CA1328953C

CA1328953C - Prosthetic device and method of implantation

Info

Publication number: CA1328953C
Application number: CA000613338A
Authority: CA
Inventors: Philip C. Noble; Mary Beth Padgett
Original assignee: Pfizer Hospital Products Group Inc
Current assignee: Howmedica Osteonics Corp
Priority date: 1988-10-07
Filing date: 1989-09-26
Publication date: 1994-05-03
Anticipated expiration: 2011-05-03
Also published as: ATE131711T1; IE70457B1; US5002580A; JPH0624544B2; EP0363151A3; EP0363151A2; EP0363151B1; AU613243B2; DE68925175T2; DE68925175D1; AU4267589A; ES2080752T3; JPH02174844A; GR3018971T3; IE893231L

Abstract

ABSTRACT

The bone prosthesis of the present invention comprises a first body member or stem for placement into a bone cavity, such as an intramedullary canal. The body member is configured and dimensioned so as to provide a nonuniform interference press-fit. The apparatus further comprises a second body member or broach for placement into and removal from a bone cavity, the broach configured and dimensioned so as to prepare the bone cavity so as to provide a nonuniform interference press-fit with the stem.
The apparatus further comprises a distal sleeve configured and dimensioned so as to be attached to the stem so as to centralize the stem in the bone cavity. The distal sleeve preferably is provided with an interior conical slope and an exterior conical slope on a portion thereof to aid in insertion into the canal. The stem further comprises at least one groove and preferably a plurality of grooves along its corners. These grooves are nonparallel to the longitudinal axis of the stem and do not extend over any one entire side of the stem. The stem can be provided with an area of cancellous texture which comprises substantially randomly patterned array of multiple curved-line surface unevenness, such as indentations or protrusions. The present invention also is directed to a method comprising utilization of the broach, the stem and the distal sleeve so as to provide a nonuniform press-fit between the bone prosthesis and the bone cavity while centralizing the stem in the bone cavity.

Description

The present invention generally relates to prostheses and in particular to a bone implant which is implanted in a press-fit manner.
Acute arthritis or trauma may necessitate the replace~ent of natural bones and jolnts with prosthetic devlces.
For example, the replacement of the hip joint is one of the more common operations performed for these reasons. Such procedures have become somewhat commonplace in the treatment of acute arthrltis or trauma not only in human beings but also in ani~als such as dogs and cats.
With respect to implantation of a hip prosthesis, rigid fixation of femoral components ls desirable to promote long term stabilization and also to mlnimize the occurrence of adverse symptoms after surgery, such as pain and limp. Such fixation is also desirable to minimize bone-implant micromotion.
One known method of prosthesis fixation involves the use of cement. However, in time cement can loosen with undesired results. Such results and other undesirable effects from cement use are described in U.S. Patent No. 4,406,023.
In an attempt to achieve such rigid flxation but wlthout cement, hip prostheses have been inserted into bone canals to obtain a press-fit arrangement. A review of known hip lmplants is presented in Noble et al., "~he Hyth of 'Press-Flt' in the Proximal Femur," America Academy of Orthopedic Surgeons 55th Annual Meeting, Atlanta, Georgia, February 4-9, 1988.
~owever, some of the shortcomings of these hip implants include that they are stabllized by contact with cortical bone in separate regions of the medullary canal and that the interfaces do ~, .

. .
:: :

` 1 328953 ` 2 64680-509 not constitute a press-fit.
Secondly, rigid fixation is also dependent on the surface texture of the hlp lmplant which is press-fit lnto the medullary canal. A typical finish in known devices includes a satin or sand-blasted finish. But thls surface is not acceptable if implant micromotion is to be minimized. A fuller discussion of surface texture is set forth in E. Kamaric, P.C. Noble and J.W.
Alexander, "The Effect of Proximal Surface Texture on the Acute Stability of Cementless Fixation".
We have invented an improved bone prosthesis which overcomes the aforementioned problems and provides for more rigid fixation within the intramedullary canal of a bone.
The present invention is directed to a prosthetic implant which achieves improved endosteal contact, and reduces the occurrence of gaps at the bone/implant interface. The prosthetic implant of the present invention minimizes implant micromotion.
The present ~nvention comprises an apparatus which comprises a body member for placement into a bone cavity, the body member configured and dlmensioned so as to provlde a nonuniform interference press-fit within the bone cavity along a portion of the proximal end surface of the body member.
The bone cavity into which the apparatus of the present invention is placed may be an intramedullary canal of a bone.
The apparatus of the present invention may be provided with at least one groove on a portion of said body member, and said grooves may extend over less than the circumference of the body member.
The apparatus of the present invention may be provided .:

_ 3 _ 64680~509 with surface unevenness on a portion of the body member.
The present lnventlon provides a bone implant comprislng a neck and stem, said stem defining a longitudinal axls and a - circumference, said stem having a distal portion, a proximal portion with a proximal end, an anterior side, a posterior side, a lateral side, a medial side, an antero-medial corner, an antero-lateral corner, a postero-medial corner and a postero-lateral corner, said stem being provided with at least one groove along each of the antero-lateral, postero-lateral, antero-medial and postero-medial corners, each of sald grooves extending transverse to the longitudinal axis of said stem and each said groove terminating adjacent each said corner, whereln on the medial side of the stem approximately 0.2 inch is maintained between a vertical line drawn parallel to the longltudinal axis and tangent to the anterior edge of each postero-medial groove and a vertical line drawn parallel to the longltudinal axis and tangent to the posterior edge of each antero-medial corner groove; and on the lateral side of the stem approximately 0.3 inch is maintained between a vertical line drawn parallel to the longitudinal axis and tangent to the anterior edge of each postero-lateral corner groove and a vertical line drawn parallel to the longitudlnal axis and tangent to the posterior edge of each antero-lateral corner groove.
The invention also provides a bone implant kit comprising a broach and an lmplantable body member, said broach having a proximal portion configured and dimensioned so as to prepare a bone cavity with a proximal region havlng a portlon of . "

.

, "' ' '-, : .

1 328q53 the side walls consisting of cancellous bone and a portlon of the side walls conslstlng of cortlcal bone; said body member comprising a neck and a stem said stem having a prox~mal portion wlth predetermlned dlmenslons relative to the proximal portlon of said broach so as to provide a nonuniform interference press-flt with said prepared bone cavity upon insertion; said nonuniform interference press-fit comprising an lnterference press-fit with those portions of the side wall conslstlng of cancellous bone and a line-to-line fit with those portions of the side wall conslsting of cortical bone, wherein the proximal portion of said stem has an anterlor slde, a posterior slde, a medial slde and a lateral slde, an anterior-lateral corner, an anterior-medlal corner, a posterior-lateral corner and a posterior-or-medlal corner; said proximal portion of said stem havlng at least one groove on each of the anterior-lateral, anterior-medial, posterior-lateral and posterior-medial corners; and each said groove terminating adjacent each said corner.
The lnvention further provldes a hip prosthe~is kit . comprising a broach and an implantable body member; said body member having a neck and a stem; said broach and said stem each having a distal portion, a proximal portion with an anterior side, a posterior si~.e, a lateral side, a medial side, an anterior-lateral corner, an anterior-medial corner, a posterior-lateral - . corner and a posterior-medial corner; said broach having on its circumference means for cutting bone tissue upon insertion of the broach into a bone cavity in the proximal femur; the proximal portion of said broach having predetermined dimensions so as to F

:: ~ ' :: ' '' ' ' 4a 64680-509 expose substantially all cortical bone on the medial side of the proximal portion of the bone cavity and substantially all cancellous bone on the lateral side of the proximal portion of the bone cavity upon singular insertion into and removal from the bone cavity; the proximal portion of said stem having predetermined dlmensions which are greater than the correspondlng predetermined dimensions of the proximal portion of said broach so as to produce an interference press-fit with cancellous bone along the lateral side of the bone cavity and a line-to-line fit with cortical bone along the medial side of the bone cavity upon insertion of said stem into a bone cavity in the proximal femur prepared by the insertion and removal of said broach.
The invention still further provides a hip prosthesis - kit comprising a broach and an implantable body member; said body, member comprising a neck and a stem and said broach comprising a stem; the proximal portions of said broach stem and said body member stem being configured and dimensioned relative to each other so that any cross section of said body member is larger in area than a corresponding cross section of said broach; the medial side of said cross section of said body member has curvature and dimensions which are the same as the corresponding curvature and dimensions of the medial side of said cross section of said broach; and the medial to lateral widths of said cross section of said body member are greater than corresponding medial to lateral widths of said cross section of said broach.
The installation comprises preparing a bone cavity for placement of a body member therein so as to provide an ~r ?
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-~ 328953 4~ 6~680-509 interference press-fit along a predetermined portion of said body member. The method comprlslng preparation of the bone cavity may comprise preparing the bone cavity for placement of the body member therein so that at least a portion of the portions of the bone cavity which possess a relatively substantial layer of cancellous bone will form an interference press-fit with a portion of the bone cavlty which does not possess a surface layer comprised substantially of cortical bone, but rather possesses a layer substantially comprised of cortical bone which will not interfere with the body member but will maintain a line-to-line flt with a portlon of the body member. The method comprises lnsertion and removal of a broach into the bone cavity .. ~

