Septum locating apparatus

#This invention relates to apparatus for accurately locating the septum through which the fluid reservoir of an implanted prosthetic device may be refilled subcutaneously.

#Relatively recently, implantable prosthetic devices in the nature of infusate pumps have been developed for dispensing infusates such as insulin at a very low flow rate to a selected location in the human body over the long term. Eventually the fluid reservoir in such a device empties so that, if the device is to continue performing its function, its reservoir must be refilled with a fresh supply of infusate. To avoid having to operate on a patient to remove the implanted device each time it is necessary to refill it, the device is designed with a penetrable self-sealing septum in a wall of the device which normally seals a passage leading to the device's reservoir.

#With the pump or other device implanted in the patient's body so that the septum underlies the skin, its reservoir can be refilled, as needed, simply by injecting a fresh supply of infusate by means of a hypodermic needle through the patient's skin, through the septum and into the infusate reservoir or chamber inside the device. In some cases, the act of refilling the device also recharges its power supply so that the unit can operate uninterruptedly for a prolonged period. Implantable pumps of this general type are disclosed, for example, in U.S. Pat. No. 3,731,681 and 3,951,147.

#For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which:

#FIG. 1 is a perspective view with parts cut away showing the subject septum locating apparatus in conjunction with an implanted infusate pump;

#FIG. 1A is a fragmentary sectional view showing a portion of the FIG. 1 apparatus and implanted pump in greater detail;

#Turning now to FIG. 1 of the drawings, the subject septum locating apparatus is designed to facilitate locating the septum S of an implantable prosthetic device such as an infusate pump P implanted in a patient's body such that the septum S is located directly under the patient's skin layers T. The locating apparatus includes an energy pattern source indicated generally at 10 which is mounted in the implanted pump P. Source 10 is juxtaposed relative to septum S so that the source's radiation pattern emanates from the patient's body and is shaped or configured so that it indicates the location of the septum.

#The locating apparatus also includes an extracorporeal hand-held detector shown generally at 12 having a reticle 14. The detector has one or more components which are responsive to the energy pattern emanating from source 10 so as to indicate the lateral deviation of the reticle from the center line of the septum. By manipulating the detector following these indications, the physician can easily center the reticle directly above the septum and mark the target point on the patient's body. Then he can inject the infusate injection apparatus through that mark with assurance that it will penetrate the underlying septum S and be positioned properly in the charging station C of pump P (FIG. 1A).

#In the apparatus embodiment illustrated in FIGS. 1 and 1A, the source 10 comprises an annular permanent magnet 15 mounted in a recess 16 in the underside of the pump wall P'. Magnet 15 is preferably a sintered rare earth magnet that is polarized in the axial direction as indicated in FIG. 1A. Thus it produces a strong toroidal magnetic field shown in dotted lines at M in that figure whose flux lines extend an appreciable distance out from the surface of the patient's body.