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PubMed1998

Comparison of the strengths of lumbosacral fixation achieved with techniques using one and two triangulated sacral screws.

STUDY DESIGN: The strength of sacral screw fixation achieved with techniques using one sacral screw and two triangulated sacral screws with Chopin block was tested on 10 fresh human sacrum specimens. OBJECTIVES: To compare the stiffness and the failure strength of single sacral screw fixation and those of two divergent triangulated sacral screw fixation under different loading conditions. SUMMARY OF BACKGROUND DATA: Weak sacral screw fixation is the major cause of failure in instrumented lumbosacral fusion. Although previous studies have evaluated the strength of anteromedially and anterolaterally inserted sacral screws, the strength of two divergent triangulated sacral screws has not been evaluated biomechanically. It is assumed that increasing the number of sacral screws and using a triangulated insertion technique may increase the strength of purchase for lumbosacral fixation. METHODS: Ten fresh human sacrum specimens were used in this study. Six specimens were from donors less than 30 years of age (younger group), and the other four were from donors more than 60 years of age (aged group). The specimens were assigned randomly to either one side one S1 pedicle screw inserted anteromedially or to the other side with two screws directed anteromedially and anterolaterally. All specimens were tested with an Instron material testing machine (Instron Limited, High Wycombe, England). The average stiffness under compression, tension, and torsion were calculated from the average slopes of the load deformation curves. The failure load was applied for the final testing. RESULTS: The results showed significant differences in stiffness between fixation with one screw and fixation with two divergent triangulated screws. With one S1 pedicle screw fixation, the average stiffness was 203 N/mm for compression, 147 N/mm for tension, and 2 Nm/degree for torsion. With two-screw fixation the average stiffness increased to 255 N/mm (126%), 185 N/mm (126%) and 2.4 Nm/degree (120%), respectively. The average failure strength under tension loads was found to be 1450 N in the younger specimens and was reduced to 980 N in the aged specimens. CONCLUSION: This study showed that fixation with two divergent triangulated screws to the sacrum was significantly stronger than one-screw fixation for lumbosacral fusion. The strength of fixation seems to have a negative correlation with aging.

Adult↗
PubMed2000

Biomechanical assessment of transoral plate fixation for atlantoaxial instability.

STUDY DESIGN: In an experimental study using human cadaver specimens the biomechanical data of anterior atlantoaxial plating according to Harms were evaluated. OBJECTIVES: The purpose of this study was to evaluate this method biomechanically. SUMMARY AND BACKGROUND DATA: The optimum fixation method to achieve fusion at the atlantoaxial joint after odontoid resection is still a matter of discussion. Isolated posterior surgical procedures for treatment of irreducible atlantoaxial kyphosis with spinal cord compression are associated with high rates of morbidity and mortality. Transoral atlantoaxial plate fixation has been designed by Harms as a fixation technique after odontoid resection. In a modification, this procedure has been combined with the posterior wire fusion according to Brooks. METHOD: Eight human cadaver craniocervical specimens were tested in flexion, extension, rotation, and bending with a nondestructive flexibility method using a nonconstrained testing apparatus. Five different groups were examined: 1) control group (intact); 2) unstable group (after dissection of the atlantoaxial ligaments and odontoidectomy), 3) Harms group (transoral atlantoaxial plate fixation) 4) Harms-Brooks group (transoral atlantoaxial plate fixation and dorsal atlantoaxial wire fixation); and 5) Magerl group (transarticular atlantoaxial screw fixation). In a second experimental series, failure loads of the Harms-Brooks and the Magerl fixation methods were determined. RESULTS: The angular displacement of the Harms-Brooks group and the Magerl group was less than in any other group. Stiffness values at 0-3.0 Nm loads in any direction were larger for the Harms-Brooks-and Magerl-fixated specimens than for the Harms, control, or unstable specimens. No statistically significant difference was observed between Harms-Brooks and Magerl reconstruction stiffness. Ultimate failure load in the Harms-Brooks group was higher than in the Magerl group. CONCLUSIONS: Experimentally, isolated anterior atlantoaxial plating was less stable than the combined reconstruction procedures. Transoral plate fixation according to Harms in combination with posterior wire fixation according to Brooks provided a failure load and stiffness equal to transarticular screw fixation according to Magerl.