.. ., : ' : ' prior to placement of the body member thereln. The broach i~
configured and dimensloned so as to provide the bone cavity with an envelope configured and dimensioned in accordance wlth the method of preparing a bone cavity described above in this paragraph.
The body member is pre$erably configured and dimensioned so as ~o be attached to a second apparatus, such as a bone prosthesis, which is configured and dimensloned so as to be placed in a bone cavity, the body member configured and dimensloned so as to centralize the second apparatus in the bone cavity, which bone cavity may be an intramedullary canal of a bone. The body member may be conflgured and designed so as to be 1 milllmeter smaller or less than 1 millimeter smaller in diameter then the intramedullary canal of the bone at the point in the intramedullary canal where the body member is placed. The body member is preferably sized so as to be identical in diameter to the intramedullary canal of the bone at the point where the body member is placed, however, it has been found that if the body member is not more than 0.5 mm smaller, and preferably not more than .25 mm smaller, in diameter a most satisfactory stabilization of the bone prosthesis is achieved.
The present invention is described in detail below with reference to the drawings wherein:
FIG. 1 is a frontal view of a hip prosthesis according to the present invention as shown implanted in the medullary canal of a human femur.
FIG. 2 is a lateral view of the hip prosthesis of FIG. 1.

.. : .

. .... . .

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5a 64680-509 FIG. 3 is a medial view of the hip prosthesls of FIG. 1.
FIG. 4 is a cross-sectional view taken along line D-D of ~IG. 1, with the distal sleeve removed therefrom.
FIG. 5 is a cross-sec~ional vlew taken along llne C-C of FIG. 1.

. .

,''' ' - ' 1 328~53 FIG. 6 is a cross-sectional view taken along line B-B of FIG. 1.
FIG. 7 is a cross-sectional view taken along line A-A of FIG. 1.
FIG. 8 is a cross-sectional view taken along line F-F of FIG. 1.
FIG. 9 is a top view of the hip prosthesis of FIG. 1 illustrating an implantation slot or threaded cavity.
FIG. 10 is a cross-sectional view taken along line H-H of FIG. 9.
FIG. 11 is a cross-sectional view taken along line 11-11 of FIG. 1.
FIG. 12 is a cross-sectional view taken along line 12-12 of FIG. 1 illustrating the distal end of the hip prosthesis of FIG. 1 positioned in a distal sleeve according to the present invention.
FIG. 13 is a cross-sectional view taken along line 13-13 of FIG. 1.
FIG. 14 is a top view of the contour of the medullary canal in comparison to the corresponding larger area of the hip prosthesis to illustrate the press-fit of the hip prosthesis according to the present invention.
FIG. 15 is an enlarged view of the uneven surface of the hip implant of FIG. 1.
FIG. 16 is an illustration of the method of preparing a bone canal utilizing a broach according to the present invention.
In the description which follows, any reference to either orientation or direction is intended primarily for the purpose of illustration and is not intended in any way as a limitation of the scope of the present invention.
While it is presently contemplated that the preferred embodiment of the present invention is a hip implant, as will be described herein, the present invention is not limited to use as a hip implant but may . ., .. . .~ ~ .

