High-impact drop exercise alters mechanical properties in osteopenic bone / Exercício de queda altera as propriedades mecânicas em osso osteopênico / El ejercicio de caída altera las propiedades mecánicas en hueso osteopénico

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.

RESUMO Introdução: A osteopenia é uma doença reversível e precede a osteoporose. A atividade física e a carga mecânica parecem desempenhar um papel importante na regulação da homeostase óssea, sem os efeitos colaterais da terapia medicamentosa direcionada. No entanto, é controverso qual tipo de estímulo promove adaptações mais eficazes com relação às propriedades mecânicas dos ossos. Objetivo: Investigar os efeitos do treinamento de queda com impacto sobre a estrutura óssea depois de osteopenia induzida por ovariectomia em 40 ratas Wistar com 10 semanas de idade. Métodos: Vinte ratas (programa de prevenção) foram distribuídas aleatoriamente em dois grupos (n = 10): Ovariectomizadas sedentárias (OVXs) e OVX treinadas (OVX + Dropt). Os animais OVX + Dropt começaram a treinar três dias após a cirurgia. Outras vinte ratas (programa de tratamento) foram alocadas aleatoriamente em outros dois grupos (n = 10): Ovariectomizadas sedentários (OVXs) e OVX exercitadas (OVX + Dropt). Os animais OVX + Dropt iniciaram o treinamento 60 dias após a cirurgia. As ratas nos grupos treinados foram deixadas cair 20 vezes/dia, 5 dias/semana, de altura de 40 cm durante um período de 12 semanas. Ao final, foram analisados os testes biomecânicos. Resultados: A carga final e a rigidez da tíbia esquerda nos grupos treinados foram maiores do que nos grupos sedentários (p < 0,05). Conclusões: O exercício de queda provocou alterações favoráveis nas propriedades mecânicas dos ossos. O exercício de queda com impacto é eficaz para prevenir a perda óssea após ovariectomia, mesmo quando a osteopenia já está estabelecida

RESUMEN Introducción: La osteopenia es una enfermedad reversible y precede a la osteoporosis. La actividad física y la carga mecánica parecen desempeñar un papel importante en la regulación de la homeostasis ósea, sin los efectos secundarios de la terapia farmacológica dirigida. Sin embargo, es controvertido qué tipo de estímulo promueve adaptaciones más eficaces con respecto a las propiedades mecánicas de los huesos. Objetivo: Investigar los efectos del entrenamiento de caída con alto impacto sobre la estructura ósea después de osteopenia inducida por ovariectomía en 40 ratas Wistar hembras de diez semanas de edad. Métodos: Se asignaron aleatoriamente veinte ratas (programa de prevención) en dos grupos (n = 10): Ovariectomizadas sedentarios (OVXs) y OVX entrenadas (OVX + Drope). Los animales OVX + Drope comenzaron a entrenar tres días después de la cirugía. Otras veinte ratas hembras (programa de tratamiento) fueron asignadas aleatoriamente a otros dos grupos (n = 10): Ovariectomizadas sedentarias (OVXs) y OVX entrenadas (OVX + Drope). Los animales OVX + Drope iniciaron el entrenamiento 60 días después de la cirugía. Las ratas en los grupos entrenados se dejaron caer de una altura de 40 cm 20 veces/día, 5 días/semana durante un período de 12 semanas. Al final, se analizaron las pruebas biomecánicas. Resultados: La carga y rigidez de la tibia izquierda en los grupos entrenados fueron mayores que en los grupos sedentarios (p < 0,05). Conclusiones: El ejercicio de caída provocó cambios favorables en las propiedades de los huesos. El ejercicio de caída con impacto es eficaz para prevenir la pérdida ósea después de la ovariectomía, incluso cuando la osteopenia ya está establecida.

The osteogenic effects of swimming on bone mass, strength, and microarchitecture in rats with unloading-induced bone loss.

