Resistance to wear, inherent stability and excellent electrical properties make ceramic an ideal material for a wide range of medial applications from implants to surgical tools.
New Production Methods Increase Application of Ceramics in Medical Applications
New developments in production methods promise to bring the proven bio-compatibility and long term durability benefits of ceramic materials to an increasingly wide range of medical applications. Now, driven by the industry’s need for ever smaller yet more complex components, materials scientists are extending their benefits to new medical applications by the use of innovative processing techniques including injection moulding, engineered coatings and ceramic-metal assemblies. The results include artificial joints, biosensor components and implantable devices.
Advanced Materials and Processing for Medical Devices
This article from world leaders Morgan Technical Ceramics discusses recent advances in ceramic materials science and production techniques and the benefits they offer for medical applications. It looks at some of the latest developments in ceramics processing and manufacturing and gives examples of the ways in which this work is helping move the boundaries for capability and cost-efficiency in the manufacture of medical devices.
The use of ceramic components in surgery began in the 1970’s with the introduction of first generation alumina products for joint replacement, when ceramic’s superior resistance to wear in comparison to more traditional metal and polyethylene materials became apparent. Advances in material quality and processing techniques and a better understanding of ceramic design led to the introduction of second generation alumina components in the 1980’s that offered even better performance than early systems.
Ceramic-on-Ceramic Implant Systems
More recently, ‘ceramic-on-ceramic’ systems have been developed to eliminate the problems associated with polyethylene and metal. Such systems have by far the lowest wear rate of all available bearing couple technologies available today. These systems have grown in popularity in Europe over the past five years or so and a milestone was reached in 2003 when the Federal Drugs Agency (FDA) gave their clearance for use in the USA. Because of the better wear properties of ceramic-on-ceramic, such systems are ideally suited for the younger and more active patients. The international golfer Jack Nicklaus famously has a replacement ceramic hip.
Bone Growth Stimulation
Building on the known benefits of ceramic as a material for bio-implants, manufacturers are now producing much smaller, more complex parts for implants, most notably hearing-assist devices, bone screws and implantable heart pumps.
Ceramic Feed-Thru for Internal Bone Growth Stimulators
For example, our Morgan Advanced Ceramic’ Alberox Products Division has recently developed a custom-designed ceramic feed-thru for use in an internal bone growth stimulator. Bone stimulators are used as a supplemental form of therapy to help enhance the body’s bone-healing process. They emit low electrical currents, similar to those created naturally by broken bone, helping stimulate growth and create successful fusion.
The internal bone growth stimulators are typically implanted in a soft pocket of tissue under the skin, and can remain there for up to twelve months. Using an innovative ceramic-to-metal seal assembly rather than traditional glass seals, the hermetic feed-thrus have a stronger bond and therefore reduce the possibility of revision surgery. The size of the implant is reduced too, as the alumina ceramic offers superior electrical properties.
Ceramics in Surgery
Surgical procedures are becoming more intricate, creating a need for smaller, more precise instrumentation. This is borne out by the increase in minimally invasive surgery (MIS) in areas including hernia, ulcer repairs and even complete hip replacement. Less invasive procedures mean patients recover more quickly, which is good for the patient and more cost-effective for the hospital.
Ceramic Injection Moulding Produces Small High Precision Implants
Injection moulding of ceramic allows production of small, high-precision instruments.
These strong and complex shapes - the hinge joints on powered hand tools for example - allow smaller designs. Traditional machining of ceramics would be more time consuming and expensive, and may not allow all the same features as ceramic injection moulding.
Ceramics in Surgical Cutting
In another development, ceramic is used as a high power transmitter of high frequency waves to assist with surgical cutting and is used in applications such as cataract removal. Piezoceramic components are sandwiched between a horn and rear mass, for example in an ultrasonic scalpel the intense vibration allows the surgeon to cut with less force to achieve less tissue damage as well as coagulating at the same time as cutting.
Piezo-electric sensors measure mechanical quantities such as force, acceleration or pressure by producing an electrical output when they experience a change in load. Alternatively when a pulsed electrical field is applied to the material it expands and contracts and in doing so sends out an acoustic pulse. When this occurs at a high frequency the ceramic vibrates, transmitting an ultrasonic signal. The signal then rebounds off tissue and is received by another piezoelectric ceramic which converts the ultrasonic pulses back into an electrical signal to generate the image. In this way it is used as internal and external ultrasonic sensors.
Piezo Ceramics in Blood Flow Measurement Sensors
For example Deltex Medical has opted for piezo ceramic on its oesophageal doppler probes. These are used in conjunction with a CardioQ haemodynamic status monitor to determine the circulative volume of blood in the patient’s body during an operation.
The ultrasonic signal from the piezo ceramic is used in a time of flight measurement to monitor the blood flow in the descending aorta. The ceramic is fixed on the end of the probe and inserted into the patient’s oesophagus so the measurement can be taken. The results are displayed on the CardioQ display.
Ceramics in Medication Infusion Pumps
Similarly, Debiotech has chosen ceramic for its miniature, lightweight IV Exprés infusion pump made used to dispense medication and fluids, such as morphine and nutrition, into a patient’s circulatory system.
A key safety feature of the pump is an ‘air-in-line’ detection system, which uses a piezoceramic sensor to monitor for the presence of air bubbles in the fluid, in order to prevent air embolisms that can lead to serious complications in blood flow and the heart’s operation.
Two pieces of piezo ceramic tuned to the same frequency are used together as a transmitter / receiver pair. If there is fluid in the line between the sensors then a signal is received, but when air is present the signal is reduced and the pump automatically stops infusion.
Morgan Technical Ceramics has nearly 20 years clinical history of development of ceramic joints using HIP Vitox® alumina and Zyranox® zirconia materials, and has amassed considerable specialist technical knowledge on the subject during this period. The company’s flexible manufacturing process is well suited to this development; it is currently involved in a number of next generation orthopaedic development projects.
Over the last 20 years, ceramic materials have been refined and there is now a range of ceramic and engineered solutions optimised for medical applications including surgical tooling, ultrasound and implants. Now, manufacturers of ceramic materials are concentrating their efforts on development of manufacturing processes to address specific medical needs.
As a result of this research and development by industry leaders such as Morgan Technical Ceramics, medical device manufacturers, doctors and their patients are all benefiting from the ability to precision engineer very high reliability components in commercial quantities.