Bone strength is reduced in a neonatal androgenized rat model

Background

Whether polycystic ovary syndrome (PCOS) affects bone health during a woman's lifespan remains controversial. An androgenized rodent model replicated many metabolic and reproductive features of women with PCOS, and we aimed to use it to investigate the impact of androgens on microarchitecture (by micro-CT), bone mechanical strength, bone formation and resorption markers in rats with intact ovaries (SHAM) who underwent oophorectomy.

Methods

Wistar rats (Rattus norvegicus albinus) were employed for the experiments in this study. The protocol of androgenization consisted of the application of 1.25 mg s.c. testosterone propionate beteween days 2-5 of life, while the controls received the same amount of corn oil s.c. as previously established. Androgenized SHAM rats exhibited chronic anovulation identified by vaginal cytology and a reduction in the proportion of corpus luteum in the ovary in comparison to control SHAM rats. The realization of the ovariectomy or SHAM procedure occurred on Day 100 of life. All groups (n = 8) were followed-up for 180 days to address the study endpoints.

Results

Micro-CT from androgenized female rats (SHAM) showed a divergence between the trabecular and cortical bone profiles. Compared to SHAM controls, these rats had an increase in trabecular bone mass with a diminution in bone resorption C-terminal telopeptide of type 1 collagen (CTX) (p < 0.05), a concomitant decrease in cortical area and thickness in the femur, and a reduction in the strength of the femur on the mechanical test (p < 0.01).

Conclusions

Our results suggest that a reduction in the cortical thickness and cortical area observed in PCOS model rats was associated with a reduced strength of the femur, despite increased trabecular formation. Ovariectomy in the androgenized OVX group limited the progression rate of cortical bone loss, resulting in bone resistance and cortical thickness comparable to those observed in the control OVX group.

Systemic effects of oral tolerance in bone healing

Bone fractures cause acute inflammation that, despite being important for initial repair, may delay the healing of the damaged bone. Parenteral injection of dietary protein has been shown to decrease inflammation and accelerate the repair of skin wounds and other inflammatory pathologies. Thus, our aim was to evaluate whether the intraperitoneal (i.p.) immunization with zein, an abundant protein in rodent chow, would favor bone healing. Wistar rats received i.p. immunization: saline (SG), adjuvant (AG) and zein associated with adjuvant (ZG). Then, a 2 mm of defect bone was performed on the right tibia, and on days 7, 14, 28 and 45 thereafter, analyses were performed. The results showed that the injection of zein reduced inflammation without impairing bone mineralization. Moreover, biomechanical tests demonstrated higher levels of maximum force (N) in ZG, indicating better mechanical resistance in relation to the others. The computerized tomography also indicated lower levels of medullary content in the ZG than in the SG, suggesting the absence of trabeculae in the medullary region in the ZG. These findings suggest that the injection of zein in previously tolerated animals may improve bone repair, leading to mechanically functional bone formation.

Collagen membrane from bovine pericardium for treatment of long bone defect

The treatment of bone regeneration failures has been constantly improved with the study of new biomaterials. Techgraft® is a collagen membrane derived from bovine pericardium, which has been shown to have biocompatibility and effectiveness in tissue repair. However, its use in orthopedics has not yet been evaluated. Therefore, the purpose of this study was to characterize a bovine pericardium collagen membrane and evaluate the effects of its use in the regeneration of a bone defect in rat tibia. Scanning electron microscopy, atomic force microscopy, weight lost and water uptake tests, and mechanical test were performed. Afterwards, the membrane was tested in an experimental study, using 12 male Sprague Dawley rats. A bone defect was surgically made in tibiae of animals, which were assigned to two groups (n = 6): bone defect treated with collagen membrane (TG) and bone defect without treatment (CONT). Then, tibiae were submitted to micro-CT. The membranes preserved their natural collagen characteristics, presenting great strength, high water absorption, hydrophilicity, and almost complete dissolution in 30 days. In the experimental study, the membrane enhanced the growth of bone tissue in contact with its surface. A higher bone volume and trabeculae number and less trabecular space was observed in bone defects of the membrane group compared to the control group at 21 days. In conclusion, the Techgraft membrane seems to have favorable characteristics for treatment of long bone repair.

Mechanical Analysis after Proximal Femoral Reinforcement with Polymethylmethacrylate in Alternated Double Holes

Objective  To evaluate, through a biomechanical assay, the maximum load, energy, and displacement necessary for the occurrence of fractures in synthetic models of femurs after the removal of cannulated screws and the performance of a reinforcement technique with polymethylmethacrylate (PMMA) in different combined positions. Methods  In total, 25 synthetic bones were used, and they were divided into 4 groups: the control group (CG), with 10 models without perforation, and the test groups (A, B and C), with 5 models each. The test groups were fixed with cannulated screws using the Asnis technique, and they had the synthesis removed, and two of the holes formed by the reinforcement technique with PMMA were filled. The biomechanical analysis was performed simulating a fall on the large trochanter using a servo-hydraulic machine. Results  All specimens of the CG and of groups A, B and C presented basal-cervical fracture of the femoral neck, except for a single model in group B, which presented a longitudinal fracture. An average of 5.4 mL of PMMA were used to reinforce the groups with filling. According to the analysis of variance (ANOVA) and the Tukey multiple comparison test, at the level of 5%, we observed that the CG presented significant differences in relation to groups A and C in the following parameters: maximum load, energy up to the fracture, and displacement. Conclusion  We observed that groups A and C, when compared to the CG, showed significant differences in the observation of displacement, maximum load, and energy until the fracture.

Analysis of performance, bone characteristics, and expression of genes involved in the balance of ionic concentrations in broilers subjected to dietary electrolyte balance levels

1. Sodium bicarbonate (NaHCO₃), potassium carbonate (K₂CO₃), and ammonium chloride (NH₄Cl) are commonly used to correct dietary electrolyte balance (DEB) in birds. However, there are many gaps in the knowledge of their effects when used simultaneously. This study investigated the effect of DEB levels on performance, femur bone characteristics and the expression of genes related to the balance of ionic concentrations in broilers at 21 days of age.2. Male Cobb broiler chickens (n = 245), aged 1-21 d, were divided into groups based on a completely randomised design with five DEB levels (110 mEq/kg, 175 mEq/kg, 240 mEq/kg, 305 mEq/kg, and 370 mEq/kg).3. The performance characteristics measured included body weight (BW), body weight gain (BWG), feed intake (FI), feed conversion (FCR) and body weight birds slaughtered (BWS).4. The bone variables assessed in the femur were weight (WE), relative bone weight (RBWE), length (L), width (WI), maximum load supported (MLS), bone-breaking resistance (BR), and Seedor index (SI). In addition, the expression of CHP1, SLC9A1, and SLC24A3 in the livers, intestines and kidneys of birds was evaluated.5. The DEB level of 370 mEq/kg, at Na⁺ content of 0.48%, resulted in the highest averages for L, MLS, and BR of the femur. This DEB level increased the expression of SLC9A1 in the liver and SLC24A3 in the intestine. A 240 mEq/kg DEB level decreased the expression of CHP1 in the liver, while supplementation with 110 mEq/kg increased the expression of SLC24A3 in the kidney.6. In conclusion, 370 mEq/kg DEB improved FCR and increased the mean bone characteristics of the femur (L, MLS, and BR) and the expression of SLC9A1 and SLC24A3 in the liver and intestine, respectively. These findings should be considered in future assessments of the effects of DEB levels on broilers.

The Role of Pedicle Screw Surface on Insertion Torque and Pullout Strength

Objective  Compare by mechanical tests the pullout resistance and the insertion torque of rough and smooth pedicle screws. Methods  Pedicle screws with rough surface and smooth surface, with diameters of 4.8; 5.5 and 6.5 mm, were inserted in polyurethane blocks with density of 10 PCF (0.16 g/cm3). Insertion torque and pullout strength were assessed. Results  The pullout strength of the rough surface and smooth surface screws did not differ, except in the group of 4.8 mm diameter screws. In this group, the rough surface screws showed greater resistance to pullout. Conclusion  Pedicle screws with a rough surface did not show increased pullout resistance in the acute phase of their insertion in polyurethane blocks compared to smooth surface screws. The rough surface screws had a higher insertion torque than the smooth surface screws, depending on the diameter of the screw and the preparation of the pilot hole.

Influence of an Alternative Implant Design and Surgical Protocol on Primary Stability

The purpose of thisin vitrostudy was to evaluate the influence of a new proposal of implant design and surgical protocol on primary stability in different bone densities. Four groups were tested (n=9): G1 - tapered, cone morse, Ø 4.3 mm x 10 mm in length (Alvim CM); G2 - experimental tapered; G3 - cylindrical, cone morse, Ø 4.0 mm x 11 mm in length (Titamax CM) and G4 - experimental cylindrical. The experimental implants were obtained from a design change in the respective commercial models. The insertion was performed in polyurethane (PU) blocks 0.24 g/cm3(20 pcf) and 0.64 g/cm3(40 pcf), according to different surgical protocols. The primary stability was measured by means of insertion torque (IT) and pullout test. Data were analyzed by ANOVA, Tukey's test (α=0.05) and Pearson's correlation. For IT and pullout, conventional and experimental implants showed no difference between them when inserted in the 20 pcf PU (p>0.05). In the 40 pcf PU, the modified implants exhibited greater IT (p<0.05) and lower pullout (p<0.05) compared to the respective conventional models. The implant design tested associated with the surgical protocol, positively influenced primary stability in higher density bones.

PRELIMINARY MECHANICAL TEST OF PROXIMAL FEMUR REINFORCEMENT WITH CEMENTED X-SHAPED PMMA

Objective:

To evaluate the mechanical behavior of the proximal end of the femur submitted to the X-shaped polymethylmethacrylate (PMMA) reinforcement technique.

Methods:

Fifteen synthetic femurs, with a Nacional^® density of 10 PCF, were divided into two groups: the DX group, with 5 units that were submitted to PMMA reinforcement, and the DP group, with 10 units, which were evaluated intact. The volume of PMMA required, the maximum load, and the absorbed energy to fracture were analyzed by means of a static mechanical bending test simulating a fall on the greater trochanter.

Results:

A mean of 6 ml of PMMA was used to model the X-reinforcement; it was observed that the DX group presented significantly higher maximum load (median = 1553 N, p = 0.005) and absorbed energy to fracture (median = 9.7 J; p = 0.050) than the DP group (median = 905 N and 6.6 J).

Conclusion:

X-reinforcement of the proximal end of synthetic femurs showed a statistically significant increase in the maximum load and absorbed energy to fracture in the mechanical assay when compared to the control group. Level of Evidence III, Experimental study.

A high-fat diet can affect bone healing in growing rats

A high-fat diet (HFD) can have a negative effect on bone quality in young and old people. Although bone healing in children is normally efficient, there is no evidence that children who have a diet rich in fat have compromised bone fracture regeneration compared with children with recommended dietary fat levels. The purpose of the present study was to evaluate the effects of an HFD on bone healing in growing female rats. Twenty-six postweaning female Wistar rats were divided into two groups (13 animals per group): a standard diet (SD) group and an HFD (with 60% of energy from fat) group. The rats received the assigned diets for 5 weeks, and in the third week they were submitted to an osteotomy procedure of the left tibia. Body mass and feed intake were recorded during the experiment. One day before euthanasia, an insulin tolerance test was performed. After euthanasia, the tibiae were removed and analyzed by densitometry, mechanical testing, histomorphometry, stereology and immunohistochemistry. An HFD caused an adaptive response to maintain energetic balance by decreasing feed intake and causing insulin insensitivity. There was no change in bone mineral density, collagen amount and immunostaining for bone formation, but maximal load and stiffness were decreased in the HFD group. In addition, bone volume had a tendency to be higher in the SD group than in the HFD group. Compared with rats receiving an SD, growing rats receiving an HFD for 5 weeks had similar bone mineral density but altered mechanical properties at the osteotomy defect site.

Effects of high-impact exercise on the physical properties of bones of ovariectomized rats fed to a high-protein diet

The aim of this study was to evaluate the effects of high-impact physical exercise as a prophylactic and therapeutic means in osteopenic bones of rats submitted to ovariectomy and protein diet intake. A total of 64 Wistar rats were divided into eight groups (n = 8 each), being: OVX, ovx, standard diet and sedentary; OVXE, ovx, standard diet and jump; OVXP, ovx, high-protein diet and sedentary; and OVXEP, ovx, high-protein diet and jump; SH, sham, standard diet and sedentary; SHE, sham, standard diet and jump; SHP, sham, high-protein diet and sedentary; and SHEP, sham, high-protein diet and jump. OVX surgery consists of ovariectomy, and sham was the control surgery. The jumping protocol consisted of 20 jumps/day, 5 days/week. The bone structure was evaluated by densitometry, mechanical tests, histomorphometric, and immunohistochemical analyses. A high-protein diet resulted in increased bone mineral density (P = .049), but decreased maximal load (P = .026) and bone volume fraction (P = .023). The benefits of physical exercise were demonstrated by higher values of the maximal load in the trained groups compared to the sedentary groups (P < .001). The sham groups had decreased immunostaining of osteocalcin (P = .004) and osteopontin (P = .010) compared to ovx groups. However, the high-protein diet (P = .005) and jump exercise (P = .017) resulted in lower immunostaining of osteopontin compared to the standard diet and sedentary groups, respectively. In this experimental model, it was concluded that ovariectomy and a high-fat diet can negatively affect bone tissue and the high-impact exercise was not enough to suppress the deleterious effects caused by the protein diet and ovariectomy.

HIGH-IMPACT DROP EXERCISE ALTERS MECHANICAL PROPERTIES IN OSTEOPENIC BONE

ABSTRACT Introduction: Osteopenia is a reversible condition and precedes osteoporosis. Physical activity and mechanical loading appear to play an important role in the regulation of bone homeostasis, without the side effects of targeted drug therapy. However, there is controversy as to which type of stimulus promotes more effective adaptations with respect to mechanical properties of bones. Objective: To investigate the effects of high-impact drop training on bone structure after ovariectomy-induced osteopenia in 40 10-week-old female Wistar rats. Methods: Twenty female rats (prevention program) were randomly assigned into two groups (n=10): Ovariectomized sedentary (OVXs), and OVX trained (OVX+Dropt). OVX+Dropt animals began training 3 days after surgery. Another twenty female rats (treatment program) were randomly assigned to two other groups (n=10): Ovariectomized sedentary (OVXs), and OVX trained (OVX+Dropt). OVX+Dropt animals began training 60 days after surgery. The rats in the trained groups were dropped from 40 cm height 20 times/day, 5 days/week over a period of 12 weeks period. At the end, the biomechanical tests were analyzed. Results: The final load and stiffness of the left tibia in the trained groups were higher than in the sedentary groups (p<0.05). Conclusions: Dropping exercise induced favorable changes in bone mechanical properties. High-impact drop exercise is effective to prevent bone loss after ovariectomy even when osteopenia is already established.

Jumping exercise preserves bone mineral density and mechanical properties in osteopenic ovariectomized rats even following established osteopenia

The effects of jump training on bone structure before and after ovariectomy-induced osteopenia in rats were investigated. Jumping exercise induced favorable changes in bone mineral density, bone mechanical properties, and bone formation/resorption markers. This exercise is effective to prevent bone loss after ovariectomy even when osteopenia is already established.

INTRODUCTION

The present study investigated the effects of jump training on bone structure before and after ovariectomy-induced osteopenia in 80 10-week-old Wistar rats.

METHODS

Forty rats (prevention program) were randomly allocated to one of four equal groups (n = 10): sham-operated sedentary (SHAM-SEDp), ovariectomized (OVX) sedentary (OVX-SEDp), sham-operated exercised (SHAM-EXp), and OVX exercised (OVX-EXp). SHAM-EXp and OVX-EXp animals began training 3 days after surgery. Another 40 rats (treatment program) were randomly allocated into another four groups (n = 10): sham-operated sedentary (SHAM-SEDt), OVX sedentary (OVX-SEDt), sham-operated exercised (SHAM-EXt), and OVX exercised (OVX-EXt). SHAM-EXt and OVX-EXt animals began training 60 days after surgery. The rats in the exercised groups jumped 20 times/day, 5 days/week, to a height of 40 cm for 12 weeks. At the end of the experimental period, serum osteocalcin, follicle-stimulating hormone (FSH) dosage, dual X-ray absorptiometry (DXA), histomorphometry, and biomechanical tests were analyzed.

RESULTS

The OVX groups showed higher values of FSH and body weight (p < 0.05). DXA showed that jump training significantly increased bone mineral density of the femur and fifth lumbar vertebra (p < 0.05). The stiffness of the left femur and fifth lumbar vertebra in the exercised groups was greater than that of the sedentary groups (p < 0.05). Ovariectomy induced significant difference in bone volume (BV/TV, percent), trabecular separation (Tb.Sp, micrometer), and trabecular number (Tb.N, per millimeter) (p < 0.05) compared to sham operation. Jump training in the OVX group induced significant differences in BV/TV, Tb.Sp, and Tb.N and decreased osteoblast number per bone perimeter (p < 0.05) compared with OVX nontraining, in the prevention groups. Osteocalcin dosage showed higher values in the exercised groups (p < 0.05).

CONCLUSIONS

Jumping exercise induced favorable changes in bone mineral density, bone mechanical properties, and bone formation/resorption markers. Jump training is effective to prevent bone loss after ovariectomy even when osteopenia is already established.

Influence of torsional strength on different types of dental implant platforms

AIM

The study assessed deformation of implant components submitted to torsion tests of 80 and 120 N · cm using an optical stereomicroscope.

MATERIAL AND METHODS

The following 3 types of Titaniumfix conical implant connections (n = 5) measuring Ø 4.0 × 11.5 mm were used: external, internal hexagon and Morse taper connections. The diagonal and lateral measurements of the hexagon implant platform were measured before and after the torsion test.

RESULTS

The torsion test using torque of 80 and 120 N · cm altered the implant dental platforms. All groups presented deformation of implant component after torque of 80 N · cm with no statistical difference among them. During torque of 120 N · cm, a difference in the Morse taper connection in relation to the internal and external hexagon connection was observed. The Morse taper connection implant, followed by the internal hex implant, underwent less deformation. Greater deformation occurred in the external hex implants.

CONCLUSION

For all the implants, high insertion torques deformed the implant platform preventing long-term maintenance and stability of implants.

Influence of High-Fat Diet on Bone Tissue: An Experimental Study in Growing Rats

BACKGROUND

The relationship between obesity and bone tissue remains contradictory, especially when the effect of high-fat diet is assessed in experimental models. The aim of this study was to evaluate the effects of high-fat diet on bone metabolism of growing rats.

METHODS

Twenty weaned female Wistar rats were equally divided into two groups: SD (standard diet) and HFD (high-fat diet with 60 % of energy as fat). After five weeks of the two diets, the rats were euthanized, and the liver, blood and bones extracted. The liver was analysed for malondialdehyde (MDA) and reduced glutathione (GSH) concentrations. Blood was analysed by the ELISA method for osteoprotegerin (OPG) and tumour necrosis factor ligand superfamily member 11 (TNFSF11/RANKL). The bone tissue was analysed by dual-energy X-ray absorptiometry (DXA), mechanical tests, computed microtomography, histological quantitative analysis and scanning electron microscopy. The gene expressions of PPAR-γ Runx-2, RANKL and Cathepsin-K were also evaluated.

RESULTS

HFD caused an increase in the MDA concentration, indicating oxidative stress. It also increased the expression of PPAR-γ, which is the gene that is related to adipocyte differentiation. There was an increase in BMD of the tibia of animals fed with the HFD, but other microstructural and mechanical properties were maintained unaltered. In addition, there were no changes in the gene expressions related to the differentiation of osteoblasts and osteoclasts, as well as no changes to the biochemical markers of bone formation and bone resorption.

CONCLUSION

Liver and gene parameters are changed in response to the HFD. However, although there was an increase in BMD, the microstructure and function of the bone did not change after a 5-week HFD.

Comparison of the mechanical properties of therapeutic elastic tapes used in sports and clinical practice

STUDY DESIGN

Cross-sectional laboratory study.

OBJECTIVE

The aim of the present study was to evaluate and compare the mechanical properties of different therapeutic elastic tapes used in sports and clinical practice.

BACKGROUND

Therapeutic tapes have been used since around the 1800s. They are composed of cotton, elastic filaments and adhesive glue that provides an effect of tactile and mechanical stimulation. However, as taping has evolved, manufacturers have implemented new materials and claim that the tensile properties and adhesion of tapes contribute more significantly in the rehabilitation process.

METHODS

Fifty samples of elastic tapes (5 different manufacturers; 10 samples from each manufacturer) were submitted to longitudinal traction until rupture as well as surface adherence assays. Information was recorded on maximum deformation, maximum load, maximum tension and relative stiffness.

RESULTS

In tensile testing the bandages brand Kinesio Tex Gold - FP^® showed higher rates, 3 in 4 properties. During surface adherence tests on the therapeutic elastic tapes the brand Premium Kinesiology 3 NS Tex^® showed higher rates, 3 in 4 properties analyzed.

CONCLUSIONS

Tapes from different manufacturers exhibit different characteristics regarding traction and adherence mechanics. Knowledge of these characteristics is fundamental for the optimized use of each tape based on specific therapeutic needs.

Effect of treatment with simvastatin on bone microarchitecture of the femoral head in an osteoporosis animal model

The objective of this study was to evaluate the microarchitecture and trabecular bone strength at the distal region of the femur, and its biomechanical properties with simvastatin administration with two different doses in ovariectomized (OVX) rats. Ninety rats were divided into six groups to evaluate treatment with the simvastatin drug (n = 15): SH (Sham surgery), SH-5 (5 mg simvastatin), SH-20 (20 mg simvastatin), OVX, OVX-5, and OVX-20. Euthanasia was performed at three different times, five animals per period: 7, 14, and 28 days. The effectiveness of the treatments was evaluated by mechanical testing and histomorphometric analysis of the femurs. The results of analysis by the linear model of mixed effects showed 20 mg of simvastatin results in increased trabecular bone after 14 days (P = 0.039) of ingestion in ovariectomized animals. However, ingestion of 5 mg of simvastatin is able to sensitize the trabecular bone only at 28 days (P = 0.005) of ingestion. In the mechanical tests stiffness improves within 28 days (P = 0.003). Regarding maximum strength, no statistical differences were observed. According to these results, it can be concluded that for a decrease in oral intake, longer treatment times are required. Microsc. Res. Tech. 79:684-690, 2016. © 2016 Wiley Periodicals, Inc.

Influence of treadmill training on bone structure under osteometabolic alteration in rats subjected to high-fat diet

Nutrition and physical training have important roles in the accumulation and maintenance of bone mass. The aim of this study was to evaluate, in ovariectomized rats (OVX), the effects of treadmill training (T) with high-fat diet (F) on weight gain and bone tissue properties with eight groups (n = 10) for 12 weeks: OVX SC (OVX, sedentary lifestyle, diet control); OVX SF; OVX TC; OVX TF; SH SC (SHAM, sedentary lifestyle, diet control); SH SF; SH TC; and SH TF. Weekly weight gain and final body composition were assessed. After euthanasia, tibiae were analyzed. The trained animals had higher body weight (P = 0.001), bone mineral density (P < 0.001), and trabecular bone (P < 0.001). The animals with a high-fat diet showed higher global fat (P < 0.001), percentage of global fat (P < 0.001) and deformation at impact (P = 0.031) and reduced tibial bone mineral content (P = 0.036). Physical training improves bone microarchitecture, without presenting an increase in impact resistance, and a high-fat diet increases body fat and impairs bone mineralization.

High-impact exercise in rats prior to and during suspension can prevent bone loss

High-impact exercise has been considered an important method for treating bone loss in osteopenic experimental models. In this study, we investigated the effects of osteopenia caused by inactivity in femora and tibiae of rats subjected to jump training using the rat tail suspension model. Eight-week-old female Wistar rats were divided into five groups (n=10 each group): jump training for 2 weeks before suspension and training during 3 weeks of suspension; jump training for 2 weeks before suspension; jump training only during suspension; suspension without any training; and a control group. The exercise protocol consisted of 20 jumps/day, 5 days/week, with a jump height of 40 cm. The bone mineral density of the femora and tibiae was measured by double energy X-ray absorptiometry and the same bones were evaluated by mechanical tests. Bone microarchitecture was evaluated by scanning electron microscopy. One-way ANOVA was used to compare groups. Significance was determined as P<0.05. Regarding bone mineral density, mechanical properties and bone microarchitecture, the beneficial effects were greater in the bones of animals subjected to pre-suspension training and subsequently to training during suspension, compared with the bones of animals subjected to pre-suspension training or to training during suspension. Our results indicate that a period of high impact exercise prior to tail suspension in rats can prevent the installation of osteopenia if there is also training during the tail suspension.

Influence of the ultimate torsion on the geometry of dental implants

This study evaluated the profile of implants subjected to torsion test. Four types of implants (Conexão®) were analyzed: Master Porous (MP - external hexagon, cylindrical, double-porous surface implants; 11.5 X 3.75 mm), Master Screw (MS - external hexagon, cylindrical, machined implants; 11.5 X 3.75 mm), Conect Conic (CC - external hexagon, cylindrical, machined implants; 11.5 X 3.5 mm) and Master Conect AR (CA - internal hexagon, cylindrical, double-porous surface implants; 11.5 X 3.75 mm). The Nikon® model C profile projector was used for the analysis before and after torsion test with a Mackena® model MK-20XX digital torque meter. The measures analyzed in the profile of implants were: diameter and height of the platform, diameter of the screw/platform connection, angle of the screw/platform connection, external diameter, internal diameter, thread pitch, height and length of the thread. Statistical analysis was performed using ANOVA and Tukey test at 5% significance level. The torsion test caused a visible deformity on the external implant profile. There was a statistical difference among the implants before and after torsion (p<0.05) for the variables: platform diameter, platform height, diameter of the screw/platform connection and length. Changes were observed in platform height of CC and CA, fracture of CA implants, fracture of the MP and MS assembler/connectors, and internal thread stripping of CC. Thus, it was concluded that excessive or some unadvised torque by the manufacturer can lead to changes in different geometric measurements of implants.

Effects of long-term administration of omeprazole on bone mineral density and the mechanical properties of the bone

OBJECTIVES

Epidemiological studies have shown a relationship between long-term use of proton pump inhibitors and bone metabolism. However, this relationship has not yet become established. The aim of the present study was to analyze the mechanical properties and bone mineral density (BMD) of rats that were subjected to long-term omeprazole use.

METHODS

Fifty Wistar rats weighing between 200 and 240 g were divided equally into five groups: OMP300 (omeprazole intake at a dose of 300 μmoL/kg/day); OMP200 (200 μmoL/kg/day); OMP40 (40 μmoL/kg/day); OMP10 (10 μmoL/kg/day); and Cont (control group; intake of dilution vehicle). The solutions were administered for 90 consecutive days. After the rats had been sacrificed, their BMD, the mechanical properties of the dissected femurs and their serum Ca++ levels were analyzed.

RESULTS

The BMD of the OMP300 group was lower than that of the controls (p = 0.006). There was no difference on comparing the OMP200, OMP40 and OMP10 groups with the controls. The maximum strength and rigidity of the femur did not differ in the experimental groups in comparison with the controls. The OMP300 group had a statistically lower serum Ca++ concentration than that of the controls (p = 0.049), but the other groups did not show any difference in relation to the controls.

CONCLUSION

Daily intake of 300 μmoL/kg/day of omeprazole decreased the BMD of the femur, but without changes to the rigidity and strength of the femur in adult rats.

Effects of swimming associated with risedronate in osteopenic bones: An experimental study with ovariectomized rats

Physical activity and risedronate sodium have effects on metabolic bone diseases, maintaining the integrity of bone tissue. Our objective was to evaluate the effects of swimming associated with risedronate as a prophylactic means in osteopenic bone of ovariectomized rats. A total of 24 animals of the Wistar strain were used and separated into four groups containing six animals: Ovariectomy (OVX), ovariectomy and swimming (OVXS), ovariectomy and risedronate (OVXM), ovariectomy, risedronate and swimming (OVXMS). The effectiveness of the treatments were evaluated using the tibia by means of biomechanical, radiographic, histomorphometric analyzes. Statistical analysis was performed by the non-parametric Kruskal-Wallis test (p<0.05). The OVXM and OVXMS groups showed higher values ​​compared to OVX in maximum strength and rigidity. Microscopic analysis showed increased trabecular bone in the OVXM group in relation to the others, and in the OVXMS compared to OVXS. Proximal densitometry in the OVXM and OVXMS groups showed higher values than the OVX and OVXS groups. There were no significant differences in overall densitometry. In conclusion, when comparing the prophylactic means, risedronate was able to preserve bone mass significantly, unlike exercise where an improvement of bone tissue was observed, although not significant, and when swimming and risedronate are combined the result was even better.

Biomechanical and microstructural benefits of physical exercise associated with risedronate in bones of ovariectomized rats

Several treatments have been developed aiming the prevention of bone loss. There are discussions about the best prophylactic and therapeutic procedures for osteoporosis. This study evaluated the effects of physical exercise associated with risedronate as a prophylactic and therapeutic procedure in osteopenic bones of rats submitted to ovariectomy. We used 48 Wistar rats divided into: ovariectomized or subjected to sham surgery. Ovariectomized rats were divided into the following sub-groups: OVX, 12 weeks sedentary; OVX-EX, treadmill training for 12 weeks; OVX-RA, 12 weeks with risedronate administration; and OVX-EX-RA, 12 weeks with risedronate administration and treadmill training. Rats subjected to sham surgery were divided into the following sub-groups: SH, 12 weeks sedentary; SH-EX, treadmill training for 12 weeks; SH-RA, 12 weeks with risedronate administration; and SH-EX-RA, 12 weeks with risedronate administration and training on the treadmill. The effectiveness of the treatment was evaluated in tibias using biomechanical, radiological, histomorphometric, and immunohistochemical analyses. Data were analyzed by statistical tests, with significance level of P < 0.05. Results of mechanical tests showed that the SH-RA group had lower values compared with OVX-RA group; densitometry showed no significant differences; according to histomorphometric methods, OVX group presented lower results than the SH-EX, OVX-RA, SH-EX-RA, and OVX-EX-RA groups, and SH-EX-RA and OVX-EX-RA groups showed values higher than SH-RA, SH, and OVX-EX groups. The SH-EX-RA and OVX-EX-RA groups had decreased immunostaining for tartrate-resistant acid phosphatase and receptor activator of nuclear factor kappa-B ligand and increased osteoprotegerin immunostaining. In this experimental model, it was concluded that the physical training associated with use of risedronate exerted positive effects on biomechanical and microstructural properties in bones of ovariectomized rats.

Analysis of stress induced by screws in the vertebral fixation system

OBJECTIVE

To compare, using photoelasticity, internal stress produced by USS II type screw with 5.2 and 6.2 mm external diameters, when submitted to three different pullout strengths.

METHODS

Two photoelastic models were especially made. The simulation was performed using loads of 1.8, 2.4 e 3.3 kgf.The fringe orders were evaluated around the screws. In all the models analyzed the shear stress were calculated.

RESULTS

Independently of the applied load, the smaller screw showed higher values of shear stress.

CONCLUSION

According to the analysis performed, we observed that the place of highest stress was in the first thread of the lead, close to the head of the screws. Experimental study.

Effect of the pilot hole preparation on the anchorage of pedicle screws

Objective

We evaluated the influence of the diameter and the preparation of the pilot hole on the resistance to the pulling out and the strength when inserting pedicle screws with conical internal diameter.

Methods

Mechanical experiments were performed with pedicle conical screws of 4.2 mm and 5.2 mm diameter. They were inserted in the vertebral pedicles of swine. The hole was manufactured with a drill and probes with different diameters.

Results

While testing the 4.2 mm screw, the perforation of holes with measure equal or inferior to the lesser internal diameter of the screw increased the torque and the resistance to pull-out strength. Perforations with different instruments have presented similar results. Perforations with probes allowed the holes manufactured with dimensions superior to the lesser internal diameter of the screw to show similar resistance to that of the perforations with dimensions equal to the lesser internal diameter of the implant, made with probes and drills.

Conclusion

For 4.2 mm screws, the diameter and the preparation of the hole influence the torque and the resistance. For 5.2 mm screws, there is only influence on the insertion torque. There is no correlation between pulling out strength and insertion torque. Level of Evidence II, Therapeutic Studies - Investigating the Results of Treatment.

Action of therapeutic laser and ultrasound in peripheral nerve regeneration

Objective

To assess the efficacy of early therapeutic laser and ultrasound in the regeneration process of an injury in rats.

Methods

We used 24 rats. Eighteen underwent surgery for sciatic nerve compression by a hemostat above the popliteal fossa. The animals were divided into three groups of six animals each. Normal control group. GI: Injured control without therapeutic intervention. GII: laser ArGaAl therapeutic intervention. GIII: therapeutic intervention of Pulsed Ultrasound. We begin therapeutic interventions 24 hours after injury, with daily applications for a period of fourteen consecutive days.

Results

In assessing the girth of the muscles of the right they, the following average decrease (in mm) for each GI: 0.45, GII: 0.42, GIII: 0.40 In relation to travel time, both GII and GIII presented significant difference when compared to GI. In the final evaluation of the IFC, GII excelled in the GIII. As for the healing observed, a major great improvement was observed in GII and GIII.

Conclusion

The results showed that nerve recovery was higher with the laser application. Level of evidence II, Therapeutic Studies - Investigation of the results of treatment.

