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.
Objective To investigate whether or not posterolateral rotatory instabil ity of the elbow is due to type-I and type-II coronoid process fracture together with anterior bundle of medial collateral l igament (AMCL) injury so as to provide a theoretic basis for its cl inical treatment. Methods Ten fresh-frozen upper extremities were collected from cadavera which was donated voluntarily with no evidence of fracture, dislocation, osteoarthritis, mechanical injury of the surrounding l igament and joint capsule. They included 9 males and 1 female with an average age of 25.1 years (range, 19-40 years), including 3 cases at left sides and 7 cases at right sides. All specimens were transected at the upper midhumeral and carpal levels preserving the distal radioulnar joints to get the bone-l igament specimens. An axial load of 100 N compressing the elbow joint was appl ied along the shaft of the forearm in the sagittal plane through the biomechanical study system. The load-displacement plot was measured and analyzed at elbow flexion of 90, 60, and 45° and under four conditions (intact elbow, type-I coronoid process fracture, type-I coronoid process fracture with AMCL deficient, and type-II coronoid process fractures with AMCL deficient). Results The posterior displacements were maximum at 90° elbow flexion. Hence, the results at 90° elbow flexion were analyzed: under condition of intact elbows, the posterior displacement was the smallest (2.17 ± 0.42) mm and the posterolateral rotatory stabil ity was the greatest; under condition of type-I coronoid process fracture, the posterior displacement was (2.20 ± 0.41) mm, showing no significant difference compared with that of the intact elbow (P gt; 0.05); under condition of type-I coronoid process fracture with AMCL deficient, the posterior displacement was (2.31 ± 0.34) mm, showing no significant difference compared with that of intact elbow (P gt; 0.05); and under condition of type-II coronoid process fracture with AMCL deficient, the posterior displacement was (2.65 ± 0.38) mm, showing a significant difference compared with that of intact elbow (P lt; 0.05). There was no macroscopic ulnohumeral dislocation or radial head dislocation during the experiment. Conclusion An simple type-I coronoid process fracture or with AMCL deficient would not cause posterolateral rotatory instabil ity of elbow and may not need to be repaired. But type-II coronoid process fractures with AMCL deficient can cause posterolateral rotatory instabil ity of elbow, so the coronoid process and the AMCL should be repaired or reconstructed to restore posterolateral rotatory stabil ity as well as valgus stabil ity.
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 make a comparison for the change of maximum tensile intensity and stiffness of a whole implant that is placed into bone tunnel with various lengths tendon, by using beagle dog’s autogenous flexor tendons to reconstruct anterior cruciate l igament (ACL). Methods Sixty male beagle dogs were included in the experiment (weighting 13-16 kg). Three dogs were used for intact flexor tendon of both knees (normal control group), 3 dogs for the intact ACL andfemur-graft-tibia complex (auto control group) and 54 dogs (108 knees) for models of reconstructed ACL (6 experimentalgroups according to different lengths of tendon: 5, 9, 13, 17, 21 and 25 mm in the bone tunnel). The tensile intensity and stiffness were measured after 45, 90 and 180 days separately after operation. Results In the normal control group, the maximum tensile intensity of the intact flexor tendon was (564.15 ± 36.18) N, the stiffness was (59.89 ± 4.28) N/ mm. In the auto control group, the maximum tensile intensity of the intact ACL was (684.75 ± 48.10) N, the stiffness was (74.34 ± 6.99) N/ mm, all ruptured through the intra-articular portion of the graft. The maximum tensile intensity of femur-graft-tibia complex in the auto control group was (301.92 ± 15.04) N, the stiffness was (31.35 ± 1.97) N/mm. After 45 days of operation, all failure occurred at the tibial or femoral insertion site. After 90 days of operation, 24 of the breakpoints were scattered in tendon-bone junction, 12 (3 in 17 mm group, 5 in 21 mm group, 4 in 25 mm group) ruptured through the intra-articular portion. After 180 days of the operation, all breakpoints were distributed inside joint of the implant. The maximum tensile intensity and the stiffness were ber in 17, 21 and 25 mm groups than in 5, 9 and 13 mm groups after operation (P lt; 0.05). Conclusion Tendon with 17 mm length, which will be implanted into bone tunnel, is an appl icable index, in reconstruction of ACL by autogenous tendons.
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.
In order to investigate the mechanical response of lumbar vertebrae during gait cycle in adolescents with idiopathic scoliosis (AIS), the present study was based on computed tomography (CT) data of AIS patients to construct model of the left support phase (ML) and model of the right support phase (MR), respectively. Firstly, material properties, boundary conditions and load loading were set to simulate the lumbar vertebra-pelvis model. Then, the difference of stress and displacement in the lumbar spine between ML and MR was compared based on the stress and displacement cloud map. The results showed that in ML, the lumbar stress was mostly distributed on the convex side, while in MR, it was mostly distributed on the concave side. The stress of the two types of stress mainly gathered near the vertebral arch plate, and the stress of the vertebral arch plate was transmitted to the vertebral body through the pedicle with the progress of gait. The average stress of the intervertebral tissue in MR was greater than that in ML, and the difference of stress on the convex and convex side was greater. The displacement of lumbar vertebrae in ML decreased gradually from L1 to L5. The opposite is true in MR. In conclusion, this study can accurately quantify the stress on the lumbar spine during gait, and may provide guidance for brace design and clinical decision making.
