Development of a Retrievable Implantable Anchor for Dorsal Root Ganglion Stimulation
Date Issued
2015
Date
2015
Author(s)
Chen, Bo-An
Abstract
Statistics have shown that more and more people suffered from chronic neurological disorders, such as Parkinson’s disease, epilepsy, rheumatoid arthritis, and other pain caused by dysfunction of nerves. Since neuropathic pain is caused by damage of somatosensory nervous system and seldom cured via pharmacological treatment, patients have to look for other therapies. Electrical stimulation on specific nerves has been proven therapeutic in several chronic disorders. However, stimulation therapy on sufferers of chronic diseases is not once and for all. Discomforts will come back just in a period of time. To avoid the injury caused by stimulation surgeries repeatedly, permanently implantable medical electrical stimulation systems are usually used in sufferers. Dorsal root ganglion (DRG) is an important neuronal structure lying along the vertebral column by the spine. DRG can influence both somatic and visceral activities, and contains the primary sensory neurons that represent the key flow of sensory information, including the feelings of pain. As a result, stimulating specific DRG can relieve chronic pain condition caused by spinal injuries. Though DRG which consists of cell bodies along the dorsal roots of spinal nerves is a convenient target for stimulation because of its expectable location disposed external to the epidural space, the weak fixation ability makes it difficult to stimulate fluently. To overcome this predicament, a three-dimensional anchor is devised to provide fixation mechanism for the stimulation system. A permanently implantable stimulation system comprises a stimulating lead, an implantable pulse generator (IPG), and an external controller for patients. The designed anchor is attached to the tip of the lead, inhibiting the unexpected movement and dislodgement of the electrodes. The umbrella-like anchor is made of polyetheretherketone (PEEK), a kind of biocompatible polymer with strong mechanical properties. The dimensions of the anchor must be small enough to be suitable for minimally invasive surgery. The beams on the anchor are initially folded inward alongside the lead while fitted into and constraint by the lumen of an introducer implanted by surgeons. After inserting out of the introducer, the beams then spread out, transforming back to their original state to stick in subcutaneous tissues. The lead is consequently positioned and fixed in muscle tissues near the target DRG. Furthermore, the anchor also possesses the ability to be retreated back form the tissues once the dysfunction of stimulation occurs. In this thesis, umbrella-like anchor has been proven its advantages of fixation mechanism over prior permanently implantable medical electrical stimulation systems. In-vitro experiment is conducted, in which a lead with an anchor is delivered into gelatin and pork spine respectively to simulate the real situation of implantation. The results show that the anchor provides great fixation ability than normal lead. In the future, the anchor will be developed to combine with DRG stimulation systems adequate for minimally invasive surgery. The lead can be implanted near DRG through straight paths instead of complicated routes across the spinal vertebra, making it conveniently performed by the doctors and reducing the damage caused by the implanting surgery at the same time.
Subjects
chronic neurological disorders
implantable stimulation system
dorsal root ganglion
anchor
minimally invasive surgery
fixation mechanism
Type
thesis
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