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PubMed2001

[Biomechanical evaluation of an anterior cervical plate-cage fixation system].

OBJECTIVES: The objective of this paper is to present the results of a biomechanical study of an original system of internal fixation of the anterior cervical spine after discectomy. MATERIAL AND METHODS: The system includes an intersomatic cage fixed to an anterior plate. The cage is placed in the intersomatic space after discectomy and is fixed to the plate with a screw. The plate is fasted to the vertebral bodies with two screws with an original blocking system. A polyethylene model of vertebral unit was tested after the placement of a 6 mm cage and 32 mm plate with 14 mm screws (plate-cage system). In a series of static studies the stiffness, the strength in the elastic limit and the ultimate or failure strength in extension, flexion, compression and torsion were calculated. The fatigue study was done in extension reaching 2.5 million cycles. The model was studied also in extension with the plate and intersomatic iliac crest grafts (plate-bone system). RESULTS: The stiffness in extension calculated for the plate-cage system was 4.16 Nm/mm, in flexión 0.56 Nm/mm, in compressión 822 N/mm and in torsión 0.46 Nm/degree. The extension stiffness of the plate-bone system was 4.29 N/mm. The plate-cage system had a strength in the elastic limit of 386.3 N in extension reaching 295 N in the plate-bone system. The ultimate strength in extension for the plate-cage system was 673.3 N and 585 N in the plate-bone system. The strength in the elastic limit and the ultimate strength were 223 N y 336 N in flexion respectively, 1976 N y 3374 N in compression and, finally, 295.7 N y 385 N in torsión. The plate-cage system reached a total of 2.5 million cycles before it broke or began its deformity. CONCLUSIONS: The results of this biomechanical study are compared in a favourably manner with those obtained in similar experiments for the intact functional cervical unit, Morscher plate and a monoblock plate-cage prototype.

Biomechanical Phenomena↗
PubMed1991

Morphologic study of repair of induced osteochondral defects of the distal portion of the radial carpal bone in horses by use of glued periosteal autografts [corrected].

The use of periosteal autografts to resurface osteochondral defects was investigated in 10 horses (2 to 3 years old), and the repair tissue was characterized morphologically. Middle carpal joint arthrotomies were made, and osteochondral defects were induced bilaterally on the distal articular surface of each radial carpal bone. Each defect measured approximately 1 cm2 and extended 3 mm into the subchondral bone plate. Residual subchondral bone plate of control and principal defects was perforated by drilling. A sterile fibrin adhesive was made by mixing a fibrinogen component and a thrombin component. A periosteal autograft was harvested from the proximal portion of the tibia and was glued onto the recipient osseous surface, with its cambium facing the joint cavity. Control defects were glued, but not grafted. Horses were walked 1 hour daily on a walker, starting at postoperative week 7 and continuing for 9 weeks. Sixteen weeks after the grafting procedure was done, carpal radiography was performed, after which horses were euthanatized. Quality of repair tissue of control and grafted defects was evaluated and compared grossly, histologically, and histochemically. Using a reticule, the proportions of various repair tissue types filling each defect were quantitated. Seven weeks after the grafting procedure was done, bilateral arthroscopy revealed synovial adhesions and marginal pannus formation in control and grafted defects. None of the autografts was found floating unattached within the respective middle carpal joints. At 16 weeks, the gross appearance of most grafted and nongrafted defects was similar, and repair was dominated by a fibrous pannus. In 4 grafted defects, bone had formed either concentrically within the defect or eccentrically in the fibrous adhesions between the defect and the joint margin. Histologically, all grafted and nongrafted defects were repaired similarly by infiltration of a mixture of fibrous tissue, fibrocartilage, and bone. Fibrous tissue was the predominant tissue in most defects and its mean proportion was 56 and 59% in the grafted and nongrafted defects, respectively. Fibrocartilaginous tissue in the deeper layers approximated 20%, and woven bone at the base of the defect was 20% in all defects. Histochemically, difference in staining for proteoglycans was not observed between grafted and nongrafted defects. Little remaining original periosteal graft tissue was evident at the defect sites. The only distinguishing feature of grafted defects was the presence of islands of bone formation either at the defect site (n = 2 horses), or in somewhat dorsally displaced tissue that was incorporated in fibrous adhesions (n = 2 horses).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

High-impact poly(L/D-lactide) for fracture fixation: in vitro degradation and animal pilot study.

