<p> With Athletes and individuals developing osteoarthritis and chondral defects at younger ages, long term treatments are in high demand. Total knee replacements only last for 10-15 years, so younger individuals would need to have multiple knee replacements within their lifetime. Allograft transplantation has shown to last long term and have high success rates, but the lack of donors and the possibility of damaging other areas of the knee to obtain tissue grafts has become a large concern. &nbsp;Xenografts derived from porcine cartilage is cost effective and the supply is abundant. Two antigen removal processes were examined: a short term antigen removal process to maintain the mechanical stability of the tissue, and a long antigen removal process to minimize the risk of triggering an immune response. The antigen removal processes were compared, and the future precautions were determined to enhance the probability of creating a viable osteochondral xenograft preparation technique. </p>

acase@tulane.edu / The application of continuum mechanics principles to biological tissues is paramount to understanding (patho)physiological changes in tissue structure and function. Experimental and mathematical approaches can be utilized to quantify tissue mechanical behavior. In particular, planar biaxial mechanical testing of soft tissues (i.e. applying loads or deformation along two axes in the same plane) has proven to mimic physiologically relevant conditions for most soft tissues. Constitutive relations can then be formulated based on biaxial data to describe and predict soft tissue mechanical behavior. These mathematical tools could aid in delineating underlying mechanisms of and evaluating treatments for various clinically relevant issues. Therefore, the overall objective of this thesis is to build a custom planar biaxial mechanical testing device to characterize the mechanical properties of soft biological tissues to identify appropriate constitutive relations. A custom planar biaxial mechanical testing device was successfully built and validated. A LabVIEW program was written to interface with the stepper motors and load cells of the device to control their movements. A mechanical testing protocol was developed and incorporated to enable the characterization of a variety of soft tissue structure-function relationships. Foundations were laid for studies using the planar biaxial device for research in a tissue-engineered nipple-areolar complex (NAC), pelvic floor disorders, and age-specific tendinopathy. The planar biaxial device has the potential to impact many areas of clinical research. / 1 / Taylor McCrady

acase@tulane.edu / Soft tissue mechanics attempts to describe biological tissues such as skin, tendon, and the reproductive organs using concepts found in mechanical engineering. By approaching soft tissues using this framework, the complex biomechanical response of such tissues, which have been implicated in the development of disease and injury, can be ascertained and quantified. Robust mechanical tests, in which tissue stress-strain behavior is characterized, are needed in order to inform constitutive models of healthy and diseased tissue. The overall objective of this thesis was to design, construct, program, and validate a planar biaxial device capable of testing soft tissues. Improvements and redesigns were made to the device to better suit the nature of testing required for soft tissue. Custom grips, modules, and software were developed and fabricated to facilitate accurate biaxial mechanical tests. Optimized for testing of small soft tissues, the biaxial device is an evolution of the standard approach towards mechanical testing. The overall device and the individual systems were validated internally and externally. Pilot studies were conducted on murine skin, compared to existing data from literature, and observed to correspond with known stress-strain and load-displacement properties. Further, experimental protocols were developed to evaluate the biaxial behavior of soft tissues, including cervical, uterine, vaginal, and uterosacral ligament tissue. Studies were described in which experimental data could be used to establish structure-function relationships describing reproductive tissue. Results from these studies could be used to elucidate the underlying mechanical etiologies of preterm birth and pelvic organ prolapse. / 1 / Jonathan Nguyen

