Although the primary aim of diagnosing and treating musculoskeletal impairments is to restore functional three-dimensional (3D) movements, the majority of the quantitative diagnostic and evaluation tools available to the clinician have remained static and two dimensional. Thus, the current focus is to develop and ultimately validate a combined set of tools that will enable the accurate and precise measurement, analysis and visualization of 3D static and dynamic musculoskeletal anatomy (i.e., bone shape, skeletal kinematics, tendon and ligament strain, muscle force, and joint space). To accomplish this, the MR imaging and analysis capabilities already developed will be combined with highly accurate, imaging-based measurement and registration methodologies in order to non-invasively quantify complete joint anatomy and tissue dynamics during functional movements. Additionally, these tools will enable the quantification of 3D bone shape so that the effect that alterations joint and tissue dynamics have on bone shape can be quantified. Accomplishing the aims of the VFA initiative will fill an important knowledge gap that exists between the relationship of normal or impaired joint structure/function and the functional movement limitations associated with performing activities of daily living. In doing so, it will position the National Institutes of Health as an international leader in diagnostic evaluation of musculoskeletal impairments by advancing musculoskeletal diagnostic and evaluation tools from primarily static 2D tools to dynamic tools that can quantify 3D musculoskeletal function during dynamic tasks. Due to the natural tiered structure of this research, two primary paths are currently being pursued, one based using the VFA project in its current state to evaluate both normative and impaired joint kinematics and the other is the continued development of the VFA tools so that full musculoskeletal kinetics can be evaluated. The latter will require the development of methodologies for creating 3D digital images of loaded and moving joint tissues (bone, cartilage, and connective tissues) to reveal joint contact patterns and tissue loads. As part of the kinematics branch, the variability of bone shape and the sensitivity of defined joint posture (translation and rotation of one bone relative to another) to osteo-based coordinate system will be quantified. We intend to use these capabilities to document and evaluate the function of normal and impaired joint structures (e.g., Cerebral Palsy, Ehlos Danof syndrome, and patellar tracking syndrome) under simulated conditions experienced during activities of daily living. VFA Dynamic Tool Development Over the past year, we have maintained a research focus on developing the backbone for VFA and began to explore the issues surrounding the dynamic MR scanning of the musculoskeletal system. The key focal points for the algorithm development remained the image registration process along with continuing improvement in the integration algorithms. Fast-PC MRI provides 3D kinematics information for the bones of a joint (e.g., knee and ankle) as the subject brings this joint through a specified range of motion. Yet, this information cannot be readily applied to 3D models of the bones, which are created from static high-resolution scans of the joint. In order to apply the kinematics from the fast-PC MRI to the static models, the two image data sets have to be aligned (e.g., registered). Visualization is made possible by programs that have been written in-house using Matlabs scripting language. The development has now advanced to incorporate the evaluation of cartilage contact mechanics and much of the research focus is now concentrated in this area. A paper detailing the accuracy of this technique and a paper providing the first dynamic quantification of in vivo patellofemoral cartilage contact mechanics has been published. Another focus of the tool development is to expand the imaging modalities that are included within the VFA toolbox. To this end, we are collaborating with George Mason University in order to develop ultrasound techniques that can accurately track muscle motion. Lastly, through a collaboration with CIT and Eramacus (Netherlands), the VFA toolbox has been expanded to include automatic segmentation of the patellar and femoral bones from MR images. In Vivo Normal and Impaired Knee Joint Function On the experimental side, a primary focus has been on evaluating the clinical applicability of the tools being developed by applying them to the study of knee joint function in children and adults diagnosed with patellofemoral pain syndrome (n=100). The ultimate goal is to evaluate pre- and post-intervention joint function. We are in the process of analyzing the data acquired in order to quantify the various musculoskeletal parameters, such as joint kinematics, tendon strains, and tendon moment arms. Much of this analysis has been completed and presented to the scientific community by way of peer-reviewed publications and conference presentations. As we complete the VFA toolbox, we should also be able to quantify forces in the quadriceps muscles, patellar tendon, the anterior cruciate ligament, and the cartilage during an extension/flexion cycle of the knee joint. The kinematics from these populations are being compared to our normative database. A major focus of this year has been on patellofemoral pain syndrome, knees that have experienced a single dislocation, and cerebral palsy. In Vivo Hip Joint Function As part of Dr. Sheehan's work as a mentor for a K-award, a project evaluating the dynamics of the hip joint in both healthy controls and female subjects with hip pain has begun. The project is in its preliminary stages. In Vivo Shoulder Function 3D static MRI has been collected for 15 children with unilateral obstetric brachial plexus palsy and 12 matched controls. The current goal is to evaluate muscle volume and bone shape in these children and correlate that to measures of shoulder kinematics and strength. To this end, we have published a paper on 3D humeral shape changes in children with OBPP and a paper on the shoulder muscle volumes in typically developing children. A paper in regards to the relationship between muscle atrophy and loss of strength in children with OBPP is in review. Finally, a paper in regards to the 3D gleno-humeral shape changes in children with OBPP is being prepared for submission. This project garnered the interest of outside clinicians and has promoted new collaborations, which will allow this project to continue to expand. PF pain in Adolescent Females In this past year, much of our attention has focused on studying the potential etiologies of PF pain in adolescent females. PF pain is typically assumed to be an overuse issue in adolescents. Yet, we have demonstrated that patellar maltracking is a likely contributor to this pain. Interestingly, these maltracking patterns are unique from those seen in adults and they appear not to change as the adolescents mature into adulthood.
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