Rapid Prototyping Assisted Design and Development of Inter-Vertebral Implants

This paper presents a case study of applying rapid prototyping in assisting in the design and development of inter-vertebral implants for spine fusions. The major process of design and implant development, its biological and mechanical requirements, the approach for developing a 3D reconstructive vertebral anatomy model, the inter-vertebral implant CAD model, and the integration with a finite element analysis for the implant's structural analysis are presented. The process of 3D Printing of the vertebral anatomy and the inter-vertebral implant is described. The application of the prototyping model in assisting in the inter-vertebral anatomic fitting, in guiding the implant's geometric design, in helping with the virtual surgical planning, and in understanding the implant's mechanical properties and structural stability are discussed.Mechanical Engineerin

Reproductive trade-offs in the colorado checkered whiptail lizard (Aspidoscelis neotesselatus): an examination of the relationship between clutch and follicle size

Life history theory predicts that there should be an inverse relationship between offspring size and number, because individuals cannot simultaneously maximize both when resources are limited. Although extensively studied in avian species, the occurrence and determinants of reproductive tradeoffs in oviparous reptiles are far less understood, particularly in parthenogenetic species. We studied this trade-off in the Colorado Checkered Whiptail, Aspidoscelis neotesselatus, a female-only parthenogenetic lizard. Using data previously collected in 2018 and 2019, we tested for clutch and egg size trade-offs and determined whether this relationship could be influenced by female size and aspects of physiological condition. Physiological condition included energy-mobilizing hormone (i.e. corticosterone ‘CORT’), oxidative stress (i.e. reactive oxygen metabolites ‘ROMs’), and innate immune function (bacterial killing ability ‘BKA’). We found the effect of clutch size on follicle size was significant, but not linear. Specifically, follicle size was on average larger in females with clutches of two follicles when compared to clutches of one follicle, but smaller in females with clutches of three when compared to clutches of two. In addition, females that were larger produced larger follicles regardless of clutch size. Neither CORT nor BKA affected the relationship between follicle size and clutch size. However, ROMs did explain variability in this relationship: oxidative stress was more elevated in females that produced larger clutches and larger follicles. We conclude that clutch size and body size are key life history traits that shape follicle size, and that investments into larger clutches and follicle size come at the cost of oxidative damage

Towards an intraoperative engineering of osteogenic and vasculogenic grafts from the stromal vascular fraction of human adipose tissue

Grafts generated by cultivation of progenitor cells from the stromal vascular fraction of human adipose tissue have been proven to have osteogenic and vasculogenic properties in vivo. However, in vitro manufacture of such implants is challenged by complex, impractical and expensive processes, and requires implantation in a separate surgery. This study investigates the feasibility of an intraoperative approach to engineer cell-based bone grafts with tissue harvest, cell isolation, cell seeding onto a scaffold and subsequent implantation within a few hours. Freshly isolated adipose tissue cells from a total of 11 donors, containing variable fractions of mesenchymal and endothelial progenitors, were embedded at different densities in a fibrin hydrogel, which was wrapped around bone substitute materials based on beta-tricalcium phosphate (ChronOS), hydroxyapatite (Engipore), or acellular xenograft (Bio-Oss). The resulting constructs, generated within 3 hours from biopsy harvest, were immediately implanted ectopically in nude mice and analysed after eight weeks. All explants contained blood vessels formed by human endothelial cells, functionally connected to the recipient's vasculature. Human origin cells were also found within osteoid structures, positively immunostained for bone sialoprotein and osteocalcin. However, even with the highest loaded cell densities, no frank bone tissue was detected, independently of the material used. These results provide a proof-of-principle that an intraoperative engineering of autologous cell-based vasculogenic bone substitutes is feasible, but highlight that - in the absence of in vitro commitment--additional cues (e.g., low dose of osteogenic factors or orthotopic environmental conditions) are likely needed to support complete osteoblastic cell differentiation and bone tissue generation