The effect of nonweight-bearing exercise on osteoporotic bones remains controversial and inconclusive. The purpose of this study was to evaluate the effects of swimming on osteoporotic tibias of rats submitted to hindlimb suspension. Initially, 20 Wistar rats were used to confirm a significant bone loss following 21 days of unloading. Thirty rats were then divided into 3 groups and followed during 51 days: CON (nonsuspended rats), S + WB (suspended rats for 21 days and then released for regular weight-bearing) and, S + Swim (suspended rats for 21 days and then released from suspension and submitted to swimming exercise). We observed that swimming exercise was effective at fully recovering the bone deterioration caused by suspension, with significant increments in BMD, bone strength and bone volume. On the other hand, regular weight-bearing failed at fully restoring the bone loss induced by unloading. These results indicate that swimming exercise may be a potential tool to improve bone density, strength, and trabecular volume in tibias with bone loss induced by mechanical unloading in suspended rats. We conclude that this modality of activity could be beneficial in improving bone mass, strength, and architecture in osteoporotic individuals induced by disuse, such as bed rest or those exposed to microgravity, who may not be able to perform weight-bearing exercises.

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.

Torsional force applied to the tibia of living lambs in an attempt to change the bone rotational axis.

PURPOSE: To evaluate the effects of torsional force on the rotational axis of living lamb tibias. METHODS: An external fixator device was designed to apply rotation to the tibias of lambs. Once a week, the bone distal extremity was rotated 2º. After achieving ~20º of internal rotation, the turning was discontinued and the device was maintained in situ for one month and euthanasia occurred in group A (n=10) after this. In group B (n=9) euthanasia occurred three months after removing the device. Computed tomography scans evaluated the rotational angle; dual-energy X-ray absorptiometry assessed the bone mineral density, and conventional and polarized light microscopy studied the bone microstructure. RESULTS: In group A, the mean angle of the external rotation in the control tibias was 24º and 8º in the twisted tibias (p<0.0001); in group B, the angle was 23º (control) and 7º (twisted, p<0.0001), with no differences between groups A and B (p=0.9567). The BMD increased in the twisted tibias in group A (p<0.0001) and in group B (p=0.0023), with no between-group differences (p>0.05). Microscopically, the twisted tibias showed asymmetrical subperiosteal bone deposition on the lateral cortex surface. CONCLUSION: Gradual torsion applied to the immature tibia significantly modified its rotational axis.

Torsional force applied to the tibia of living lambs in an attempt to change the bone rotational axis

To evaluate the effects of torsional force on the rotational axis of living lamb tibias. METHODS: An external fixator device was designed to apply rotation to the tibias of lambs. Once a week, the bone distal extremity was rotated 2º. After achieving ~20º of internal rotation, the turning was discontinued and the device was maintained in situ for one month and euthanasia occurred in group A (n=10) after this. In group B (n=9) euthanasia occurred three months after removing the device. Computed tomography scans evaluated the rotational angle; dual-energy X-ray absorptiometry assessed the bone mineral density, and conventional and polarized light microscopy studied the bone microstructure. RESULTS: In group A, the mean angle of the external rotation in the control tibias was 24º and 8º in the twisted tibias (p<0.0001); in group B, the angle was 23º (control) and 7º (twisted, p<0.0001), with no differences between groups A and B (p=0.9567). The BMD increased in the twisted tibias in group A (p<0.0001) and in group B (p=0.0023), with no between-group differences (p>0.05). Microscopically, the twisted tibias showed asymmetrical subperiosteal bone deposition on the lateral cortex surface. CONCLUSION: Gradual torsion applied to the immature tibia significantly modified its rotational axis.

Efeito de regimes de treinamento físico de alto impacto nas propriedades mecânicas de ossos: estudo experimental em ratas wistar / Effects of high-impact exercise training on bone mechanical proprieties: an experimental study in female wistar rats

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.

INTRODUCTION: Physical activity has well established benefits on bone mechanical proprieties and is a non-pharmacological treatment strategy of bone weakening pathologies where given loading stress promotes adaptive responses that enhance bone strengthening. OBJECTIVE: to investigate the effect of high-impact exercise training protocols with different durations and weekly frequencies on bone mechanical proprieties of female Wistar rats. METHODS: fifty-four female Wistar rats, 10 weeks old, were divided into six groups (n=9 each): GCI (four week sedentary group, control), GTI3 (trained three times per week, four weeks), GTI5 (trained five times per week, four weeks), GCII (eight week sedentary group, control), GTII3 (trained three times per week, eight weeks) and GTII5 (trained five times per week, eight weeks). The high-impact training protocol was based on the completion of 10 vertical jumps by the animals per session. RESULTS: Bone mechanical proprieties in the groups that trained with higher weekly frequency for longer periods had greater maximum strength and stiffness when compared with the animals that trained less. CONCLUSIONS: the present results indicate that performance of high-impact training protocol has beneficial effects on bone mechanical proprieties, even with low weekly frequency, suggesting hence, that for bone gain, daily work volume is not necessary; however, for greater result, daily exercise does present better outcome.

