 complete skeletal muscle bundles obtained from 6 SD rats were treated with the optimal decellularization condition (experimental group), and the rest 7 muscle bundles served as normal control (control group). The muscle bundles of each group were evaluated with gross observation, Masson staining and biomechanical test. Results HE staining: there was no significant difference between groups T1, T2, C1, C2 and C3 and group A in terms of muscle fiber; portion of muscle fibers in group C4 were removed; muscle fibers in group T3 were fully removed with a complete basement membrane structure; muscle fibers of group T4 were fully removed, and the structure of basement membrane was partly damaged. Hydroxyprol ine content detection: there was no significant difference between group A and groups C1, C2, C3, T1 and T2 (P gt; 0.05); significant difference was evident between group A and groups C4, T3 and T4 (P lt; 0.05); the difference between group C4 and groups T3and T4 was significant (P lt; 0.05); no significant difference was evident between group T3 and group T4 (P gt; 0.05). The optimal decellularization condition was 4 , 1.0% SDS and 72 hours according to the results of HE staining and hydroxyproline content detection. Gross observation: the muscle bundles of the experimental group were pall id, half-transparent and fluffier comparing with the control group. Masson staining observation: the collagen fibers of the experimental group had a good continuity, and were fluffier comparing with control group. Biomechanics test: the maximum breaking load of the experimental group and the control group was (1.38 ± 0.35) N and (1.98 ± 0.77) N, respectively; the maximum extension displacement of the experimental group and the control group was (3.19 ± 3.23) mm and (3.56 ± 2.17) mm, respectively; there were no significant differences between two groups (P gt; 0.05). Conclusion Acellular matrix with intact ECM and complete removal of muscle fibers can be obtained by oscillatory treatment of rat skeletal muscle at 4℃ with 1% SDS for 72 hours.
To evaluate the changes in stabil ity of the wrist after experimental traumatic triangular fibrocartilage complex (TFCC) lesions, and to provide basic theoretical criteria for cl inical treatment. Methods Fourteen adult cadaver upper extremities specimens were included. Two of 14 specimens were tested in pre-experiment. The specimens were tested in a INSTRON 8874 biomechanics measuring instrument. First a dorsal arthrotomy (ART) was performed, and second test was with 1 of 4 different experimental lesions according to Palmer’s classification of traumatic TFCC lesions (n=3). 1A: central perforation; 1B: ulnar avulsion with or without fracture of processus styloideus ulnae; 1C: distal avulsion with l igament injury; 1D: radial avulsion. Forced internal∕external rotation torque were recorded in the interval — 60° to 60° of flexion. Results The average torque of the dorsal ART was (0.713 ± 0.121) Nm, and the 1B-1 lesion (ulnar avulsion without ulnar styloid fracture) was (0.709 ± 0.134) Nm, the 1B-2 lesion (ulnar avulsion with ulnar styloid fracture) was (0.409 ± 0.113) Nm. The difference between the 1B-1 lesion and the dorsal ART was not significant but the difference between the 1B-2 lesion and the dorsal ART was significant (P lt; 0.05). The average torque of the 1C lesion in about 45° of wrist extention and flexion were (0.878 ± 0.184) Nm and (0.988 ± 0.197) Nm, and the dorsal ART were (1.510 ± 0.173) Nm and (1.540 ± 0.093) Nm. The difference between the two groups was significant (P lt; 0.05). The 1A lesion and 1D lesion did not alter significantly wrist stabil ity. Conclusion The 1B-2 lesion and 1C lesion alter significantly the stabil ity of the wrist.