The impact strength of amorphous lactide copolymers can be significantly improved by blending with biodegradable rubbers. Rubber toughening of amorphous poly(85L/15D -lactide) with the copolymer poly (50/50-trimethylenecarbonate-co-epsilon-caprolactone) results in a high-impact polymer (PDLLA/P(TMC-CL)). In vitro, the PDLLA/P(TMC-CL) blend retained its tensile and impact strength for a long period of time. Up to 45 weeks, the amount of water absorbed by the blend remained very low and no significant mass loss was observed. To test the suitability for fracture fixation, in a dog study mandibular fractures were fixated with PDLLA/P(TMC-CL) bone plates and screws. Bone healing was uneventful without premature failure of the implants. Although long-term degradation studies have to be carried out, PDLLA/P(TMC-CL) seems to be promising for application in fracture fixation.

Animals↗
PubMed2004

[Intracystic allograft in management of long bone cyst merging pathologic fracture].

OBJECTIVE: To investigate the efficiency of intracystic allograft fixed with bone plate and steel plate in management of long bone cyst merging pathologic fracture. METHODS: Twelve cases of long bone cysts with pathologic fractures were treated from January 1996 to April 2002. The median dimension of the cyst on the radiograph was 3. 6 cm x 8.1 cm. We regularly revealed the sites of cysts, cut the anterior wall, got cystic membrane away, implanted allo-bone fibula, ulna or radius shafts which were defatted and deproteined. The auto-bone and the allo-bone of all cases were fixed with bone plate and steel plate; external fixation was managed for 3 weeks after operation. RESULTS: All incisions achieved primary healing. All cases were followed up 2. 7 years on average. According to Capanna's standard, 9 cases completely healed, 3 cases basically healed, no cases recurred. The function in shoulder joint was slightly limited in 2 cases that cysts were located on the upper humerus, while that of the other 10 cases were recovered completely. CONCLUSION: Intracystic allograft fixed with bone plate and steel plate is safe and effective in management of long bone cyst merging pathologic fracture.

Adolescent↗
PubMed2006

[Development of the anterior cervical postdiscectomy arthrodesis: bone graft, plate, intersomatic cage and plate-cage].

The surgical techniques for anterior cervical postdiscectomy arthrodesis are reviewed, including bone graft, cervical plates, intervertebral cages and plate-cage systems. The biomechanical advantages of each method are discussed. An alternative to arthrodesis are simple discectomy and arthroplastia with disc prosthesis. Integrated plate-cage systems are the final result in the evolution of the cervical arthrodesis developments. The available plate-cage systems are described.

Arthrodesis↗
PubMed1991

Scanning electron microscopic study of subchondral bone tissues in osteoarthritic femoral head.

During total hip replacement for 12 cases of advanced osteoarthritis of the hip joint in aged women, three types of diseased or abnormal articular cartilage with different degrees of severity (white articular cartilage, white and hyperplastic articular cartilage, and yellowish articular cartilage) and ivory bone were obtained together with their subchondral bone tissues. These specimens were processed and studied under scanning electron microscope and were compared with sex- and age-matched non-osteoarthritic femoral head articular cartilage specimens. The following findings were observed: 1. In non-osteoarthritic femoral head, the subchondral bone plate was quite thin. The bone plate connected on its deep surface with the lattice-work of trabeculae of the epiphyseal region. The trabeculae were fine and smooth and some revealed round or spindle-shaped callus resulted from microfracture. 2. In osteoarthritic femoral heads, with increased the severity of the articular lesion, the articular cartilage gradually became thinned out and eventually lost. The subchondral bone plate was markedly thickened. The epiphyseal trabeculae were also thickened and turned rough so that the lattice-work pattern gradually disappeared. The thickened trabeculae finally fused into a large piece of dense bone tissue. No microfracture was detected. These changes were attributable to the increased stress imposed on the subchondral bone tissues as a result of defective articular cartilage. Consequently, the changes on the part of the subchondral bone tissues of the osteoarthritic femoral heads were the sequent, rather than the cause, of the articular lesions.

