A. James Clark School of Engineering

Permanent URI for this communityhttp://hdl.handle.net/1903/1654

The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

Browse

Subject: search.filters.subject.biomechanics

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Effect of Load History on Ovine Intervertebral Disc Biomechanics
    (2014) Goodley, Addison; Hsieh, Adam H; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Loading of the intervertebral disc (IVD) alters biomechanical properties by modifying fluid distribution in the nucleus pulposus -changing hydrostatic pressure and tissue response- during force transmission along the spine. This study combines pressure, vertical displacement, and radial bulge measurements to assess biomechanical function during healthy and adverse loading of ovine lumbar motion segments. High compressive loads and simultaneous transient exertions, representative of obesity or other high-load lifestyles, are expected to limit fluid recovery and inhibit IVD biomechanical function compared to low compressive load controls with similar transient exertions. Specifically, the adverse group will (1) lose the ability to generate intradiscal pressures equivalent to control discs at equal loads and (2) exhibit a greater degree of deformation and bulge during comparable loading. This study contributes a greater understanding of the effects of load on IVD health. Findings may inform future efforts to preserve disc biomechanics and reverse IVD loss of function.
  • Thumbnail Image
    Item
    Physical properties of lamprey spinal cord regeneration: adaptive vs. maladaptive recovery
    (2014) Luna Lopez, Carlos; Aranda-Espinoza, Helim J.; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Spinal cord injury (SCI) is a physical trauma that can result in paralysis and even death; to date no treatment exists that can successfully promote functional or adaptive recovery. Although humans are unable to regenerate after complete SCI, there are animal models that have been studied for their ability to regrow and reconnect their nerve fibers. From the group of animals that are capable of spinal cord regeneration, in the best studied is the lamprey (Petromyzon Marinus) it has been noted that recovery can be maladaptive. When left to recover at warm temperature (23 ⁰C) most lampreys had adaptive behavior, but at cold temperature (10 ⁰C) most lampreys showed maladaptive behavior. In this thesis we studied the physical factors that influence adaptive and maladaptive recovery in lampreys. In the first part, we analyzed axonal regeneration and blood clot formation at early time points after injury (1-2 weeks). We found that lampreys in cold temperature have a blood clot that could be blocking spinal cord regeneration. In the second part of this work, we analyzed the biomechanical and structural differences between lampreys in warm and cold temperature. We used in vivo X-ray imaging and tensile loading testing of the spinal cord and notochord structures, before and after injury. We found that lampreys at warm temperature are more favorable to create a permissive mechanical and structural environment for regeneration. Lastly, we used those lessons learned previously to enhance regeneration of maladaptive animals. We removed the blood clot at the injury site and created a time frequency analysis to measure the recovery of coordination. We found that lampreys in cold temperature with clot removal had a more adaptive recovery after injury than those without removal. In summary, by using the lamprey we were able to compare the differences between regeneration in warm and cold temperature and found the physical factors that influence maladaptive recovery. Removing one of these factors, in this case the blood clot, successfully enhanced the recovery of coordination. These results have the potential to be translated to higher animals and aid in the creation of successful treatments for SCI.
  • Thumbnail Image
    Item
    MODELING CRUTCH COMPENSATION OF HIP ABDUCTOR WEAKNESS AND PARALYSIS
    (2011) Borrelli, James Rocco; Balachandran, Balakumar; Haslach Jr, Henry W; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Hip abductor weakness or paralysis is prevalent in the half a million cases of low level spinal injuries in the United States alone. Crutches are often used as an ambulatory aid by individuals with this type of permanent disability. This study investigates whether using a crutch with a wide stance, as opposed to a conventional vertical stance, returns the hip rotation and pelvic obliquity to a more normal range of motion for individuals with weak or paralyzed hip abductors. An inverse dynamics six link model of the body with ten degrees of freedom and a forward dynamics six link model with six degrees of freedom were used to simulate the swing and stance phases of gait with hip abductor weakness/paralysis while using either compensatory motions (hip hiking or lateral displacement of the torso) or crutches. The forward dynamics model characterizes the effect of hip abductor weakness on the gait kinematics hip rotation and pelvic obliquity. The model also characterizes the effect of compensatory motions and crutch use on gait with paralyzed hip abductors. The inverse dynamics model calculates the time varying body weight that must be supported on a contralateral crutch to achieve normal gait kinematics even with paralyzed hip abductors. The forward dynamics model predicts that hip abductor paralysis reduces the range of pelvic obliquity and increases the range of hip rotation. The model also predicts that compensatory motions and crutch use restore the range of motion of hip rotation and pelvic obliquity in gait with paralyzed hip abductors to more normal. The inverse dynamics model predicts that the portion of body weight that must be supported on a crutch for normal gait kinematics with paralyzed hip abductors is lowered by using a wide crutch stance. This study suggests that contralateral crutch use replaces the need for the compensatory motions hip hiking and lateral displacement of the torso while restoring the range of hip rotation and pelvic obliquity to more normal ranges in an individual with weak or paralyzed hip abductors. Furthermore, angling the crutch side-to-side restores the range while supporting less body weight on a contralateral crutch.
  • Thumbnail Image
    Item
    Humeral Fracture Fixation Techniques: A FEA comparison of locing and compression techniques with cadaveric pullout comparison of cortical compression and internal locking screws.
    (2007-08-13) Johnson, Aaron; Barker, Donald; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Locking and non-locking humeral repair techniques provide different mechanical constructs for securing fractures, and consequently could generate different strain fields at the callus. The purpose of this study was to investigate the strain field callus, and to compare to determine if one construct offers a healing advantage over another. An FEA analysis was conducted using ABAQUS, with all contact surfaces modeled as friction interfaces; additionally, a pretension was applied to the non-locking construct to simulate the effect of installation. The models were subjected to axial tension loads, and results were compared with existing cadaveric and synthetic experimental loading. Additional validation involved screw pullout testing conducted on cadaveric humeri. Results showed that the strain fields at the fracture site showed no significant variation in distribution, shape, or magnitude, therefore concluding that the locking plate offered no biomechanical healing advantage.