Bearings in Implantable Medical Devices

Implantable medical devices have revolutionized the field of healthcare, providing advanced solutions for treating serious medical conditions. One crucial development has been the integration of specialized bearings providing reliable smooth operation. Leading bearing manufacturing companies like Myonic, NHBB, Barden, Timken, SKF, Schaeffler Group and NMB have led the revolution in the development of medical bearings.

Bearings in implantable medical devices require biocompatibility, longevity, and performance. 

This article looks at  the different types of bearings, bearing material, designs, and other key performance considerations for both standard and implantable medical devices.

To deal with the caustic issues bearings encounter in the human body manufacturers have turned to special materials like Cronidur® 30 Stainless Steel.

Cronidur®30 is a stainless martensitic steel, having greater corrosion resistance than 440C, and is longer wearing. Aside from enormous success in medical applications Cronidur is finding uses in aviation, Nascar racing engines and numerous industrial applications.  

Why is Cronidur®30 so successful in medical applications?  It is primarily due to its superior corrosion resistance, higher than 1.2083, 1.4112,1.4301, 1.4571. Cronidur has excellent machinability, high dimensional stability after heat treatment, excellent grinding and polishing to obtain optimal surface quality. Also due its high durability and maximum hardness it is useful in both static and dynamic situations.

Miniature bearings are used in all types of medical devices including implantable ones and some of the key applications include micro-blood pumps, surgical power tools, robot-assisted surgery, prosthesis and exoskeleton, respirators, analysis equipment, turbine and contra-angle handpieces, and handpieces for implantology and facial surgery.

Micro-Blood Pumps

Hospitals are now performing life saving heart surgeries employing the use of tiny ball bearings incorporated into implantable devices. Highly customized miniature bearings are important elements used in micro-blood pumps. Micro blood pumps are often compared to heart-lung machines but much less burdensome for the patient. Leading Bearing manufacturers like Myonic and NMB have developed specialized small bearings for exclusive use in medical device components.

Surgical Power Tools and Robot-Assisted Surgery

In certain medical applications like brain and eye surgeries the doctor must rely on the precision of the machine . Precision ball bearings are relied upon in these applications and are designed to hold a patient’s head perfectly still and in position during surgery.

Robot Assist Bearings

Dental Applications 

A dental bearing must be able to withstand the most extreme conditions and at the same time is one of the most decisive components for the performance of a dental instrument. To consistently improve this performance, an individual solution must always be sought and implemented consistently.

For decades, Myonic has supplied customers worldwide with its innovative and reliable dental bearings and has earned itself an exceptional market position.

Rotational speeds of up to 500,000 rpm, vibrations, superheated steam or different cleaning media as well as penetrating soiling such as blood and tooth dust are the biggest challenges for such special ball bearings.

Aside from the individual design, these challenges are met with a systematic selection of materials and lubricants.

The result is a product that is custom-tailored for this application and that meets all requirements over a long period. Challenge us! Our developers are looking for new, difficult problems to solve.

Prostheses and Exoskeletons

Myonic, NMB and other manufacturers offer specialized high precision ball bearings for use in prostheses and exoskeletons to help patients move comfortably again. Highly toleranced and precise bearings meeting the highest ABEC standard are often specified for use in prosthesis and exoskeletons.

Respirators

Myonic Bearing and NMB Bearing specialize in small ball bearings used in respirators. Quiet running , high precision, anti-corrosive features make for this life saving  device’s reliable operation. 

Scientific and Analytic Medical Equipment

Ball bearings are widely used also in medical laboratories. For handling and processing samples bearings must perform to exacting standards. Manufacturers like SKF, NMB and others provide the highest quality and precision required in scientific and analytic devices. 

Types of Bearings in Implantable Devices

Pacific International works with the best bearing manufacturers like SKF, NMB, Myonic, Schaeffler Group, FAG, INA, and TPI. These are the very best manufacturers who design ball bearings especially for the high standards required in medical applications.

Medical applications often mean bearings come in contact with blood, caustic cleaning agents, high pressure steam sterilization and other bodily fluids. Bearings must be manufactured from materials like Cronidur30, and ceramics to overcome some of these challenges .

Ball bearing manufacturers supplying medical applications will employ some or all of the following features to achieve the best operating bearings.

Bearing Features required in implantable medical and other medical devices:

• NSF-certified cage materials and lubricants (e.g. H1/H2)
• Corrosion resistant ring- and ball steels
• Ceramics ideally suited for healthcare applications
• Media resistant shields and seals
• Biocompatible lubricants according to DIN EN ISO 10993

Implantable medical devices will use several types of bearings to facilitate motion within the device. Each type has its own merits and considerations, based on the specific application and requirements. Contact us at [email protected] for assistance in the type of bearing most suitable for your medical application. 

Dimensional Specifications

In implantable devices like pacemakers and cochlear implants, bearings are typically micro-sized, with diameters often ranging between 1mm and 5mm. The reduced size ensures the devices are compact enough for implantation, but this small scale introduces challenges in manufacturing precision. Standard tolerances for these micro-bearings fall within ±0.001 mm to ensure consistent rotational performance.

Material Selection and Properties

As I have discussed, bearings used in medical applications can make great use of Cronidur 30.  

Other materials used for medical bearings need to exhibit a high degree of biocompatibility. 

Medical grade titanium (Ti6Al4V) and stainless steel (316L) are commonly used due to their corrosion resistance in physiological environments, characterized by a pH level of approximately 7.4 and a chloride ion concentration of 0.15 mol/L. Ceramics, such as zirconia (ZrO2) and alumina (Al2O3), have also been employed due to their wear resistance and reduced friction coefficients, typically in the range of 0.2-0.3 in unlubricated conditions.

Lubrication Considerations

Unlike conventional applications, implantable devices can’t undergo regular maintenance. Therefore, the initial lubrication needs to remain effective throughout the device’s operational lifespan, often exceeding 10 years. Self-lubricating materials, such as polytetrafluoroethylene (PTFE) coatings, can reduce the coefficient of friction to as low as 0.05, enhancing the wear lifespan of the bearing components.

Manufacturing and Quality Control

The manufacture of medical bearings for implantable applications requires stringent quality control. Surface roughness values (Ra) are typically kept below 0.05 µm to minimize wear. Advanced manufacturing techniques, such as electrical discharge machining (EDM) and laser micro-machining, are commonly employed to achieve these tolerances. Each bearing undergoes rigorous testing, often using methods like X-ray diffraction and electron microscopy, to verify structural integrity and material homogeneity.

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