The practice of neurostimulation has been used for more than 50 years to treat the symptoms of a wide variety of diseases, including chronic pain, epilepsy, and bladder dysfunction. The technologies used act directly upon nerves and work by sending mild electrical impulses via insulated leads to targeted areas of the spinal cord, the nerves, or brain, to block the transmission of signals. The technological improvements in this area have led the medical community to turn to experienced medical device manufacturers for new and improved solutions.
 
Implantable neurostimulation technologies typically involve three hardware components:
 

• A lead—surgically implanted, special insulated wires with an electrode at the tip that delivers mild electrical pulses to the affected area.
• Extension wires—wires that connect the electrodes to the neurostimulator.
• A neurostimulator, or pulse generator—a small robust electronic device similar to a cardiac pacemaker. The neurostimulator is typically implanted under the skin in a variety of places depending on the patient’s ailment.

 
One of the key components in many neurostimulation systems that has not seen a great deal of innovation is the lead interface located between the implantable lead and the neurostimulator. In addition, the use of external pulse generators, or so-called “trial” neurostimulator units, that create challenges in interaction with traditional lead interface technology has been introduced. For these reasons, development costs and time to market of neurostimulation devices can become unnecessarily high.
 
The traditional approach of lead interface design in neuromodulation devices uses complex leaf-springs or fixed pad methods, which often require precision alignment techniques to manufacture and add significant process development time to the development schedule. Other drawbacks to traditional lead interface designs include higher lead insertion force, higher electrode contact resistance, and lower robustness during insertion and removal cycling, which create clinical challenges for both the surgeon and the user. Because of the proprietary nature of the leads used by different neurostimulator manufacturers, the lead interface often needs to be redesigned with every product, a costly and time-consuming design and manufacturing roadblock to bringing a new system to market.
 
To overcome the challenges of the traditional approach, medical hardware manufacturers must consider a new design method. One such solution is an innovative, novel lead interface design, which utilizes spherical ball contacts that replace the complex and expensive leaf spring or fixed pad methods. This design approach allows the lead interface to be dynamic and unfixed, which makes a variety of design constraints more achievable, including:
 

• Low lead insertion force
• Low electrode contact resistance
• Corrosion, thermal and humidity resilience
• Robustness during insertion and removal cycling
• Drop and vibration resilience

 
The ball contact method allows medical device OEMs to cut development times down consistently because they aren’t required to utilize expensive and limited manufacturing processes such as laser welding or other high precision techniques. Such a design can easily be configured for multiple lead types and shapes while allowing a consistent manufacturing approach. And due to this configurability, clinically important parameters can be designed for, allowing ease of setup by the surgeon.
 
As innovation in neuromodulation continues to expand the capabilities of neurostimulation technology, medical device manufacturers will be incentivized to optimize the lead interface designs they use in their new products. A change to what seems like a minor sub-assembly can make an immense difference in the product’s reliability and can save manufacturers significant time and money bringing their product to market.
 

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Matt Hedlund works as a senior applications engineer within the Engineering Services & Solutions Sales team serving as a technical resource for the business development team. A biomedical engineer and physiologist by training, Hedlund has working industry experience in cardiac rhythm management and neuromodulation technologies from both the research and manufacturing perspectives. Originally from Minneapolis/St. Paul, Hedlund now resides in Seattle, Washington where he supports teams in both engineering and manufacturing services.