Darryl Dickerson

In vitro and in vivo evaluation of orthopedic interface repair using a tissue scaffold with a continuous hard tissue-soft tissue transition

Tendon tears produce pain and decrease joint stability; each year, over 1.1 million rotator cuff tendon surgical procedures are performed worldwide. However, surgical success is highly variable, and the inability of the procedure to drive the regeneration of the normal tendon-bone interface has been identified as a key factor in surgical failure. This study focuses on the development, in vitro evaluation, and in vivo assessment of a tissue scaffold derived from bovine cancellous bone with the potential to direct regeneration of a bone-soft tissue interface. The scaffold is a highly porous scaffold with a continuous hard tissue-soft tissue transition that facilitates load transfer across the interface and contains all of the extracellular matrix components of the orthopedic interface. This study demonstrated the in vitro characterization of the mechanical properties and successful in vivo assessment using an ovine model.

Functional MRI can detect changes in intratissue strains in a full thickness and critical sized ovine cartilage defect model

Functional imaging of tissue biomechanics can reveal subtle changes in local softening and stiffening associated with disease or repair, but noninvasive and nondestructive methods to acquire intratissue measures in well-defined animal models are largely lacking. We utilized displacement encoded MRI to measure changes in cartilage deformation following creation of a critical-sized defect in the medial femoral condyle of ovine (sheep) knees, a common in situ and large animal model of tissue damage and repair. We prioritized visualization of local, site-specific variation and changes in displacements and strains following defect placement by measuring spatial maps of intratissue deformation. Custom data smoothing algorithms were developed to minimize propagation of noise in the acquired MRI phase data toward calculated displacement or strain, and to improve strain measures in high aspect ratio tissue regions. Strain magnitudes in the femoral, but not tibial, cartilage dramatically increased in load-bearing and contact regions especially near the defect locations, with an average 6.7% ± 6.3%, 13.4% ± 10.0%, and 10.0% ± 4.9% increase in first and second principal strains, and shear strain, respectively. Strain heterogeneity reflected the complexity of the in situ mechanical environment within the joint, with multiple tissue contacts defining the deformation behavior. This study demonstrates the utility of displacement encoded MRI to detect increased deformation patterns and strain following disruption to the cartilage structure in a clinically-relevant, large animal defect model. It also defines imaging biomarkers based on biomechanical measures, in particular shear strain, that are potentially most sensitive to evaluate damage and repair, and that may additionally translate to humans in future studies.

Development of non-cognitive skills in minority engineering outreach programs

A broad array of efforts have focused on multiplying student pathways to engineering, particularly for groups that have been historically under-represented such as ethnic minorities in the United States. Among such efforts, summer programs have been a widely used mechanism to stimulate and nurture engineering identity and agency in students from a relatively young age. At a large Midwestern University in the US, summer engineering workshops (SEWs) are executed for grades 6-12 to create awareness, increase student interest in engineering careers, enhance student preparation, and improve student access to resources required to pursue an engineering career. This paper presents an overview of the efforts of the aforementioned university to embed non-cognitive skills into the targeted learning outcomes of SEWs for secondary school students. These workshops range in duration from one to five weeks and the majority of instructors and staff are undergraduate and graduate students. Specifically, the paper outlines targeted non-cognitive learning outcomes and the elements designed to address them in 1) instructor/staff training and 2) workshop curriculum. Initial efforts will include the integration of active engagement strategies with the use of formative assessments and effective feedback tools as well as exposure to self-theories such as growth and fixed mindsets.