Sensor Provides Control for Noninvasive Disc Procedure

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Sensor Provides Control for Noninvasive Disc Procedure

Shana Leonard

Surgical options to treat Degenerative Disc Disease-the erosion of invertebral discs-are relatively limited. Operations such as spinal fusions can be very painful and require a lengthy recovery period. However, a minimally invasive procedure that employs sensor technology may alleviate pain without the discomfort of major surgery.

The MTS Systems Corp., Sensors Div. (Cary, NC) C-series linear sensor was incorporated into a surgical tool to ensure controlled release of essential elements. The Dascor disc arthroplasty system provides patient relief by removing the damaged nucleus of an invertebral disc and replacing it with an artificial one.

In order to do this, a minor incision is made in the outer rim of the disc and the damaged nucleus is extracted. Then, a two-part curable polymer is injected into the disc and bonds with an expandable polyurethane balloon to form a faux nucleus. The implant restores the disc to a healthy position and serves to minimize back pain.

However, early iterations of the system delivered the two-part polymer to the disc site pneumatically. Surgeons were concerned with the difficulty of controlling the amount of polymer injected into the disc. The integration of the MTS Temposonics sensor into a reconfigured microprocessor-based unit enabled controlled dispensation of the polymer. The revamped surgical tool design depends on sensor monitoring of a ball screw driven by a brushless motor for measured release of the polymer.

"Temposonics was chosen because of its no-wear nature, no drift-over-time, no required calibration, and ease of connection to the mechanical system," says MTS Temposonics commercial product marketing manager Jesse Russell.

In addition to its application in a minimally invasive surgical tool, the Temposonics sensor also boasts the claim of smallest magnetostrictive sensor available. At 36 mm, the product measures 45% smaller than its predecessors, according to the company. "Its small size, enhanced sensitivity, and automatic-adjustment features make it ideal for this application," Russell says.

Other features include a 4-mm shaft diam, an 18-mm dead zone, and a 21-mm null zone. The sensor has a repeatability of ±25 µm and an operating temperature ranging from -40° to 75°C.

Additional medical applications for the sensor include its use in medical beds, grippers, filling mechanisms, and dispensing tools. The Dascor disc arthroplasty system has been approved for use in Europe and is currently undergoing U.S. clinical trials.

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