Biomechanical adaptations of mice cortical bone submitted to three different exercise modalities.

OBJECTIVE: To compare the adaptive effects of three non-weight bearing exercise on bone mechanical properties. METHODS: 24 male Balb/c mice (22-25g), were randomly divided into four groups (n=6): sedentary group (S); swimming group (N) which performed sessions five times per week for 60 min progressively; resistance group (R), which performed climbing exercise with progressive load, three times per week; and combined group (C), which performed the same protocols aforementioned being three times a week according to N protocol and two times a week the R protocol during eight weeks. Biomechanical tests, load until failure and stiffness evaluation of shinbone was performed after animals have been sacrificed. RESULTS: Stiffness values were statistically higher only in the isolated modalities groups (N and R, 41.68 ± 10.43 and 41.21 ± 11.38 N/mm, respectively) compared with the S group (28.48 ± 7.34 N/mm). However, taking into consideration the final body mass, relative values, there was no difference in the biomechanical tests among the groups. CONCLUSION: Data from the present investigation demonstrated a favorable influence of muscle contraction in lower impact isolated exercise modalities on absolute stiffness values, i.e.groups N and R, whereas the combined group (C) did not present any statistical significant difference compared to sedentary group. Level of Evidence II, Prospective Comparative Study .

Adaptações biomecânicas do osso cortical de camundongos submetidos à três diferentes modalidades de exercício (AU) / Biomechanical adaptations of mice cortical bone submitted to three different exercise modalities

OBJETIVO: Comparar os efeitos adaptativos de três modalidades de exercício de impacto reduzido nas adaptações mecânicas do osso cortical.MÉTODOS: Vinte e quatro camundongos machos, espécie Balb/c (25±3g), foram divididos aleatoriamente em quatro grupos (n=6): grupo sedentário (S); grupo natação (N) realizado cinco vezes por semana, 60 minutos progressivos; grupo resistido (R) submetido ao exercício de escalada com sobrecarga progressiva, três vezes por semana; e o grupo combinado (C) que realizou os mesmos protocolos em dias alternados sendo três vezes na semana do protocolo N e duas vezes na semana protocolo R. Após o sacrifício dos animais, foi realizado o ensaio mecânico de flexão em três pontos na tíbia dos grupos experimentais para se determinar a rigidez e a força máxima de fratura.RESULTADOS: A rigidez nos grupos N (41,68 ± 10,43 N/mm) e R (41,21 ± 11,38 N/mm) foi significativamente maior comparada ao grupo S (28,48 ± 7,34 N/mm), p < 0,05. Entretanto, considerando a massa corporal final dos animais como variável, valores relativos, não houve diferença significativa nos testes biomecânicos do osso.CONCLUSÕES: Dados do presente estudo evidenciaram que o estímulo mecânico gerado pela contração muscular das modalidades isoladas de baixo impacto, grupo N e R, favoreceu o coeficiente absoluto de rigidez óssea, fato que não ocorreu na modalidade combinada, grupo C.Nível de Evidência II, Estudo Prospectivo e Comparativo.

OBJECTIVE: To compare the adaptive effects of three non-weight bearing exercise on bone mechanical properties.METHODS: 24 male Balb/c mice (22-25g), were randomly divided into four groups (n=6): sedentary group (S); swimming group (N) which performed sessions five times per week for 60 min progressively; resistance group (R), which performed climbing exercise with progressive load, three times per week; and combined group (C), which performed the same protocols aforementioned being three times a week according to N protocol and two times a week the R protocol during eight weeks. Biomechanical tests, load until failure and stiffness evaluation of shinbone was performed after animals have been sacrificed.RESULTS: Stiffness values were statistically higher only in the isolated modalities groups (N and R, 41.68 ± 10.43 and 41.21 ± 11.38 N/mm, respectively) compared with the S group (28.48 ± 7.34 N/mm). However, taking into consideration the final body mass, relative values, there was no difference in the biomechanical tests among the groups.CONCLUSION: Data from the present investigation demonstrated a favorable influence of muscle contraction in lower impact isolated exercise modalities on absolute stiffness values, i.e.groups N and R, whereas the combined group (C) did not present any statistical significant difference compared to sedentary group.Level of Evidence II, Prospective Comparative Study.