Aged↗
PubMed1975

C(4) Photosynthesis: Light-dependent CO(2) Fixation by Mesophyll Cells, Protoplasts, and Protoplast Extracts of Digitaria sanguinalis.

Mesophyll cells, protoplasts, and protoplast extracts of Digitaria sanguinalis were used for comparative studies of light-dependent CO(2) fixation. CO(2) fixation was low without the addition of organic substrates. Pyruvate, oxaloacetate, and 3-phosphoglycerate induced relatively low rates (10 to 90 mumoles/mg chlorophyll.hr) of CO(2) fixation when added separately. However, a highly synergistic relationship was found between pyruvate + oxaloacetate and pyruvate + 3-phosphoglycerate for inducing light-dependent CO(2) fixation in the mesophyll preparations. Highest rates of CO(2) fixation were obtained with protoplast extracts. Pyruvate, in combination with oxaloacetate or 3-phosphoglycerate induced light-dependent rates from 150 to 380 mumoles of CO(2) fixed/mg chlorophyll.hr which are equivalent to or exceed reported rates of whole leaf photosynthesis in C(4) species. Concentrations of various substrates required to give half-maximum velocities of CO(2) fixation were determined, with the protoplast extracts generally saturating at the lowest substrate concentrations. Chloroplasts separated from protoplast extracts showed little capacity for CO(2) fixation. The results suggest that CO(2) fixation in C(4) mesophyll cells is dependent on chloroplasts and extrachloroplastic phosphoenolpyruvate carboxylase.The stimulation of pyruvate-induced CO(2) fixation by oxaloacetate and 3-phosphoglycerate is thought to be due to induction of noncyclic electron transport which generates ATP for the conversion of pyruvate to phosphoenolpyruvate by pyruvate Pi dikinase. The primary products of the substrate-induced CO(2) fixation were oxaloacetate and malate, which provides further evidence for carbon fixation through the beta-carboxylation pathway. High rates of light-dependent CO(2) fixation with a significant percentage of (14)C fixed into malate suggest an efficient operation of both photosystems I and II.The substrate inductions are discussed with respect to the proposed role of the mesophyll cell in C(4) photosynthesis, and schemes suggesting the stoichiometry of energy requirements for photosynthetic carbon metabolism in C(4) mesophyll cells are presented.

Journal Article↗
PubMed1985

Relationship between Ureide N and N(2) Fixation, Aboveground N Accumulation, Acetylene Reduction, and Nodule Mass in Greenhouse and Field Studies with Glycine max L. (Merr).