<p>To get the maximal output of your exercise in gym machines, there are different factors</p><p>to be considered. For example the strength of the muscle varies dependent on the position</p><p>of the muscles. To get the best results of the exercise the load has to reduce and increase</p><p>at specific positions.</p><p>This study was made in cooperation with Caretaker Scandinavia AB, a company for</p><p>sales, marketing and development in health care. They are general agent for Nordic Gym</p><p>who works with manufacturing of equipment and machines for gym and fitness.</p><p>The aim of this study was to generate a method of measurement to evaluate and control</p><p>the biomechanics of Nordic Gym´s workout equipment. A protocol for an ergonomic</p><p>analysis on the equipment has also been elaborated.</p><p>One of the methods to measure the biomechanics was to measure the torque through the</p><p>whole movement. The other method was electromyography (EMG). The EMGequipment</p><p>registers electric signals that are generated in a working muscle, and makes it</p><p>possible to see when the maximum muscle activity achieves. The results of those</p><p>measurements will be compared to the muscles strengthprofile which describes how the</p><p>muscle generates power in different positions throughout the movement.</p><p>To measure the ergonomics an ergonomic protocol where produced, which was based on</p><p>ergonomics aspect, adapted to gym machines.</p><p>The method of measurement where tested on Nordic Gym´s training machine 101SE leg</p><p>extension and Free Motion´s machine Leg Extension GZF18013 and this machines where</p><p>controlled and evaluated. Two test persons tried out the machines and the machines</p><p>where analysed in an ergonomic and a biomechanical perspective. The result shows that</p><p>the biomechanics of Nordic Gym´s machine where a bit better than the biomechanics of</p><p>FreeMotion´s machine. But in the both case the difference between the values of torque is</p><p>marginal, to improve the biomechanics insistence a bigger different should be necessary</p><p>to use. The ergonomic analyse of the machines showed that the ergonomics where good</p><p>and well planed. Both machines had some small ergonomic lacks, which can be</p><p>improved.</p>

Surgery to correct cam femoroacetabular impingement (FAI) is increasingly popular. Despite this, no known study has used motion analysis and ground reaction forces to quantify the outcome of surgery for FAI. The goal of this study was to compare the preoperative and postoperative lower-extremity joint kinematic and kinetic measurements of cam FAI patients during activities of daily living with use of a high-speed motion capture system and force platforms. We hypothesized that the lower-extremity joint mechanics of FAI patients during level walking and maximal squatting would resemble more those of healthy control subjects, after surgery. Ten patients with unilateral symptomatic cam FAI, who underwent corrective surgery using an open or combined technique, performed walking and maximal depth squatting trials preoperatively and postoperatively. Thirteen healthy control subjects, matched for age, sex and body mass index, provided normative data. Results showed that postoperatively, FAI patients had reduced hip ROM in the frontal and sagittal planes, produced smaller peak hip abduction and external rotation moments, and generated less peak hip power compared to the control group during level walking. During maximal squatting, postoperative FAI patients squatted to a greater depth, and had larger knee flexion and ankle dorsiflexion angles, as well as the sum of all joint angles of the affected limb at maximal depth compared to the preoperative values. The lower-extremity joint and pelvic mechanics of FAI patients did not fully return to normal after surgery. Although surgery seemed to reduce hip pain and restore a normal femoral head-neck offset, it further impaired muscle function as a result of muscle incisions. More research is needed to determine the effects of muscle incisions, which could help improve surgical techniques and develop better rehabilitation programs for FAI patients.

