Subcutaneous injection and withdrawal site

An implantable fluid transfer device or septum which includes a hollow spherical housing containing a chamber therein for receiving fluid. A needle infuses fluid into or withdraws fluid from the chamber. The housing has a surface that is capable of both omni-directional penetration by the needle and sealing itself when the needle is withdrawn from the housing. A spherical needle stop is provided with the housing to prevent the needle that accesses the chamber from one side of the housing from passing through the opposite side of the housing.

FIELD OF THE INVENTION 
The present invention relates to an implantable fluid transfer device and 
more particularly to a subcutaneous injection and withdrawal site or 
septum that permits omni-directional access by a needle to an internal 
chamber for infusion or withdrawal of fluid. 
BACKGROUND OF THE INVENTION 
Prosthetic devices, generally known as tissue expanders, are implanted in 
the body to restore shapes and contours that have been surgically altered 
or accidentally deformed. These devices usually require periodic infusion 
or withdrawal of fluid to maintain or achieve the desired shape of the 
prosthesis or to vary the volume of fluid within the prosthesis for the 
purpose of establishing proper tension to the prosthesis. 
Rather than inject the fluid directly into a prosthesis it has been found 
beneficial to infuse the fluid into a fluid transfer device, occasionally 
referred to as a septum, which directs the fluid into the prosthesis. 
These transfer devices or septums, which facilitate the administration of 
fluid to an interconnected prosthesis are usually implanted below the skin 
in the vicinity of the prosthesis. Each device is typically connected to 
the prosthesis by a fill tube. 
One type of subcutaneously implanted septum includes a chamber with a dome 
shaped elastomeric cover and a rigid flat base. The cover provides a 
needle-penetrable member to infuse liquid into the chamber. A needle is 
directed through the patient's skin where it accesses the chamber through 
the cover. When the needle is withdrawn, the cover self-seals so as to 
prevent fluid leakage from the chamber. The rigid base acts as a needle 
stop so as to prevent the needle from penetrating entirely through the 
device and into the patient's body. It is highly desirable to have a 
septum with a chamber that is easy to access without fear of having the 
needle passing through the device. 
Occasionally, a septum will twist or even flip over after implantation in a 
patient. This happens especially in obese patients where the skin and 
tissue that surround the septum are somewhat soft and loose. The twisting 
occurs when torque is applied to the septum that exceeds the skin and 
tissue forces which hold the septum in its desired orientation. Known ways 
of reducing the undesirable movement of the septum include widening the 
flat base and suturing the septum in place. 
Once a septum has twisted, the fill chamber is no longer easily accessible 
by a needle since the dome is no longer easy to locate and penetrate. 
Furthermore, twisting of a septum connected to a prosthesis can kink the 
fill tube preventing fluid from being infused into or withdrawn from the 
prosthesis. 
It is an object of the present invention to provide a septum that is easily 
accessible for fluid infusion and for fluid withdrawal even when the 
septum has twisted within the patient. 
It is a further object of the present invention to provide a septum that 
has a substantial needle-penetrable surface area for its size so as to 
facilitate ease of needle accessibility to the fluid chamber. 
It is also an object to reduce the possibility of needle penetrating 
through the septum into the patient's body while facilitating ease of 
needle accessibility to the fluid chamber. 
It is also considered desirable to accomplish these objectives while 
reducing the possibility of kinking the fill tube connecting the septum to 
the prosthesis. 
SUMMARY OF THE INVENTION 
In accordance with these and other objects there is provided by the present 
invention an implantable fluid transfer device or septum that is adapted 
for attachment to an inflatable prosthesis. This device includes a hollow 
spherical housing containing a chamber therein for receiving fluid. The 
housing has a surface which is capable of penetration by a needle and 
which seals itself when the needle is withdrawn from the housing. Fluid is 
added to or removed from the chamber through the needle. A needle stop is 
provided within the housing which prevents the needle that accesses the 
chamber from penetrating through the opposite side of the housing and into 
the patient's body where it may cause pain or internal damage. 
Preferably, the needle stop is spherical in shape and slightly smaller than 
the housing so as to define a space between the housing and needle stop. 
It is within this space that the fluid is injected into or withdrawn from 
the chamber by the needle. The needle stop may be moved by the needle 
accessing the chamber so as to widen the space proximate to the needle 
tip. 
It is contemplated that fluid will be retained within the chamber and that 
the needle stop will float within the housing. This floatation will 
facilitate movement of the needle stop by the tip of the needle. 
The septum is connected to the inflatable prosthesis through a fluid flow 
means, preferably composed of tubing, that permits fluid to flow from the 
septum to the prosthesis during infusion, and from the prosthesis to the 
septum during withdrawal. The fluid flow means includes a connector that 
permits the septum to rotate relative to the prosthesis. An example of 
this arrangement is a flow mechanism that includes a length of tubing 
composed of two segments; a conduit extending from the septum and a fill 
tube from the prosthesis. The fill tube and conduit are connected by a 
connector that permits rotation of septum and conduit relative to the fill 
tube and prosthesis. Alternatively, the connector may be placed at the 
junction of the conduit and the septum. The connector allows the septum to 
rotate relative to the conduit and prosthesis. The ability of the septum 
to rotate cuts down on the possibility of kinking the tubing. 
