Biomechanical and histological comparison of two suture configurations for soft tissue grafts: speedtrap™ versus krackow stitch.

To compare 2 different graft preparation techniques to determine biomechanical strength and resultant tissue trauma evaluated by histology. Twelve common flexors of the finger's tendons were prepared with either tubulization (SpeedTrap™) or transtendon stiches (Orthocord™). The stiffness, resistance and energy at maximum load were tested for biomechanical assessment in both groups. After load testing, Samples were stained with hematoxylin and eosin (HE) to evaluate histological damage. We observe that the time to prepare tendons with SpeedTrap™ was 8.3 times faster (1:25 min) than traditional ones (15:02 min). In all cases, the mean values for SpeedTrap™ were higher in terms of strength, stiffness and energy at maximum load than for traditional suture but without significant difference (p > 0.05). The Krackow stitch produces greater structural damage to the collagen fibers while SpeedTrap™ maintains better organized arrangement of the fibers after tubulization preparation. With the results obtained, we can conclude that the tubulization technique allows faster graft preparation with less structural damage to the manipulated tissue without altering the biomechanical resistance provided by the transtendon suture technique.

Comparative study of two retrograde locked intramedullary nail designs for ankle arthrodesis: A finite element analysis.

Ankle arthrodesis is the gold standard for treatment of end-stage arthritis. The goal of ankle arthrodesis is to obtain bony union between the tibia and the talus. Retrograde intramedullary nailing is typically reserved for ankle and subtalar joints arthrodesis. The purpose of this study is to evaluate the effect of two different materials, two locking pin configurations and two nail designs of a retrograde locked intramedullary nail used for ankle arthrodesis. Using the finite element analysis, a numerical study of ankle arthrodesis was developed to evaluate the effect of materials: TI-6Al-4V and stainless steel AISI 316 LVM; two locking pin configurations: five and six pins, on two intramedullary nails: Ø10 × 180 mm and Ø11 × 200 mm. A model of a healthy foot was created from tomographic scans. It was found that the mechanical stimulus required to achieve bone fusion were higher for Ø10 × 180 nails (6.868 ± 0.047) than the Ø11 × 200 nails (5.918 ± 0.047; p < 0.001; mean ± SEM). We also found that six-pin configuration had a higher mechanical stimulus (6.470 ± 0.047) than the five-pin configuration (6.316 ± 0.046; p = 0.020). Similarly, it was higher for titanium (6.802 ± 0.047) than those for stainless steel (5.984 ± 0.046; p < 0.001). Finally, the subtalar zone presented higher values (7.132 ± 0.043) than the tibiotalar zone (5.653 ± 0.050; p < 0.001). The highest mechanical stimulus around the vicinity of tibiotalar and subtalar joint was obtained by Ø10 × 180 nails, made of titanium alloy, with 6P.

A castor oil plant (Ricinus communis)-derived implant improves the biomechanical properties of noncritical bone defects.

PURPOSE: The biomechanical properties of the polyurethanes implant material derived from castor oil plant (Ricinus communis) were evaluated in a noncritical bone defect model in rat tibia. METHODS: After three weeks of the implant application, the tibias were tested by means of the biomechanical three-point flexion test and resistance, rigidity, energy at maximum load and maximum energy were evaluated. Nonparametric statistical analysis was performed. RESULTS: It was found that the group that received the implant behaved the same as the intact control group and also showed a significant increase in maximum load compared to the spontaneous repair group. CONCLUSIONS: Our results indicate that the tibias with the implant material in a noncritical bone defect recover normal biomechanical parameters in less time than spontaneously.

A castor oil plant (Ricinus communis)-derived implant improves the biomechanical properties of noncritical bone defects

ABSTRACT Purpose The biomechanical properties of the polyurethanes implant material derived from castor oil plant (Ricinus communis) were evaluated in a noncritical bone defect model in rat tibia. Methods After three weeks of the implant application, the tibias were tested by means of the biomechanical three-point flexion test and resistance, rigidity, energy at maximum load and maximum energy were evaluated. Nonparametric statistical analysis was performed. Results It was found that the group that received the implant behaved the same as the intact control group and also showed a significant increase in maximum load compared to the spontaneous repair group. Conclusions Our results indicate that the tibias with the implant material in a noncritical bone defect recover normal biomechanical parameters in less time than spontaneously.