In spite of burgeoning of new technologies in the field of maxillofacial surgery, such as novel methods for osteosynthesis, bone substitution and bone regeneration, the reconstruction of the craniofacial skeleton (CFS) remains a challenge. Complications and failure in existing technologies and treatments for the CFS may be attributed in part to an incomplete understanding of the biomechanical environment in which these technologies are expected to perform. Characterizing the morphology and biomechanical behaviour of this complex and unique structure is important to understanding its global response to mechanical demands. This thesis aims to characterize the biomechanical behaviour of thin bone regions and sutures in the CFS. We investigated the impact of image degradation in CT scans on the ability to develop accurate specimen-specific FE models. Image degradation resulted in large increases in cortical thickness and decreases in scan intensity, which corresponded to significant changes in maximum principal strains in the FE models. A new semi-automated connectivity technique was developed to quantify the degree of fusion in sutures and revealed varying degrees of connectivity and interdigitation depending on the suture location. Morphological features characterized using this technique were incorporated into idealized suture FE models and analysed under multiple loading directions. The idealized FE models revealed that the impact of the number of interdigitations on the strain energy absorption in the suture/bone complex is dependent on the loading direction (inversely related under pressure and directly related under perpendicular and pressure loading); similar behaviour was seen in a μCT based specimen-specific FE model. Three-point bending tests on bone samples containing sutures revealed a positive correlation between the number of interdigitations and bending strength. Finally, experimental testing of full cadaveric heads demonstrated inter-specimen consistency in strain magnitude and direction under muscle loading in spite of morphological differences. Overall, these findings provide new insight into the complex morphology of the CFS, limitations of current clinical imaging and the biomechanical behaviour of thin bone structures and their articulations. This work forms a solid foundation for future development of image analysis, modeling and experimental investigations focused on characterizing the global behaviour of the CFS.

In spite of burgeoning of new technologies in the field of maxillofacial surgery, such as novel methods for osteosynthesis, bone substitution and bone regeneration, the reconstruction of the craniofacial skeleton (CFS) remains a challenge. Complications and failure in existing technologies and treatments for the CFS may be attributed in part to an incomplete understanding of the biomechanical environment in which these technologies are expected to perform. Characterizing the morphology and biomechanical behaviour of this complex and unique structure is important to understanding its global response to mechanical demands. This thesis aims to characterize the biomechanical behaviour of thin bone regions and sutures in the CFS. We investigated the impact of image degradation in CT scans on the ability to develop accurate specimen-specific FE models. Image degradation resulted in large increases in cortical thickness and decreases in scan intensity, which corresponded to significant changes in maximum principal strains in the FE models. A new semi-automated connectivity technique was developed to quantify the degree of fusion in sutures and revealed varying degrees of connectivity and interdigitation depending on the suture location. Morphological features characterized using this technique were incorporated into idealized suture FE models and analysed under multiple loading directions. The idealized FE models revealed that the impact of the number of interdigitations on the strain energy absorption in the suture/bone complex is dependent on the loading direction (inversely related under pressure and directly related under perpendicular and pressure loading); similar behaviour was seen in a μCT based specimen-specific FE model. Three-point bending tests on bone samples containing sutures revealed a positive correlation between the number of interdigitations and bending strength. Finally, experimental testing of full cadaveric heads demonstrated inter-specimen consistency in strain magnitude and direction under muscle loading in spite of morphological differences. Overall, these findings provide new insight into the complex morphology of the CFS, limitations of current clinical imaging and the biomechanical behaviour of thin bone structures and their articulations. This work forms a solid foundation for future development of image analysis, modeling and experimental investigations focused on characterizing the global behaviour of the CFS.

Surgery to correct cam femoroacetabular impingement (FAI) is increasingly popular. Despite this, no known study has used motion analysis and ground reaction forces to quantify the outcome of surgery for FAI. The goal of this study was to compare the preoperative and postoperative lower-extremity joint kinematic and kinetic measurements of cam FAI patients during activities of daily living with use of a high-speed motion capture system and force platforms. We hypothesized that the lower-extremity joint mechanics of FAI patients during level walking and maximal squatting would resemble more those of healthy control subjects, after surgery. Ten patients with unilateral symptomatic cam FAI, who underwent corrective surgery using an open or combined technique, performed walking and maximal depth squatting trials preoperatively and postoperatively. Thirteen healthy control subjects, matched for age, sex and body mass index, provided normative data. Results showed that postoperatively, FAI patients had reduced hip ROM in the frontal and sagittal planes, produced smaller peak hip abduction and external rotation moments, and generated less peak hip power compared to the control group during level walking. During maximal squatting, postoperative FAI patients squatted to a greater depth, and had larger knee flexion and ankle dorsiflexion angles, as well as the sum of all joint angles of the affected limb at maximal depth compared to the preoperative values. The lower-extremity joint and pelvic mechanics of FAI patients did not fully return to normal after surgery. Although surgery seemed to reduce hip pain and restore a normal femoral head-neck offset, it further impaired muscle function as a result of muscle incisions. More research is needed to determine the effects of muscle incisions, which could help improve surgical techniques and develop better rehabilitation programs for FAI patients.

