Billfishes (marlins, spearfishes, sailfishes and swordfish) are one of the fastest and largest marine apex predators, and perhaps their most recognizable attribute is their bill or rostrum. The proposed function for this novel structure has ranged from hydrodynamic enhancement to defensive weaponry. However, the most supported hypothesis for its function has been linked to feeding. Billfishes have been observed to subdue their prey with their rostrum, either stunning or cutting them into pieces before ingestion. Due to their large body sizes and pelagic lifestyles a thorough investigation of the function of this structure has been logistically challenging. The goal of my dissertation is to investigate the role of the rostrum during feeding from a functional, mechanical and morphological standpoint. By the use of interdisciplinary approaches that blend engineering with biology, the function of the rostrum and billfish putative feeding behavior was investigated. By the use of different approaches that involve morphological characterizations, histology, estimation of performance measurements such as bite force and the investigation architectural tradeoffs from geometric morphometrics analysis, my dissertation aims to characterized the role of the rostrum in billfishes as a possible adaptation for feeding. Results showed that the rostrum in billfishes is mechanically capable of acting as a feeding weapon; continuous stress distribution along its length suggest no particular point that could lead to breakage during feeding. Finite element analysis, as well as bending experiments suggest feeding behavior may be species specific and strictly associated with rostrum morphology. While istiophorids may be morphologically suited to strike their prey with a wide range of motions, swordfish appear to be specialized from a mechanical and hydrodynamic standpoint to hit their prey with lateral strikes. Biting performance is relatively low in these top predators compared to other non-billfish species suggesting the rostrum may facilitate prey processing reducing the need for powerful biting. However contrary to my expectations rostrum length was not a predictor of bite force. Skull variation was evident among billfish species. Swordfish, the species with the longest rostrum, had the smallest head and the lowest relative bite force whereas blue marlin, the species with the stiffer, most compact rostrum, had the largest head and one of the greatest relative bite forces. The shortbill spearfish showed a relatively low bite force indicating predatory success in this species may be linked to an extended lower jaw that may facilitate a speed efficient jaw during prey capture. Whether the rostrum in billfishes has evolved as an adaptation for feeding, remains uncertain. However results from this study demonstrate that rostrum material properties, morphology and head architecture, in addition to relatively low biting performance in billfishes, favor a role of prey capture for the rostrum.

<p>The aim of this study was to understand injury mechanisms behind fractures of the upper extremities in car accidents. Volvo Car Corporation initiated this project based on the fact that no safety system today focuses on preventing injuries to the upper extremity. A literature study was undertaken focusing on the basic anatomy of the upper extremity, different fracture types and fracture mechanisms. Three subsets, from 1998 – January 2009, were selected from Volvo’s statistical accident database: 1) all occupants involved in an accident 2) all occupants with a MAIS2+ injury 3) all occupants with an upper extremity fracture. These subsets were used in a comparison, using frequency analyses. The comparison analysis showed that frontal impact is the dominating accident type for all three subsets. The comparison analysis also indicated that the risk for upper extremity fractures follows the pattern of MAIS2+ injury risk. An in-depth study using 92 selected cases, including 80 occupants, was also performed. All available information, such as medical records, questionnaires completed by the occupants and photographs from the accident scene was collected and analysed. The analysis of the in-depth study, together with knowledge retrieved from the literature study, resulted in six different mechanism groups that were used to categorise fractures. The groups were then analysed individually in regard to accident type and fractured segment of the upper extremity. Analysis of the mechanism groups showed that frontal impact is the dominating accident type in these subsets as well. It could also be seen that the fractures occurring in the in-depth study are quite evenly distributed along the upper extremities. Upper extremity injuries are relatively infrequent in car accidents but may result in long-term disability, including chronic deformity, pain, weakness and loss of motion. More attention is therefore necessary in order to develop a safer environment for car occupants.</p>