Mandibular anterior intrusion using miniscrews for skeletal anchorage: A 3-dimensional finite element analysis.

INTRODUCTION: Deepbites can be corrected by intrusion of mandibular anterior teeth. Direct anchorage with miniscrews simplifies complex tooth movements; however, few studies have reported their use for mandibular anterior intrusion. The purpose of this study was to evaluate, by means of the finite element method, initial tooth displacement and periodontal stress distribution using various mandibular anterior intrusion mechanics. Miniscrews were used as skeletal anchorage devices. METHODS: Cone-beam computed tomography scans were used for 3-dimensional reconstruction of the mandible and the mandibular anterior dentition. Models included the 4 incisors with or without the canines. After all surrounding periodontal and bony structures were determined brackets, segmental archwires, and miniscrews were added. Finite element studies were performed to assess initial tooth displacement and periodontal stress distribution with multiple intrusion force vectors. Changes in the location of the miniscrews and loading points on the archwire created 14 scenarios. RESULTS: Minimum buccolingual displacements, a uniform distribution of periodontal stress, and overall group intrusion for both 4-tooth and 6-tooth scenarios were best achieved when applying distointrusive vectors. The highest peaks of periodontal stress were observed when the force was directed at the corners of the segmental archwire. It was found that, in addition to distointrusive vectors, 4 loading points on the archwire were necessary for pure intrusion and uniform distribution of periodontal stress in the 6-tooth scenarios. CONCLUSIONS: The simulations in this study suggest that group intrusion of all 6 mandibular anterior teeth might be achieved by applying distointrusive vectors. Inserting a pair of miniscrews distal to the canine roots, 1 screw per side, and directing 4 loading points on the archwire generates uniform periodontal stress distribution and minimum buccolingual displacements. Local conditions, such as narrow bone width and attached gingiva level, play significant roles in the clinical viability of the proposed virtual scenarios.

The monocyte locomotion inhibitory factor inhibits the expression of inflammation-induced cytokines following experimental contusion in rat tibia.

Entamoeba histolityca produces the monocyte locomotion inhibitory factor (MLIF), a pentapeptide with powerful anti-inflammatory properties. MLIF may regulate trauma-induced inflammation through the effects it exerts directly or indirectly on immune cells, modulating the production and/or expression of the cytokines involved in the inflammatory processes that occur after damage. The aim of the present study was to evaluate the effect of MLIF on production of pro/anti-inflammatory cytokines after contusion in the rat tibia. Fifty-four Wistar rats were subjected to controlled contusion with a special guillotine-type device, and 36 rats were injected with MLIF or tenoxicam into the tibia. Eighteen animals received saline; the animals were sacrificed 24 or 48 hours after injection. Cytokine mRNA and protein production were determined by reverse transcriptase-polymerase chain reaction (RT-PCR), immunofluorescence, and hematoxylin-eosin staining was performed to visualize cellular infiltration in the rats' injured tissue. Expression levels of the cytokines interferon gamma (IFN-γ), tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and transforming growth factor-beta (TGF-ß) mRNA were inhibited significantly by MLIF at 24 hours post-contusion. MLIF significantly increased the expression levels of IL-10 at 24 hours compared with tenoxicam or the control group. These changes were associated with a significant decrease in protein production levels of TNF-α, IFN-γ, IL-6 and TGF-ß at 24 hours. Histological evaluation showed the presence of infiltration by neutrophils, monocytes and leucocytes in control tissues. This infiltration was decreased after MLIF administration, and intense infiltration was observed in tenoxicam-treated group. MLIF inhibited the expression of pro-inflammatory cytokines and increased the expression of anti-inflammatory cytokine IL-10.

