Three Dimensional Printed Bone Implants in the Clinic.

Implants are being continuously developed to achieve personalized therapy. With the advent of 3-dimensional (3D) printing, it is becoming possible to produce customized precisely fitting implants that can be derived from 3D images fed into 3D printers. In addition, it is possible to combine various materials, such as ceramics, to render these constructs osteoconductive or growth factors to make them osteoinductive. Constructs can be seeded with cells to engineer bone tissue. Alternatively, it is possible to load cells into the biomaterial to form so called bioink and print them together to from 3D bioprinted constructs that are characterized by having more homogenous cell distribution in their matrix. To date, 3D printing was applied in the clinic mostly for surgical training and for planning of surgery, with limited use in producing 3D implants for clinical application. Few examples exist so far, which include mostly the 3D printed implants applied in maxillofacial surgery and in orthopedic surgery, which are discussed in this report. Wider clinical application of 3D printing will help the adoption of 3D printers as essential tools in the clinics in future and thus, contribute to realization of personalized medicine.

Fat tissue: views on reconstruction and exploitation.

Transplantation of autologous fat as pedicle or transposition flaps has been a classical method in plastic surgery for tissue reconstruction. The injection of fat for soft tissue reconstruction is also an old innovation. This approach has some significant drawbacks such as resorption of the fat transplant. To regenerate additional and self-regenerating adipose tissue for reconstructive purposes, a thorough understanding of adipose tissue (mesodermal stem cells, adipoblasts, pre-adipocytes, mature, lipid-synthesizing, and lipid-storing white or brown adipocytes) on cellular and molecular levels is required. Several transcription factors that play a central role in the control of adipogenesis have been identified. Among these are the CCAAT/enhancer binding protein gene family and peroxisome proliferator-activated receptor-gamma. Hormones and growth factors, such as insulin and insulin-like growth factor (IGF), transfer external signals to differentiating adipocytes. In an attempt to improve the quality of tissue-engineered fat by culture-expanded adipocytes, various pre-adipocyte and stem cell culture conditions and expansion methods have been developed. In the presence of fetal calf serum, spontaneous differentiation of pre-adipocytes into fat cell clusters occurs to some degree. This in vitro differentiation can be enhanced by addition of inducing agents such as dexamethasone, isobutylmethylxantine, and insulin into the culture medium. Recent work has shown the multipotency of pre-adipocytes, which are fibroblast-like precursors of adipocytes. With use of specific culture conditions, human adipose tissue-derived stem cells can be induced to express markers of adipocyte, osteoblast, and myocyte cell lineages. The multipotent characteristics of adipose tissue-derived stem cells, as well as their abundance and accessibility in the human body, make them a potential cell source for tissue engineering applications.

Histologic analysis of bioabsorbable scleral buckling implants: an experimental study on rabbits.

PURPOSE: To analyze histologically tissue reactions to bioabsorbable PLA96 in rabbit eyes. METHODS: Scleral buckling operations were carried out in 48 rabbits. Two materials were used: bioabsorbable PLA96 (polylactide 96/4; L/D molar ratio 96/4) and silicone sponge. One eye of each rabbit was operated on and the other eye served as a nonoperated control. After follow-up times of 1, 3, 5, and 12 months, the rabbits were killed and the eyes enucleated for histology. RESULTS: All rabbits recovered well. Histologically, tissue reactions were very localized; implant fragments were not seen within the sclera. The amounts of fibrous tissue and inflammatory cells (mainly macrophages) inside the implant area increased over time. One rabbit from the silicone group was killed 4 months postoperatively owing to refusal to eat. In the PLA96 group, acute or chronic infections occurred in four rabbits. The bioabsorbable implant was macroscopically easily detectable at 12 months postoperatively. CONCLUSIONS: The PLA96 material used for scleral buckling in rabbits showed good biocompatibility. The material did not undergo biodegradation during the follow-up period of 12 months. PLA96 implants were associated with thicker fibrous tissue encapsulation and more inflammatory cells compared with silicone sponge implants.

Persistence of indentation with bioabsorbable poly-L/D-lactide versus silicone sponge scleral buckling implants.

PURPOSE: To measure the amount and duration of indentation depth achieved with biodegradable poly-L/D-lactide 96/4 (PLA96) and silicone sponge implants. METHODS: Thirty rabbits underwent a scleral buckling procedure. A PLA96 buckling implant was used in 15 rabbits and a silicone sponge buckling implant was in 15 rabbits. A circumferential scleral buckling implant was sutured episclerally on the left eye of each rabbit, just temporal to the superior rectus muscle and 7 mm posterior to the limbus. Computed tomography was performed at 1 week, 3 months, and 5 months after surgery. RESULTS: The PLA96 buckling implant (implant diameter, 3-3.5 mm) used in this study created lower indentation than the silicone sponge implant (implant diameter, 4 mm). The indentation created by the PLA96 implant decreased over time compared with that created by the silicone implant. There were no complications related to either kind of implant. CONCLUSION: Both the silicone sponge implant and the PLA96 implant caused indentation that decreased in a comparable manner over the follow-up period (5 months).