Engineering 101

Cable and connector technology for spinal pain relief

Living with chronic neuropathic pain as a result of an accident or aging that includes nerve damage can become a constant battle in our daily lives. Modern solutions include the installation of electrical signal pain modulations that help mask some of the pain signals.

Patients with nerve damage can experience physical symptoms ranging from paresthesia (a tingling and burning sensation like pins and needles) to extreme soreness and aching that limits mobility. The constant aching affects the patient’s emotions and attitudes that can wear the patient down and seriously destroy their quality of life.

Attending physicians will often follow a number of steps to reduce the effects of the pain. The first step can include physical therapy and/or taking anti-inflammatory drugs. If the pain continues to be an issue, the patient is sometimes directed to try heat and/or electrical stimulation, including dry needling or use of TENs (transcutaneous electrical nerve stimulation).

This can be assisted by use of opioids and/or injected nerve blocks. In some cases, problems can evolve with chemical addictions and/or side effects from the consumption of the drugs. If chronic pain persists, surgery can be considered when appropriate, but very often, spinal cord stimulation (SCS) is a safer and easier solution. Spinal modulation is accomplished by installing an electro-stimulation (signal vibrator) system that actively modulates the pain signals that are being sent to the brain.

Successful spinal modulation procedures follow a carefully worked out method of finding and defining exactly where the pain signals are being generated, testing various modulating signals to find the best frequency to reduce the pain effect, and then finally installing a more permanent system the patient can wear for very long periods and receive relief from the pain in their spinal column.

Medical grade cable and connectors are designed to interface directly with the implantable pain management stimulation system. Support for the first step in defining the patient service includes specialty cable that are fabricated for the external trial simulators that are worn outside the body for two to four weeks.

The cable quality used in the trial pain therapy process is critical in enabling the patient to live as normal a life as possible. The cable should provide comfort and endure high portability. Cable will be made as small in diameter as possible to carry the signals, remain limp and flexible, and retain a natural tactile feel to the patient.

Cable bend radius is tested and assured to meet the application of daily wear and tear. The exterior of the cable and connector will be made with medical grade materials that can be disinfected. Connectors will be made to match the modulation tool system and/or have a docking station within the modulation tool and be easily connected and disconnected when needed.

Overmolded circular connector shells match the shape and feel of the smaller and flexible cable being used for the modulation tools. Strain relief designs assist the assembly as well as maintain connector closure during patient movements. Connector pin to socket assemblies include BeCu (beryllium copper) spring pin to solid circular receptacles to assure constant mated conditions, even during high shock and vibration that may occur to the patient when riding in vehicles, running, or the rigors of daily life.

During the spinal modulation trial period, the patient can vary settings on their temporary modulator. This allows the patient to tell the surgeon exactly where and what modulation appears to help them the most. In a number of cases, trials are done many times to define the final spinal cord catheter position and settings. The surgeon will finally implant a signal vibrator in the key area that can reduce signal pain to the brain.

This is most often placed near the dorsal root ganglia (DRG) along the spinal column. This sensory neural structure in the epidural space is a collection of many of the nerve cells gathered together to send signals and commands to the brain. When chronic pain exists, the cell groups become over activated and send somewhat exaggerated signals to the brain in somewhat continuous waves. The introduced signal transmitter is set to the best signal setting determined by the two to three week test procedure that the patient wore earlier.

These modulating electrical signals seem to soothe and quiet the active ganglia cells in the DRG and reduce feelings of pain during normal daily life. A big advantage of placing the transducer in the DRG area is that it is also less position sensitive. This reduces the chance of erroneous signals being conducted by spinal fluids in the main spinal channel. Multiple sensor leads can be placed along the spine and routed to the implanted device.

Cable quality and assembly of the remote modulation trial assembly is a key part of the medical treatment for chronic pain management. Clean room assembly and test certification to medical grade electronics is necessary to serve this ever evolving industry.

Source Omnetics

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