Influência do local de ancoragem dos implantes na vértebra sobre o torque de inserção e resistência ao arrancamento / Influencia de la ubicación de los implantes en la vértebra cuanto al torque de inserción y resistencia de arrancamiento / Influence of anatomical vertebral site on screw insertion torque and pull-out strength

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.

OBJECTIVE: To evaluate the influence of anatomical site of implants on vertebra about insertion torque and pull-out strength of conical and cylindrical core screws. METHODS: Conical and cylindrical core screws were inserted into the pedicle and vertebral body of 10 lumbar vertebrae (L4-L5) of calves. In the study were evaluated insertion torque and pull-out strength of screws inserted into the body and pedicle. RESULTS: The insertion torque and pull-out strength were higher for conical and cylindrical core screws inserted into vertebral pedicle. CONCLUSIONS: The anchoring of implants into the pedicle showed higher insertion torque and pull-out strength than implants inserted into the vertebral body in both types of screws used.

OBJETIVO: Evaluar la influencia de la localización anatómica de la fijación de los implantes en la vértebra cuanto al torque de inserción y resistencia de arrancamiento de los tornillos con alma cónica y cilíndrica. MÉTODOS: Los tornillos con alma cilíndrica y cónica se insertan en el cuerpo y el pedículo vertebral de diez vértebras lumbares (L4-L5) de los terneros. Se evaluó el torque de inserción y resistencia al arrancamiento de tornillos insertados en el cuerpo y el pedículo. RESULTADOS: El torque de inserción y resistencia al arrancamiento fue mayor para los tornillos con alma cónica y cilíndrica insertados en el pedículo. CONCLUSIONES: La fijación de los implantes en el pedículo mostró mayor torque de inserción y resistencia al arrancamiento en comparación con los implantes en el cuerpo vertebral, en ambos tipos de tornillos.

BIOMECHANICAL AND HISTOLOGICAL ANALYSIS OF THE GASTROCNEMIUS IN RATS SUBJECTED TO MUSCLE INJURY AND TREATMENT WITH LOW-LEVEL LASER THERAPY.

OBJECTIVE: To mechanically and histologically evaluate the application of low-level laser therapy to the reparative process on lesions caused by impact on the gastrocnemius muscles of rats. METHODS: 45 female Wistar rats were divided into three groups (n=15/ group): C (control, no lesion), ML (muscle lesion) and ML-L (muscle lesion and laser therapy). The experimental muscle lesion was produced by letting a 250 g load drop from a height of 30 cm, directly onto the muscle. The animals in the ML-L group were subjected to application of 960 nm laser, 2 J/cm(2), on the lesion site, for three days, twice a day. Mechanical tests were performed on an Emic(®) universal testing machine. RESULTS: The mean values for the maximum force were: 35.70 (± 2.69) N in group C, 31.77 (± 2.59) N in group ML and 34.36 (± 3.63) N in group ML-L, with a statistically significant difference between groups C and ML (p < 0.05). The mean values for relative stiffness were: 3.75 (± 0.98) N/mm in group C, 3.84 (± 0.32) N/mm in group ML and 4.43 (± 0.68) N/mm in group ML-L, with no statistically significant differences (p>0.05). Histological analysis showed the presence of blood vessels in group ML-L and hematomas during the repair process. CONCLUSION: Laser therapy had a positive effect on the regeneration process of the muscle injury.

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.

Efeito do macheamento do orifício piloto na resistência ao arrancamento e no torque de inserção dos parafusos pediculares com alma cônica / Effect of pilot hole tapping on pullout strength and insertional torque of dual core pedicle screws

OBJETIVO: Avaliar a influência do macheamento do orifício piloto na resistência ao arrancamento e no torque de inserção dos parafusos pediculares com alma cônica. MÉTODOS: Ensaios mecânicos de arrancamento em máquina universal de ensaios foram realizados com parafusos pediculares com alma cônica inseridos nos pedículos da quinta vértebra lombar de vitelo. As medidas do torque de inserção foram realizadas com torquímetro com capacidade de 10Nm, sendo considerado o maior valor de torque. O preparo do orifício piloto foi realizado por meio de sonda com 3,8 mm de diâmetro externo e o macheamento do orifício com macho de rosca com as mesmas dimensões e características de rosca do parafuso. RESULTADOS: Foi observada redução do torque de inserção e da resistência ao arrancamento dos implantes no grupo com o macheamento prévio do orifício piloto. CONCLUSÕES: O macheamento do orifício piloto reduziu o torque de inserção e a força de arrancamento dos parafusos pediculares com alma cônica inseridos no pedículo da quinta vértebra lombar de vitelos.

