Bakgrund: Truppgymnastik är en relativt ung tävlingsgren inom gymnastik med ursprung från de Nordiska länderna. I Sverige är det den mest utövade formen av tävlingsgymnastik med flest rapporterade  skador i nedre extremiteten samt återkommande besvär i ryggen. Tester i syfte att förebygga skador är efterfrågade och få studier har utvärderat tester för idrottande barn och ungdomar. Syftet med studien var att beskriva en grupp unga truppgymnaster utifrån bakgrundsvariabler, och rörelsekontroll med screeningtestet Performance Base Matrix samt att mäta förekomst av muskuloskelettala skador under en period på sju månader.  Metod: Nitton unga truppgymnaster (flickor,7-9 år) genomförde screeningtestet Base Matrix i syfte att bedöma deras rörelsekontroll vid låg respektive/ low threshold och hög belastning/ high threshold. Testerna analyserades visuellt och genom videoupptagning. Resultatet av testerna dokumenterades i ett protokoll som bearbetades on-line samt för beräkning av procentuell förekomst av sämre utförd test i form av svaga länkar. Information om skadeförekomst inhämtades från föräldrar och tränare. Resultat: Alla försökspersoner genomförde screeningtesterna i sin helhet. Försökspersonerna hade en medelpoäng av 15 (max 50), där fler poäng anger fler svaga länkar/ weak links. Vid låg belastning var ländrygg/bäcken i flexion/ Low back/pelvis flexion den mest förekommande svaga länken (58%). Vid hög belastning var anterior rotation i skuldran / shoulder tilt den mest förekommande (63%). Tre skador rapporterades under tidsperioden: två fotledsskador och ett nackbesvär.  Konklusion: Denna studie indikerar att screeningtestet Base Matrix är genomförbart på unga truppgymnaster. Resultaten visar att skuldra framför allt under hög belastning samt ländrygg/bäcken framför allt under låg belastning är områden som uppvisar flest svaga länkar. Detta indikerar att dessa områden vore särskilt att beakta i skadeförebyggande träning av unga truppgymnaster. / Background: Team gym is a relatively new kind of competition in gymnastics with its origin from the Nordic countries. In Sweden it is the most practiced form of competitive gymnastics. Correlations have been found between altered trunk control and injuries in the extremities. Injury prevention testing is performed more frequently and tests requested for improving the training regimen.The purpose of this study was to describe a group of young team gymnasts regarding background variables, test results from Performance Base Matrix screening test and injury incidence during a period of seven months. Method: Nineteen team gymnasts, 7-9 year-old, were screened with the protocol Base Matrix for uncontrolled movement (weak links) under low and high load (threshold). Background data were collected on age, height, weight, dominant side, injuries in the recent year and the practice of other sports. The coaches were asked to register the number of injuries over a period of seven months.Results: The mean age was 8.8 years, BMI 16.1, 89% were right-handed and the average value of the Base Matrix score of 15 out of 50. Two injuries to the ankle and one on the neck reported totally from coaches and parents. Among the most apparent weak links were Low back / pelvis flexion at low load (58% of group) while the shoulder tilt at high load (63% of the group).Conclusion: The result indicates that the Base Matrix screening test is ​​feasible to use in young gymnasts. More studies are needed to confirm the results. The result indicates that the shoulder especially under high load and the lower back especially under low load were the body segments that showed the most weak links. These parts of the body are the most important to take  into consideration in the training of the young team gymnasts.

