Demand for donor hearts has increased globally due to cardiovascular diseases. Recently, three-dimensional (3D) bioprinting technology has been aimed at creating clinically viable cardiac constructs for the management of myocardial infarction (MI) and associated complications. Advances in 3D bioprinting show promise in aiding cardiac tissue repair following injury/infarction and offer an alternative to organ transplantation. This article summarizes the basic principles of 3D bioprinting and recent attempts at reconstructing functional adult native cardiac tissue with a focus on current challenges and prospective strategies.
A partial skeleton of a sauropod dinosaur, Museum of Western Colorado 8028, was recovered from the Upper Jurassic Morrison Formation near Snowmass, Colorado, USA, and in 2014 it was referred to Haplocanthosaurus sp. The material includes four proximal caudal vertebrae, which are unique in having strongly amphicoelous vertebral bodies, in which the centrum is reduced to a thin vertical plate of bone between the concave articular surfaces, and neural canals that are laterally and ventrally expanded and strongly sloped relative to the centrum. To reconstruct the soft tissues that left these traces on the skeleton, we rebuilt these vertebrae using both physical and digital techniques. We CT scanned the specimens, generated digital models, 3D-printed the vertebrae, physically sculpted missing material onto the printed models, optically scanned the sculpted vertebrae to create second-generation digital models, and finally, retro-deformed and articulated those digital versions of the vertebrae. The spaces between the deeply amphicoelous caudal centra were likely filled by large, ellipsoidal intervertebral discs, as in the amphicoelous vertebrae of Sphenodon and gekkotan lizards. The expanded neural canals remain enigmatic. In ostriches, the lumbosacral spinal cord is expanded laterally and ventrally in each vertebra, lending the spinal cord a shape that roughly resembles beads on a string. Similar spinal cord morphology might explain the expanded neural canals in the Snowmass Haplocanthosaurus, but it is not clear why a relatively small-bodied, small-tailed sauropod would need such a spinal expansion, given that similar expansions have not been reported in larger-bodied and larger-tailed taxa.
Cranial cruciate ligament deficiency (CCLD) results in internal rotational instability of the stifle (RLS). By contrast, tibial torsion (TT) is an anatomical feature of the tibia along its longitudinal axis. The objective of this study was to validate a dynamic radiographic technique to measure internal rotational laxity of the stifle and differentiate it from TT. Models included transection of the CCL for RLS and an osteotomy for TT. One limb within eight pairs of canine cadaveric hind limbs was randomly assigned to CCLD. The contralateral limb underwent TT, followed by CCLD. Neutral and stress radiographs were taken with the limb in a custom rotating 3-D printed positioning device before and after each modification. The position of the calcaneus on neutral views and the magnitude of its displacement under standardized torque were compared within limbs and between groups. Transection of the CCL increased the magnitude of displacement of the calcaneus by 1.6 mm (0.3–3.1 mm, p < 0.05) within limbs. The lateral calcaneal displacement (dS-dN) tended to be greater when CCLD limbs were compared to limbs with intact CCL. A magnitude of calcaneal displacement of 3.45 mm differentiated limbs with RLS from intact limbs with 87.5% sensitivity and 68.7% specificity. The calcaneus was displaced further laterally by about 3 mm on neutral radiographs (dN) when limbs with experimental TT were compared to those without TT (p < 0.05). A calcaneus located at least 3.25 mm from the sulcus differentiated limbs with TT from intact limbs with 87.5% sensitivity and 87.5% specificity. The technique reported here allowed detection of RLS, especially within limbs. A calcaneus located at least 3.25 mm on neutral radiographs of large dogs should prompt a presumptive diagnosis of TT.
A partial skeleton of a sauropod dinosaur, Museum of Western Colorado 8028, was recovered from the Upper Jurassic Morrison Formation near Snowmass, Colorado, USA, and in 2014 it was referred to Haplocanthosaurus sp. The material includes four proximal caudal vertebrae, which are unique in having strongly amphicoelous vertebral bodies, in which the centrum is reduced to a thin vertical plate of bone between the concave articular surfaces, and neural canals that are laterally and ventrally expanded and strongly sloped relative to the centrum. To reconstruct the soft tissues that left these traces on the skeleton, we rebuilt these vertebrae using both physical and digital techniques. We CT scanned the specimens, generated digital models, 3D-printed the vertebrae, physically sculpted missing material onto the printed models, optically scanned the sculpted vertebrae to create second-generation digital models, and finally, retro-deformed and articulated those digital versions of the vertebrae. The spaces between the deeply amphicoelous caudal centra were likely filled by large, ellipsoidal intervertebral discs, as in the amphicoelous vertebrae of Sphenodon and gekkotan lizards. The expanded neural canals remain enigmatic. In ostriches, the lumbosacral spinal cord is expanded laterally and ventrally in each vertebra, lending the spinal cord a shape that roughly resembles beads on a string. Similar spinal cord morphology might explain the expanded neural canals in the Snowmass Haplocanthosaurus, but it is not clear why a relatively small-bodied, small-tailed sauropod would need such a spinal expansion, given that similar expansions have not been reported in larger-bodied and larger-tailed taxa.
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