Cartilage, Articular↗
PubMed1993

Pantarsal arthrodesis in dogs and a cat: 11 cases (1983-1991).

Bone plates applied to the cranial surfaces of the tibia, the tarsus, and the metatarsus were used in 10 dogs and 1 cat that underwent pantarsal arthrodesis. Lengthening plates were used in 7 dogs, and 2.7- and 3.5-mm dynamic compression plates were used in the remaining dogs and the cat. Radiography was used to determine whether bone plates became loose or broke, and whether the joint fused completely. Bone plates became loose in 5 dogs; mean time between surgery and development of radiographic evidence of plate loosening was 19.4 months. The bone plate used in the cat broke 4 months after surgery. Overall, 9 of 11 animals had evidence of complete bony fusion of the tarsus at the time of the last radiographic evaluation. One dog had incomplete healing of the talocalcaneocentral joint and another dog had incomplete healing of the tarsometatarsal joint.

Animals↗
PubMed1994

Effect of internal fixation plates on microcirculation in under-plate cortical bones. Microangiography and scanning electronmicroscopy.

To elucidate the effect of the internal fixation plates on the local bone blood supply, we used microangiography and scanning electron microscopy to observe the morphological changes of microcirculation in the cortical bones obtained from intact rabbit tibiae on which plates of two different stiffness had been fixed for comparison. The results indicated that both rigid stainless steel plate and less rigid methyl methacrylate plate could induce the bone microcirculation under the plate to undergo a process from early depression to late reactive recruitment. The features of the microcirculation recruitment such as vascular number, arrangement and dilatation varied with plates of different stiffness and were more obvious in the cortex fixed by rigid stainless steel plate.

Animals↗
PubMed1991

The bonding behavior of calcite to bone.

Plates of calcite (CaCO3) were implanted in rabbit tibiae, and their biocompatibility and bonding ability to bone were studied. The plates were also implanted subfascially in rabbit muscle for 8 weeks, and changes on their surfaces in the body were examined. Contact microradiography and Giemsa surface stain demonstrated direct bonding between calcite and bone without interpositions. The average failure load of the interface between calcite and bone was 4.11 kg, indicating an adequate strength of bonding. However, a Ca-P-rich layer, which formed on the surfaces of other bioactive ceramics in vivo, was not detected by a scanning electron microscope-electron probe x-ray microanalyzer. Scanning electron micrographs of the surface of calcite implanted subfascially for 8 weeks showed marked degradation and a rough surface. However, the surface apatite layer was not detected by thin-film x-ray diffraction analysis and Fourier transform infrared reflection spectroscopy. Calcite is a biodegradable material that bonds to bone without a surface apatite layer. The mechanical bonding provided by the anchoring effect of the newly formed bone into the surface roughness of calcite is considered to be a major factor in calcite-bone bonding.

Animals↗
PubMed2000

Carrageenan-induced arthritis in the rat.

This study documents a model of carrageenan-induced chronic inflammatory arthritis in the rat, using quantitative histomorphometric assessment. Ten Sprague-Dawley female rats were randomly assigned to one of two groups. Arthritis was induced in the right tibiofemoral joint by 7 intra-articular injections of 0.02 mL of 1% carrageenan in the arthritic group over 24 days. The control (normal) group was injected with 0.02 mL of saline in the right tibiofemoral joint. Sagittal sections of the right knee joint (distal femur and proximal tibia) were assessed by histomorphometry using the LECO 2001 image analysis system. Articular cartilage thickness, epiphyseal plate thickness, subchondral bone plate thickness, trabecular bone volume and thickness of the synovial lining cell layer were measured. Differences between normal and arthritic groups were statistically significant for articular cartilage thickness of the femur, epiphyseal plate thickness of both the femur and tibia, subchondral bone plate thickness of the tibia and the thickness of the synovial lining cell layer. These findings demonstrate that carrageenan-induced arthritic changes are similar to other, established models of arthritis in the rat.