The housing includes a portal through which the fluid outlets to the 
prosthesis and through which the fluid inlets the housing when withdrawn 
from the prosthesis. The housing may include an offset means composed of a 
circular array of projections extending from the inner housing wall about 
the portal so as to prevent the needle stop from blocking and sealing the 
portal. The projections keep the needle stop offset from the portal 
thereby permitting fluid to flow through the portal unimpeded by the 
needle-stop.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings wherein a fluid transfer device or septum is 
generally designated by the numeral 10. This septum includes a housing 12 
composed of an elastomeric material that is biocompatible with the human 
body. An acceptable and preferable material is a silicone elastomer. The 
housing 12 includes a spherical surface 14 that is capable of being 
penetrated by a needle 15 and sealing itself when the needle 15 is 
withdrawn. 
The housing 12 defines an inner chamber 16 for receiving fluid which is to 
be introduced or withdrawn from the chamber 16 through the needle 15 (FIG. 
3). The area of the spherical surface 14 and the volume of the chamber 16 
can be chosen according to the contemplated use of the septum 10. The 
spherical shape of the surface 14 provides a substantial target area for 
the needle to access the inner chamber 16. The septum 10 shown in FIG. 5 
is interconnected to an inflatable prosthesis or tissue expander 18. The 
septum 10 will permit infusion of a fluid into or withdrawal of a fluid 
from the prosthesis 18 so as to achieve the desired fluid volume. 
The housing 12 contains a needle stop member 20 which is impenetrable by a 
needle 15. The needle stop member 20 may be composed of such material as 
polycarbonate, polyethylene or the like. This needle stop member 20 is 
slightly smaller in size and spherical so as to be congruently shaped with 
respect to the housing 12. Shapes other then spherical will work as a 
needle stop but do not function as effectively in preventing the needle 15 
accessing the chamber 16 from passing through the other side of the 
housing 12 and into the patient's body. The needle stop member 20 helps to 
insure that the fluid added or withdrawn occurs within the chamber 16 of 
the device. The needle stop member 20 is shown as a solid but may be 
hollow and still properly accomplish its function. 
The housing 12 and needle stop member 20 define a space 22 therebetween. 
This space 22 is the site where the fluid is added or removed from the 
chamber 16. 
The needle stop 20 is constructed of a material that permits it to float 
within the chamber 16 when the chamber 16 contains a fluid. Accordingly, 
the needle stop 20 should be the same specific gravity or close to the 
specific gravity of the injected fluid to allow buoyancy behavior by the 
needle stop 20. Saline or a silicone based gel are typically used to 
inflate tissue expanders. 
Floating within the chamber 16 permits the spherical needle stop member 20 
to be moved or easily repositioned by the needle 15 accessing the chamber 
16 so as to increase or widen the space 22 in the vicinity of the needle 
15 tip. This space 22, when widened, facilitates the addition or removal 
of fluid from the chamber 16. 
The housing 12 includes a portal 23 through which the fluid outlets to the 
prosthesis 18 and through which the fluid inlets the housing 12 when 
withdrawn from the prosthesis 18. The housing 12 includes an offset means 
composed of a circular array of projections 24 extending from the inner 
housing wall 25 about the portal 23 so as to prevent the needle stop 
member 20 from blocking and sealing the portal 23. The projections 24 keep 
the needle stop member 20 offset from the portal 23 thereby permitting 
fluid to flow through the portal 23 unimpeded by the needle-stop member 
20. 
The septum 10 shown in FIG. 5 communicates with an inflatable prosthesis 
18. In FIG. 6 the septum 10 is attached to a catheter 26 having a conical 
dispensing tip 27. The septum 10 and catheter 26 act as a medication 
infusion system with the fluid chamber 16 communicating through the 
catheter tip 27 into a blood vessel or organ of the human body instead of 
a prosthesis. 
The chamber 16 is interconnected by a fluid flow means generally designated 
by the numeral 28 to an inflatable prosthesis or tissue expander 18. The 
flow means includes an access tube or conduit 30 and a fill tube 32. The 
conduit 30 shown is integrally molded with the spherical housing 12. The 
conduit 30 is connected to the fill tube 32 by a connecting means. The 
connecting means is a connector 34 that permits flow therethrough but 
permits the housing 12 to rotate relative to the fill tube 32 and to the 
prosthesis 18. Consequently, the septum 10 which provides a spherical 
surface 14 as an injection site may turn or rotate within the patient's 
body without cutting down on the surface area targeted by the needle 15 
for injection. FIG. 4 shows a septum 10 having a spherical housing 12 that 
is elliptical instead of circular.