Correlation Between Peritonitis and Incisional Infections in Horses.

Surgical site infection of abdominal incisions is an important complication after laparotomy with increased risk of incisional hernia formation in horses. This study aims to evaluate the healing process of abdominal incisions and correlate peritonitis with the occurrence of surgical site infection and incisional hernias. Nine horses underwent standardized laparotomy, intestinal exploration, and induced septic peritonitis. Standardized relaparotomy was performed two (n = 3), four (n = 3), and six (n = 3) months later to evaluate the abdominal cavity for adhesions and to collect the sutured ventral abdominal wall to evaluate and prepare it for histopathological and tensile strength study. All horses presented with endotoxemia, controllable peritonitis, heat and touch-sensitive ventral abdominal edema and surgical wound infection with presence of purulent discharge. Adhesion of the cecum or colon to the internal portion of the surgical wound was observed. Healing of the infected surgical wounds occurred by second intention and a space between the rectus abdominis muscles developed because of the presence of a scar, which was related to incisional hernia. In the histopathological evaluation, the collagen content increased, and the inflammation decreased over time. The tensile strength increased over time and was highest after 6 months. After the second surgical intervention, there was no infection of the surgical wound in any of the animals and healing by first intention occurred. Surgical site infection may be a symptom of peritonitis in horses recovering from abdominal surgery. Infected surgical wounds heal by second intention, which favors the spacing of rectus abdominis muscle and the formation of incisional hernia.

Biomechanical Test after Hip Cannulated Screw Removal (in vitro Analysis).

Objective This study aims to evaluate, through biomechanical tests, the resistance and energy required for proximal femoral fracture in synthetic bones after removing cannulated screws shaped as an inverted triangle, comparing the obtained results to those of a reinforcement technique with polymethylmethacrylate (PMMA) as bone cement. Methods Twenty synthetic bones were used: 10 units for the control group (CG), 5 units for the test group without reinforcement (TGW/O), and 5 units for the test group using a reinforcement technique with PMMA (TGW). The biomechanical analysis simulated a fall on the large trochanter using a servo-hydraulic machine. Results All TGW/O and CG specimens had a basicervical fracture. Three TGW specimens presented a basicervical fracture, and two suffered a fracture near the fixation point of the device (femoral diaphyseal region), with one of them being associated with a femoral neck fracture. A mean PMMA volume of 8.2 mL was used to fill the 3 screw holes in the TGW group. According to the one-way analysis of variance (ANOVA) and the Tukey multiple comparisons tests at a 5% level, the TGW presented a statistically significant difference when compared with the other groups in all parameters: maximal load ( p = 0.001) and energy until fracture ( p = 0.0001). Conclusion The simple removal of the cannulated screws did not reduce significantly the maximum load and energy for fracture occurrence, but the proximal femoral reinforcement with PMMA significantly increased these parameters, modifying the fracture pattern.

Biomechanical Test after Hip Cannulated Screw Removal (in vitro Analysis) / Ensaio biomecânico após retirada de parafusos canulados do fêmur proximal (análise in vitro)

Abstract Objective This study aims to evaluate, through biomechanical tests, the resistance and energy required for proximal femoral fracture in synthetic bones after removing cannulated screws shaped as an inverted triangle, comparing the obtained results to those of a reinforcement technique with polymethylmethacrylate (PMMA) as bone cement. Methods Twenty synthetic bones were used: 10 units for the control group (CG), 5 units for the test group without reinforcement (TGW/O), and 5 units for the test group using a reinforcement technique with PMMA (TGW). The biomechanical analysis simulated a fall on the large trochanter using a servo-hydraulic machine. Results All TGW/O and CG specimens had a basicervical fracture. Three TGW specimens presented a basicervical fracture, and two suffered a fracture near the fixation point of the device (femoral diaphyseal region), with one of thembeing associated with a femoral neck fracture. A mean PMMA volume of 8.2 mL was used to fill the 3 screw holes in the TGWgroup. According to the one-way analysis of variance (ANOVA) and the Tukey multiple comparisons tests at a 5% level, the TGW presented a statistically significant difference when compared with the other groups in all parameters: maximal load (p = 0.001) and energy until fracture (p = 0.0001). Conclusion The simple removal of the cannulated screws did not reduce significantly the maximum load and energy for fracture occurrence, but the proximal femoral reinforcement with PMMA significantly increased these parameters, modifying the fracture pattern.