Animals↗
PubMed1976

Biocompatibility of nitinol alloy as an implant material.

The biocompatibility of nitinol alloy as a potential implant material was investigated through in vivo studies on beagles. A high-purity alloy was fabricated into prototype bone plates and implanted into the femurs of beagles. Commercial cobalt-chromium (Co-Cr) alloy bone plates served as reference controls, an additional control data were obtained from beagles subjected to "sham" operations. The bone plates were removed from the animals and examined after exposures of 3, 6, 12, and 17 months. There was no evidence of either localized or of general corrosion on the surfaces of the bone plates and screws. Gross clinical, radiological, and morphological observations of the tissue at the implantation sites during the autopsies uncovered no signs of adverse tissue reactions resulting from the implants. Histological analyses were performed on samples of muscle and bone adjacent to the implantation sites, and of tissues removed from such organs as the liver, spleen, brain, and kidneys. No significant differences were noted between samples taken from controls and those taken from dogs exposed to the implants. Neutron activation analyses were carried out on suitable samples. The analysis data suggest that there is no metallic contamination in the organs due to the implants; however, there does appear to be some chromium contamination from the Co-Cr alloy implants in the adjacent bone. On the basis of the totality of the data, it is concluded that nitinol alloy is sufficiently compatible with dog tissue to warrant further investigation of its potential as a biomaterial.

Activation Analysis↗
PubMed1991

Posterior cervical arthrodesis with AO reconstruction plates and bone graft.

The efficacy of posterior arthrodesis of the cervical spine with AO reconstruction plates and autogenous bone graft was evaluated in a prospective study. The technique of surgical exposure and the application of the reconstruction plates fixed with screws to the lateral masses is described in detail. Of 30 patients with unstable cervical spines, all had solid fusions based on flexion and extension radiographs at follow-up averaging 17.8 months. No patient's neurologic function deteriorated. All incomplete spinal cord injuries improved at least one Frankel level. There were no neurologic or vascular complications. At follow-up, three patients had fusions extending one level longer than those instrumented. Three other patients had an increase in kyphosis compared with the operative reduction, which was not clinically significant. Although a single screw loosened in three other patients, none had an increased deformity, and all progressed to successful arthrodesis. This technique is particularly advantageous when spinous processes, laminas, and facets are injured or deficient, or when facet-type fusions are indicated.

Adolescent↗
PubMed2000

Effect of plate position relative to bending direction on the rigidity of a plate osteosynthesis. A theoretical analysis.

Mechanical unloading of the plated bone segment is observed after plate osteosynthesis because the implant takes over a part of the physiological loading. Strain reduction in the bony tissue depends on the rigidity of the plate (cross-sectional area, geometrical form, and modulus of elasticity). The aim of the present study was to calculate theoretically the effect of plate position relative to bending direction on the overall bending stiffness of the composite system plate-bone. To calculate the rigidity, a cylindrical bone model with mechanical characteristics similar to a sheep tibia and a rectangular plate cross-section corresponding to a DC-plate with either a modulus of elasticity of steel or titanium was used. Calculations under different bending directions were performed according to the laws of the linear bending theory and the composite beam theory. The bending stiffness of a plate osteosynthesis reaches a minimum and a maximum respectively, in cases in which the bending moment acts in the direction of the main axis of the area moment of inertia of the plate. The minimum is present with the plate bent vertically, the maximum with the plate bent horizontally, e.g. on the tension side of the composite system--on the assumption that the bone structure opposite the plate is capable of withstanding compressive loading. For steel and titanium plates, factors of 2 and 2.25 respectively were calculated between the minimum and the maximum bending stiffnesses of the osteosynthesis. The bending rigidity of the plate alone has only a minimal effect on the total stiffness of the osteosynthesis. With a plate bent vertically, the difference between steel and titanium plates was 18%, with the plate bent horizontally (situated on the tension side), it was only 7%. The bending stiffness of a plate osteosynthesis depends on the cross-section, the geometrical form, and the modulus of elasticity of the plate, as well as on the plate position relative to the bending direction of the composite system. The modulus of elasticity of the plate is relatively unimportant, while with a given plate the individual plate position relative to the bending direction is of crucial importance. Thus, changing the modulus of elasticity of the plate cannot solve the problem of implant induced unloading of the bone cortex because the bending stiffness of the composite system depends much more on the plate position relative to the bending direction.

