**6.1.3 Avoiding manual adjustment of standard implants**

Another very important benefit of using customized implants is that surgical operations are shorter. During the operation, surgeon must adjust standard implants manually to the patient's anatomy and pathology in order to be able to place and fix them. This cannot be done until the surgeon has intervened the damaged zone (Figure 16).

Additive Manufacturing Solutions for Improved Medical Implants 165

In addition, the adaptation of the conventional implant shape during the surgical operation

 When deformed, the implant has been damaged since the material has suffered plastic deformation. This deformation produces local strengthening while reducing ductility, which leads to the change of implant behaviour. This is especially critical in long term prostheses that bear cyclic loads, since this plastic deformation may reduce its fatigue strength and total implant durability, the implant has suffered a very harmful

 The second inconvenience is that corrosion may appear due to the fact that plastic deformation may break the passive layer of the contact area (Pitting Corrosion). Localized corrosion can occur as a result of imperfections in the oxide layer. This can result in a large degree of localized damage because the small areas of active corrosion become the anode and the entire remaining surface becomes the cathode (Ratner, 2004).

After above mentioned, the benefits of using customized implants seem to be clear. Anyhow, the customization design process of an implant can drive to very complex geometries difficult or even impossible to manufacture by conventional manufacturing techniques such as machining, casting, forging, etc. Conventional manufacturing processes

Casting, forging and HPDC are not economically viable due to the investment in the

 In case that machining of customized geometry is possible, the more complex the geometries to produce, the more machining operations and setups are needed and the

In order to show above explained benefits of implant customization and fabrication with additive technologies, several case studies have been made with customized implants for animals. In these case studies, implants have been manufactured using EBM technology and implanted in dogs in a close collaboration of Metal-Processing Technology Institute AIMME, CIMA Research Group (University of Vigo) and FAUNA Veterinary Clinic (Rodiño, 2010), (CIMA, 2011). Customized implants for ten different patients have been developed, three of which are going to be presented in this section. Specific osteosynthesis plates were designed by researchers from CIMA together with the veterinary surgeon using the procedure mentioned in the Supply Chain section - upon medical images of each patient the model was reconstructed and manufactured on the EBM technology to be implanted. AIMME has offered technical advice related with the manufacturing technology (EBM) during the design process, has manufactured implants by means of EBM and also has performed

finishing operations in order to get the optimum surface roughness in every case.

The first patient Baby, is a 3-year old Yorkshire Terrier. He was admitted in December 2009 presenting a radius-cubital diaphysal oblicuous fracture with severe loss of radiographic density due to osteoporosis and disuse of the leg in question. If the X-ray images of healthy and injured leg are compared (Figure 17), it is evident that a 20-25% of radius-cubital length

deformation equivalent to lots of cycles in normal conditions of use.

can be normally discarded for the following reasons:

less economically competitive, comparing with AM.

mould only for a unique part.

**6.1.4 Case studies of customized plates** 

**Case of BABY** 

produces 2 important drawbacks:

Fig. 16. Tooling for standard plate deformation and adaptation. (Courtesy of AO Foundation Engineering).

In the case of customized implants is not necessary for surgeon to perform these modifications because the implant has been designed and manufactured totally adapted to the patient from direct scanned information (CAT, RMI, etc). It has been proved that the shorter the surgical operation the faster the patient's recovery and this improves patient's life quality. Further advantages of shorter surgical operation are:


Fig. 16. Tooling for standard plate deformation and adaptation. (Courtesy of AO Foundation

In the case of customized implants is not necessary for surgeon to perform these modifications because the implant has been designed and manufactured totally adapted to the patient from direct scanned information (CAT, RMI, etc). It has been proved that the shorter the surgical operation the faster the patient's recovery and this improves patient's

 *Lower exposition to external bacteriological agents* (even in sterile atmosphere) leads to lower infection probability (one of major risks during traumatologic and orthopaedic

*Less recovery time in the hospital.* Therefore the costs of the surgical operation are reduced

*Lower dosis of anesthesia is necessary.* This factor may be critical in certain cases.

life quality. Further advantages of shorter surgical operation are:

Engineering).

operations).

and more patients can be treated.

In addition, the adaptation of the conventional implant shape during the surgical operation produces 2 important drawbacks:


After above mentioned, the benefits of using customized implants seem to be clear. Anyhow, the customization design process of an implant can drive to very complex geometries difficult or even impossible to manufacture by conventional manufacturing techniques such as machining, casting, forging, etc. Conventional manufacturing processes can be normally discarded for the following reasons:

