Development of a Diagnostic Method for Spinal Fusion, 10-9177

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Principal Investigators
Susan W. Zogbi
Larry D. Canady
Jerome A. Helffrich

Inclusive Dates: 01/01/00 - 12/31/00

Background - The current practice of spinal fusion surgery is being impeded by the inability to determine objectively if the fusion surgery was successful. Today’s diagnostic methods for fusion assessment include flexion-extension radiographs to measure relative motion and computed tomography (CT) scans to measure bony ingrowth, both of which have proven to be unreliable and time consuming.

Approach - The objective of this project was to develop a noninvasive prototype that incorporates available sensor technology to diagnose spinal fusion, postoperatively, by measuring the changes in separation of the vertebrae involved in the fusion. Changes in the sensor response can be correlated to an assessment of motion between vertebrae and, in the future, success of the surgical fusion.

Accomplishments - A product requirement and specification document for a spinal fusion diagnostic method was prepared after consultation with a spine surgeon. The document contains a list of device features, capabilities, and functions that describes the overall clinical requirements for the product. This document was used to drive development of the method to satisfy the product requirements and to test the method with respect to the product requirements.

The method incorporates implantable passive sensor technology and an external interrogator to diagnose spinal fusion, postoperatively, by measuring the changes in separation of the vertebrae. The changes in the response of the sensor(s) measured externally can be correlated to the relative motion of the vertebrae, enabling an assessment of the success of the surgical fusion. The system consists of sensors attached to each vertebrae involved in the spinal fusion or on each end of the spinal fusion segment. Implantation would occur at the time of surgery. During postoperative visits, the physician would be able to monitor successful fusion attainment without radiographic flexion/extension X-rays, CT scans, or unnecessary followup surgeries. This monitoring could be accomplished by measuring the sensor response with an external interrogator device at the physician's office. Information from this interrogator would then be processed to determine the relative distance between the sensors, and, ultimately, the vertebrae. With accurate fusion information, the physician can give a differential diagnosis to patients returning with pain or could prescribe a more aggressive rehabilitation program that provides a faster recovery time. 

The implantable sensor is shown attached to the spinous process of the human lumbar spine model. A sheath covers the sensor to make the implantable biocompatible and to insulate the sensor against body fluids.

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