Producing hip implants of titanium alloys by additive manufacturing

Abstract

Additive manufacturing (AM) technologies, in particular selective laser melting (SLM) allows the production of complex-shaped individual implants from titanium alloys with high biocompatibility, mechanical properties, and improved osseointegration by surface texturing. In this work, the possibility of producing a custom-made hip implant from Ti-6Al-4V powder according to the data acquired via computed tomography of the patient is shown. Different heat treatments were applied in order to achieve better combination of tensile strength and elongation by partial decomposition of the martensitic phase. The implant was installed to the patient, postoperative supervision has shown good results, and the patient is able to move with the installed implant. A successful case of applying AM for producing custom hip implant is demonstrated in the paper. Using AM allowed the production of a custom-made hip implant in a short time and decreases the operation time and lessens the risk of infection ingress.

Development of AM Technologies for Metals in the Sector of Medical Implants

“…A custom-made component of a hip implant endoprosthesis was obtained in titanium alloy with the same technique. The implant matched the anatomical features of the patient, with porous structures to favor osseointegration, and with good mechanical properties [166].…”

A Review of Metal Fabricated with Laser‐ and Powder‐Bed Based Additive Manufacturing Techniques: Process, Nomenclature, Materials, Achievable Properties, and its Utilization in the Medical Sector

“…Thus, there is at the current state the necessity of a costly post-surface finishing independent from the chosen fabrication method. [292,293] Considering implants, where the key criterions are to have a compatible contact between the implant and the human body, the possibilities AM offers have been proven to be beneficial and lower the likelihood of implant rejections. [290] A recent investigation on CoCr stents came to the conclusion that the productivity of their fabrication is higher when fabricated via SLM as opposed to the conventional schemes, even though the surface finish has to be improved in a subsequent step.…”

“…[291] In addition, the combination of CT-scanning with AM has been shown to be very promising for the fast and efficient supply of restorations, offering perfect compatibility of the implant due to customized design. [293] A recent design study on a femur showcased the future of bone replacements, whereby the implant's stiffness varies based on Table 31. [189,200,[294][295][296] Most importantly, the fabrication of designed rough and porous surfaces, which promote bone ingrowth and increase the contact surface area, as well as the opportunity to design and adjust the stiffness to achieve the best possible compatibility between the implant and the human counterpart, should be highlighted.…”

“…[22,264,297,298] One example for this is a recent study on a custom designed hip implant with distinct surface features to enhance the osseointegration. [293] A recent design study on a femur showcased the future of bone replacements, whereby the implant's stiffness varies based on Table 31. Summary of the directional and location dependencies of the surface quality, adapted from refs.…”

“…Removal of the attached powder particles and controllable surface roughness on highly porous strut structures [307] Pore geometry on open porous structures Growth of human periosteum-derived cells in dependency to the pore shape and size; optimization of the bone ingrowth behavior [298] Functionally graded bone implants Designed compressive characteristics of femoral stems with a porous core and a beaded surface morphology for cementless fixation [308] Functionally graded dental implants Implants with a gradient porosity from the inner core to the outer surface [18] Feasibility study on micro-actuators Micro actuators for cochlear implants; treatment for deaf people suffering from damages in the inner ear [309] Clinical study on the bone ingrowth behavior Various bone implants were fabricated with SLM and EBM and implanted in goats and sheep [310,311] Clinical study on the survival rate of dental mini implants 231 dental mini implants were placed in 62 patients, the survival rate after 4 years was 96.9% [312] Custom made dental root implant Congruent (root-analogue) implants for perfect fit, geometrical data acquired via CT scan and subsequent 3D reconstruction; faulty tooth directly replaced after removal [294,313,314] Custom made dental blade implant Non-conventional treatment; proven solution for patients which cannot be treated with regular root-form implants due to atrophied posterior mandible [315] Custom made sternum and rib cage Reconstruction of a partial rib-cage for a patient suffering from chest wall sarcoma [316] Custom made heel implant Reconstruction of the heel bone for a patient with cancer of the calcaneus [317] Custom made hip implant Production of a polymer prototype of the patients hip bone based on CT-data; designing and fabrication a polymer hip implant as intermediate step, fabrication of a Ti6Al4V hip implant based on the optimized geometry, implant was implanted into an patient and good results were reported [293] Artificial beak for a rare crane bird Reconstruction of the upper beak of a Grus japonensis bird, iterative optimizations undertaken by utilizing polymer printing; final design of the prosthetic beak fabricated with SLM and successfully installed in a surgery [318] Fabrication of cardiovascular stents via SLM SLM coupled with conventional electrochemical polishing was found as a suitable manufacturing approach, outperforming the conventional stent manufacturing scheme [291] Osseointegration in EBM fabricated mesh and foam scaffolds Study the osseointegration and seeding efficiency based on the scaffold design; trial study on a pelvic bone implant (custom-made periacetabular phrosthesis) for a tumor patient [319] Acetabular shells Fabrication of acetabular shells ...…”