Prosthesis technology

The inflatable prosthesis has several parts, inclnding two inflatable rods and a pnmp-reservoir mechanism. When activated, the device pnmps saline solntion from the reservoir into the rods, cansing inflation. The inflatable prosthesis prodnces a more natnral erection, in that the patient only develops an erection when the device is activated. Some newer advances in inflatable prosthesis technology have resulted in devices with the pump, reservoir, and rods aU in one nnit, and these can be placed dnring shorter snrgical procednres and are less likely to malfunction (Fig. 81-9). 

A significant contribution of Raman spectroscopy to the analytical characterization of biomedical issues has been made in the area of biomaterials, especially in the identification of biodegradation and deterioration [1, 2]. The general impact of Raman spectroscopy on the study of biomaterials has been described by this author in three recent review articles [3-5]. In this chapter, the topic of Raman characterization of biomaterials is revisited with particular emphasis placed on those biomaterials widely employed for load-bearing surfaces in artificial joints. Important recent case studies are presented to illustrate the power of the Raman technique to answer key questions of broad medical, scientific, and technological interest. The analytical and physical science lying behind the Raman effect is shown to contribute to the accumulation of a wealth of fundamental information about the medical and technical achievements of prosthesis makers. 

Diamond-like carbon since its inception in 1962 has found applications in some very important areas. These applications include coatings used in scratch-resistant optics, razor blades, prosthesis in medical applications electron emission surfaces in electronics as an insulator material for copper heat sinks in semiconductors such as solar cells and sensors for visible to infrared radiations and as structural materials such as deuterated DLC film used for neutron storage in advanced research instrumentation. As technology matures the unique properties of DLC will find new and important applications. 

Adverse effects of prosthesis insertion can occnr early or late after the surgical procedure. The most common early comphcation is infection. Late complications include mechanical failnre of the prosthesis, particularly when inflatable prostheses have been inserted. With improved technology, the mechanical failure rate has decreased to 5%. Other late complications include erosion of the rods through... 

Since membrane lungs as extracorporeal devices are in wide use, thoughts have turned to an implantable artificial lung prosthesis based on membrane technology. Developing such a device with the adequate characteristics and long-term reliability is a much more difficult task than encountered with the extracorporeal device developed for intermittent use. However, a small prototype device made of porous Teflon has been fabricated and tested by Richardson and Galletti. ... 

The Neural Prosthesis Program, launched in 1972 and spearheaded by F. Terry Hambrecht, MD, brought funding, focus, and coordination to the multidisciplinary effort to develop technologies to restore motor function in paralyzed individuals. The initial efforts were in electrode-tissue interaction, biomaterials and neural interface development, cochlear and visual prosthesis development and control of motor function using implanted and nonimplanted electrodes. 

Minneapolis, MN.) (b) Chitra tilting disc valve prosthesis with the occluder made of ultra high molecular weight polyethylene. (Courtesy of Sree Chitra Tirunal Institute for Medical Sciences and Technology, India.)... 

The externally controlled knee is a recent development that provides some solutions that fulfill the said requirements. Two microprocessor controlled pneumatic knee prosthesis using the Kobe technology [82] are available the EndoHte Intelligent Prosthesis (Blatchford and Sons, London, UK) and the Seattle Limb Systems Power Knee (Seattle Limb Systems, Seattle, WA). InteUigent Prosthesis was first developed in 1993 and an improved version was further introduced in 1995 (InteUigent Prosthesis Plus) and 1998 (Adaptive Prosthesis) [83]. 

Popovid, M.R., Keller, T. et al.. Surface stimulation technology for grasping and walking neural prosthesis, lEEEEngng. Med. Biol. Mag. 20 82-93,2001. 

Several implants are commercially available for total or partial disk replacements. For instance, currently, two polymer-based cervical and two lumbar disk prostheses approved by the FDA are being widely used for disk replacement applications [103]. The first artificial disk (DePuy Inc.), approved by the FDA in 2004, was based on a hard-on-soft technology, which employed a CoCrMo alloy in conjunction with UHMWPE. Alternatively, ProDisc-C (Eigure 19.3b,i), approved in 2006 and 2007 for both lumbar and cervical replacements, respectively, was based on similar types of polymer composites. More recently, Medtronic developed Bryan prosthesis using titanium alloys and PU polymer (Figure 19.3b,ii) [104]. 

In view with microelectrode arrays F. Blair Simmons in 1965 performed the first multichannel auditory prosthesis stimulation study with five stainless steel electrodes insulated with Formvar inserted into the auditory nerve (and not into the ST) and emerging out from cochlea [27]. In recent years the interest in alternative stiff electrodes, to be inserted directly into the auditory nerve, has revived. In research conducted at University of Michigan, a batch-fabricated cochlear electrode array with stacked layers of parylene and metal was fabricated by silicon micromachining techniques. The 32-site array contained IrO (Iridium Oxide) stimulation sites with a centre-to-centre site spacing of 250 pm [28]. In the following sections the stiff and flexible electrode designs from the Delft University of the Technology (TU Delft), The Netherlands are described with its micro-fabrication sequence done at The Delft Institute of Microsystems and Nanoelectronics (DIMES), TU Delft, The Netherlands. 

Thus it is apparent that while the user-prosthesis interface is a major impediment to the advancement of prosthetic technology, there is much room for improvement in the prosthetic components themselves. The limitations of current systems are not due to a lack of innovative design but rather are due to the very severe nature of the physical constraints that are placed on the designer and the inability of current technology to match the power and energy density of natural muscle. 

The basic configuration of Bowden cables in prostheses has changed little over the intervening years and is stiU in use today. In fact, if prehensile function is the primary goal of the prosthetic fitting, the device of choice for most persons with amputations is a body-powered, Bowden-cable-operated prosthesis with a split hook-shaped terminal device. This is in spite of all the technological advances in electronics, computers, and dc motor technology that have occurred since the end of World War H. 

Low technology does not imply wrong or bad technology. In fact, ease of maintenance, ease of repair in the event of failures in the field (one can use a piece of heavy cord to get by if the control cable should break), and the intuitive understanding of pulling on one end of the cable to effect motion at the other are probably major reasons for the success of Bowden cables in prosthetics. This is in addition to the ability of users to sense prosthesis state by the pull or feel of the control cable and harness on their skin. 

Battery technology, specifically rechargeable battery technology, is vital to portable electronic equipment and is driven by the billions of dollars spent by the laptop computer and cellular phone industries. The field of prosthetics and orthotics (P O) sits on the sidelines and picks up anything that looks like it could be of use. In an electrically powered prosthesis, the main current draw comes from the dc motor(s) used to actuate the device. In a dc motor, the output torque is directly proportional to the amount of current drawn. Motor use in prostheses is not continuous but is intermittent. Consequently, it is important not only to know how much energy a battery can provide but also how fast the battery can provide it. 

Two primary limitations of these modeling efforts involve the representation of tissue properties across the entire limb and the interface condition between the residual limb and prosthesis. The ability of current finite-element models to estimate prosthetic interface stresses, while performing reasonably well in some cases, has not been highly accurate. Nevertheless, the methodology has potential. Advances in finite-element software enabling nonlinear elastomeric formulations of bulk soft tissue, contact analysis, and dynamic analysis may help address some of the current model limitations. Corresponding advances in pressure-transducer technology will help validate the computer models and facilitate interpretation of the analyses. 

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