OBJECTIVE: To evaluate the influence of pilot hole tapping on pullout resistance and insertional torque of dual core pedicle screws. METHODS: Mechanical assays using a universal testing machine were performed on dual core screws inserted into fifth lumbar calf vertebrae. The insertion torque was measured by torque meter with capacity of 10 Nm, which was considered the highest value of torque. The pilot holes were prepared using a 3.8 mm diameter probe and tapping of the same size and thread characteristics as the implant. RESULTS: A decrease of the insertion torque and pullout strength were observed in the group of screws whose pilot holes were tapped. CONCLUSIONS: Tapping pilot holes reduced the insertion torque and pullout strength of dual core pedicle screws.

Análise biomecânica e histológica de músculos gastrocnêmios de ratas submetidas à lesão muscular e tratados com laserterapia de baixa intensidade / Biomechanical and histological analysis of the gastrocnemius in rats subjected to muscle injury and treatment with low-level laser therapy

OBJETIVO: Avaliar, mecânica e histologicamente, a aplicação do laser terapêutico de baixa potência, no processo reparativo de lesões provocadas por impacto em músculos gastrocnêmios de ratas. MÉTODOS: 45 ratas Wistar foram divididas em três grupos (n=15/grupo): C (controle, sem lesão), LM (lesão muscular) e LM-L (lesão muscular e laserterapia). A lesão muscular experimental foi produzida pela queda de uma carga de 250 g, de uma altura de 30cm, diretamente sobre o músculo. Os animais do grupo LM-L foram submetidos à aplicação de laser 960nm, 2J/cm², durante três dias, duas aplicações por dia, no local da lesão. Foi realizado ensaio mecânico na máquina universal de ensaio Emic®. RESULTADOS: As médias dos valores de força máxima foram: (35,70 ± 2,69) N no grupo C, (31,77 ± 2,59) N no grupo LM e (34,36 ± 3,63) N no grupo LM-L, com diferença estatística significativa nos grupos C e LM (p < 0,05). As médias dos valores de rigidez relativa foram (3,75 ± 0,98) N/mm no grupo C, (3,84 ± 0,32) N/mm no grupo LM e (4,43 ± 0,68) N/mm no grupo LM-L, sem diferença estatística (p > 0,05). A análise histológica evidenciou presença de vasos sanguíneos no grupo LM-L e hematomas em processo de reparação. CONCLUSÃO: A laserterapia influencia de forma positiva no processo de regeneração da lesão muscular.

OBJETIVE: To evaluate, by means of biomechanical and histological analysis, the effect of low-level laser therapy on the gastrocnemius of rats subjected to muscle lesion by impact. METHODS: 45 female Wistar rats, weighing 250g, were divided into 3 groups (n=15/group): C (control), ML (animals submitted to muscle lesion) and ML-L (animals submitted to muscle lesion and laser therapy). The animals from groups ML and ML-L were subjected to an experimental muscle lesion by means of an impact of a 250g load, released from a height of 30 cm, directly on the gastrocnemius. The animals from group ML-L were submitted to a treatment with a 960 Nm laser, 2 J/cm², for 3 days, twice a day. RESULTS: The mechanical tests were performed on the Universal Testing Machine. The average values of maximum force were: 35.70 (± 2.69) N in group C, 31.77 (± 2.59) N in group ML and 34.36 (± 3.63) N in group ML-L, with a statistically significant difference between groups C and ML (p < 0.05). The average values of stiffness were: 3.75 (± 0.98) N/mm in group C, 3.84 (± 0.32) N/mm in group ML and 4.43 (± 0.68) N/mm in group ML-L, with no statistically significant differences (p>0.05). Histological analysis showed a presence of blood vessels in group ML-L and a hematoma in the healing stage. CONCLUSION: Treatment with low-level laser had a positive effect in the healing process of muscle injury.