Objective To discuss the effect of the calcaneocuboid arthrodesis on three-dimensional kinematics of talonavicular joint and its clinical significance. Methods Ten freshfrozen foot specimens, three-dimensional kinematics oftalonavicular joint were determined in the case of neutral position, dorsiflexion, plantoflexion, adduction, abduction, inversion and eversion motion by meansof threedimensional coordinate instrument（Immersion MicroScribe G2X） before and after calcaneocuboid arthrodesis under non-weight with moment of couple, bending moment, equilibrium dynamic loading. Calcaneocuboid arthrodesis was performed on these feet in neutral position and the lateral column of normal length. Results A significant decrease in the three-dimensional kinematics of talonavicular joint was observed（P＜0.01）in cadaver model following calcaneocuboid arthrodesis. Talonavicular joint motion was diminished by 31.21%±6.08％ in sagittal plane; by 51.46%±7.91％ in coronal plane; by 36.98%±4.12％ in transverse plane; and averagely by 41.25%±6.02％. Conclusion Calcaneocuboid arthrodesis could limite motion of the talonavicular joints, and the disadvantage of calcaneocuboid arthrodesis shouldn’t be neglected.
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 There is few report on dynamic stabil ization for posterior cervical reconstruction. To investigate the biomechanical properties of a novel cervical spine posterior fixation using the bio-derived freeze-dried tendon in posterior cervical spine reconstruction. Methods The palmaris longus flexor tendon and metacarpal extensor tendon were collected from the death donors’ stump to prepare bio-derived tendon. Twenty fresh cervical vertebrae (C1-7) were harvested from goats and were randomly divided into 4 groups (n=5): intact group (group A); injury control group (group B); screwrods fixation group, fixed with screw-rods on C3，4 (group C); tendon reconstruction group, cross-fixed with bio-derived freezedried tendon on C3，4 bilatera facet joints (group D). The range of motion (ROM) values in flexion, extension, lateral bending, and axial rotation were measured. Results In flexion, the ROM values of group C were significantly lower than those of the other 3 groups (P lt; 0.05), and the ROM values of group B were significantly higher than those of groups A and D (P lt; 0.05). In extension, lateral bending, and axial rotation, the ROM values of group C were significantly lower than those of groups A, B, and D (P lt; 0.05), and no significant difference was found within the other 3 groups (P gt; 0.05). Conclusion The novel cervical spine posterior fixation using the bio-derived frozen-dried tendon can provide enough stabil ity in flexion motion, but it can not limit the lateral bending and axial rotation motion, which can provide dynamic stabil ization in animal model.
ObjectiveTo investigate the effects of different concentrations of osteoprotegerin (OPG) combined with deproteinized bone (DPB) on the bone tunnel after the anterior cruciate ligament (ACL) reconstruction. MethodsThe femoral epiphyseal side was harvested from newborn calf, and allogenic DPB were prepared by hydrogen peroxide-chloroform/methanol method. Then, DPB were immersed in 3 concentrations levels of OPG (30, 60, 100 μg/mL) and 3 concentration ratios (30%, 60%, 100%) of the gel complex were prepared. Sixty healthy New Zealand white rabbits, male or female, weighing (2.7±0.4) kg, were divided randomly into 4 groups (n=15):control group (group A), 30% (group B), 60% (group C), and 100% (group D) OPG/DPB gel complex. The ACL reconstruction models were established by autologous Achilles tendon. Different ratios of OPG/DPB gel complex were implanted in the femoral and tibial bone tunnel of groups B, C, and D, but group A was not treated. The pathology observation (including the percentage of the femoral bone tunnel enlargement) and histological observation were performed and the biomechanical properties were measured at 4, 8, and 12 weeks after operation. ResultsOne rabbit died of infection in groups A and D, 2 rabbits in groups B and C respectively, and were added. General pathology observation showed that the internal orifices of the femoral and tibia tunnels were covered by a little of scar tissue at 4 weeks in all groups. At 8 weeks, white chondroid tissues were observed around the internal orifices of the femoral and tibia tunnels, especially in groups C and D. At 12 weeks, the internal orifices of the femoral and tibia tunnels enlarged in groups A, B, and C, but it was completely closed in group D. At each time point, the rates of the femoral bone tunnel enlargement in groups B, C, and D were significantly lower than that in group A, and group D was significantly lower than groups B and C (P<0.05); group C was significantly lower than group B at 8 weeks, but no significant difference was found at 4 and 12 weeks (P<0.05). Hisological observation showed that fresh fibrous connective tissue was observed in 4 groups at 4 weeks; there was various arrangements of Sharpey fiber in all groups at 8 weeks and the atypical 4-layer structure of bone was seen in group D; at 12 weeks, Sharpey fiber arranged regularly in all groups, with typical 4-layer structure of bone in groups B, C, and D, and an irregular "tidal line" formed, especially in group D. Biomechanics measurement showed that the maximum tensile load in group D was significantly higher than that in groups A and B at 4 weeks (P<0.05), but no significant difference was shown among groups A, B, and C, and between groups C and D (P>0.05); at 8 weeks, it was significantly higher in groups C and group D than group A, and in group D than group B (P<0.05), but there was no significant difference between groups A, C and group B (P>0.05); at 12 weeks, it was significantly higher in groups C and D than groups A and B, and in group D than group C (P<0.05), but difference was not significant between groups A and B (P>0.05). ConclusionDifferent concentrations ratios of OPG/DPB gel complexes have different effects on the bone tunnel after ACL reconstruction. 100% OPG/DPB gel complex has significant effects to prevent the enlargement of bone tunnel and to enhance tendon bone healing.