S P E C I F I C A T I O N
TITLE:
'BALLOON JACK"
FIELD OF THE INVENTION This utility application claims domestic priority from U.S. Provisional
Application Serial No. 60/085,896, filed May 18, 1998.
BACKGROUND OF THE INVENTION
This invention relates generally to separators for approximated bones,
and more specifically relates to intervertebral body separators. The invention also
relates to surgical procedures associated with the introduction of the balloon j ack
and the manner in which it is configured to relate to the surfaces upon which the
jack will act.
The distraction or separation of vertebral bodies on either side of the disc
space is undertaken to facilitate a surgical procedure between the two bones which
is best undertaken when the space is enlarged. This applies also to other joints.
Mechanical means of separating bones, in particular the vertebral bodies, usually
utilizes firm, usually metal, surfaces which apply a mechanical load to the
engaged bony surfaces, which in turn facilitates the separation of the two
interposed surfaces. Often times, however, the surface upon which the
mechanical force is exerted is small, and frequently the bone surfaces not
configured to the form of the metallic surface acting on it. Consequently, as the distractor force is increased, mechanical disruption of the bony surface occurs
leading to uneven and compromised bone surfaces. This becomes especially important during implant procedures wherein the maintenance of the integrity of
the bone surface is essential to the proper performance of the functional implant device to be inserted.
In the past, Cloward and Smith-Robinson popularized anterior surgical spinal approaches, and, more recently, Ray and others have developed means to
distract the intervertebral disc spaces mechanically for the insertion of bone grafts,
fusion cages, hydrogel nuclei replacement, etcetera. In every instance, mechanical
devices have been utilized, including metallic spreaders, metallic shims, wedges,
and, in the case of Kaspar, distracters attached to posts inserted in the
approximating bone. In every instance, bone damage on the surface or in the
softer central portion of the bone itself may result if the distraction force on a
relatively small area exceeds the inherent strength of the bone at that area.
It is the primary aim of the present invention to provide a means of
distraction which will exert the forces required for such distraction over a larger
surface, and in a manner wherein that force can be configured, during the period
of distraction, to mate with the bone surface area.
It is another object to maintain such distraction, once the desired degree of distraction has been achieved without loss of separation over time.
It is another object to be able to introduce the means of distraction, i.e.,
the balloon, through a very small opening, to inflate it to a much larger size than
the entry port, and to remove it through the same small opening without
compromising surrounding tissue.
It is yet another object to achieve the pressures within the balloon
necessary to fulfill the goal of distraction and have a means of determining what
such pressures are at any given time and, thereby, to limit excessive pressures
which might cause either failure of the balloon or deformation of the bony surface
upon which it is acting.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.
Throughout the drawings, like reference numerals refer to like parts.
SUMMARY OF THE INVENTION
To accomplish these objects, the invention compromises an inflatable
balloon made of non-compliant polyethylene terephthalate (PET) designed to
distribute the force sufficient to provide the distraction in the intervertebral disc
space or in whatever joint space it might be placed, such that separation of the
opposing bony surfaces will take place as desired, although pressures on the bone
will be below pressures that would lead to bony deformation. Thus, the
relationship of the size of the balloon to the insert space and the deformation
pressure factor can be computed for any given joint space, and the balloon sized
accordingly. The shape of the balloon is configured in a somewhat rectilinear or
cubical fashion, though it is not limited to such. The non-compliant (PET) sides limit the expansion of the balloon except in those areas of the opposing bones with the sides of the balloon being of such length as to allow the balloon jack to
be effective through the desired distraction range.
The stem assembly to the balloon must be of significant thickness to
allow the pressure required to perform the distraction and to inflate the balloon to
such pressures to be maintained without deformation of the stem. It is yet another object to provide a method of inserting the balloon jack through a narrow tube
such as might be used in microsurgery or endoscopic surgery.
To accomplish these objectives, the invention comprises an inflatable
balloon with attached catheter which serves to distract the vertebral bodies at the site of the implant. The insertable balloon catheter is preferably made of non- compliant polyethylene terephthalate (PET) and is fashioned in its shape and size
in accordance with the requirements of load and surface area described above.
Once inflated, the predetermined geometric shape conforms to the surrounding
bony surfaces. Continued inflation initiates the distraction process to the desired
degree.
To construct the balloon jack for any given application — as for
specifically the intervertebral disc space — information is obtained regarding the
size, shape, and desired distraction of the vertebral bodies for a particular indication and then the balloon is fabricated to provide such distraction within the
framework of the load limitations described above — i.e., the compressibility
leading to deformation of the surrounding bony surfaces in that area. The length
of the stem is determined by the surgical technique, such that the surgeon may inflate the balloon through the stem while the hands are well free of the wound
area. It is important that the balloon, prior to insertion, be collapsible, and that its
width together with that of the stem be of such size that it can be readily passed
through the openings in the various tissue planes as well as through any canulus
which may provide access to the desired location.
DETAILED DESCRIPTION While initially described in connection with the preferred embodiment and procedure, it will be understood that it is not intended to limit the invention to
this embodiment or procedure. On the contrary, it is intended to cover all
alternatives, modifications and equivalents as may be included within the spirit
and scope of the invention as defined by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an isometric view of the novel balloon jack in its deflated
condition;
Figure 2 is an isometric view of the novel balloon jack in its inflated
condition;
Figure 3 is a fragmentary elevational view showing the balloon jack in its
inflated, distracting condition between two vertebrae; and
Figure 4 is an isometric view of the enplaced balloon jack; adjacent
vertebrae, the balloon jack stem and a pressure-supplying syringe.
DETAILED DESCRIPTION Turning more specifically to the drawings, the deflated balloon jack 10
(and its attached stem 12) is shown in its inflated form in Figures 2-4 has been
placed into an intervertebral disc space 20 located between adjacent vertebral
bodies 17 and 18. The balloon jack can be inflated in the intervertebral disc space by liquid or gas delivered through a syringe 15 attached to the stem 12. Later, the balloon jack may be deflated and removed. Maintenance of the intervertebral disc
space may be sustained by means of a known retractor (not shown) placed into the
intervertebral disc space, the blades of which straddle the inflated balloon before
inflation, thereby allowing distraction to be mechanically maintained following
removal of the deflated balloon jack.
To encourage maximal distraction with minimal load applied to any
given segment of the opposing bones, it is the intention of the design of the
balloon jack to occupy the maximum area available between the opposing bones so as to spread the force over the maximum area, thereby decreasing bone
deformation. It should be noted that the surface of the deflated balloon 10, when
expanded as shown in Figures 2-4, by the injection of a fluid from the syringe 15
through the stem 12, can, by the properties of the material, conform when under
load to the anatomical shape of the opposing bony surfaces.
Though the material described in the description (PET) is essentially non-expansile, any other polymeric material possessing similar properties may be
utilized in the manufacture of the balloon.