Crosslinking soft tissue has become more common in tissue engineering applications, and recent studies have demonstrated that soft tissue mechanical behavior can be directly altered through crosslinking, but increased understanding of how crosslinking affects intervertebral disc mechanical behavior is needed. In vitro testing of bovine disc and motion segments was used to characterize several important aspects of disc behavior in response to crosslinking after both soaking and injection treatment. The first study was a comparison of different crosslinkers to determine the effect on tensile properties of disc tissue. Circumferential specimens were taken from bovine annulus and then soak treated with an optimized crosslinking formulation or sham solution. A non-contacting laser micrometer was used to measure cross sectional area, after which tension testing until failure was performed to determine yield strain, yield stress, ultimate stress, peak modulus, and resilience. The crosslinkers were observed to produce different changes in the properties, with the measured properties generally increasing. The second study used bilateral annular injections to simulate a clinically relevant delivery method. The dose response of the motion segment’s neutral zone stability metrics against injection concentration was mapped. Concentrations of 20 mM and less had no significant effects on the stability metrics. 40mM demonstrated a change in neutral zone stiffness, while at least 80mM was required to significantly affect neutral zone length. Thus, meaningful changes in joint neutral zone stability were demonstrated using clinically relevant injection and chemical formulations. The third study used combinations of biochemical and accelerated mechanical cyclic loading to degrade gelatin and annulus fibrosus specimens with and without genipin treatment. Genipin crosslinking attenuated changes during cyclic loading to specimen geometry and compliance relative to control samples. Full recovery of genipin treated samples appeared to be hampered, at least partially from continued crosslinking during the accelerated testing. The fourth study tested the effect of genipin crosslinking to resist interlamellar shearing of the annulus lamella. Using a recently reported test method that shears adjacent lamella, crosslinked specimens were noted to have significantly higher yield force, peak force, and resilience compared to sham treated controls, supporting the hypothesis that crosslinking would increase the load bearing ability of the interface.

Background: Prolonged sitting in an automobile seat may alter the passive tissue stiffness of the lumbar spine differentially in males and females. Gender specific ergonomic interventions may be indicated for the automobile seat design. Purpose: To compare time-varying passive lumbar spine stiffness in response to a two hour simulated driving trial with time-varying lumbar spine and pelvic postures during sitting in an automobile seat. A secondary purpose was to investigate gender differences in lumbar spine stiffness, seat/occupant pressure profile, discomfort rating and posture. Methods: Twenty (10 males, 10 females) subjects with no recent history of back pain were recruited from a university population. Participants completed a simulated driving task for two hours. Passive lumbar range of motion was measured on a customized frictionless jig before, halfway through and at the end of the two-hour driving trial. Changes in the passive moment-angle curves were quantified using the transition zone slopes, breakpoints and maximum lumbar flexion angles. Lumbar spine and pelvic postures were monitored continuously during the simulated driving trial with average and maximum lumbar flexion angles as well as pelvic tilt angles being calculated. Results: Both men and women initially demonstrated an increase in transitional zone stiffness after 1 hour of sitting. After 2 hours of sitting, transitional zone stiffness was found to increase in males and decrease in females. During sitting, women were found to sit with significantly greater lumbar flexion than males and to significantly change the amount of lumbar flexion over the 2 hour period of simulated driving. Conclusions: Postural differences during simulated driving were demonstrated between genders in this study. In order to prevent injury to the passive elements of the spine during prolonged driving, gender specific ergonomic interventions, such as improved lumbar support, are indicated for the automobile seat.