Analysis of behavior of forces in a pelvis-soft tissue mechanical model / Análisis del comportamiento de fuerzas en un modelo mecánico de pelvis-tejido blando

Pressure ulcers are tissue damage resulting from the constant pressure on the underlying soft tissue to bony prominences for long periods. Some of the most common ulcers are developed at the ischial tuberosities area (ITs). It has been found that stresses produced in the underlying tissue to the ITs may exceed 5 to 11 times the surface stresses, making it necessary to estimate the forces generated between the soft tissue and the ITs. However, it is not possible to determine these stresses in vivo in a patient, due to ethical reasons. This paper presents a mechanical model of the pelvis-soft tissue in order to study the behavior of contact forces. The model simulates the load on the ITs of a male subject of 70 kg weight and 1.70 m height, which were recorded for 8 min. The registered forces in the model were compared with the surface forces estimated from pressure records measured by the Force Sensing Array system in a patient with spinal cord injury. After 2 min, both forces measured in the model, and the ones estimated in the patient followed the trend described by Crawford during clinical measurements of pressures during sitting. It was also found in the model that measured forces below the ITs are higher than those measured below soft tissue, which suggests that the model may be valid for the study of the forces generated inside the tissue.

Las úlceras por presión son daños en el tejido, derivados de la presión constante por periodos prolongados sobre el tejido blando subyacente a una prominencia ósea, algunas de las úlceras más comunes se desarrollan en la zona de las tuberosidades isquiáticas (TI´s). Se ha detectado que esfuerzos generados en el tejido subyacente a las TI´s pueden exceder entre 5 a 11 veces a los esfuerzos superficiales, lo que hace necesario conocer las fuerzas que se generan entre el tejido blando y las TI´s, sin embargo medir estos esfuerzos in vivo en un sujeto, no es posible por razones éticas. Este trabajo presenta un modelo mecánico del sistema pelvis-tejido blando con la finalidad de estudiar el comportamiento de las fuerzas, el modelo simula la carga en las TI´s de un sujeto masculino de 70 kg y 1,70 m, en el cual se registraron por 8 min. Las fuerzas registradas en modelo fueron comparadas con las fuerzas superficiales estimadas a partir de los registros de presión medidas por el sistema Force Sensing Array, en un paciente con lesión medular. A partir de 2 min, tanto fuerzas medidas en el modelo, como estimadas en el paciente, siguen la tendencia descrita por Crawford para mediciones de presiones clínicas durante la sedestación, también se encontró en el modelo que las fuerzas medidas por debajo de las TI's son mayores a las medidas debajo del tejido blando; lo que sugiere que el modelo puede ser válido, para el estudio de las fuerzas que se generan al interior del tejido.

Finite-element analysis of the effect of basic hip movements on the mechanical stimulus within a proximal femur.

Osteoporosis is a serious and multifactorial disease. The number of people affected with osteoporosis is increasing due to the lengthening of life expectancy. Currently, unlike the genetic, nutritional and hormonal factors that have been the focus of most studies of osteoporosis, mechanical stimuli that potentially can produce an increase in bone strength have not been well studied. Studies suggest that the relationship between the health of the bone and mechanical stimuli occurs through bone adaptive remodeling, which is activated by means of the shear stress transmitted by the interstitial fluid flow. The present work consists of a finite element analysis of a femur to simulate the basic movements of the hip (flexion, extension, abduction, and adduction) to compare the shear stresses in a common zone of fracture and in the critical mechanical strength zones of the femoral head. A comparison of the distribution and magnitude of the shear stresses was performed to estimate the movement that could induce a more rapid adaptive bone remodeling. This study is the first step in the development of a physical therapy for a preventive rehabilitation that helps to prevent patients with low bone mineral density to avoid suffering osteoporosis hip fractures. The finite element model was constructed using a free-access three-dimensional standardized femur obtained from the Instituti Ortopedici Rizzoli, Bologna, Italy. The mechanical properties and the muscular forces were obtained from a specialized bibliography. We conclude that the movements that exhibit a higher mean value and a good shear stress distribution in the femoral neck are hip extension and abduction.