Animals↗
PubMed2005

Effects of hyaluronan on three-dimensional microarchitecture of subchondral bone tissues in guinea pig primary osteoarthrosis.

Hyaluronan (HA) has received increasing interest as a potential agent in therapeutic intervention in osteoarthrosis (OA). HA has been shown to reduce arthritic lesions in experimental animal models of articular cartilage injury. This study was to investigate the effects of high molecular weight HA intra-articular injection on subchondral bone tissues. Fifty-six male guinea pigs were randomly divided into 5 groups. During the initial 2.5-month period, three groups received intra-articular injection of HA 0.4 mg/kg/week for 5 weeks in both knee joints. Two control groups received vehicle. After 2.5 months, one HA group and one control group were sacrificed. The remaining 3 groups (5.5-month groups) were left for an additional 3 months before sacrifice during which time one HA group received additional 5 weeks injections, one HA group received no more injections, and the control group received vehicle. The left tibiae were harvested and micro-CT scanned to quantify three-dimensional microarchitecture of subchondral bone plate, cancellous bone and cortical bone, followed by mechanical testing and collagen and mineral determinations. All HA-treated groups had almost normal cartilage, whereas the control groups had typical OA-related cartilage degradation. In the 2.5-month group, HA resulted in significantly decreased subchondral plate volume fraction and thickness and HA-treated cancellous bone had significantly lower bone volume fraction, and typical rod-like structure. After 5.5 months, these changes were more pronounced, with an additional marked decrease in connectivity and bone surface density. HA-treated cortical bone had significantly greater volume fraction at both observation times. HA groups had greater bone mineral concentration and reduced collagen to mineral ratio with similar mechanical properties of cancellous bone but less stiff cortical bone. The effects of HA on cartilage and subchondral bone were maintained when treatment was discontinued. In summary, HA effectively protects against cartilage degeneration, decreases subchondral bone density and thickness, changes trabecular structure toward rod-like, so that subchondral bone becomes more compliant and thereby reduces cartilage stress during impact loading. HA preserved cancellous bone mechanical properties by increasing bone mineralization. Early HA administration is effective for intervention of OA initiation and progression, and short-term early HA treatment is sufficient to maintain treatment effects.

Animals↗
PubMed1976

[The vessel behavior of the bone following plate osteosynthesis and subsequent osteomyelitis. An experimental study at the dog tibia (author's transl)].

In this paper the revascularisation pattern of the dog tibia diaphyse following osteotomy and plate osteosynthesis with subsequent osteomyelitis is described at various stages. As compared to undisturbed plate osteosynthesis the differences and conformities in revascularisation are shown. It is attempted to interpret the vessel behaviour under clinical aspects.

Animals↗
PubMed1995

[Experimental deformation in a bone fixation plate: measurement using holographic interferometry].

The minute mechanical properties of the tibia fixed by a metal plate and screws were investigated under various simulated loading conditions. The bracing technique and the design of the osteosynthetic plate are discussed based on the measurement results. The specimens were eight dried human tibias. Four different fixation method were employed using an AO plate system, and also using an Eggers plate system. The bending force, torsion force and axial force were applied to the tibia. Deformation in the tibia and/or metal plate was measured using double exposure holographic interferometry. The mechanical properties were estimated from the fringe pattern and from the deformation curve obtained from the reconstruction image of the holographic interferometry. The fixation capability of the plate systems differed according to the direction of the loading. The reconstruction image of the hologram showed that deformation increased mainly in the plate corresponding to the fracture line of the tibia. Screws nearer the fracture line were more important in increasing the fixation capability of the plate. Twisted deformations in the plate were observed under a simple bending force. The new measurement method of holographic interferometry clearly showed the two dimensional bending and the twisted deformation in detail.

Biomechanical Phenomena↗