Articular cartilage surface shaping apparatus and method

The invention disclosed is a method and apparatus for imparting a desired shape to a surface-to-be-shaped of articular cartilage in the joint of a mammal. The method discloses applying steam to a surface-to-be-shaped to soften the cartilage at and near that surface and positioning a form defining the desired shape adjacent to that softened region. A bias pressure is applied to impart the desired shape and the form is removed. An apparatus for practicing the method includes an element for generating and delivering steam to the surface-to-be-shaped to soften the surface and includes a form for molding the softened surface.

The present invention relates to the field of surgical methods and 
instruments for treatment of certain articular cartilage defects in the 
joint of a mammal, and more particularly, for imperting a desired shape to 
the surface of articular cartilage. 
BACKGROUND OF THE INVENTION 
Irregular surfaces on articular cartilage in the joints of mammals are 
considered defects known to compromise the function of such joints. When 
possible, arthroscopic surgery is the preferred method for remediating 
such defects. Presently, there exist several arthroscopic devices for the 
treatment of such articular cartilage defects. These devices can generally 
be divided into three categories. The first category includes bipolar 
heating devices such as a bipolar wand produced, for example, by 
Arthrocare. The second category includes laser devices. The third category 
includes radio frequency devices produced, for example, by Mitek and 
Oratec. 
All of these prior art devices effect the application of heat to the 
surface-to-be-treated, in response to which the collagen fiber bundles 
that make up articular cartilage at or near the surface "melt", or soften, 
and become moldable. Articular cartilage that has been melted or softened 
by application of heat is referenced to hereinafter as "softened". The 
depth of the penetration of heat, however, has a negative effect on the 
cartilage consequences. It is preferred that the heat penetration is 
minimized in order to prevent damage to the underlying bone. In fact, 
laser devices have been virtually abandoned for treatment of articular 
cartilage defects because the laser energy often penetrates the bone, 
sometimes resulting in osteonecrosis. Invariably, all the prior art 
devices have the additional drawback of having tips with elevated 
temperatures, which often burn the surrounding tissue. This burning can 
leave a charred residue in the joint which can later cause complications 
in the joint after the surgery. Thus, a need remains for a device and 
method for treating articular cartilage defects which would have 
relatively little heat penetration and would not burn the surrounding 
tissue in the mammalian joint. 
SUMMARY OF THE INVENTION 
The present invention provides a surgical technique in which articular 
cartilage can be repaired without damaging the surrounding tissue or the 
underlying bone. In one embodiment, the invention provides a method for 
imparting a desired contour to the surface articular cartilage in a joint, 
for example smoothing a rough surface of the cartilage. The method may be 
performed arthroscopically or in an open joint. The method comprises a 
first step of applying steam to the surface-to-be-treated, resulting at 
least partial melting i.e., "softening" of collagen fiber bundles at and 
near that surface. A form is provided having an applicator surface that 
has a contour which defines the desired contour to be imparted to the 
surface-to-be-shaped. The applicator surface is positioned opposite the 
surface-to-be-shaped and following the softening step and, pressure is 
applied to bias that applicator against the surface-to-be-shaped. 
Preferably, the contour of the applicator surface is smooth so that the 
form smooths the softened surface. The form is removed. Upon cooling of 
the cartilage, the surface maintains the shape of the form. 
The invention includes an apparatus that may be used to effect the above 
described surgical technique. The apparatus preferably includes a 
elongated element having a proximal end and a distal end. The elongated 
element is preferably cylindrical and has dimensions suitable for use in 
arthroscopic procedures. 
The elongated element defines an internal void region at the distal end. A 
conduit for fluid extends from the proximal end of the elongated element 
into the void region. An applicator element at the distal end of the 
elongated element spans the void region, thereby closing the void region 
within the elongated element. In various forms of the invention, the 
applicator element has a smooth shaped exterior applicator surface which 
can be used to form or mold a "melted" cartilage region to a desired 
shape. For example, the exterior surface may be shaped as planar, 
cylindrical concave, cylindrical convex, ellipsoidal concave, ellipsoidal 
convex, spherical concave, and spherical convex. 
In preferred forms of the invention, the void region is thermally coupled 
to a heating element. Liquid is directed through the conduit into the void 
region. In or near that void region, the liquid is exposed to heat from 
the heating element and the liquid is changed to gas phase. Preferably, 
the liquid is water, which is vaporized into steam. Other fluids may be 
used. The applicator element has a plurality of passages extending 
therethrough which allow the steam to pass from the void region through 
the applicator tip to the exterior of the elongated element. In use, the 
perforated applicator element is positioned adjacent to the 
surface-to-be-shaped of the articular cartilage. The steam from the 
elongated element melts or softens collagen fiber bundles at and near the 
surface of the cartilage. Then the applicator tip is pressed against the 
melted or softened cartilage, causing the cartilage to conform to the 
shaped of the exterior surface of the tip, for example smoothing the 
heretofore rough surface.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Articular cartilage defects in the joints of any mammal may be repaired in 
accordance with the invention. Preferably, articular cartilage defects in 
the joints of humans are repaired using the method and apparatus of the 
invention. The invention is suitable for use in many joints, preferably 
arthroscopically, but alternatively in a surgically opened joint. 