The relationship between ureide N and N(2) fixation was evaluated in greenhouse-grown soybean (Glycine max L. Merr.) and lima bean (Phaseolus lunatus L.) and in field studies with soybean. In the greenhouse, plant N accumulation from N(2) fixation in soybean and lima bean correlated with ureide N. In soybean, N(2) fixation, ureide N, acetylene reduction, and nodule mass were correlated when N(2) fixation was inhibited by applying KNO(3) solutions to the plants. The ureide-N concentrations of different plant tissues and of total plant ureide N varied according to the effectiveness of the strain of Bradyrhizobium japonicum used to inoculate plants. The ureide-N concentrations in the different plant tissues correlated with N(2) fixation. Ureide N determinations in field studies with soybean correlated with N(2) fixation, aboveground N accumulation, nodule weight, and acetylene reduction. N(2) fixation was estimated by (15)N isotope dilution with nine and ten soybean genotypes in 1979 and 1980, respectively, at the V9, R2, and R5 growth stages. In 1981, we investigated the relationship between ureide N, aboveground N accumulation, acetylene reduction, and nodule mass using four soybean genotypes harvested at the V4, V6, R2, R4, R5, and R6 growth stages. Ureide N concentrations of young stem tissues or plants or aboveground ureide N content of the four soybean genotypes varied throughout growth correlating with acetylene reduction, nodule mass, and aboveground N accumulation. The ureide-N concentrations of young stem tissues or plants or aboveground ureide-N content in three soybean genotypes varied across inoculation treatments of 14 and 13 strains of Bradyrhizobium japonicum in 1981 and 1982, respectively, and correlated with nodule mass and acetylene reduction. In the greenhouse, results correlating nodule mass with N(2) fixation and ureide N across strains were variable. Acetylene reduction in soybean across host-strain combinations did not correlate with N(2) fixation and ureide N. N(2) fixation, ureide N, acetylene reduction, and nodule mass correlated across inoculation treatments with strains of Bradyrhizobium spp. varying in effectiveness on lima beans. Our data indicate that ureide-N determinations may be used as an additional method to acetylene reduction in studies of the physiology of N(2) fixation in soybean. Ureide-N measurements also may be useful to rank strains of B. japonicum for effectiveness of N(2) fixation.

Journal Article↗
PubMed1996

Biomechanical characteristics of C1-2 cable fixations.

The biomechanical characteristics of four different methods of C1-2 cable fixation were studied to assess the effectiveness of each technique in restoring atlantoaxial stability. Biomechanical testing was performed on the upper cervical spines of four human cadaveric specimens. Physiological range loading was applied to the atlantoaxial specimens and three-dimensional motion was analyzed with stereophotogrammetry. The load-deformation relationships and kinematics were measured, including the stiffness, the angular ranges of motion, the linear ranges of motion, and the axes of rotation. Specimens were nondestructively tested in the intact state, after surgical destabilization, and after each of four different methods of cable fixation. Cable fixation techniques included the interspinous technique, the Brooks technique, and two variants of the Gallie technique. All specimens were tested immediately after fixation and again after the specimen was fatigued with 6000 cycles of physiological range torsional loading. All four cable fixation methods were moderately flexible immediately; the different cable fixations allowed between 5 degrees and 40 degrees of rotational motion and between 0.6 and 7 mm of translational motion to occur at C1-2. The Brooks and interspinous methods controlled C1-2 motion significantly better than both of the Gallie techniques. The motion allowed by one of the Gallie techniques did not differ significantly from the motion of the unfixed destabilized specimens. All cable fixation techniques loosened after cyclic loading and demonstrated significant increases in C1-2 rotational and translational motions. The bone grafts shifted during cyclic loading, which reduced the effectiveness of the fixation. The locations of the axes of rotation, which were unconstrained and mobile in the destabilized specimens, became altered with cable fixation. The C1-2 cables constrained motion by shifting the axes of rotation so that C-1 rotated around the fixed cable and graft site. After the specimen was fatigued, the axes of rotation became more widely dispersed but were usually still localized near the cable and graft site. Adequate healing requires satisfactory control of C1-2 motion. Therefore, some adjunctive fixation is advocated to supplement the control of motion after C1-2 cable fixation (that is, a cervical collar, a halo brace, or rigid internal fixation with transarticular screws).

Aged↗
PubMed2005

Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation.