Efeito de regimes de treinamento físico de alto impacto nas propriedades mecânicas de ossos: estudo experimental em ratas wistar

INTRODUÇÃO: A realização de atividade física garante benefícios ao tecido ósseo uma vez que o estresse provocado pelo carregamento promove adaptações positivas em suas propriedades mecânicas, sendo sua utilização uma estratégia não farmacológica para fortalecimento ósseo. OBJETIVO: investigar o efeito de protocolos de treinamento de alto impacto com frequências semanais e períodos diferentes nas propriedades mecânicas de ossos de ratas Wistar. MÉTODOS: Foram utilizadas 54 ratas Wistar, idade média de 10 semanas, divididas em seis grupos (n = 9): GCI (grupo controle, quatro semanas, sedentário), GTI3 (treinou três vezes por semana durante quatro semanas), GTI5 (treinou cinco vezes por semana, quatro semanas), GCII (grupo controle, oito semanas, sedentário), GTII3 (treinou três vezes por semana, oito semanas) e GTII5 (treinou cinco vezes por semana, oito semanas). O protocolo de alto impacto consistiu de 10 saltos verticais por sessão. RESULTADOS: Os ossos dos animais que receberam treinamento de alto impacto com frequência semanal elevada por um período maior de tempo mostraram valores superiores de suas propriedades mecânicas força máxima e rigidez relativa quando comparados aos demais grupos. CONCLUSÃO: Os resultados indicam que a realização de um protocolo de treinamento de alto impacto na forma de saltos verticais possui efeitos positivos sobre o tecido ósseo mesmo com frequência semanal reduzida, embora a realização de uma frequência semanal maior por um período mais elevado garanta melhores resultados.

Biomechanics of four techniques for fixation of the four-part humeral head fracture

OBJECTIVE:

To carry out a biomechanical study of four techniques for fixation of four-part humeral head fractures.

METHODS:

The fracture was reproduced in 40 plastic humeri, divided into groups of ten according to the fixation technique, each one employing different fixation resources, in different configurations. The humeral models were mounted on an aluminum scapula, with leather straps simulating the rotator cuff tendons, and submitted to bending and torsion tests in a universal testing machine, using relative stiffness as an evaluation parameter. Assemblies with intact humeri were analyzed for comparison.

RESULTS:

The biomechanical behavior of the fixation techniques varied within a wide range, where the assemblies including the DCP plate and the 4.5mm diameter screws were significantly more rigid than the assemblies with the Kirschner wires and the 3.5mm diameter screws.

CONCLUSION:

The four fixation techniques were able to bear loads compatible with the physiological demand, but those with higher relative stiffness should be preferred for clinical application.

Laboratory investigation

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Novo sistema para acoplamento de parafusos de interferência: ensaio biomecânico de torção

OBJETIVO: Apresentar um novo sistema de acoplamento solidário entre chave e parafuso de interferência, assim como ensaios biomecânicos que avaliem a segurança de sua utilização. MÉTODOS: O novo sistema foi submetido a ensaios biomecânicos de torção. Foram realizados dois tipos de análise: torque máximo de inserção manual dos parafusos em osso bovino; ensaios destrutivos de torção do sistema em máquina INSTRON 55MT. Os mesmos testes foram realizados em um grupo controle utilizando um sistema de acoplamento já disponível no mercado. (Acufex®) RESULTADOS: Nos ensaios de inserção em fêmures bovinos as médias de valores aferidos com torquímetro digital foram 1,958 N/m para Acufex® e 2,563 N/m para FMRP. Considerando p<0,05, não houve diferença significativa (p=0,02) nos valores de torque máximo de inserção nos dois sistemas estudados. Os valores médios de torque máximo para deformar o parafuso foram de 15 N/m para o parafuso Acufex® e 13 N/m para o parafuso FMRP, portanto, sem diferença estatística (p>0,05). Ao avaliar a deformação angular, não houve diferença significativa entre os grupos de parafuso (p=0,15). CONCLUSÃO: O novo sistema de acoplamento para parafusos de interferência desenvolvido na FMRP-USP revelou resistência à torção comparável a sistema já disponível no mercado e regulamentado para uso internacional.

Influência do instrumento de perfuração do orifício piloto nas propriedades mecânicas dos parafusos vertebrais

OBJETIVO: Determinar a influência do modo de preparo do orifício piloto utilizando sonda romba, sonda cortante e broca na resistência ao arrancamento dos implantes. MÉTODO: Foram utilizados parafusos do sistema de fixação vertebral (USS) com 5 mm, 6 mm e 7 mm de diâmetro externo. Os parafusos foram implantados nos corpos de prova de osso bovino após a realização do orifício piloto com três diferentes modos de preparo: sonda romba, sonda cortante e broca. O diâmetro de perfuração do orifício piloto era menor, igual e maior que o diâmetro interno dos parafusos. No mesmo corpo de prova, três orifícios do mesmo diâmetro foram confeccionados por meio dos três modos de preparo utilizados no estudo, os parafusos foram inseridos e, em seguida, foram realizados os ensaios mecânicos de arrancamento. Os ensaios mecânicos foram realizados em máquina universal de ensaio Emic®, Software Tesc 3.13, célula de carga de 2000N, velocidade de aplicação de força de 2 mm/min, pré-carga de 5N e tempo de acomodação de 10 segundos. A propriedade avaliada nos ensaios mecânicos foi a força máxima de arrancamento. RESULTADOS: O modo de preparo do orifício piloto influencia na resistência ao arrancamento dos implantes de 5 e 6 mm utilizados no estudo. Foi observada maior resistência ao arrancamento os orifícios piloto que foram confeccionados com sonda. A resistência ao arrancamento dos parafusos de 7 mm não foi influenciada pelo modo de preparo do orifício piloto. CONCLUSÃO: O modo de preparo do orifício piloto influenciou a resistência ao arrancamento dos parafusos de 5 e 6 mm de diâmetro externo.

Influência do local de ancoragem dos implantes na vértebra sobre o torque de inserção e resistência ao arrancamento

OBJETIVO: Avaliar a influência do sítio anatômico da ancoragem dos implantes na vértebra sobre a resistência ao arrancamento e o torque de inserção dos parafusos pediculares com alma cônica e cilíndrica. MÉTODOS: Parafusos cilíndricos e com alma cônica foram inseridos no pedículo e corpo vertebral de 10 vértebras lombares (L4-L5) de vitelos. Foram avaliados o torque de inserção e a resistência ao arrancamento dos parafusos inseridos no corpo e no pedículo vertebral. RESULTADOS: Os valores do torque de inserção e resistência ao arrancamento foram maiores nos parafusos de alma cilíndrica e alma cônica inseridos no pedículo vertebral. CONCLUSÕES: A ancoragem dos implantes no pedículo vertebral apresentou maiores valores do torque de inserção e da força de arrancamento que os implantes inseridos no corpo vertebral nos dois tipos de parafusos utilizados.

