Expandable fixation mechanism

Abstract

In general, the invention is directed to a medical device implantable in a body of a patient. The device includes a housing with a plurality of collapsible fixation structures coupled to the housing, and can be in a collapsed configuration or an expanded configuration. The device assumes a collapsed configuration when in the bore of an insertion device, and assumes the expanded configuration when expelled from the insertion device into the body of the patient. The extended fixation structures engage the tissues in the body and restrict migration. One exemplary application of the invention is in the context of a microstimulator, with a pulse generator housed in the housing and one or more electrodes coupled to the housing. The fixation structures help keep the electrodes proximate to the tissues that are to receive the stimulation.

1 . A system comprising:
 an elongated element configured to be coupled to a medical device to deliver a therapy from the medical device to target tissue in a patient; and   a plurality of hydrogel fixation structures extending from the elongated element and configured to expand from a dehydrated state to a hydrated state, wherein in the hydrated state, at least two of the hydrogel fixation structures radially extend from the elongated element in different directions.   
     
     
         2 . The system of  claim 1 , wherein in the hydrated state, each of the hydrogel fixation structures extends from the elongated element at an acute angle with respect to a longitudinal axis of the elongated element. 
     
     
         3 . The system of  claim 1 , wherein in the hydrated state, each of the hydrogel fixation structures extends substantially orthogonally from a longitudinal axis of the elongated element. 
     
     
         4 . The system of  claim 1 , wherein the elongated element comprises a lead comprising an electrode. 
     
     
         5 . The system of  claim 4 , further comprising the medical device, wherein the medical device is configured to deliver electrical stimulation to the target tissue via the electrode. 
     
     
         6 . The system of  claim 4 , further comprising the medical device, wherein the medical device is configured to sense a parameter of a patient via the electrode. 
     
     
         7 . The system of  claim 6 , wherein the parameter comprises at least one of blood pressure, temperature or electrical activity of the patient. 
     
     
         8 . The system of  claim 1 , wherein the elongated element comprises a catheter. 
     
     
         9 . The system of  claim 8 , further comprising the medical device, wherein the medical device comprises a drug delivery pump configured to deliver a drug to the target tissue via the catheter. 
     
     
         10 . The system of  claim 1 , wherein each of the plurality of hydrogel fixation structures defines at least one of a tine, a spur, a flange or a rib in the hydrated state. 
     
     
         11 . The system of  claim 1 , further comprising a sleeve sized to fit over a portion of the elongated element, wherein at least one of the hydrogel fixation structures is attached to the sleeve. 
     
     
         12 . The system of  claim 1 , wherein the plurality of hydrogel fixation structures comprises a first hydrogel fixation structure and a second hydrogel fixation structure axially displaced from the first hydrogel fixation structure. 
     
     
         13 . A method comprising:
 implanting a medical system in a patient, the medical system comprising:
 an elongated element being configured to be coupled to a medical device to deliver a therapy from the medical device to target tissue in a patient; and 
 a plurality of hydrogel fixation structures extending from the elongated element and configured to expand from a dehydrated state to a hydrated state, wherein in the hydrated state, at least two of the hydrogel fixation structures radially extend from the elongated element in different directions. 
   
     
     
         14 . The method of  claim 13 , further comprising:
 implanting the medical device in the patient; and   coupling the medical device and the elongated element.