Ultrasonic-assisted drilling of cortical and cancellous bone in a comparative point of view.

Background: During bone drilling, a common procedure in clinical surgeries, excessive heat generation and drilling force can cause damage to bone tissue, potentially leading to failure of implants and fixation screws or delayed healing. With this in mind, the aim of this study was to evaluate the efficiency of ultrasonic-assisted drilling compared to conventional drilling as a potential method for bone drilling. Methods: This study examined optimal drilling parameters based on previous findings and investigated both cortical and cancellous bone. In addition to evaluating drilling force and temperature elevation, the effects of these factors on osteonecrosis and micro-crack formation were explored in ultrasonic-assisted and conventional drilling through histopathological assessment and microscopic imaging. To this end, three drilling speeds and two drilling feed-rates were considered as variables in the in vitro experiments. Furthermore, numerical modeling provided insight into temperature distribution during the drilling process in both methods and compared three different vibration amplitudes. Results: Although temperature elevations were lower in the conventional drilling, ultrasonic-assisted drilling produced less drilling force. Additionally, the latter method resulted in smaller osteonecrosis regions and did not produce micro-cracks in cortical bone or structural damage in cancellous bone. Conclusions: Ultrasonic-assisted drilling, which caused less damage to bone tissue in both cortical and cancellous bone, was comparatively more advantageous. Notably, this study demonstrated that to determine the superiority of one method over the other, we cannot rely solely on temperature variation results. Instead, we must consider the cumulative effect of both temperature elevation and drilling force.

Simulation of the female pelvic mobility and vesical pressure changes employing fluid-structure interaction method.

INTRODUCTION AND HYPOTHESIS: This study aims to develop a fluid-structural interaction (FSI) method to pinpoint the effects of pressure changes inside the bladder and their impact on the supporting structure and the urethra mobility. METHODS: A physiological model of the nulliparous female pelvis, including the organs, supportive structures, and urine, was developed based on magnetic resonance images. Soft tissues with nonlinear hyperelastic material characteristics were modeled. The Navier-Stokes equations governing the fluid flow within the computational domain (urine) were solved. The urine and soft tissue interactions were simulated by the FSI method. The vesical pressure and its impact on the urethral mobility and supportive structures were investigated during the Valsalva maneuver. Moreover, the simulation results were validated by comparing with a urodynamic test and other research. RESULTS: The results demonstrated that the vesical pressure simulated by the FSI method could predict the nonlinear behavior of the urodynamic test pressure. The urethra retropubic bladder neck and the bladder neck-pubic bone angle changed 58.92% and -55.76%, respectively. The retropubic urethral length distance changed by -48.74%. The error compared to the statistical results of other research is < 5%. CONCLUSIONS: The total deformation and mobility of the urethra predicted by the FSI model were consistent with clinical observations in a subject. The urethra supports dependence on the tissues' mechanical properties, interaction between the tissues, and effect of urine fluid inside the bladder. This simulation effectively depicts the patterns of urethra mobility, which provides a better understanding of the behavior of the pelvic floor.

Effects of low-intensity pulsed ultrasound stimulation on cell seeded 3D hybrid scaffold as a novel strategy for meniscus regeneration: An in vitro study.

Menisci are fibrocartilaginous structures in the knee joint with an inadequate regenerative capacity, which causes low healing potential and further leads to osteoarthritis. Recently, three-dimensional (3D) printing techniques and ultrasound treatment have gained plenty of attention for meniscus tissue engineering. The present study investigates the effectiveness of low-intensity pulsed ultrasound stimulations (LIPUS) on the proliferation, viability, morphology, and gene expression of the chondrocytes seeded on 3D printed polyurethane scaffolds dip-coated with gellan gum, hyaluronic acid, and glucosamine. LIPUS stimulation was performed at 100, 200, and 300 mW/cm2 intensities for 20 min/day. A faster gap closure (78.08 ± 2.56%) in the migration scratch assay was observed in the 200 mW/cm2 group after 24 h. Also, inverted microscopic and scanning electron microscopic images showed no cell morphology changes during LIPUS exposure at different intensities. The 3D cultured chondrocytes under LIPUS treatment revealed a promotion in cell proliferation rate and viability as the intensity doses increased. Additionally, LIPUS could stimulate chondrocytes to overexpress the aggrecan and collagen II genes and improve their chondrogenic phenotype. This study recommends that the combination of LIPUS treatment and 3D hybrid scaffolds can be considered as a valuable treatment for meniscus regeneration based on our in vitro data.