EFFECT OF PILOT HOLE TAPPING ON PULLOUT STRENGTH AND INSERTION TORQUE OF DUAL CORE PEDICLE SCREWS

Objective: To evaluate the influence of pilot hole tapping on pullout resistance and insertion torque of pedicle screws with a conical core. Methods: Mechanical tests using a universal testing machine were performed on pedicle screws with a conical core that were inserted into pedicles in the fifth lumbar vertebra of calves. The insertion torque was measured using a torque meter with a capacity of 10 Nm, which was considered to be the highest torque value. The pilot holes were prepared using a probe of external diameter 3.8 mm and tapping of the same dimensions and thread characteristics as the screw. Results: Decreased insertion torque and pullout resistance were observed in the group with prior tapping of the pilot hole. Conclusions: Pilot hole tapping reduced the insertion torque and pullout resistance of pedicle screws with a conical core that had been inserted into the pedicle of the fifth lumbar vertebra of calves.

Osteotomia alta da tíbia com cunha de abertura medial: relevância biomecânica da cortical oposta

OBJETIVO: Avaliar o impacto da integridade da cortical lateral osteo-tomia alta de tíbia (OAT) com cunha de abertura. MÉTODOS: Modelos experimentais artificiais em poliuretano foram fixados com placa DCP® 4,5mm. Cunhas de abertura foram confeccionadas para simular a distração da osteotomia alta da tíbia. Realizadas falhas na cortical lateral para simular fraturas e fixadas com diferentes tipos de parafusos. Ensaios de torção e compressão axial foram realizados. 04 diferentes grupos foram constituídos. RESULTADOS: As medidas de torção registradas no grupo com cortical íntegra foram superiores àquelas obtidas no grupo com cortical rompida (p<0,001) e estatisticamente equivalentes aos grupos com cortical rompida associado à parafuso de estabilização lateral de compressão ou de posição (p>0,05). As medidas de compressão obtidas no grupo com cortical íntegra foram superiores aos demais grupos (p<0,001). Em torção e compressão não houve diferença estatística entre os tipos de parafuso de estabilização lateral (p>0,05). CONCLUSÃO: A cortical lateral íntegra agrega estabilidade às osteotomias com cunha de abertura medial. Modelo com cortical íntegra evidenciou superioridade biomecânica em rigidez nos ensaios de torção e compressão. Nos ensaios torcionais, os modelos com falha de continuidade cortical com parafusos de estabilização lateral de compressão ou de posição apresentaram equivalência aos modelos com cortical íntegra.

O ultra-som terapêutico não aumentou as propriedades mecânicas de tendões flexores após reparo

OBJETIVO: Estudo experimental idealizado para investigar as propriedades mecânicas de tendões flexores profundos de coelhos submetidos à tenotomia seguida de tenorrafia e aplicação precoce de ultra-som terapêutico com diferentes intensidades, em comparação com tendões submetidos somente à tenorrafia. MATERIAL E MÉTODOS: Quarenta e quatro coelhos foram divididos em quatro grupos experimentais de acordo com a aplicação do ultra-som. Todos foram submetidos a uma secção do tendão flexor profundo na zona 2 e imobilizados com uma órtese mantida durante todo o experimento. O grupo A recebeu tratamento ultra-sônico com uma intensidade de 1,4 W/cm², o grupo B com 0,6 W/cm², ambos no modo contínuo, o grupo C com 0,6 W/cm² SATA, no modo pulsado à 50% e o grupo D não recebeu tratamento ultra-sônico algum. A frequência ultra-sônica empregada foi de 1 MHz. Após a eutanásia os tendões foram dissecados e submetidos ao ensaio mecânico de tração e análise histológica qualitativa. As propriedades mecânicas avaliadas foram: força máxima, deformação na força máxima e rigidez. RESULTADO: Não houve diferença estatisticamente significante entre os grupos experimentais. CONCLUSÃO: O ultra-som terapêutico não melhorou as propriedades mecânicas dos tendões flexores após reparo.

Influência do macheamento na interface do parafuso e do tecido ósseo na fase imediata pós-implante

OBJETIVO: analisar experimentalmente as alterações agudas da interface entre o osso e o implante nas vértebras cervicais após a realização do macheamento do orifício piloto. MÉTODOS: foram utilizados cinco carneiros da raça Santa Inês deslanados. Na terceira vértebra cervical, foram feitos orifícios de 2,5 mm, de ambos os lados, na parte proximal e distal. No orifício proximal direito, foi realizado o macheamento antes da inserção do parafuso cortical de 3,5 mm (Grupo A); no orifício proximal esquerdo, o parafuso foi inserido sem macheamento (Grupo B); os outros dois orifícios distais foram utilizados como controle (Grupo C). As alterações da interface entre o osso e o implante foram analisadas por meio de estudo histomorfométrico, considerando o número de trabéculas fraturadas entre os filetes de rosca; a maior distância da fratura trabecular transversal provocada pela inserção do parafuso; a maior extensão da fratura trabecular longitudinal provocada pela inserção do parafuso e a linha de contato na interface osso-parafuso. RESULTADOS: o macheamento do orifício piloto provocou alterações da microestrutura do tecido ósseo ao redor do implante quando comparado às alterações produzidas pela inserção do parafuso sem o macheamento ou orifício piloto. A avaliação do contato entre o osso e o implante foi o parâmetro que apresentou diferença estatística na comparação entre a colocação do implante com e sem machemanto. CONCLUSÃO: na comparação com o orifício piloto, todos os parâmetros analisados apresentaram diferença estatística.

Histomorphometric analysis of the response of rat skeletal muscle to swimming, immobilization and rehabilitation

The objective of the present study was to determine to what extent, if any, swimming training applied before immobilization in a cast interferes with the rehabilitation process in rat muscles. Female Wistar rats, mean weight 260.52 +/- 16.26 g, were divided into 4 groups of 6 rats each: control, 6 weeks under baseline conditions; trained, swimming training for 6 weeks; trained-immobilized, swimming training for 6 weeks and then immobilized for 1 week; trained-immobilized-rehabilitated, swimming training for 6 weeks, immobilized for 1 week and then remobilized with swimming for 2 weeks. The animals were then sacrificed and the soleus and tibialis anterior muscles were dissected, frozen in liquid nitrogen and processed histochemically (H&E and mATPase). Data were analyzed statistically by the mixed effects linear model (P < 0.05). Cytoarchitectural changes such as degenerative characteristics in the immobilized group and regenerative characteristics such as centralized nucleus, fiber size variation and cell fragmentation in the groups submitted to swimming were more significant in the soleus muscle. The diameters of the lesser soleus type 1 and type 2A fibers were significantly reduced in the trained-immobilized group compared to the trained group (P < 0.001). In the tibialis anterior, there was an increase in the number of type 2B fibers and a reduction in type 2A fibers when trained-immobilized rats were compared to trained rats (P < 0.001). In trained-immobilized-rehabilitated rats, there was a reduction in type 2B fibers and an increase in type 2A fibers compared to trained-immobilized rats (P < 0.009). We concluded that swimming training did not minimize the deleterious effects of immobilization on the muscles studied and that remobilization did not favor tissue re-adaptation.