STUDY DESIGN: This study was conducted by retrospective case selection and prospective observation of longitudinal changes of the multifidus muscle cross-sectional area and of trunk extension muscle strength in percutaneous and open pedicle screw fixations. OBJECTIVES: To compare postoperative multifidus muscle atrophy and trunk muscle performance of percutaneous pedicle screw fixation against those of open pedicle screw fixation. SUMMARY OF BACKGROUND DATA: Recent attempts to combine percutaneous pedicle screw fixation with minimally invasive fusion techniques are based on an anecdotal presupposition that percutaneous pedicle screw fixation is superior to its open counterpart. However, the benefits of percutaneous pedicle screw fixation are currently poorly defined. METHODS: Nineteen enrolled patients were divided as follows: 11 in the open pedicle screw fixation group (OPF group) and eight in the percutaneous pedicle screw fixation group (PPF group). The preoperative and postoperative cross-sectional area and T2-weighted signal intensity of multifidus muscle were measured by MRI, and trunk extension muscle strength was measured. In addition, various clinical variables were compared between two groups. RESULTS: There was significant decrease in the cross-sectional area of multifidus muscle in the OPF group. In contrast, the results in the PPF group showed no statistical difference between preoperative results and that of the follow-up MRI. Although percutaneous pedicle screw fixation had positive effects on postoperative trunk muscle performance, clinical outcomes were not significantly different in areas of pain score, JOA score, and patient's opinion regarding the outcome of the surgery. However, percutaneous pedicle screw fixation caused less blood loss, and the proportion of patients who did not need postoperative oral analgesics was greater in the PPF group. CONCLUSIONS: Percutaneous pedicle screw fixation caused less paraspinal muscle damage than open pediclescrew fixation and had positive effects on postoperative trunk muscle performance.

Aged↗
PubMed2001

Biomechanical properties of quadruple tendon and patellar tendon femoral fixation techniques.

Two femoral fixation techniques for quadruple hamstring tendon grafts were compared under cyclic loading with the patellar tendon: the rectangular inserted pin (TransFix) and biodegradable interference screw fixation of the quadruple tendon and titanium interference screw fixation of the middle third of the patellar tendon. Porcine specimens were mounted onto a tension load machine, and the tendon-fixation-femur-complex was tested for stiffness, displacement during 800 cycles of loading between 50 and 250 N and ultimate tension load. TransFix fixation showed the greatest stiffness at 183.6 N/mm ( P<0.05). The least displacement under cyclic loading was observed for the titanium interference screw followed by the TransFix and biodegradable interference screw ( P<0.01). The ultimate tension load was greatest for the TransFix fixation at 1303+/-282 N, followed by patellar tendon fixation with 763+/-103 N and the biodegradable interference screw fixation with 480+/-133 N ( P<0.001). To reduce initial elongation of the graft and displacement at the fixation site, preconditioning of both the tendon and tendon-fixation complex is especially important when using quadruple tendons. TransFix fixation provides better stability and greater stiffness and pull-out strength than the other techniques. This finding is of clinical relevance to surgeons of the anterior cruciate ligament.

Absorbable Implants↗
PubMed2005

Complications of temporary and definitive external fixation of pelvic ring injuries.

OBJECTIVES: To determine the incidence of complications of external fixation in pelvic ring injuries, comparing fixator use for temporary and definitive treatment. DESIGN: Retrospective case-note review. SETTING: A regional centre for pelvic trauma in the UK. PATIENTS: 100 consecutive patients. INTERVENTION: All patients were treated with pelvic external fixation for a pelvic ring injury. RESULTS: In 52 patients, external fixation was intended for use as the definitive treatment of the pelvic ring injury and was maintained for a mean duration of 60 days (17-113). In 48 patients, it was used temporarily for a mean duration of 8 days (1-20) before internal fixation of the pelvic ring. The complication rate for definitive and temporary fixators was 62 and 21%, respectively. Pin-site infection occurred in 50% of definitive fixators and 13% of temporary fixators but rarely led to more serious complications. In five patients, the definitive management was changed as a result of a complication of the external fixator. The commonest cause for revision of either fixator was aseptic pin loosening. Revision for loose pins in eight patients was associated with the use of two pins in each iliac crest rather than three. CONCLUSIONS: The temporary use of external fixation is safe and effective, but use for definitive treatment is associated with a high rate of infection and aseptic pin loosening.