<p>Osseointegrated titanium implants have become a commonly used method in edentulous jaws and today there are success rates in the magnitude of 82 % in the lower jaw and 98 % in the upper. During first year after implantation a fully normal marginal bone loss of 1-2 mm occurs. If the bone loss continues there is a risk of implant failure. High tensions in bone and inflammation caused by bacteria are possible reasons for this problem. It has been shown that a leakage of bacterias occurs between the parts of the implant and there are theories that this has effects on the marginal bone loss.</p><p>The aim of this thesis has been to increase the knowledge about microbial leakage with help of in vitro tests and virtual simulations. The goal was to create a test method to measure differences of microbial leakage in two implant systems.</p><p>The developed test method includes an in vitro test of six implants and Finite Element Analysis. The test method is the product of a process with several small tests. The final test method measures leakage of a coloured fluid with a spectrophotometer. The results are then compared with the virtual simulations to draw conclusions and find explanations how the implants are functioning.</p><p>The result of test on six implants, four Ospol and two Nobel Replace, indicates that there are differences in the magnitude of microleakage in different implant systems in due to the implant-abutment interface. No conclusions can be drawn before the test method is refined and more implants are tested.</p>

Background: Unilateral transtibial amputees (TTAs) show subtle gait variations while using different prosthetic feet. These variations have not been detected consistently with previous experimental measures. In this research project a novel measure for quantifying kinetic gait differences among prosthetic feet, called Symmetry in External Work (SEW), was introduced. The reliability of the SEW measure was calculated and its correlation with selected clinical measures was determined. The SEW measure was then applied to determine gait differences among four categories of prosthetic feet during various functional activities. Methodology: The study was conducted in three phases. Phase I was a single subject Pilot study to determine the sensitivity of the SEW measure to different prosthetic feet and functional activities. In Phase II, test-retest reliability of the SEW measure was determined for 5 TTAs during the functional activities of level walking, incline walking, decline walking, ascending stairs, descending stairs, sit-to-stand and stand-to-sit. The agreement between SEW values obtained from F-scan and force plates was also calculated. In Phase III, 11 subjects underwent 6 testing sessions over a period of 10-12 weeks. In session 1 subjects were tested wearing their existing prostheses (Baseline session), were given specialized prosthetic training and were tested again after 2 weeks (Training session). For sessions 3 through session 6, subjects were tested with a study socket and one of four randomized test feet. The test feet were SACH, SAFE, Talux and Proprio foot, classified as K1_foot, K2_foot, K3_foot and MP_foot, based on Medicare Functional Classification Level. The Step Watch Activity Monitor (SAM) recorded their daily activities in the 10-14 day accommodation period between two sessions. At each testing session, subjects completed the Prosthesis Evaluation Questionnaire (PEQ-13) and Usability questionnaire, and were evaluated using the Amputee Mobility Predictor (AMP) and the 6-minute walk test (6MWT). Ground reaction forces were collected using F-scan in-sole sensors as subjects performed the above mentioned functional activities. SEW values between the intact limb and the prosthetic limb were computed by integrating vertical ground reaction forces. Intra-class Correlation Coefficients (ICCs) were calculated to determine test-retest reliability and a repeated measure ANOVA was used to establish differences between the prosthetic feet. Results: The ICC values for Test-Retest reliability ranged from 0.84-0.94 for the various functional activities. There was moderate agreement between the SEW values calculated with F-scan and force plates. The SEW values were significantly different between the K3_foot and other feet during level walking and decline walking. During stair ascent, the MP_foot had a significantly higher SEW value than the other feet. There were no differences between feet during incline walking and stair descent. Training resulted in a significant improvement in symmetry from the Baseline session during sit-to-stand, while for stand-to-sit there were no differences between sessions. The PEQ-13 score was not different between sessions, while the Usability scores were significantly different between the K3_foot/MP_foot and K1_foot/K2_foot. The AMP score had a significant increase following Training while the 6MWT score showed a significant increase in the distance walked with the K1_foot, K3_foot and MP_foot over Baseline. The output of SAM did not show any difference in the number of steps or activity level of subjects. There was good to excellent correlation between the SEW values for level walking and other clinical outcome measures. Discussion and Conclusion: The SEW measure had excellent test-retest reliability and the agreement between the F-scan and force plates values could not be established because of a small sample size. The variations in SEW values were the result of distinctive designs of prosthetic feet. The high SEW value of the K3_foot can be attributed to its heel-toe foot plate and "J" shaped ankle spring design, which allowed for greater late stance stability. The active dorsiflexion feature of the MP_foot caused a change in strategy, typically used during stair ascent, resulting in a greater inter-limb symmetry. The SEW measure is a viable method to detect kinetic gait differences among prosthetic feet and represents a resource-effective alternative to traditional gait laboratories. It has several advantages and with further development of in-sole sensor technology, the potential for clinical use due to its relatively low cost instrumentation and minimal subject intervention.