Resumo Objetivo Avaliar, pormeio de ensaio biomecânico, a resistência e a energia necessária para ocorrência de fratura do fêmur proximal em osso sintético após retirada de parafusos canulados em forma de triângulo invertido e comparar os resultados obtidos com técnica de reforço utilizando polimetilmetacrilato (PMMA). Métodos Foramutilizados 20 ossos sintéticos: 10 unidades para o grupo controle; 5 o grupo teste sem reforço, sem preenchimento após a retirada dos parafusos canulados, e 5 o para grupo teste com reforço com PMMA. A análise biomecânica foi realizada simulando queda sobre o grande trocânter utilizando máquina servo-hidráulica. Resultados Todos os corpos de prova dos grupos controle e sem cimento apresentaram fratura baso-cervical. No grupo teste com preechimento, três corpos de prova apresentaram fratura baso-cervical, enquanto que dois deles apresentaram fratura na parte próxima ao ponto de fixação no dispositivo (região diafisária do fêmur), sendo um deles associado a fratura do colo femoral. Foi utilizada uma média de 8.2 ml de polimetilmetacrilato no preenchimento dos três pertuitos do grupo com preenchimento. Segundo a análise de variância (ANOVA, na sigla em inglês) para um fator e o teste de comparações múltiplas de Tukey, ao nível de 5%, o grupo com cimento apresentou diferença significativa em relação aos outros grupos em todos os parâmetros. Conclusão A simples retirada dos parafusos canulados não apresentou redução significativa da carga máxima e da energia necessárias para a ocorrência de fratura; porém, o reforço do fêmur proximal com polimetilmetacrilato aumentou significativamente esses parâmetros, causando mudanças no padrão fraturário.

Glycosaminoglycans and vitamin C affect broiler bone parameters.

The purpose of this study was to determine if in ovo feeding and rearing with glycosaminoglycans and vitamin C could influence bone and cartilage macroscopy, mineral composition, mineral density and surface area, bone breaking strength, and bone histology in broilers. Fertile eggs from breeders (Cobb) were either uninjected or injected with 4 µg of additive/100 µL water on day 4 of incubation. Every 100 g of in ovo additive contained 30 g of chondroitin sulfate, 30 g of glucosamine, and 5 g of vitamin C. After hatching, the chicks from both incubation treatments were submitted to additional treatments during the growth phase from 1 to 42 D of age (diet without and with 0.74 g of additive/kg of feed). Every 100 kg of feed contained 30 g of glucosamine sulfate, 24 g of chondroitin sulfate, and 20 g of vitamin C. A completely randomized factorial design (2 × 2) was applied. The data were submitted to variance analysis using the general linear model procedure of SAS (SAS Institute). In ovo feeding with 4 µg of additive plus dietary supplementation with 0.74 g of additive/kg of feed resulted in the highest cartilage weight of the femur proximal epiphysis in birds (P = 0.0098). The highest ash, phosphorus and calcium percentage, mineral density and mineral composition were identified for femur and tibia in the following treatments: in ovo feeding plus diet without additive during rearing, or uninjected eggs plus dietary supplementation during rearing. In ovo feeding with 4 µg of the additive reduced (P = 0.0008) the number of chondrocytes in the proximal epiphysis of the tibia cartilage and increased (P < 0.0001) the number of osteocytes in the tibia diaphysis of broilers. We conclude that in ovo feeding or dietary supplementation during broiler rearing with glycosaminoglycans (chondroitin sulfate and glucosamine sulfate) and vitamin C benefits the development of bird bones and cartilage, and may represent a solution to bone problems in broilers.

Biomechanical Test Following Removal of a Dynamic Hip Screw: In Vitro Analysis.

The objective of this study was to evaluate, by means of a static flexural test, the biomechanical parameters necessary for the occurrence of a proximal femoral fracture in a synthetic bone model after the removal of a dynamic hip screw (DHS) and comparing the results obtained with a reinforcement technique using polymethylmethacrylate (PMMA). Twenty synthetic bones made of the same material and from the same manufacturer were used: ten units as the control group (CG), five units as the test group without reinforcement (TG), and five units as the test group with reinforcement (TGR). The biomechanical analysis was performed simulating a fall over the trochanter using a servo-hydraulic machine. In the control group, the assay was performed with its integrity preserved. In the TG and TGR groups, a DHS model was introduced, and the tests were performed as follows: TG after simple removal of the synthesis material, and in the TGR group, after removal of the synthesis material and filling the orifice of the femoral neck with PMMA. All groups presented with a basicervical fracture of the femoral neck. The CG group presented a mean of 935 newtons (N) of maximum load and 7.0 joules (J) of energy for fracture occurrence. TG and TGR groups presented, respectively, a maximum load of 750 N and 1,068 N, and energy of 6.0 J and 7.3 J. According to the one-way analysis of variance (ANOVA), there was no significant difference in flow load (p = 0.16), energy to flow (p = 0.16), stiffness (p = 0.28), maximum load (p = 0.10), and energy to fracture (p = 0.54) between the studied groups. The removal of the DHS implant from the synthetic bone did not present a significant increase of the maximum load and the energy necessary for the occurrence of a fracture with the use of the PMMA reinforcement technique.

Effect of the addition of glycosaminoglycans on bone and cartilaginous development of broiler chickens.

Locomotion issues in broiler production may decrease performance (carcass yield and traits) and lead to high financial losses. This study evaluates the addition of glucosaminoglycans in broiler diets to minimize the lack of proper bone development and joint weakening. The experiment was conducted using 2,160 broilers randomly distributed in a factorial pattern (3 × 3) using 3 levels of glucosamine sulfate (0, 0.12, and 0.24%) and 3 levels of chondroitin sulfate addition (0, 0.08, and 0.16%). Eight repetitions were used for each treatment, distributed in 72 pens with 30 broilers each. There was a quadratic effect on feed conversion for broilers from 1 to 42 d old (P = 0.0123) for the addition of chondroitin, and better feed conversion was obtained by adding 0.08% of chondroitin. The relative tibia weight, the width of the proximal epiphysis and diaphysis presented a linear increased effect in broilers at 42 d old. An interaction was found between the amount of chondroitin × glucosamine and the number of chondrocytes in the proximal cartilage of the tibia (P = 0.0072). There was a quadratic effect of glucosamine levels (P = 0.0107) in the birds that had received the 0.16% addition of chondroitin, and the presence of 0.18% glucosamine increased the number chondrocytes in the cartilage of broilers. These results provide the first evidence that broilers may benefit from increased dietary chondroitin sulfate. These results indicate that the addition of glucosamine and chondroitin sulfates in broiler feed rations might alleviate leg conditions and decrease financial losses in the broiler industry.

Effect of Electrical Stimulation and Vibration Therapy on Skeletal Muscle Trophism in Rats with Complete Spinal Cord Injury.

OBJECTIVE: The goals of this work were to analyze the skeletal muscle changes after complete spinal cord injury (SCI) in rats and to compare the effects of electrical stimulation and whole-body vibration on prevention of muscle hypotrophy in these animals. DESIGN: Seven-week-old male Wistar rats were divided into four groups: (1) sham operation (sham, n = 12), (2) SCI (n = 10), (3) SCI + electrical stimulation (n = 9), and (4) SCI + whole-body vibration (n = 9). Complete SCI was generated by surgical transection of the cord at the T10 level. Therapies were initiated 3 days after the surgery and continued for 30 days at a frequency of 3 days per week, 20 mins per day. The animals were killed on day 33 after injury for subsequent analyses. RESULTS: SCI caused a significant decrease in muscle mass and fibers, perimeter measurements, and mechanical resistance to traction as well as an increase in fibrotic tissue. Electrical stimulation, but not whole-body vibration, resulted in significant partial muscle hypotrophy prevention. CONCLUSIONS: Electrical stimulation may be a potentially beneficial therapeutic modality to prevent muscle hypotrophy after SCI.

Anatomic changes in the macroscopic morphology and microarchitecture of denervated long bone tissue after spinal cord injury in rats.

To study the effects of mechanical loading on bones after SCI, we assessed macro- and microscopic anatomy in rats submitted to passive standing (PS) and electrical stimulation (ES). The study design was based on two main groups of juvenile male Wistar rats with SCI: one was followed for 33 days with therapies starting at day 3 and the other was followed for 63 days with therapies starting at day 33. Both groups were composed of four subgroups (n = 10/group): (1) Sham, (2) SCI, (3) SCI + PS, and (4) SCI + ES. Rehabilitation protocol consisted of a 20-minute session, 3x/wk for 30 days. The animals were sequentially weighed and euthanized. The femur and tibia were assessed macroscopically and microscopically by scanning electronic microscopy (SEM). The SCI rats gained less weight than Sham-operated animals. Significant reduction of bone mass and periosteal radii was observed in the SCI rats, whereas PS and ES efficiently improved the macroscopic parameters. The SEM images showed less and thin trabecular bone in SCI rats. PS and ES efficiently ameliorated the bone microarchitecture deterioration by thickening and increasing the trabeculae. Based on the detrimental changes in bone tissue following SCI, the mechanical loading through weight bearing and muscle contraction may decrease the bone loss and restore the macro- and microanatomy.

Effect of local anaesthetic infiltration with bupivacaine and ropivacaine on wound healing: a placebo-controlled study.

Infiltration of surgical wounds with long-acting local anaesthetics (LA) is used to reduce postoperative incisional pain. We hypothesised that infiltration with LA interferes with wound healing in rats. Seventy-two rats were allocated into nine groups. After intraperitoneal anaesthesia, the interscapular dorsal region was infiltrated with equivolumes of saline, 0·5% bupivacaine or ropivacaine, in a randomised double-blind fashion. A standardised incision was performed in the infiltrated area and sutured closed. The rats were euthanised on the 3rd or 14th day after the operation and tissue from the incision site was subjected to histochemical analyses and mechanical testing (MT). Compared with the control group, bupivacaine displayed a significant increase in the macrophage number on day 3 (+63% versus +27% for ropivacaine). The transforming growth factor ß-1 expression had a significant increase in the LA (versus saline) groups, +63% in ropivacaine group and +115% in bupivacaine group on day 3 (P < 0·05). The collagen fibres as measured by dyed area were significantly higher in the bupivacaine group on day 3 (+56%, P < 0·01 versus +15% for ropivacaine). CD34 was reduced in bupivacaine group (-51%, P < 0·05 versus +3% for ropivacaine). On day 14, no statistical differences were observed in either LA group (versus saline) with respect to histopathologic or inflammatory mediators. MT on day 14 showed no differences between the LA and saline groups. The LA-induced increases in histological markers did not extend beyond the third day, suggesting that wound infiltration with long-acting LA does not impair the wound healing process in rats.

Avaliação morfológica e por imagem radiográfica da matriz óssea mineralizada heteróloga fragmentada e metilmetacrilato, preservados em glicerina para reparação de falhas ósseas em tíbias de coelhos / Morphological evaluation and radiographic image of fragmented heterolog mineralized bone matrix and methylmethacrylate preserved in glycerin to repair osseous defects in tibias of rabbits

Os traumas que resultam em fraturas ósseas, principalmente as cominutivas, têm uma importância muito grande na rotina clínico-cirúrgica veterinária e humana. Foi realizada falha segmentar de 6mm na região metafisária medial da tíbia esquerda de 12 coelhos, a qual foi preenchida com implante constituído de matriz óssea mineralizada heteróloga fragmentada e metilmetacrilato, preservados em glicerina (98%) para a sua reconstrução. Foi realizada avaliação morfológica e radiológica aos 30, 60, 90 e 120 dias e observou-se a incorporação do implante ao leito receptor, em 100% dos casos, mostrando ser biologicamente compatível, pois promoveu a reparação das falhas ósseas, sem sinais de infecção, migração e/ou rejeição, sendo uma opção de substituto para preencher defeitos ósseos.

The traumas that result in bone fractures, especially comminuted, have high importance in veterinary and human surgical routine. A 6mm of segmental defect was performed at the medial metaphyseal region of the left tibia of 12 rabbits and an association of fragmented heterologue mineralized bone matrix and methylmethacrylate conserved in glycerin (98%) was used as a graft to fill the bone defect. To evaluate the procedure morphological and radiological exams were performed after 30, 60, 90 and 120 days. There was gradual integration of the bone graft in the receptor bed in 100% of the cases showing that the material is biologically compatible as it promotes bone defect reparation without signs of infection, migration and/or rejection and can be considered one more option to be used as a substitute to fill bone defects.

Standing frame and electrical stimulation therapies partially preserve bone strength in a rodent model of acute spinal cord injury.