Adolescent↗
PubMed1997

A new RNA-friendly fixative for the preservation of penaeid shrimp samples for virological detection using cDNA genomic probes.

In situ hybridization analysis of shrimp histological sections, utilizing Taura syndrome virus (TSV) specific cDNA probes, is the most sensitive diagnostic technique presently available for the detection of this penaeid shrimp viral disease. However, false negative genomic probe results are obtained frequently from samples of Pacific white shrimp, Penaeus vannamei, that have been preserved with Davidson's AFA (acetic acid, formaldehyde, alcohol) fixative and that, otherwise, demonstrate pathognomonic TSV lesions by routine histology. This problem was linked to prolonged storage of shrimp samples in Davidson's fixative, which is highly acidic (pH approximately 3.5-4). Degradation of TSV genomic RNA was hypothesized to be due to either fixative- induced acid hydrolysis and/or acidophilic endogenous ribonuclease activity. Routine H and E histology and in situ hybridization analyses were conducted on equal numbers of TSV infected P. vannamei juveniles that were preserved for four different time periods (2, 6, 10 and 14 days) with either Davidson's fixative or a new, near neutral (pH approximately 6.0-7.0), RNA-friendly fixative (R-F) that was developed by the authors. In situ hybridization assays were conducted with and without R Nase precautions and all of the samples tested contained moderate to severe TSV lesions by routine histology. Davidson's preserved samples produced weak TSV probe signals after 2 days fixation, but did not react with the probes in those samples that were stored for > 6 days in the fixative. In contrast, TSV was detectable by gene probe in all of the time treatment samples preserved with the new R-F fixative. Equivalent in situ hybridization results were obtained when the same samples were analyzed in the absence of RNase-free conditions. These findings suggest that TSV RNA is degraded when samples are stored in an acidic fixative, such as Davidson's, for more than 2 days and that this problem can be prevented through preservation of shrimp samples with R-F fixative. The efficacy of this new fixative is demonstrated and the results show that RNase-free conditions are not necessary for conducting TSV in situ hybridization analyses.

Animals↗
PubMed2003

The strength of different fixation techniques for bicondylar tibial plateau fractures--a biomechanical study.

OBJECTIVE: To compare the mechanical strength of fixation of bicondylar tibial plateau fractures using internal and external fixation techniques. DESIGN: A randomised laboratory testing of fixation methods currently in clinical use. BACKGROUND: To reduce the high complication rate associated with the double plating, many surgeons have started to use less invasive techniques. However the literature comparing the mechanical performance of these methods is still scarce. METHODS: Bicondylar tibial plateau fractures were simulated on Sawbones tibiae and fixed with one of the five fixation methods: dual plating, a two-ring hybrid fixator with inter-fragmentary screws, a ring-bar hybrid fixator with inter-fragmentary screws, lateral plate and medial monolateral external fixator, lateral plate and medial inter-fragmentary screws. Following statistical power calculations, seven tibiae were used for each fixation method. The specimens were tested in cyclical compression to failure. The vertical subsidence in the medial or lateral plateau was measured using extensometers. RESULTS: In all cases the mode of failure was consistent with collapse occurring in the medial plateau. There was no significant difference in the failure load between dual plating and the two-ring hybrid fixator (4218 N and 4184 N respectively; P=0.28, t-test). Failure was seen at significantly lower loads with the other fixation systems. CONCLUSION: Weight-bearing mobilisation of the patient may be undertaken earlier with more confidence by using the double plating or two-ring hybrid fixator rather than other less strong techniques. The choice on which of these two methods to use may depend on tissue viability and surgeon preference.

Compressive Strength↗
PubMed2004

The external fixator: a tool for evaluation of complex low back pain problems.