The goal of this research work was to introduce the whole process of developing and validating a 3D lower extremity musculoskeletal model and to test the ability of the model to predict the muscles recruitment of the different muscles involved in human locomotion as well as determining the corresponding forces and moments generated around the different joints in the lower extremity. Therefore the model can be applied in one of the important fields of orthopaedics which is joint replacement; the case study used in such application is the total knee replacement. The knee reaction forces were compared to the pattern obtained by Harrington (1992), where the hip moment components (Flexion/extension, internal/external, and abduction/adduction) were all compared to the patterns obtained from the Hip98 data base. It was shown in the different graphs of joints forces and moments that the model was able to produce very close results when comparing pattern and magnitude to the literature data. Thus, this 3D biomechanical model is sophisticated enough to be used for surgery evaluation such as in total knee replacement, where the damaged cartilage and bone are removed from the surface of the knee joint and replaced with a man-made. The case study of the second part of the research work presented involved the comparison of the gait pattern between two main knee joint types, Metallic and Allograft knee joints against normal subjects (Control group). A total of fifteen subjects participated in this study, five subjects in each group. It was concluded that based on the study conducted and the statistical evidence obtained that the introduced model can be used for applications that involves joint surgeries such as knee replacement that ultimately can be utilized in surgery evaluation.

With increasing rates of obesity, research has begun to focus of co-morbidities of obesity such as osteoarthritis. The majority of existing research has focused on older adults as the group most likely to suffer from osteoarthritis. The purpose of this study was to determine if overweight and obese young adults exhibit biomechanical risk factors for knee osteoarthritis, and to determine if young adults with biomechanical risk factors of osteoarthritis can modify these with instruction. This purpose was divided into two separate studies. Study 1: Thirty adults between 18-35 years old were recruited into three groups according to body mass index: normal, overweight, and obese. Participants walked through the lab while we collected 3-d kinematic and kinetic data. Overweight and obese young adults walked with similar gait compared to normal weight young adults. Study 2: Nine young adults between 18-35 years were recruited who walked with stiff-knee gait. Baseline measures of gait were collected in the form of 3-d kinematics and kinetics as participants walked through the laboratory. They then completed the gait instruction program which consisted of four blocks of training. Each block included ten single steps where the participant was provided feedback, followed by 100 practice steps around the laboratory. Participants were successful in increasing sagittal plane kinematics and kinetics of interest in the study. Conclusion: Identifying individuals who had biomechanical risk factors of osteoarthritis according to body mass index was not possible. According to the results of our study, obese and overweight young adults are not at increased risk of osteoarthritis compared to normal weight young adults. Individuals who may be at increased risk due to stiff-knee gait were able to improve their gait following instruction.

Background: Epidemiological studies have demonstrated higher ACL injury rates in female athletes when compared to males involved in the same sport. A recent meta-analysis of ACL injury prevention programs found that technique training was a common component of programs that were successful in reducing ACL injury. Purpose: The primary purpose was to determine the immediate and long-term effects of technique training aimed at minimizing medial knee displacement during jump-landings in female recreational athletes. The secondary purpose was to determine if any transfer of skill occurred as a result of our technique training. Study Design: Controlled laboratory study. Methods: A total of 26 participants who presented with medial knee displacement during a basketball rebound screening task completed the study protocol. Participants were randomly assigned to two groups (experimental and control groups, 13 each). The experimental groups received jump landing instructions aimed at minimizing medial knee displacement. The control group received "sham" training consisting of jump training for maximum height. Baseline motion analyses of participants performing a basketball rebound task were performed prior to participants receiving technique training. Immediate and delayed retentions tests were performed after the initial instructional session and after home-based training. Additionally, motion analyses were also performed on a stop-jump task during the baseline assessment and the delayed retention test to help in determining if any transfer occurred. Results: The initial instructional session resulted in increased knee excursion and reduced peak knee adduction moments in the experimental group. Following home-based training, the experimental group continued to exhibit increased knee excursion along with decreased landing forces. No evidence of transfer was present following the initial training session or after home-based training. Conclusion: Our jump training instructions led to temporary changes, most notably increased knee excursion about the sagittal plane. No transfer of skill occurred as a result of our training. Clinical Relevance: Technique training instructions aimed at reducing medial knee displacement resulted in increased sagittal plane motion, but were unable to minimize medial knee displacement. ACL injury prevention programs may need to include a variety of drills, tasks, and sport-specific movements.