OBJECTIVE: The aim of this study was to compare the effect of standing frame and electrical stimulation on bone quality in a rodent transection model of spinal cord injury (SCI). DESIGN: Seven-week-old male Wistar rats were divided into four groups: sham, n = 10; SCI, n = 7; SCI + standing frame, n = 7; and SCI + electrical stimulation, n = 7. Complete SCI was generated by surgical transection of the cord at the T10 level. Therapies were initiated 3 days after the surgery, 3 days/wk, 20 mins/day, for 30 days. Animals were killed on day 33 postinjury. RESULTS: No treatment preserved bone mineral density at any skeletal site tested (P = 0.08-0.99). Standing frame therapy preserved maximal load at the lumbar vertebral body (14% vs. 37% reduction, P = 0.01) and prevented SCI-induced loss of stiffness at both the femur (8% vs. 37% reduction, P = 0.03) and the tibia (35% vs. 56% reduction, P < 0.0001). Electrical stimulation therapy reduced SCI-induced loss of stiffness at the tibia only (40% vs. 56% reduction, P = 0.003). CONCLUSIONS: Standing frame and electrical stimulation may have potential as future therapeutic modalities to treat or prevent bone loss after SCI.

Biological evaluation of the bone healing process after application of two potentially osteogenic proteins: an animal experimental model.

OBJECTIVE: The aim of this work was to analyse qualitatively and quantitatively the newly formed bone after insertion of rhBMP-2 and protein extracted from Hevea brasiliensis (P-1), associated or not with a carrier in critical bone defects created in Wistar rat calvarial bone, using histological and histomorphometrical analyses. MATERIALS AND METHODS: Eighty-four male Wistar rats were used, divided into two groups, according to the period of time until the sacrifice (2 and 6 weeks). Each one of these groups was subdivided into six groups with seven animals each, according to the treatments: (1) 5 µg of pure rhBMP-2, (2) 5 µg of rhBMP-2/monoolein gel, (3) pure monoolein gel, (4) 5 µg of pure P-1, (5) 5 µg of P-1/monoolein gel and (6) critical bone defect controls. The animals were euthanised and the calvarial bone tissue removed for histological and histomorphometrical analyses. RESULT AND CONCLUSION: The results showed an improvement in the bone healing process using the rhBMP-2 protein, associated or not with a material carrier in relation to the other groups, and this process demonstrated to be time dependent.

Photogrammetry on the identification of postural asymmetries in cadets and pilots of the Brazilian air force academy.

OBJECTIVE: To identify whether flight training activities cause postural changes in cadets and pilots of the Brazilian Air Force Academy (AFA). METHODS: Eighty subjects were assessed through photographic images in anterior and right side views. Four groups of cadets (n=20 per group) divided according to the year since enlistment and a fifth group of fifteen pilots from the Air Demonstration Squadron (ADS) were included. Pictures were analyzed using the Postural Analysis Program (SAPO) and angles related to head vertical alignment (HVA), head horizontal alignment (HHA), acromion horizontal alignment (AHA) and anterior-superior iliac spine horizontal alignment (HAS) were plotted. RESULTS: We did not find statistical significant differences in the angles: HVA, HHA and AHA. However, a significant difference was found for the HAS angle with pilots having lower values than cadets, suggesting greater postural stability for this variable in pilots. CONCLUSION: The horizontal alignment of the anterior-superior iliac spine was the only measure that showed significant difference in the comparison between pilots and cadets. The remaining alignments were not different, possibility because of the strict criteria used for admission of cadets at the AFA and the efficiency of the physical training that is performed periodically.

Fotogrametria na identificação de assimetrias posturais em cadetes e pilotos da academia da força aérea brasileira / Photogrammetry on the identification of postural asymmetries in cadets and pilots of the Brazilian air force academy