Intervertebral disc herniations have been indicated as a possible injury development pathway due to occupational vibration exposures in seated postures through epidemiological investigations. Little experimental evidence exists to corroborate the strong epidemiological link between intervertebral disc herniations and vibration exposures using basic scientific approaches. The purpose of the current investigation was to provide some basic experimental evidence of the epidemiological link between intervertebral herniation and exposure to vibration. Partial intervertebral disc herniations were created in in-vitro porcine functional spinal units using a herniation protocol of repetitive flexion/extension motions under modest compressive forces. After herniation initiation, functional spinal units were exposed to 8 different vibration and postural constraint loading protocols consisting of two postural conditions (full flexion and neutral) and 4 vibration loading conditions (whole-body vibration, shock loading, static compressive loads, and whole-body vibration in addition to shock loading) to assess the effects of vibration and posture on functional spinal unit damage progression. There were three main outcome variables used to quantify damage progression; average stiffness changes, herniation distance progression (distance of tracking changes), and specimen height changes, while cumulative loading factors were considered. Additionally the concordance between two types of contrast enhanced medical imaging (Computed Tomography and discograms) was qualified to a dissection ‘gold standard’, and an attempt was made to classify disc damage progression via three categorical variables. Concordance to a dissection ‘gold standard’ was higher for the Computed Tomography medical imaging type that for the Discograms. The categorical criteria used to qualify disc damage progression were insufficiently sensitive to detect damage progressions illustrated through dissection and medical imaging techniques. The partial herniation loading protocol was quantified to be more damaging overall to the functional spinal units compared to the vibration and postural constraint loading protocols. However, the vibration and postural constraint loading protocols provided sufficient mechanical insult to the functional spinal units to progress damage to the intervertebral discs. Vibration loading exposures were found to alter specimen height changes and distance of tracking changes, however posture had no significant effects on these variables. Neither posture nor vibration loading had any meaningful significant effects on average stiffness changes.

Background: Prolonged sitting in an automobile seat may alter the passive tissue stiffness of the lumbar spine differentially in males and females. Gender specific ergonomic interventions may be indicated for the automobile seat design. Purpose: To compare time-varying passive lumbar spine stiffness in response to a two hour simulated driving trial with time-varying lumbar spine and pelvic postures during sitting in an automobile seat. A secondary purpose was to investigate gender differences in lumbar spine stiffness, seat/occupant pressure profile, discomfort rating and posture. Methods: Twenty (10 males, 10 females) subjects with no recent history of back pain were recruited from a university population. Participants completed a simulated driving task for two hours. Passive lumbar range of motion was measured on a customized frictionless jig before, halfway through and at the end of the two-hour driving trial. Changes in the passive moment-angle curves were quantified using the transition zone slopes, breakpoints and maximum lumbar flexion angles. Lumbar spine and pelvic postures were monitored continuously during the simulated driving trial with average and maximum lumbar flexion angles as well as pelvic tilt angles being calculated. Results: Both men and women initially demonstrated an increase in transitional zone stiffness after 1 hour of sitting. After 2 hours of sitting, transitional zone stiffness was found to increase in males and decrease in females. During sitting, women were found to sit with significantly greater lumbar flexion than males and to significantly change the amount of lumbar flexion over the 2 hour period of simulated driving. Conclusions: Postural differences during simulated driving were demonstrated between genders in this study. In order to prevent injury to the passive elements of the spine during prolonged driving, gender specific ergonomic interventions, such as improved lumbar support, are indicated for the automobile seat.

Intervertebral disc herniations have been indicated as a possible injury development pathway due to occupational vibration exposures in seated postures through epidemiological investigations. Little experimental evidence exists to corroborate the strong epidemiological link between intervertebral disc herniations and vibration exposures using basic scientific approaches. The purpose of the current investigation was to provide some basic experimental evidence of the epidemiological link between intervertebral herniation and exposure to vibration. Partial intervertebral disc herniations were created in in-vitro porcine functional spinal units using a herniation protocol of repetitive flexion/extension motions under modest compressive forces. After herniation initiation, functional spinal units were exposed to 8 different vibration and postural constraint loading protocols consisting of two postural conditions (full flexion and neutral) and 4 vibration loading conditions (whole-body vibration, shock loading, static compressive loads, and whole-body vibration in addition to shock loading) to assess the effects of vibration and posture on functional spinal unit damage progression. There were three main outcome variables used to quantify damage progression; average stiffness changes, herniation distance progression (distance of tracking changes), and specimen height changes, while cumulative loading factors were considered. Additionally the concordance between two types of contrast enhanced medical imaging (Computed Tomography and discograms) was qualified to a dissection ‘gold standard’, and an attempt was made to classify disc damage progression via three categorical variables. Concordance to a dissection ‘gold standard’ was higher for the Computed Tomography medical imaging type that for the Discograms. The categorical criteria used to qualify disc damage progression were insufficiently sensitive to detect damage progressions illustrated through dissection and medical imaging techniques. The partial herniation loading protocol was quantified to be more damaging overall to the functional spinal units compared to the vibration and postural constraint loading protocols. However, the vibration and postural constraint loading protocols provided sufficient mechanical insult to the functional spinal units to progress damage to the intervertebral discs. Vibration loading exposures were found to alter specimen height changes and distance of tracking changes, however posture had no significant effects on these variables. Neither posture nor vibration loading had any meaningful significant effects on average stiffness changes.