Preferably, the method of the invention is used to smooth articular 
cartilage surfaces in the hip. More preferably, the method of the 
invention is used to smooth articular cartilage surfaces in the ankle. 
Most preferably, the method of the invention is used to smooth articular 
cartilage surfaces in the knee. 
By way of example, after a rough surface of articular cartilage is 
identified during routine arthroscopic surgery, the method of the 
invention maybe performed on a knee as follows. The method is preferably 
performed with the articular cartilage apparatus of the invention. 
The rough surface-to-be-smoothed is first located within the knee joint. 
Steam is applied to the defect. The heat from the steam melts or softens 
the collagen fiber bundles in the cartilage. Once the collagen bundles 
melt or soften, the cartilage is moldable. While the cartilage remains 
soft, pressure is applied via a shaped form to substantially smooth a 
rough area of the cartilage defect. As the heat from the steam dissipates, 
the cartilage cools and the collagen bundles solidify. When the shaped 
form is removed, the surface of the surface of the cartilage remains in 
the substantially smoothed state. 
The method of the invention is preferably performed using the articular 
cartilage surface shaping system 10 illustrated in FIGS. 1 and 2. The 
system 10 includes an elongated wand element 12 extending along a central 
axis A. The wand element 12 has a proximal end 14 and a distal end 16. The 
wand element 12 has cylindrical interior void region 20 near the distal 
end 16. A fluid channel 21 extends along axis A between the proximal end 
14 and the void region 20. An applicator element 22, spans the void region 
20 and thereby encloses the void region 20 within the distal end 16 of the 
wand element 12. The applicator element 22 contains one or more (two in 
the illustrated embodiment) passages 26, which allow fluid communication 
between the void region 20 and the exterior to the wand element 12. The 
exterior surface S of the applicator 22 is spherical or ellipsoidal 
concave. 
In the illustrated embodiment, a resistive heating element 30 is disposed 
within the void region 20. The heating element 30 is helical in shape and 
is affixed to the sidewall defining void region 20. A power supply PS is 
coupled in series with a switch SW and conductor 40 and 42 across heating 
element 30. In operation, the distal end 16 is placed so that the surface 
S of applicator element 22 is adjacent to a cartilage 
surface-to-be-shaped. Then, a voltage is selectively applied (in response 
to operation of switch SW) across the heating element 30. In response to 
the applied voltage, the heating element 30 heats the void region 20. A 
fluid pump (not shown) delivers water via valve V and tubes 36 and 38 to a 
water inlet 39 of the system. The water travels through the fluid conduit 
21 and into the void region 20. The water is then exposed to heat from the 
heating element 30 and the water is vaporized into steam. The steam 
escapes from the void region 20 through the passages 26 of the applicator 
element 22. FIG. 2 shows an applicator element 22 with convex exterior 
surface S. 
In response to that escaping steam, the collagen fiber bundles at and near 
the cartilage surface soften. Following opening of switch SW, the distal 
tip 16 cools, and may be pressed against the surface-to-be-smoothed so 
that the surface S of the applicator element 22 can impart a smooth 
surface to the cartilage. 
FIGS. 3 through 8 illustrate alternative forms for applicator element 22. 
The surface S may be spherical convex or ellipsoidal convex (FIG. 3), 
planar at an oblique transverse angle with respect to axis A (FIG. 4) 
planar perpendicular to axis A (FIG.5), cylindrical concave (FIG. 6), 
cylindrical convex (FIG. 7), or any other desired shape, smooth or rough. 
These various forms for surface S allow the system of the invention to be 
used in different regions of various affected joints as necessary. 
In another form of the invention, the heating element 30 may be disposed 
fully within the cavity 20, i.e. apart from the sidewall, and in yet 
another form, that element 30 may be embedded within the material forming 
wand element 12 as shown in FIG. 8. 
Those of skill in the art will recognize that the invention may be embodied 
in other specific forms without departing from the spirit or essential 
characteristics thereof. The presently described embodiments are therefore 
to be considered in all respects as illustrative and not restrictive, the 
scope of the invention being indicated by the appended claims rather than 
by the foregoing description, and all variations of the invention which 
are encompassed within the meaning and range of equivalency of the claims 
are therefore intended to be embraced therein.