OBJETIVO: Identificar se a atividade de treino de voo pode desencadear alterações posturais em cadetes e pilotos da Academia da Força Aérea Brasileira (AFA). MÉTODOS: Os sujeitos foram avaliados por meio de registro fotográfico em vista anterior e lateral direita, tendo como casuística 80 cadetes da AFA, divididos em quatro grupos, 20 em cada, e 15 pilotos do Esquadrão de Demonstração Aérea (EDA), formando o quinto grupo. As fotos foram transferidas para o Software de Avaliação Postural (SAPO), sendo traçados ângulos relacionados ao alinhamento vertical da cabeça (AVC), alinhamento horizontal da cabeça (AHC), alinhamento horizontal dos acrômios (AHA) e alinhamento horizontal das espinhas ilíacas ântero-superiores (AHE). RESULTADOS: Os resultados mostraram que, após comparação das médias das assimetrias posturais entre os grupos, não houve diferença estatisticamente significante em relação aos ângulos AVC, AHC e AHA. No entanto, na variável AHE, observou-se que o grupo de pilotos apresentou valores significativamente menores que os dos cadetes, sugerindo maior estabilidade postural em relação a essa variável. CONCLUSÃO: O AHE foi a única medida que apresentou diferença estatisticamente significate na comparação entre os pilotos e cadetes dos diferentes anos. Quanto aos demais alinhamentos, não houve diferença, podendo atribuir esse fato aos critérios exigentes de ingresso dos cadetes na AFA e a eficiência do treinamento físico realizado periodicamente.

OBJECTIVE: To identify whether flight training activities cause postural changes in cadets and pilots of the Brazilian Air Force Academy (AFA). METHODS: Eighty subjects were assessed through photographic images in anterior and right side views. Four groups of cadets (n=20 per group) divided according to the year since enlistment and a fifth group of fifteen pilots from the Air Demonstration Squadron (ADS) were included. Pictures were analyzed using the Postural Analysis Program (SAPO) and angles related to head vertical alignment (HVA), head horizontal alignment (HHA), acromion horizontal alignment (AHA) and anterior-superior iliac spine horizontal alignment (HAS) were plotted. RESULTS: We did not find statistical significant differences in the angles: HVA, HHA and AHA. However, a significant difference was found for the HAS angle with pilots having lower values than cadets, suggesting greater postural stability for this variable in pilots. CONCLUSION: The horizontal alignment of the anterior-superior iliac spine was the only measure that showed significant difference in the comparison between pilots and cadets. The remaining alignments were not different, possibility because of the strict criteria used for admission of cadets at the AFA and the efficiency of the physical training that is performed periodically.

Influence of the number of layers of paris bandage plasters on the mechanical properties speciments used on orthopedic splints / Influência do número de camadas na propriedade mecânica de espécimes fabricados com atadura gessada usados para confeccionar splints ortopédicos

OBJECTIVE: To evaluate the effects of varying numbers of layers of plaster of Paris bandages on the mechanical properties of specimens used on the construction of orthopedic splints. METHODS: Rectangular plate-shaped and cylinder-shaped specimens were constructed and assigned to two groups simulating plaster slabs and cast and further divided into six subgroups according to the number of layers used: 3, 6, 8, 10, 12 and 14 layers. The specimens were subjected to either a three-point bending test (plates/slab) or compressive strength test (cylinders/cast). The following mechanical properties were evaluated: maximum load, elastic limit load and stiffness. Specimen weight was also calculated. Data was analyzed using Kruskal-Wallis and the least significant difference (LSD) tests. RESULTS: Pairwise comparisons of the subgroups 10x12 and 10x14 revealed significant differences for all mechanical properties (p<0.05). The results of this study suggest that when the goal is to construct appliances with high mechanical strength, regardless of weight, such as serial plaster slabs splints for stimulating tissue growth through the application of gradual load, splints made with plaster of Paris bandages with 12 or 14 layers should be preferred. For orthotic devices such as positioning orthotics, the use of 10 layers plaster bandages slab splints is advisable as they were found to have better correlation between mechanical strength and weight in comparison to those made wtih 6 or 8 layers. CONCLUSION: Based on the findings of this study, we suggest the use of 10 layers of plaster of Paris for the construction of orthopedic splints.