BACKGROUND: The selection of patients with low back pain for fusion is especially difficult when previous surgical interventions failed and/or invasive tests (discograms, facet blocks) do not allow or do not clearly identify the painful motion segment. Test fixation with an external fixator may mimic a definite internal fixation, such as a fusion, and may help select patients for a more favorable result. The purpose of the study was to clarify if temporary back pain relief by external fixation is predictive for back pain relief after final internal fixation and fusion. METHODS: A retrospective study of 63 patients up to 6 years after evaluation of low back pain problems with an external fixator (index operation) was conducted. The data were collected from the charts based on a protocol that patients had to fill in during evaluation, and the actual state was checked during a clinical investigation at the outpatient clinic. The protocol monitored pain (Visual Analog Scale), pain medication, and work status. Based on the first two parameters, the effect of external fixation was defined as a general estimation as positive, doubtful, or negative. The same parameters were reassessed at follow-up control. RESULTS: In 38 patients, the immobilization test did improve the pain situation, in 11 it remained unchanged, and in 14 the pain got worse. Thirty-eight patients (not identical with the above) underwent definitive fusion afterward, whereas 25 were not operated on. Twenty-one of 30 patients with a positive effect undergoing surgery showed an improved situation after fusion, and 8 of 22 patients without further operation were improved at follow-up. Nine of 12 patients with a negative immobilization test did stay in a bad situation at follow-up. CONCLUSION: The external fixator as a tool for evaluation of patients with low back pain is an expensive measure with a considerable complication risk and only justified in selected patients when any other measure fails to assess and evaluate a patient's situation. If the test fixation reveals no benefit, the patients will remain in a bad situation whatever the therapeutic measure will be. Therefore the main value of the external fixator assessment is the selection of these patients that should not undergo surgery. A positive test fixation means a 72% chance for a satisfactory outcome at least two years after surgery, whereas without surgery the chance for some spontaneous improvement is 57% if the test immobilization did show some improvement. With respect of the "negative" selection of this group of patients (complex history, previous interventions) in our as well as in others series, the obtained results seem acceptable and the use of this invasive diagnostic measure in this group of patients seems justified. Statistical analysis did not show differences of significance as the numbers in the individual groups was too small.

Adult↗
PubMed1998

Carnoy's fixative reduces the number of chymase-positive cells in immunocytochemical staining of cord-blood-derived human cultured mast cells.

KleinJan et al. (Allergy 1996;51:614-20) reported that Carnoy's fixative reduced the number of chymase-positive mast cells in the nasal mucosa. Therefore, in the present study, we investigated whether Carnoy's fixative reduces the number of chymase-positive cells from cord-blood-derived human cultured mast cells when compared with other types of fixatives. Human mast cells were obtained by culturing cord-blood-derived CD34-positive cells in the presence of stem cell factor and interleukin-6. Staining procedures of the cells in fixation with Carnoy's fixative and with other fixatives gave no differences among the number of tryptase-positive cells, whereas fixation with Carnoy's fixative for 15 min gave a significant decrease in the number of chymase-positive cells compared with acetone for 10 min. The number of chymase-positive cells decreased in a time-dependent manner under fixation with Carnoy's fixative, indicating that Carnoy's fixative had a negative effect on the number of chymase-positive cells from cord-blood-derived human cultured mast cells.

Acetic Acid↗
PubMed2003

External fixation of distal radial fractures: four compared with five pins: a randomized prospective study.

BACKGROUND: The purpose of this study of distal radial fractures was to compare the radiographic and clinical results after use of a standard four-pin external fixator with those after use of a five-pin fixator with the fifth pin stabilizing the distal radial articular fragment. METHODS: In an open prospective trial, fifty patients with an unstable distal radial fracture were randomized for treatment with closed reduction and either a standard small Association for the Study of Internal Fixation (ASIF) four-pin fixator (twenty-five patients) or a five-pin external fixator (twenty-five patients). The fixators were removed at nine weeks, and all patients were assessed radiographically and clinically at six months. RESULTS: Follow-up radiographs demonstrated significantly less loss of alignment and length with the five-pin external fixator. Pin site infections were more prevalent with the four-pin fixator. The range of motion of the wrist and forearm, the grip strength, and the Lidstrom functional ratings at six months were all significantly better after use of the five-pin fixator. CONCLUSIONS: The use of a five-pin external fixator, with the fifth pin stabilizing the distal radial articular fragment, yields better radiographic and functional results than does a four-pin fixator.