With the popularity of outdoor activities like hiking, the demands of certain types of employment, or being a student, an individual’s ability to carry a load is an important mobility consideration. By understanding the changes to an individual’s gait when supporting a backpack load, an individual’s ability to carry heavy loads for prolonged periods could be improved. Most biomechanical studies have examined the changes in able-bodied gait when carrying a load. However, research is lacking on the effect of backpack loads on amputee gait patterns. This project examined the effects of a backpack load on the gait patterns of unilateral transtibial amputees. Ten participants performed walking trials on four surfaces (level ground, uneven ground, walking up an incline, and walking down an incline), without a pack and with a pack. A total of 40 trials were collected per subject, with 10 trials collected on each surface. Three-dimensional motion data were collected with an eight-camera Vicon Motion Analysis system to describe limb motion as well as compare kinematic outcomes between tasks and conditions. Force platform data were collected during the level ground trials and used to calculate kinetic measures for both limbs. With the addition of the pack changes were seen on each surface, with different changes occurring to each limb. The ramp up surface created the most changes when comparing the two conditions. The only change seen across all four surfaces was a decrease in ankle dorsiflexion before push-off on the prosthetic limb. The two next most common changes were increases in knee and hip flexion during weight-acceptance.

The varied impact parameters that characterize an impact to the head have shown to influence the resulting type and severity of outcome injury, both in terms of the dynamic response, and the corresponding deformation of neural tissue. Therefore, when determining head injury risks through event reconstruction, it is important to understand how individual impact characteristics influence these responses. The effect of inbound mass had not yet been documented in the literature. The purpose of this study was to determine the effects of inbound mass on the dynamic impact response and brain tissue deformation. A 50th percentile Hybrid III adult male head form was impacted using a simple pendulum system. Impacts to a centric and a non-centric impact location were performed with six varied inbound masses at a velocity of 4.0 m/s. The peak linear and peak angular accelerations were measured. A finite element model, (UCDBTM) was used to determine brain deformation, namely peak maximum principal strain and peak von Mises stress. Inbound mass produced significant differences for peak linear acceleration for centric (F(5, 24) = 217.55, p=.0005) and non-centric (F(5, 24) = 161.98, p=.0005), and for peak angular acceleration for centric (F(5, 24) = 52.51, p=.0005) and non-centric (F(5, 24) = 4.18, p=.007) impact locations. A change in inbound mass also had a significant effect on peak maximum principal strain for centric (F(5, 24) = 11.04, p=.0005) and non-centric (F(5, 24) = 5.87, p =.001), and for peak von Mises stress for centric (F(5, 24) = 24.01, p=.0005) and non-centric (F(5, 24) = 4.62, p=.004) impact locations. These results indicate the inbound mass of an impact should be of consideration when determining risks and prevention to head and brain injury.

Bone changes composition and structure to adapt to its mechanical environment. Osteocytes are putative mechanosensors responsible for orchestrating the bone remodeling process. Recent in vitro studies showed that osteocytes could sense and respond to substrate strain and fluid shear. However the capacity of osteocytes to sense cyclic hydraulic pressure (CHP) associated with physiological mechanical loading is not well understood. In this study, osteocyte-like MLO-Y4 cells were subjected to CHP of 68 kPa at 0.5 Hz, and the effects of CHP on intracellular calcium concentration, cytoskeleton organization, mRNA expression of genes related to bone remodeling, and osteocyte apoptosis were investigated. The results indicate that osteocytes could sense CHP and respond by increased intracellular calcium concentration, altered microtubule organization, an increase in COX-2 mRNA level and RANKL/OPG mRNA ratio, and decreased apoptosis. Therefore cyclic hydraulic pressure in bone a mechanical stimulus to osteocytes and may play a role in regulating bone remodeling.