OBJETIVO: Avaliar as propriedades mecânicas de amostras fabricadas a partir de ataduras de gesso que são utilizadas em órteses ortopédicas e que variam quanto ao número de camadas. MÉTODOS: Foram confeccionados espécimes em forma de placa retangular e em forma cilíndrica, divididos em dois grupos que simulavam splint e gesso circular, os quais foram divididos em seis subgrupos de acordo com o número de camadas utilizadas, ou seja, três, seis, oito, dez, 12 e 14 camadas. Os espécimes foram submetidos a um teste de inclinação de três pontos (placas/splint) ou teste de resistência à compressão (cilindros/gesso circular). As seguintes propriedades mecânicas foram avaliadas: carga máxima e carga no limite de elasticidade e rigidez. O peso da amostra foi calculado. Os dados foram analisados estatisticamente pelos testes de Kruskal-Wallis e diferença mínima significativa (DMS). Comparações pareadas entre os subgrupos 10x12 e 10x14 revelaram diferenças significativas para todas as propriedades mecânicas (p<0,05). RESULTADOS: Os resultados sugerem que, quando o objetivo é construir aparelhos com alta resistência mecânica, independente do peso, tais como órteses seriadas de posicionamento para simular força gradual aplicada no tecido para a melhoria da amplitude de movimento, talas de 12 ou 14 camadas devem ser preferidas. Para os aparelhos ortopédicos que irão ser submetidos a esforços de baixa intensidade, aconselha-se a utilização de dez camadas para as órteses, porque houve uma melhor correlação entre a resistência mecânica e peso para as amostras fabricadas com dez camadas de atadura gessada comparadas com aquelas confeccionadas com seis ou oito camadas. CONCLUSÂO: Baseado nos achados deste estudo, sugere-se a utilização de dez camadas na confecção de órteses ortopédicas.

Influence of the number of layers of paris bandage plasters on the mechanical properties speciments used on orthopedic splints.

OBJECTIVE: To evaluate the effects of varying numbers of layers of plaster of Paris bandages on the mechanical properties of specimens used on the construction of orthopedic splints. METHODS: Rectangular plate-shaped and cylinder-shaped specimens were constructed and assigned to two groups simulating plaster slabs and cast and further divided into six subgroups according to the number of layers used: 3, 6, 8, 10, 12 and 14 layers. The specimens were subjected to either a three-point bending test (plates/slab) or compressive strength test (cylinders/cast). The following mechanical properties were evaluated: maximum load, elastic limit load and stiffness. Specimen weight was also calculated. Data was analyzed using Kruskal-Wallis and the least significant difference (LSD) tests. RESULTS: Pairwise comparisons of the subgroups 10x12 and 10x14 revealed significant differences for all mechanical properties (p<0.05). The results of this study suggest that when the goal is to construct appliances with high mechanical strength, regardless of weight, such as serial plaster slabs splints for stimulating tissue growth through the application of gradual load, splints made with plaster of Paris bandages with 12 or 14 layers should be preferred. For orthotic devices such as positioning orthotics, the use of 10 layers plaster bandages slab splints is advisable as they were found to have better correlation between mechanical strength and weight in comparison to those made wtih 6 or 8 layers. CONCLUSION: Based on the findings of this study, we suggest the use of 10 layers of plaster of Paris for the construction of orthopedic splints.

Anterior C2-C3 fixation with screws: proposal of a new technique and comparative mechanical assays.

The technical difficulties involved in the anterior fixation of the C2-C3 vertebral segment by means of plates and screws, related to retraction of the structures around the vertebral segment, appropriate exposure of the site and positioning of the screws and plate, motivated the development of a new modality of fixation of this segment using only screws. Fixation of the C2-C3 vertebral segment according to the technique proposed requires less exposure of the vertebral segment and does not involve the technical difficulties of standard fixation with plates and screws. In order to study the mechanical properties of this new modality of vertebral fixation, mechanical tests were performed comparing the proposed technique (fixation solely with screws positioned in the craniocaudal direction) and routinely used fixation (H plate and screws). The tests were performed using 80 cervical spine segments from Landrace pigs aged 5 months. The vertebral segments fixed by the two techniques were divided into experimental groups of ten specimens each and submitted to mechanical tests of flexion, extension, lateral bending and rotation in a universal testing machine. The mechanical properties used to compare the results were the load necessary to produce a pre-established deformation and stiffness. No significant differences were observed between the values obtained for the production of the pre-established deformation in the flexion and rotation tests. In the extension and lateral bending tests, the mean values obtained for vertebral segments fixed only with screws were significantly higher. Analysis of stiffness showed no significant difference in the flexion, rotation and lateral bending tests, whereas in the extension tests, the mean values for the group fixed only with screws were significantly higher. The results of the mechanical tests performed showed that fixation of the C2-C3 segment only with screws was not inferior from a mechanical point of view when compared to fixation with H plates of the Orozco type.