Fabrication and assessment of a novel hybrid scaffold consisted of polyurethane-gellan gum-hyaluronic acid-glucosamine for meniscus tissue engineering.

The meniscus has inadequate intrinsic regenerative capacity and its damage can lead to degeneration of articular cartilage. Meniscus tissue engineering aims to restore an injured meniscus followed by returning its normal function through bioengineered scaffolds. In the present study, the structural and biological properties of 3D-printed polyurethane (PU) scaffolds dip-coated with gellan gum (GG), hyaluronic acid (HA), and glucosamine (GA) were investigated. The optimum concentration of GG was 3% (w/v) with maintaining porosity at 88.1%. The surface coating of GG-HA-GA onto the PU scaffolds increased the compression modulus from 30.30 kPa to 59.10 kPa, the water uptake ratio from 27.33% to 60.80%, degradation rate from 5.18% to 8.84%, whereas the contact angle was reduced from 104.8° to 59.3°. MTT assay, acridine orange/ethidium bromide (AO/EB) fluorescent staining, and SEM were adopted to assess the behavior of the seeded chondrocytes on scaffolds, and it was found that the ternary surface coating stimulated the cell proliferation, viability, and adhesion. Moreover, the coated scaffolds showed higher expression levels of collagen II and aggrecan genes at day 7 compared to the control groups. Therefore, the fabricated PU-3% (w/v) GG-HA-GA scaffold can be considered as a promising scaffold for meniscus tissue engineering.

Appraising efficiency of OpSite as coolant in drilling of bone.

BACKGROUND: During drilling of bone, which is common in clinical surgeries, heat generation increases local temperature in the drilling site. Transmission of excessive heat to the surrounding bone tissue can cause thermal osteonecrosis. Consequently, it may lead to failure of implants and fixation screws or delay in healing process. Using cooling is a method for limiting temperature elevation. MATERIALS AND METHODS: In this study, through comparing three conditions of drilling without cooling, external cooling with normal saline, and external cooling with OpSite spray, the efficiency of OpSite as coolant is studied. In this regard, 2 drill bit diameters, 3 drilling speeds, and 3 drilling feed-rates are considered as drilling variables in the experiments. RESULTS: For the whole experiments, while cooling with normal saline resulted in lower maximum temperatures than without cooling condition, OpSite had even better results and limited the temperature elevation during drilling of bone efficiently. CONCLUSION: OpSite spray, which has lower infection risks than normal saline on one hand and lower maximum temperature rise with all combinations of drilling parameters on the other hand, can be considered in clinical surgeries for cooling applications.

The effect of Knee-Ankle-Foot orthosis stiffness on the parameters of walking.

The purpose of this simulation study was to analyze the effect of variation in Knee-Ankle-Foot-Orthosis stiffness on the joint power and the energy cost of walking. The effect of contractile tissue was simulated using linear elastic spring and viscous dampers in knee and ankle joints. Then, joint angles, ground reaction force, were collected from Twenty chronic hemiparesis subjects (15 males and 5 females) and twenty control subjects (14 males and 6 females), and spring stiffness were considered as the inputs. In this new study, the generated muscle torques were optimized by changing the stiffness as the desired output in the mathematical model attained by the MATLAB SimMechanics toolbox. Finally, the simulated mathematical model was introduced as an appropriate substitute in obtaining the optimized stiffness with a more convenient and efficient designed orthosis.

Effects of Different Angles of the Traction Table on Lumbar Spine Ligaments: A Finite Element Study.

BACKGROUND: The traction bed is a noninvasive device for treating lower back pain caused by herniated intervertebral discs. In this study, we investigated the impact of the traction bed on the lower back as a means of increasing the disc height and creating a gap between facet joints. METHODS: Computed tomography (CT) images were obtained from a female volunteer and a three-dimensional (3D) model was created using software package MIMICs 17.0. Afterwards, the 3D model was analyzed in an analytical software (Abaqus 6.14). The study was conducted under the following traction loads: 25%, 45%, 55%, and 85% of the whole body weight in different angles. RESULTS: Results indicated that the loading angle in the L3-4 area had 36.8%, 57.4%, 55.32%, 49.8%, and 52.15% effect on the anterior longitudinal ligament, posterior longitudinal ligament, intertransverse ligament, interspinous ligament, and supraspinous ligament, respectively. The respective values for the L4-5 area were 32.3%, 10.6%, 53.4%, 56.58%, and 57.35%. Also, the body weight had 63.2%, 42.6%, 44.68%, 50.2%, and 47.85% effect on the anterior longitudinal ligament, posterior longitudinal ligament, intertransverse ligament, interspinous ligament, and supraspinous ligament, respectively. The respective values for the L4-5 area were 67.7%, 89.4%, 46.6%, 43.42% and 42.65%. The authenticity of results was checked by comparing with the experimental data. CONCLUSIONS: The results show that traction beds are highly effective for disc movement and lower back pain relief. Also, an optimal angle for traction can be obtained in a 3D model analysis using CT or magnetic resonance imaging images. The optimal angle would be different for different patients and thus should be determined based on the decreased height of the intervertebral disc, weight and height of patients.