No description available.

The low back loading to which an individual is exposed has been linked to injury and the reporting of low back pain. Despite extensive research on the spine and workplace loading exposures, statistics indicate that efforts to date have not led to large reductions in the reporting of these injuries. One possible cause for the apparent ineffectiveness of interventions may be a poorly defined understanding of the mechanical exposures of the spine during work related activities. There are sophisticated models that can predict spine loads and are responsive to how an individual moves and uses their muscles, however the models are complex and require extensive data collection to be implemented. This fact has prevented these models from being employed in industrial settings and the simplified surrogate methods that are being employed may not be predicting load exposures well. Therefore, this work focused on examining surrogate methods that can produce estimates of spine loading equal to our most complex laboratory based models. In addition, our understanding of spine tolerance to combined motion and load has been based upon in-vitro work that has not accurately represented coupled physiologic compression and flexion or has not investigated potentially beneficial loading scenarios. The result has been a lack of clear data indicating when motion should be treated as the primary influence in injury development or when load is the likely injury causing exposure. As a result, research was conducted to determine the interplay between load and motion in cumulative injury development, as well as investigating the potential of static rest periods in mitigating the effects of cumulative compression. Study one examined the potential utility of artificial neural networks as a data reduction approach in obtaining estimates of time-varying loads and moments equal in magnitude to those of EMG-assisted and rigid link models. It was found that the neural network approach under predicted peak force and moment exposures, but produced strong predictions of average and cumulative exposures. Therefore this method may be a viable approach to document cumulative loads in industrial settings. Study two compared the load and moment estimates from a currently employed, posture match based ergonomic assessment tool (3DMatch) to those obtained with an EMG-assisted model and those predicted with a rigid link modeling approach. The results indicated that 3DMatch over predicted peak moments and cumulative compression. However, simple correction approaches were developed which can adjust the predictions to obtain more physiologic estimates. Study three employed flexion/extension motion with repetitive compression loading profiles in an in-vitro study, with both load and motion profiles being obtained from measures in study 1. It was found that at loads above 30% of a spine’s compressive tolerance, repetitive flexion/extension would not lead to intervertebral disc injury prior to an endplate or vertebral fracture occurring. However, as loads fall below 30% the likelihood of experiencing a herniation increases, while the overall likelihood of an injury occurring decreases. Comparison to relevant studies indicated that while repetitive flexion did not alter the site of injury it appeared to degrade the ability of the spine to tolerate compression. Finally, study four employed dynamic compression while the spine was maintained in a neutral posture to investigate the effects of ‘rest’, or periods of static low level loading, on altering the amount of load tolerated prior to injury. It was found that there was a non-linear relationship between load magnitude and compressive tolerance, with increasing load magnitude exposures leading to decreasing cumulative load tolerances. Periods of low level static loading did not alter the resistance of the spinal unit to cumulative compression or impact the number of cycles tolerated to failure. In summary, this work has examined methods that may allow for better predictions of spine loading in the workplace without the large data demands of sophisticated laboratory approaches. Where possible, suggestions for optimal implementation of these surrogates have been developed. Additionally, in-vitro work has indicated a load threshold of 30%, above which herniation is not likely to occur during dynamic repetitive loading. Furthermore, the insertion of static rest periods into dynamic loading scenarios did not improve the spine’s failure tolerance to loading, indicating that care should be exercised when determining optimal loading paradigms. In combination, the applied methods that have been developed and the information regarding injury development that has been obtained will help to refine our understanding of the exposures and tolerances that define mechanical injury in the spine.