Comparação entre pinos absorvíveis de poliparadioxanona e de poliuretana da mamona na fixação de segmentos osteocondrais do fêmur distal de coelhos / Comparison between absorbable polyparadioxanone and castor oil polyrethane pins in the fixation of distal femur osteotomies in rabbits

Os polímeros absorvíveis constituem uma nova etapa nas pesquisas destinadas ao desenvolvimento do implante ortopédico ideal. Os autores realizaram trabalho experimental no qual compararam as propriedades mecânicas e o comportamento biológico de dois polímeros distintos, a poliparadioxanona, disponível comercialmente em nosso meio mediante importação (Orthosorb), e a poliuretana da mamona, obtida em território nacional a baixo custo. Pinos de aproximadamente 1,3mm de diâmetro foram submetidos a ensaios mecânicos de cisalhamento, nos quais foram analisadas propriedades tais como a carga máxima, carga no limite de proporcionalidade, resistência e rigidez destes implantes. Os resultados foram analisados mediante o teste t de Student não pareado, com nível de significância fixado em 5 por cento (p < 0,05). A superioridade dos pinos de poliparadioxanona foi evidente em todas as propriedades mecânicas estudadas, exceto a rigidez. O comportamento biológico desses pinos foi estudado em coelhos. Submeteram-se 31 animais da raça Nova Zelândia a osteotomia do côndilo femoral medial direito no plano axial. A fixação do segmento osteocondral foi realizada com pinos absorvíveis, sendo os animais diferenciados em dois grandes grupos, de acordo com o polímero utilizado na cirurgia. O sacrifício dos animais ocorreu às três, seis e 12 semanas de pós-operatório, quando os espécimes femorais foram submetidos a estudo macroscópico, radiográfico e histológico. Nos diferentes períodos estudados neste experimento, a poliparadioxanona apresentou comportamento biológico superior ao da poliuretana da mamona no que diz respeito a bioabsorção dos pinos e à osteogênese em seus sítios de implantação.

Efeitos da orientação das fibras de colágeno nas propriedades mecânicas de flexão e impacto dos ossos / Effects of collagen fiber orientation in bending and impact properties of bones

Foi estudada a relação entre as propriedades mecânicas de fêmures de coelhos adultos jovens obtidas nos ensaios de flexão em três pontos e impacto, e a orientação das fibras de colágeno, bem como a energia absorvida nos dois ensaios. O ensaio de flexão em três pontos foi realizado nos 20 fêmures esquerdos para obtenção das seguintes propriedades: limite máximo, limite proporcional, rigidez, resiliência e tenacidade. O ensaio de impacto foi realizado nos 20 fêmures direitos para obtenção da energia absorvida no impacto. A orientação das fibras de colágeno de secções próximas às fraturas dos fêmures ensaiados foi estimada utilizando a técnica de polarização da luz. A análise de regressão mostrou que, na flexão, a rigidez teve correlação positiva (r = 0,43) e a resiliência, correlação negativa (r = -0,46) com a orientação das fibras de colágeno. A tenacidade no impacto não apresentou índice de correlação significante (p < 0,05). A energia absorvida pelos fêmures no ensaio de impacto foi 4,73 vezes a energia absorvida no ensaio de flexão em três pontos.

Ensaio mecânico de flexäo nas faces côncava e convexa da diáfise do fêmur de ratas / Mechanical testing in flexon with forces applied to the concave and convex surface of rato femur

Foi avaliado o comportamento mecânico do fêmur de ratas imaturas e próximas da maturidade, em ensaios de flexao, com forças aplicadas na face côncava e convexa da diáfise do osso. A idade dos animais era de 25 e de 79 dias. Oitenta animais foram casualmente distribuídos em quatro grupos, de acordo com a idade e a superfície testada. Os ensaios foram em flexao e realizados à temperatura ambiente, após período de estocagem a -20º em freezer, durante um mês. Das curvas tensao x deformaçao foram obtidos: módulo de elasticidade, tensao máxima, tensao no limite de proporcionalidade e energia absorvida na fase elástica. Os dados mostraram que os animais próximos da maturidade tinham ossos mais fortes quando testados em flexao, mas quando foi comparada, para a mesma idade, a resistência aplicada na face côncava e convexa da diáfise, a maioria dos parâmetros nao apresentou diferenças significativas. Isto levou à conclusao de que o osso praticamente tem a mesma resistência aos esforços de flexao aplicados a favor e contra a concavidade. Postulou-se que pode haver rearranjo da arquitetura óssea interna no sentido de compensar alguma desvantagem mecânica em um dos sentidos.