The present invention relates to an apparatus for positioning a cutting guide in order to cut or re-cut a bone, notably a tibia and/or a femur to which a knee prosthetic shall be applied.
An apparatus for positioning a cutting guide of the above type is known from the prior art, notably from French patent application No. 98 03421 (FR 2776 176 AFSA29) dated Mar. 20, 1998 by the present applicant. The prior art positioning apparatus disclosed therein features numerous disadvantages.
Firstly, the apparatus is particularly cumbersome when cutting a tibia, as it includes a main stem and fixating means located at the bottom of a tibia.
Secondly, this positioning apparatus is not universal, e.g. an identical apparatus for positioning a cutting guide is not suitable for both a tibia cutting guide and a femur cutting guide. As can be ascertained in the prior art cited above, the apparatus for positioning the tibia cutting guide is very different from the equivalent apparatus for a femur. Consequently, manufacturers of apparatuses of this type require two distinct manufacturing lines for said two positioning apparatuses surgeons also require both positioning apparatuses at hand, which is a disadvantage.
An apparatus is described in document FR-2.776.176 which includes first adjusting means for adjusting the orientation of the cutting angle relative to a second axis perpendicular to the first anchoring axis, but which does not includes second adjusting means to adjust the height of the cutting guide relative to the positioning system along the third perpindicular axis, wherein said height is constant because brackets 83 do not slide. Moreover, this system may only be used on a femur and cannot be adapted to a tibia.
According to the present invention, an apparatus for positioning a cutting guide is provided which overcomes the prior art disadvantages detailed above and which is universal, i.e. which may be used to position a tibia cutting guide as well as a femur cutting guide, and which is much less cumbersome than the known prior art apparatuses. Moreover, the apparatus according to the invention is particulary well suited ti CAMSP (computer-assisted medical-surgical procedure) techniques.
According to the present invention, the apparatus for positioning the cutting angle of a bone cutting guide, notably a tibia and/or femur cutting guide, includes
first fastening means to fasten the positioning apparatus to the bone such that both the apparatus and the cutting guide may rotate relative to the fastening axis;
second fastening means to fasten the positioning apparatus to said bone at a second location different from the first fastening location, to fasten said apparatus at a desired location within said rotation relative to said first fastening axis;
first adjusting means for adjusting the orientation of the cutting angle rotating relative to a second axis perpendicular to first fastening axes, notably the orientation known as the antero-posterior slope; and
second adjusting means to adjust the height of the cutting guide relative to the positioning apparatus along a third axis perpendicular to said fastening axis and second axis.
According to a particularly simple embodiment of reduced proportions, said first fastening means comprises a bore implemented in the body of said positioning apparatus and a screw or broach or similar to be screwed or inserted within said bore so as to fasten to the bone. Said second fastening means comprise a second bore parallel to said first bore and a second screw or broach or similar to be screwed or inserted within said second bore to fasten to the bone.
According to a preferred embodiment of the present invention, said first adjusting means includes two brackets mounted perpendicularly to the fastening axis, wherein said two brackets are linked to the fastening means of the cutting guide and are linked to one another by a transversal bracket perpendicular to said brackets and also perpendicular to said fastening axes. Said first adjusting means also includes a screw actionable by means of a knob, which acts upon the transversal bracket so as to displace it relative to the body of the positioning apparatus following the direction of said fastening axes.
This adjusting system is relatively simple because the adjustment is performed by means of simply translating said transversal bracket. However, said translation is performed relative to the fixed body which includes a plurality of contact points located onto the bone, namely a contact point fixed relative to the bone, e.g. said fastening locations, and another contact point, e.g. a portion of the area of contact of said cutting guide with said bone. Said translation is therefore transformed into a rotation of said cutting angle within a reduced rotation angle such that the antero-posterior cutting angle is best adjusted, i.e. the cutting angle along the sagittal plane for instance. A simple apparatus is therefore obtained to adjust the knee""s antero-posterior slope contrary to particularly complicated apparatuses of the prior art.
According to another preferred embodiment of the present invention, said two vertical brackets slide relative to the main body within said third direction as a knob is acted upon, such that the height of the cutting guide to which they are attached by means of said fixating means can be adjusted relative to the body of said cutting guide and thus relative to the bone to which said cutting guide is fastened to.
According to yet another preferred embodiment of the present invention, further precision adjusting means are implemented in order to precisely adjust said rotation angle relative to said first fastening axis. Said precision adjusting means result from mounting said second bore onto a knob-operable stem, rendering said bore slideably mobile relative to the main body of the apparatus.
As first and second fixating screws are fastened into the bone to define an angle known as the varus/valgus angle with a certain amount of precision, said positioning can thus be refined by acting upon said knob, whereby said second fastening axis translates slightly relative to the body of the positioning apparatus. The varus/valgus angle can thus be slightly modified by acting upon the fastening configurations of the positioning apparatus by an angle comprised within plus or minus 3xc2x0, without however gravely deteriorating the bone. It is therefore a particularly simple structure of the apparatus.
According to still another preferred embodiment of the present invention, the cutting guide or the positioning apparatus thereof include a sensor to position the cutting angle within a space, notably within a system known as CAMSP, for instance as described in German utility patent No 297 04 393.5 dated Mar. 11, 1997 in the name of Aesculap AG.
According to another preferred embodiment of the present invention, the apparatus includes fastening means which may be removed from said cutting guide, wherein said fastening means comprises clasping pegs that may be clasped within respective appropriate lodgings implemented within the cutting guides.
The present invention also relates to the use of a positioning apparatus according to the invention, whether for a tibia or a femur.
The present invention also relates to the method of using a cutting guide including a positioning apparatus for positioning the cutting angle of a cutting guide for a bone, notably a tibia and/or a femur, including
first fastening means to fasten said positioning apparatus to the bone such that the whole of the apparatus and the fastening means of the cutting guide may rotate relative to the fastening axis; and
second fastening means to fasten said positioning apparatus at a second fastening location onto the bone, different from said first fastening location, such that said apparatus can be fastened in a required position within said rotation relative to said first fastening axis, comprising the steps of
first fastening the cutting guide positioning apparatus at a location following a first fastening axis,
when so fastened, pivoting said apparatus relative to said fastening axis into a required position, and then only
fastening said positioning apparatus at a second location following a second fastening axis.