Porous titanium scaffolds fabricated using a rapid prototyping and powder metallurgy technique.

One of the main issues in orthopaedic implant design is the fabrication of scaffolds that closely mimic the biomechanical properties of the surrounding bone. This research reports on a multi-stage rapid prototyping technique that was successfully developed to produce porous titanium scaffolds with fully interconnected pore networks and reproducible porosity and pore size. The scaffolds' porous characteristics were governed by a sacrificial wax template, fabricated using a commercial 3D-printer. Powder metallurgy processes were employed to generate the titanium scaffolds by filling around the wax template with titanium slurry. In the attempt to optimise the powder metallurgy technique, variations in slurry concentration, compaction pressure and sintering temperature were investigated. By altering the wax design template, pore sizes ranging from 200 to 400 microm were achieved. Scaffolds with porosities of 66.8 +/- 3.6% revealed compression strengths of 104.4+/-22.5 MPa in the axial direction and 23.5 +/- 9.6 MPa in the transverse direction demonstrating their anisotropic nature. Scaffold topography was characterised using scanning electron microscopy and microcomputed tomography. Three-dimensional reconstruction enabled the main architectural parameters such as pore size, interconnecting porosity, level of anisotropy and level of structural disorder to be determined. The titanium scaffolds were compared to their intended designs, as governed by their sacrificial wax templates. Although discrepancies in architectural parameters existed between the intended and the actual scaffolds, overall the results indicate that the porous titanium scaffolds have the properties to be potentially employed in orthopaedic applications.

Pressure distribution at the seating interface of custom-molded wheelchair seats: effect of various materials.

OBJECTIVE: To identify which of 4 materials has the most favorable pressure distribution when used in custom-molded seats (CMSs) to assist clinicians in providing appropriate seating for wheelchair-bound individuals who are prone to develop pressure ulcers. DESIGN: Repeated-interface pressure measurements for all materials, followed by statistical analysis. SETTING: The general community and referral centers. PARTICIPANTS: Seven subjects, 5 with cerebral palsy, 1 with Schilder's disease, and 1 with postmeningitis effects. All subjects were seated in a CMS and had spinal deformities. INTERVENTIONS: Viscoelastic polyurethane foams (Pudgee, Sunmate) and gels (Floam trade mark, Jay) were used as inserts in the CMSs. Evazote foam was used as a control material. MAIN OUTCOME MEASURES: Pressure readings were taken at the seat interface with pneumatic pressure sensors and the Talley Pressure Monitor. Peak pressure readings, mean pressure ratio, and peak pressure ratio for the different materials were compared. RESULTS: Foams, Sunmate in particular, produced lower peak-interface pressures and also showed better pressure distribution than did gels. CONCLUSION: Foams are the preferred insert material with CMSs when increased tissue breakdown risk is present.