Biomechanical assessment of new surgical method instead of kyphoplasty to improve the mechanical behavior of the vertebra: Micro finite element study.

AIM: To reduce post treatments of kyphoplasty, as a common treatment for osteoporotic vertebrae. METHODS: This study suggests a new method for treating vertebrae by setting the hexagonal porous structure instead of the rigid bone cement mass in the kyphoplasty (KP). The KP procedure was performed on the fresh ovine vertebra of the level L1. Micro finite element modeling was performed based on micro computed tomography of ovine trabecular cube. The hexagonal porous structure was set on one cube instead of the bone cement mass. For the implant designing, two geometrical parameters were considered: Spacing diameter and thickness. RESULTS: The results of micro finite element analyses indicated the improvement in the mechanical behavior of the vertebra treated by the hexagonal porous structures, as compared to those treated by vertebroplasty (VP) and KP under static loading. The improvement in the mechanical behavior of the vertebra, was observed as 54% decrease in the amount of maximum Von Misses stress (improvement of stress distribution), in trabecular cube with embedded hexagonal structure, as compared to VP and KP. This is comparable to the results of the experimental study already performed; it was shown that the improvement of mechanical behavior of the vertebra was observed as: 83% increase in the range of displacements before getting to the ultimate strength (increasing the toughness) after setting hexagonal pearls inside vertebrae. Both the material and geometry of implant influenced the amount of Von Mises stress in the structure. CONCLUSION: The new proposed method can be offered as a substitute for the KP. The implant geometry had a more obvious effect on the amount of Von Mises stress, as compared to the implant material.

Investigating the effect of external trauma through a dynamic system modeling approach for clustering causality in diabetic foot ulcer development.

Diabetes and its associated complications are realized as one of the most challenging medical conditions threatening more than 29 million people only in the USA. The forecasts suggest a suffering of more than half a billion worldwide by 2030. Amid all diabetic complications, diabetic foot ulcer (DFU) has attracted much scientific investigations to lead to a better management of this disease. In this paper, a system thinking methodology is adopted to investigate the dynamic nature of the ulceration. The causal loop diagram as a tool is utilized to illustrate the well-researched relations and interrelations between causes of the DFU. The result of clustering causality evaluation suggests a vicious loop that relates external trauma to callus. Consequently a hypothesis is presented which localizes development of foot ulceration considering distribution of normal and shear stress. It specifies that normal and tangential forces, as the main representatives of external trauma, play the most important role in foot ulceration. The evaluation of this hypothesis suggests the significance of the information related to both normal and shear stress for managing DFU. The results also discusses how these two react on different locations on foot such as metatarsal head, heel and hallux. The findings of this study can facilitate tackling the complexity of DFU problem and looking for constructive mitigation measures. Moreover they lead to developing a more promising methodology for managing DFU including better prognosis, designing prosthesis and insoles for DFU and patient caring recommendations.

Finite element analysis of post dental implant fixation in drilled mandible sites.

BACKGROUND: Implant loosening may occur after dental implant placement as a result of the mechanical conditions created around the implant. In this research, the effect of bone drilling conditions on the magnitude of stress created in newly-formed bone around the implant, after placement, was investigated using FEA analysis. METHOD: The simulations performed in this study were based on the three-dimensional (3D) shape of the created cavities, extracted from the drilled cortical bone of the jaws. With this aim, a dental implant model was placed in the jaw and a shell of the 3D bone cavity remained as a newly-formed cortical bone after implant placement. Then, a load was exerted on the implant model and the value of stress created on the newly-formed bone was obtained. Overall, eight combined models were used in all the eight drilling and loading simulations. The examined variables were rotational speed of drill bit, its feed rate and head angle. Also, an animal test was performed to investigate the accuracy of the simulation results. RESULTS: The results of this study showed that the amount of principal stress was the least (16.7MPa) for a newly-formed cortical bone whose cavity was created under drilling condition at the same head angle and feed rate of the drill bit with a rotational speed of 400rpm. The same results were obtained for the head angle and feed rate of a drill bit of 70° and 1.5mm/s, respectively. CONCLUSIONS: Drilling conditions have effect on the stress created in a newly-formed cortical bone after dental implant loading.

