ABSTRACT
OBJECTIVES: The goal of this project was to develop and validate a patient-specific, anatomically correct graft for cartilage restoration using magnetic resonance imaging (MRI) data and 3-dimensional (3D) printing technology. The specific aim was to test the accuracy of a novel method for 3D printing and implanting individualized, anatomically shaped bio-scaffolds to treat cartilage defects in a human cadaveric model. We hypothesized that an individualized, anatomic 3D-printed scaffold designed from MRI data would provide a more optimal fill for a large cartilage defect compared to a generic flat scaffold. METHODS: Four focal cartilage defects (FCDs) were created in paired human cadaver knees, age <40 years, in the weight-bearing surfaces of the medial femoral condyle (MFC), lateral femoral condyle (LFC), patella, and trochlea of each knee. MRIs were obtained, anatomic grafts were designed and 3D printed for the left knee as an experimental group, and generic flat grafts for the right knee as a control group. Grafts were implanted into corresponding defects and fixed using tissue adhesive. Repeat post-implant MRIs were obtained. Graft step-off was measured as the distance in mm between the surface of the graft and the native cartilage surface in a direction perpendicular to the subchondral bone. Graft contour was measured as the gap between the undersurface of the graft and the subchondral bone in a direction perpendicular to the joint surface. RESULTS: Graft step-off was statistically significantly better for the anatomic grafts compared to the generic grafts in the MFC (0.0 â± â0.2 âmm vs. 0.7 â± â0.5 âmm, p â< â0.001), LFC (0.1 â± â0.3 âmm vs. 1.0 â± â0.2 âmm, p â< â0.001), patella (-0.2 â± â0.3 âmm vs. -1.2 â± â0.4 âmm, p â< â0.001), and trochlea (-0.4 â± â0.3 vs. 0.4 â± â0.7, p â= â0.003). Graft contour was statistically significantly better for the anatomic grafts in the LFC (0.0 â± â0.0 âmm vs. 0.2 â± â0.4 âmm, p â= â0.022) and trochlea (0.0 â± â0.0 âmm vs. 1.4 â± â0.7 âmm, p â< â0.001). The anatomic grafts had an observed maximum step-off of -0.9 âmm and a maximum contour mismatch of 0.8 âmm. CONCLUSION: This study validates a process designed to fabricate anatomically accurate cartilage grafts using MRI and 3D printing technology. Anatomic grafts demonstrated superior fit compared to generic flat grafts. LEVEL OF EVIDENCE: Level IV.
ABSTRACT
This Viewpoint discusses the feasibility of a model that uses venture capital to seed innovation in academic medical centers and generate cost savings through creative solutions.
Subject(s)
Academic Medical Centers , Investments , HumansABSTRACT
The loss of inner ear hair cells causes permanent hearing and balance deficits in humans and other mammals, but non-mammals recover after supporting cells (SCs) divide and replace hair cells. The proliferative capacity of mammalian SCs declines as exceptionally thick circumferential F-actin bands develop at their adherens junctions. We hypothesized that the reinforced junctions were limiting regenerative responses of mammalian SCs by impeding changes in cell shape and epithelial tension. Using micropipette aspiration and atomic force microscopy, we measured mechanical properties of utricles from mice and chickens. Our data show that the epithelial surface of the mouse utricle stiffens significantly during postnatal maturation. This stiffening correlates with and is dependent on the postnatal accumulation of F-actin and the cross-linker Alpha-Actinin-4 at SC-SC junctions. In chicken utricles, where SCs lack junctional reinforcement, the epithelial surface remains compliant. There, SCs undergo oriented cell divisions and their apical surfaces progressively elongate throughout development, consistent with anisotropic intraepithelial tension. In chicken utricles, inhibition of actomyosin contractility led to drastic SC shape change and epithelial buckling, but neither occurred in mouse utricles. These findings suggest that species differences in the capacity for hair cell regeneration may be attributable in part to the differences in the stiffness and contractility of the actin cytoskeletal elements that reinforce adherens junctions and participate in regulation of the cell cycle.