Adult↗
PubMed1993

Pathological specimens of rat temporal bone--comparison between different fixative solution.

We investigated the difference in temporal bone specimens fixated by three sorts of fixative solution (10% formalin fixative, Wittmaack's fixative and Heidenhein-SuSa fixative). 1. 10% Formalin's fixative solution We found many pinkish precipitates, which are stained by hematoxy-eosin, in the scala media of the cochlea. Same substance is found in the perilymphatic space and endolymphatic space in the vestibulum. The fusion of the cells is indicated in the tectorial membrane, inner sulucus cell, outer sulucus cell especially in the apical turn of the cochlea. 2. Wittmaack's fixative solution The detachment of inner and outer sulucus cells are found from basilar membrane at the basal turn of the cochlea. The tendency in convex and concave form of the Reissner's membrane is most remarkable in these three fixative solution. 3. Heidenhein-SuSa fixative solution In this solution, no precipitates, no fusion of cells are found. No detachment of the inner or outer sulucus cells is also found. This study indicates that Heidenhein-SuSa fixation is most excellent fixative method.

Animals↗
PubMed1976

External fixation in maxillofacial surgery.

The role of external fixation in the treatment of facial fractures is well defined. If standard open reduction and internal fixation techniques do not yield a satisfactory result, external fixation techniques may be required. Open reduction has the advantage of effecting precise approximation of fragments. However, this type of fixation may be inadequate, either because no stable point is available or because the angle of traction involved in fixation may result in displacement of the reduced fracture and subsequent malunion. When the facial skeleton is fractured, it tends to collapse inward, and if injury is severe, an external traction point anterior, lateral, or superior to the facial skeleton may be required to obtain a satisfactory result. There are occasions when intermaxillary fixation may be inadvisable, and in these instances external fixation techniques may be an appropriate means of immobilization. Finally external fixation techniques may be required in instances in which massive tissue loss precludes the use of standard open reduction and internal fixation techniques. It must be reemphasized that the methods of external fixation described here are not meant to supplant the standard techniques of open reduction and interosseous wiring, but when judicially employed complement them in achieving the desired result of precise reduction and firm fixation of the fractured facial skeleton.

Fracture Fixation↗
PubMedDate not supplied

Fracture fixation.

The basic goal of fracture fixation is to stabilize the fractured bone, to enable fast healing of the injured bone, and to return early mobility and full function of the injured extremity. Fractures can be treated conservatively or with external and internal fixation. Conservative fracture treatment consists of closed reduction to restore the bone alignment. Subsequent stabilization is then achieved with traction or external splinting by slings, splints, or casts. Braces are used to limit range of motion of a joint. External fixators provide fracture fixation based on the principle of splinting. There are three basic types of external fixators: standard uniplanar fixator, ring fixator, and hybrid fixator. The numerous devices used for internal fixation are roughly divided into a few major categories: wires, pins and screws, plates, and intramedullary nails or rods. Staples and clamps are also used occasionally for osteotomy or fracture fixation. Autogenous bone grafts, allografts, and bone graft substitutes are frequently used for the treatment of bone defects of various causes. For infected fractures as well as for treatment of bone infections, antibiotic beads are frequently used.

Casts, Surgical↗
PubMed1996

Studies on epoxy compound fixation.