A new approach to measure stability during quiet standing.

BACKGROUND: Stability during standing is achieved by a complex process which involves the performance of various systems. Using a force plate for analysing the stability for a period of one minute has been reported exclusively by many investigators. Most of people stand for a long period of time when chatting with somebody, doing a job and when waiting in a queue. However nobody has analysed the stability during quiet standing for a prolonged standing (5 minutes). OBJECTIVE: The main aim of this research study was to analyse the performance of the subjects regarding stability for a period of 5 minutes. METHOD: A group of 40 normal subjects from the staff and students of Rehabilitation Faculty of Isfahan University of Medical Sciences were recruited in this research project. They were asked to stand on the force plate (Kistler) for a period of 5 minutes. They were instructed to look straight ahead and with their head erect and their arms at their sides in a comfortable position. The excursions of the COP sway in both planes were measured for all 20 seconds periods of data collection. RESULTS: The results of this research study showed that stability analysing based on the sway of the COP, while the test was collected for one minute, is not recommended. There is a significant difference between the excursions of the COP during the first to fifth minutes. The stability of the subject was optimum in the third and fourth minutes of standing. CONCLUSION: Using the COP sway, based on the first minute of standing, is neither a good representative of the more stable position nor the unstable position. It is recommended to discuss the stability of subjects based on their ability to return from an unstable position to a more stable position.

Design and testing of statistical methods to classify the severity of steppage gait based on center of pressure data.

In this research kinematics parameters derived from ground reaction forces were evaluated to limit differential diagnoses and measure the degree of disabilities during walking among neuropathic subjects. 25 neuropathic subjects affected by drop foot and 20 normal subjects were enrolled in the study. Each subject was tested in average 10±2 times for calculating kinetics parameters derived from ground reaction forces. The results revealed that the center of pressure displacement pattern in sole of foot can be a good index for differential diagnoses and measuring the degree of disabilities. This research can extend the clinical applications of ground reaction force plate and introduce suitable criteria to measure the degree of disability among neuropathic patients.

The magnitude of errors associated in measuring the loads applied on an assistive device while walking.

Measurement of the loads exerted on the limb is a fundamental part of designing of an assistive device, which has been done by using strain gauges or a transducer. Although calculation of loads applied on an orthosis coefficients achieved from calibration is a standard way, most of researchers determined the loads based on available equations. Therefore, the aim of this research is finding the accuracy of this method with respect to calibration. Some strain gauges were attached on the lateral bar of a reciprocal gait orthosis. It was calibrated for axial force and the anteroposterior and mediolateral moments. The outputs of strain gauge were changed to force, and moments based on the coefficients were achieved from calibration using available equations, while 5 normal subjects were walking with the orthosis. There was a significant difference between the force and moments exerted on the orthosis during walking based on the two methods (mostly extension moment and compression force). The results of this research indicated that the output of strain gauge varies based on the methods of calculation. As calibration the gauge is a standard method, it is recommended to calibrate it before use.

Differences in center of pressure trajectory between normal and steppage gait.

BACKGROUND: This pilot study aimed to assess the differences in center of pressure trajectory in neuropathic patients with steppage gait. Steppage gait has previously been evaluated by several biomechanical methods, but plantar pressure distribution has been much less studied. The purpose of this study was to analyze the changes in center of pressure trajectory using a force plate. METHODS: The steppage gait group was selected from the patients using drop foot brace (25 male) and the control group was selected from Isfahan university students (20 male). They walked at self- selected speed at a mean of ten trials (+2) to collect the center of pressure using a force plate. Center of pressure patterns were categorized into four patterns based on the center of pressure displacement magnitude (spatial features) through time (temporal features) when the longitudinal axis of the insole was plotted as the Y- axis and the transverse axis of the insole as X- axis during stance phase. RESULTS: The horizontal angle measured from center of pressure linear regression was positive in the control group (4.6 ± 2.4) (p < 0.005), but negative in the patient group (- 2.3 ± 1.6) (p < 0.005). CONCLUSIONS: The finding of this research measured center of pressure trajectory in steppage gait over time, which is useful for designing better shoe sole and also orthopaedic device and better understanding of stability in patients with drop foot.