The cervical spine must provide structural support for the head, allow large range of motion and protect both the spinal cord and branching nerves. There are two types of spinal joints: the intervertebral discs which are flexible connections and the facets, which are articulating synovial joints. Both types degenerate with age. Current surgical treatments include spinal fusion and articulating disc replacement implants. If both disc and facet joints are degenerated, fusion is the only option. In spinal fusion, the disc is removed and the adjacent vertebrae are fused which causes abnormally high stress levels in adjacent discs. In disc replacement, an articulating device is inserted to restore intervertebral motion and mimic healthy spinal kinematics. Disc arthroplasty does not significantly increase adjacent level stress but the lack of rotational constraint causes increased facet contact pressures. Thus, there is a need for a cervical total level arthroplasty system (CTLAS) that has a disc implant specifically designed to preserve the facet joints and implants for facet arthroplasty that can act independently or in-unison with the disc replacement. The conceptual design of a CTLAS implant system was proposed that would replace the disc and the facet joints. To facilitate medical imaging, PEEK (polyetheretherkeytone) was selected as the structural and bearing material. In the present thesis, multi-station pin-on-plate wear testing was initiated for pairs of unfilled (OPT) and carbon-fiber-reinforced (CFR) PEEK. Wear is important in arthroplasty implant design because wear particles can cause osteolysis leading to loosening. A variety of experiments were performed to investigate the effects of load, contact geometry and lubricant composition on wear. CFR PEEK was found to have much lower and more predictable wear than OPT PEEK in the present experiments. The wear of OPT PEEK pairs showed sensitivity to lubricant protein concentration. The coefficient of friction during testing was found to be quite high (up to 0.5), which might have clinical implications. Also, some subsurface fatigue was found, exposing carbon fibers of CFR PEEK. This remains a concern for its long-term application. Further wear testing is recommended using actual implants in a spine wear simulator.