Bioprostheses derived from collagenous tissues have to be fixed and subsequently sterilized before they can be implanted in humans. Clinically, the most commonly used fixative is glutaraldehyde. However, the tendency for glutaraldehyde to markedly alter tissue stiffness and promote tissue calcification are well-recognized drawbacks of this fixative. To address the deficiencies with the glutaraldehyde-fixed tissue, a new fixative, epoxy compound, was used to fix biological prostheses. The study was undertaken to investigate the fixation rates and crosslinking densities of biological tissues fixed with various epoxy compounds. These epoxy compounds are different in their chemical structures. Glutaraldehyde was used as a control. The fixation rates and crosslinking densities of the fixed tissues were determined by measuring their fixation indices and denaturation temperatures, respectively. Generally, the epoxy-fixed tissues were more pliable than the glutaraldehyde-fixed one. Furthermore, the tissues fixed with monofunctional epoxy compound were more pliable than those fixed with multifunctional epoxy compounds. With increasing pH or temperature, the fixation rate of epoxy compound increased. However, the number of epoxide functional groups did not seem to affect the fixation rate of the epoxy compound. The fixation rate of glutaraldehyde was faster than that of epoxy compounds. Additionally, the crosslinking density of the glutaraldehyde-fixed tissue was greater than that of the epoxy-fixed counterparts. Moreover, it was noted that the denaturation temperatures of the tissues fixed with glutaraldehyde or multifunctional epoxy compounds were significantly higher than the fresh ones (p < 0.05), while that fixed with monofunctional epoxy compound stayed roughly the same throughout the entire fixation process (p > 0.05). The results obtained in this study may be used to optimize the fixation process for developing bioprostheses fixed with epoxy compounds.

Animals↗
PubMed1989

The influence of fixation on the relative amount of cytoplasmic ribosomes in mouse epidermal basal keratinocytes. A morphometric study of so-called "dark cells" and their putative role in epidermal carcinogenesis.

The nature and significance of so-called dark keratinocytes in the epidermis during chemical carcinogenesis is still a matter of concern and debate. Based on ultrastructural observations it has been suggested that dark cells most often are shrunken cells. Reports on skin carcinogenesis, however, claim that dark cells are a sign of ongoing tumor promotion and represent those stem cells in the epidermis from which the tumors originate. It is therefore important to find out whether these cells are simply injured and shrunken cells, or vital cells of great importance for carcinogenesis. Dark cells are assumed to be rich in ribosomes. There is evidence, however, that the observed number of dark cells is highly dependent on tissue fixation. In the present ultrastructural study, morphometric methods were used to compare the effects of two different fixation procedures on the amount of cytoplasmic ribosomes in dark cells from both untreated and carcinogen-treated hairless mouse epidermis. The results show that the ultrastructural features of both dark and clear cells vary considerably with different fixation procedures. In acetone-treated controls typical dark cells are only observed when the fixative has a lower osmotic activity than the plasma. With iso-osmolal fixation typical dark cells are not observed. After an abortive two-stage carcinogenesis treatment, in which a single application of 9,10-dimethyl-1,2-benzanthracene (DMBA) in acetone was followed by a single application of 12-O-tetradecanoyl-13-acetate (TPA) in acetone, signs of cell injury could be found after both fixation procedures. With DMBA/TPA and hypo-osmolal fixation the number of dark cells seemed to increase, whereas only signs of cell injury with occurrence of some heavily altered "clear cells" dominated the picture with iso-osmolal fixation. Morphometry showed that both the numerical and the volumetric densities of cytoplasmic ribosomes in basal keratinocytes varied most significantly with the fixation procedure used. The cytoplasmic volumes did not vary in a way that could explain these differences. One might therefore assume that the number of ribosomes depends on the fixative. Large swelling artifacts occurred when a fixative with low osmotic activity was used, leading to compression of neighboring cells. Hence, an increased ribosomal density reported previously in dark cells is probably related to such cell volume artifacts and does not reflect an actually increased quantity of ribosomes.(ABSTRACT TRUNCATED AT 400 WORDS)

9,10-Dimethyl-1,2-benzanthracene↗