Análise fotoelástica de parafuso de sistema de fixação vertebral

INTRODUÇÃO: A fotoelasticidade é utilizada para avaliar as tensões/deformações produzidas nos materiais fotoelásticos, quando submetidos a determinado carregamento, através da observação de efeitos óticos. O desempenho do parafuso e as funções mecânicas estão diretamente relacionados com a qualidade da fixação dos parafusos nas vértebras. A fotoelasticidade é uma ferramenta importante para realizar estudos comparativos desta natureza. OBJETIVO: O objetivo deste estudo foi comparar por meio da fotoelasticidade, as tensões internas produzidas pelo parafuso com 6 mm de diâmetro externo, quando submetido a duas diferentes forças de arrancamento. MATERIAIS E MÉTODOS: Para isso, foram confeccionados quatro modelos fotoelásticos. A simulação foi realizada utilizando duas forças de arrancamento 0,75 e 1,50 kgf. As tensões cisalhantes foram calculadas nos 19 pontos em torno dos parafusos, utilizando o método de compensação de Tardy. RESULTADOS: Os valores das tensões cisalhantes foram maiores quando utilizada a força de arrancamento de 1,50 kgf. CONCLUSÃO: Assim sendo, o parafuso estará mais suscetível ao arrancamento com a aplicação de força de maior intensidade. De acordo com as análises realizadas verificamos também que o local de maior tensão cisalhante foi observado no pico das cristas, principalmente próxima às pontas dos parafusos, independente da força utilizada.

Recuperação mecânica muscular com laser

OBJETIVO: Avaliamos a influência da irradiação a laser, associada ou não a imobilização, nas propriedades mecânicas do músculo gastrocnêmio submetido à lesão experimental. MÉTODOS: Foram utilizadas 70 ratas (Wistar), divididas em 7 grupos: grupo 1- controle; grupo2 - lesão; grupo3 - lesão-irradiação laser; grupo 4 - lesão-imobilização 24 horas-irradiação laser; grupo 5 - lesão- imobilização 72 horas-irradiação laser; grupo 6 - lesão-imobilização 24 horas; grupo 7 - lesão-imobilização 72 horas. Os músculos foram submetidos a ensaios mecânicos de tração e, utilizando gráficos carga x alongamento calculadas as propriedades mecânicas no limite de proporcionalidade e no limite máximo. RESULTADOS: A lesão provocou diminuição da carga nos limites máximo e de proporcionalidade em relação ao grupo1 (p< 0,05). . Os grupos 2, 4, 5 e 7 apresentaram diferença estatística em relação ao grupo 1. A propriedade de alongamento no limite de proporcionalidade apresentou diferença significante entre o grupo 1 e os grupos 4, 5, 6 e 7 e, entre os grupos 2 e 4. A propriedade de alongamento no limite máximo apresentou diferença entre os grupos 1 e 5 e, entre os grupos 3 e 5. CONCLUSÕES: A associação da imobilização por 24 e 72 horas à terapia laser não melhorou os resultados nas propriedades mecânicas do músculo. O uso isolado de cada modalidade de tratamento foi mais efetivo.

Ultra-som terapêutico e imobilização na reparação do trauma muscular

INTRODUÇÃO: Avaliamos os efeitos do ultra-som terapêutico (UST), adicionado ou não à imobilização gessada (IG), como forma de tratamento à lesão muscular por impacto analisando as propriedades mecânicas de alongamento e carga nos limites de proporcionalidade e máximo, rigidez (R) e resiliência do músculo gastrocnêmio. METODOLOGIA: Utilizamos 70 ratas divididas em 7 grupos:Grupo 1-Controle;Grupo 2-Sem tratamento,Grupo 3-IG por 24 horas;Grupo 4-IG por 72 horas; Grupo 5-UST sem presença de IG;Grupo 6-IG por 24 horas associada ao UST;Grupo 7-IG por 72 horas associada ao UST. RESULTADOS: As propriedades de carga no limite de proporcionalidade e carga máxima mostraram que o grupo estimulado com o UST comportou-se de modo semelhante ao grupo controle. A propriedade de alongamento no limite de proporcionalidade não diferenciou os grupos; o alongamento máximo do grupo estimulado com (UST) e dos grupos imobilizados por 72 horas foram comparáveis ao grupo controle. CONCLUSÃO: O grupo estimulado (UST) apresentou rigidez similar ao grupo controle e resiliência superior a todos os grupos. A utilização isolada do UST forneceu resultados similares àqueles considerados como normais, o mesmo não sendo observado quando o UST foi associado à IG.

Análise fotoelástica de um modelo de vértebra humana com parafuso pedicular

INTRODUÇÃO: O sistema de fixação vertebral utilizando o parafuso pedicular é um dos métodos mais eficientes no tratamento de patologias da coluna vertebral. Quando o parafuso estiver submetido á força de arrancamento, este gera tensões ao seu redor, principalmente próximas do canal medular, situação esta que pode ser analisada pela técnica da fotoelasticidade. OBJETIVO: Foram analisadas as tensões internas geradas próximas ao canal medular de modelos fotoelásticos de vértebras utilizando diferentes medidas de parafusos do sistema de fixação vertebral submetidos à força de arrancamento. MÉTODO: Foi utilizado um modelo de vértebra lombar em material fotoelástico utilizando três medidas de parafusos pediculares (5, 6 e 7mm) do tipo USS1. As tensões internas ao redor do parafuso foram avaliadas em 12 pontos pré-determinados utilizando um polariscópio de transmissão plana. RESULTADOS: As regiões de maiores concentrações de tensões foram observadas entre o canal medular e as curvas do processo transverso. Nas comparações das médias das tensões cisalhantes máximas entre os parafusos 5 e 7, e 6 e 7 foram observadas diferenças estatísticas significativas e entre 5 e 6 não. CONCLUSÃO: Foi observada que as tensões internas são mais elevadas em áreas irregulares próxima ao canal medular, mostrando ser uma região crítica.

Propriedades tensiométricas comparadas entre fragmentos do centro tendíneo do diafragma, pericárdio fibroso e peritônio parietal de bovinos não conservados e conservados em glicerina

Objetivou-se descrever o comportamento do centro tendíneo do diafragma, pericárdio fibroso e peritônio parietal de bovinos não conservados e conservados em glicerina a 98% durante 30, 60 e 90 dias submetidos a ensaios mecânicos de tração. Utilizou-se para tanto dez bovinos com idade entre 30 meses e 36 meses, mestiços, machos e fêmeas, coletando-se de cada animal fragmentos das membranas referidas. O centro tendíneo do diafragma e o peritônio parietal não sofreram alteração significante (p>;0,05) para os valores de tensão quando comparados os testes de resistência à tração do material não conservado com aqueles conservados em glicerina. Entretanto, todos os tecidos avaliados exibiram aumento significante (p£0,05) para os valores de alongamento quando conservados em glicerina 98% por até 90 dias. Verificou-se que o pericárdio fibroso é a membrana que suporta as maiores tensões, ou seja, maior força de tração por área de secção. Assim, concluiu-se que a glicerina é eficaz para conservação de membranas biológicas, além de alterar suas propriedades mecânicas.