The cervical spine ligaments play an essential role in limiting the physiological ranges of motion in the neck; however, traumatic loading such as that experienced in automotive crash scenarios can lead to ligament damage and result in neck injury. The development of detailed finite element models for injury simulation requires accurate ligament mechanical properties at relevant loading rates. The objective of this research was to provide detailed mechanical properties for the cervical spine ligaments, by performing tensile tests at elongation rates relevant to automobile crash scenarios, using younger specimens (less than 50 years old), and to provide a comprehensive investigation of spinal level and gender effects. The five primary ligaments (present between C2-T1) investigated were: the anterior longitudinal ligament, posterior longitudinal ligament, capsular ligament, ligamentum flavum, and interspinous ligament. The craniovertebral ligaments (Skull/C0-C2) investigated were the tectorial membrane/vertical cruciate/apical/alar ligament complex, transverse ligament, anterior atlanto-occipital membrane, posterior atlanto-occipital membrane, anterior atlanto-axial membrane, and posterior atlanto-axial membrane. Tests were performed within an environmental chamber designed to mimic in vivo temperature and humidity conditions, and specimens were preconditioned for 20 cycles at 10% strain prior to testing to failure. Ligaments were tested at quasi-static (0.5s-1), medium (20s-1) and high (150-250s-1). These strain rates were predicted by an existing cervical spine finite element model under typical crash scenarios. Two hundred sixty-one total primary ligament tests were performed, with approximately even distribution within elongation rate, spinal level, and gender. Another forty-four craniovertebral ligaments were tested. Results were plotted as force-displacement curves and the response characteristics determined from the curves were: failure force, failure elongation, stiffness of the linear region, toe region elongation, failure stress, failure strain, modulus and toe region strain. The measured force-displacement data followed expected trends when compared with previous studies. The younger ligaments had less scatter, and were both stiffer and stronger than the older specimens that were reported in previous studies at both quasi-static and comparable higher elongation rates. Statistical analysis was performed on the results to establish significant effects. Strain rate effects were most significant whereas spinal level effects were not found. In general, gender effects were not found to be significantly different, but consistent trends were identified with male ligaments having a higher stiffness and failure force than female ligaments. The post-ultimate load region of the curves was reported to offer insight into the ligament failure mechanism. The characteristic values obtained were used to develop average curves for each ligament, with the intention to eventually be directly integrated into finite element models to better represent the ligament structures. Curves were developed to incorporate the strain rate, spinal level and gender effects for each ligament based on the statistical analyses. Post-failure response was incorporated into these curves because this region has been shown to have an effect on neck behaviour in mathematical models. Recommendations for future studies include measuring accurate cross sectional areas of ligaments during tensile testing to obtain true stress and true strain measurements to better understand if differences in mechanical properties are structural or material. Other possible improvements would be further testing of young cervical spine ligaments with larger sample sizes to further explore spinal level and gender effects. Additional testing performed under identical testing conditions as the current study would allow for pooling of the results effectively increasing the sample size.

<p>Traumatic injuries are the leading cause of death to children between the ages of one to nineteen years in the United States. The primary source of these traumatic injuries is motor vehicle traffic, with the head being the primary region of the body to suffer injury. While the pediatric neck is also prone to injury, it is particularly notable since it governs head excursion and acceleration, thus influencing head impacts and injuries. Pediatric fatalities can be prevented through safety improvements to vehicle compartments and child restraints by way of advanced biofidelic pediatric anthropomorphic testing devices (ATDs) and a more complete understanding of pediatric biomechanics. Computer models of the pediatric head and neck provide a valuable tool to combine results from pediatric postmortem human specimen (PMHS), radiological, and human volunteer studies to investigate the dynamics of the pediatric head and neck. The current study produced the first validated computer model of the pediatric head and neck which were created using the framework of a validated adult model. Radiology studies were conducted to determine pediatric cervical muscle cross sectional areas, vertebral anthropometry, and vertebral inertial properties. The results of these studies were combined with available pediatric PMHS properties to create the six and ten year old models. The models were validated against pediatric volunteer low speed frontal impacts and were then used to simulate higher rate and injurious inducing loading scenarios. The six and ten year old flexion bending stiffnesses were found to be 36% and 45% of the adult bending stiffness, respectively. The pediatric tensile stiffnesses were found to be 67% and 76% of the adult tensile stiffness. The tensile failure tolerance of the six year old was between 1490 and 2300 N and of the ten year old between 2040 and 3170 N. The adult and pediatric Hybrid III ATDs were found to be on average 2.5 times stiffer in flexion bending than the computer models. Biofidelity corridors were created with the models to be used to guide future ATD designs. Overall, the pediatric models provide a general tool that can be used to assess the safety of children during motor vehicle crashes.</p> / Dissertation

This particular study is about the main boulevard of the city center of Tirana that is the capital of Albania since 1920. The main boulevard, which has a function of a &quot / spine&quot / of the central business district, was designed as an idea by the Italian architects in 1925. The new government needed immediately governmental buildings like minstries, a palace and a strong form that connects all of these facilities together in a monumental way. This &quot / spinal&quot / circulation system was inspired from the urban movements of that time like near city and city beautiful movement. Tirana is studied as the case by the light of historical developments of other cities. The power of the spine and its effect to the macro form of the whole city is analyzed and determined.