be used as a prosthetic implant of any type. While it is also presently contemplated that the preferred embodiment of the present invention is particularly well suited for press-fit implantation, the present invention is not limited to`press-fit implantation, but embodies implantation in any manner. Further, the dimensions recited herein are typical of one of the many various sizes of hip implants embodying the present invention and are not intended to limit the invention.
The apparatus of the present invention may be provided with surface unevenness on a portion of the body member. The surface unevenness may comprise a substantially randomly patterned array of multiple curved-line surface unevenness, such as indentations or protrusions, defining a cancellous texture, and as used herein the term "cancellous texture" will define such a surface unevenness. The surface unevenness and the grooves may both be provided on the body member, but the present invention is not limited thereto. The cancellous texture can be a macro texture.
As used herein, an "interference press-fit" is defined as a mechanical connection formed by two components, at least one of which is deformable, where the adjacent boundary lines of the two components overlap 2S and interfere with each other such that the two components must be forced into a position adjacent each other whereupon the deformation of one component causes a reaction force to be developed over the area of contact between the two components. As used herein, a "line-to-line fit" is defined as a mechanical connection formed bytwo components where the adjacent boundary lines of the two components match each other evenly without any overlap or interference. As used herein, the term "press-fit" is a mechanical connection formed by the substantial matching of two components and encompasses both an interference press-fit and a line-to-line fit.
The term "nonuniform interference press-fit" herein defines a press-fit comprising both an interference 1 328q53 press-fit and a line-to-line fit wherein the interference press-fit comprises a varying amount of overlapping and interference.
As used herein, when defining a texture, the term "macro" defines a roughness, such as indentations or protrusions, comprising various features which are 1 mm or greater in depth or height and which are spaced from one another by a distance of 1 mm or great~er. A macro texture in accordance with the present invention can in~lude features ranging from 1 to 5 mm in depth or height and spaced from one another by a distance ranging from 1 to 5 mm. As used herein, the term "predetermined length" includes a partial or entire circumference of a body member and the longitudinal length of a body member.
15 A predetermined length can extend in any direction. As used herein, the term "proximal" refers to t~e portion of the prosthesis positioned closest the entrance ~f the bone cavity, and the term ~distal" refers to the portion of the prosthesis positioned farthest within the bone cavity.
As used herein, the term "central axis~ defines a line defined by the center points of two cross sections of the body member at the distal end, such as center point CPl of Fig. 4 and a center point of a cross section of the body member adjacent the cross section of Fig. 4, and extends in a proximal-distal direction through the entire body member. Referring to Fig. 14, point X is the point on the proximal end of the body member at which the central axis terminates. Referring to Fiq. 14, point Pl is a point on the lateral side of the proximal end of the body member from which an isosceles triangle can be formed by drawing two lines, R and S, each which terminate at a point equidistant from point X and drawing a third line, RXS, connecting the terminating points of R
and S with a line which intersects X. As used herein, the term "centerline " will define a line which extends the width of the proximal end of the body member and , ~ 328953 includes line RXS as a segment thereof.
The maximum interference is achieved along the lateral edge of the proximal end of the implant, and more particularly at point Pl thereon, as shown in Fig. 14.
At Pl the amount of interference ranges from 1 to 3 mm, preferably 1 to 2 mm. The term "percent interference" at any given point Z on the circumference of the body member is defined as the amount of interference, measured in length, at Z divided by the dista~ce from X to a point Q
on a line drawn from X to Z defined by the point at which the side of the bone cavity terminated prior to insertion of the body member. At Pl, the percent interference ranges from 11 to 30 percent and preferably 11 to 20 percent.
Predetermined amounts of interference are also provided at points P3, which is the termination point of the centerline at its posterior end, and P4, which is the termination point of the centerline at its anterior end.
At P3 and P4, the amounts of interference ranges from 1 to 2 mm and preferably 1 to 1.5 mm, and the percent interference ranges from 11 to 18.7 percent and preferably 11 to 14 percent. Furthermore, the amount of interference at P3 and P4 is preferably less than the amount of interference at Pl for a given body member in a given bone cavity.
Further predetermined amounts of interference are also provided at points P5 , which is the termination point of a line drawn through X to the posterior side of the body member and 30 degrees to the lateral side of the centerline, and P6, which is the termination point of a line drawn through X to the anterior side of the body member and 30 degrees to the lateral side of the centerline. At P5 and P6, the amount of interference ranges from 3/4 to 1.5 mm, and preferably 3/4 to 1 mm, and the percent interference ranges from 7.5 to 13.8 percent and preferably 7.5 to 9.2 percent. Furthermore, the amount of interference at P5 and P6 is preferably less than the amount of interference at P3 and P4 for a -lo- 132a953 given body member in a given bone cavity.
Chart 1 lists the amounts of interference and the percents of interference measured for eight sizes of an embodiment according to the present invention. In Chart 1, "amt" defines amount of interference and "%"
defines percent interference. While the amounts of interference are listed to the third decimal place, the present invention is in no way limited to such a degree.

P % amt. .039 .046 .046 .068 .055 .078 .065 .07 P3,P4 % amt. .037 .039 .039 .042 .042 .055 .048 .055 15 P ,P % amt. .029 .031 .031 .037 .037 .039 .044 .039 5 6 7.5 7.6 7.6 8.6 8.6 8.6 9.2 7.5 The present invention further comprises a body member for placement in a femur, the body member configured and dimensioned so as to provide a nonuniform press-fit with the femur intramedullary canal, the body member defining a circumference, a centerline and a central axis, the interference press-fit comprising an interference press-fit at Pl comprising an amount of interference equal to the maximum amount present between the body member and the sides of the bone cavity, a predetermined amount of interference at P3 and P4 which is less than the maximum amount, and a predetermined amount of interference occurring at P5 and P6 which is less than the amount occurring at P3 and P4.
The apparatus according to the present invention comprises the maximum amount of interference comprising 1 to 3 millimeters of interference, preferably 1 to 2 millimeters, the amount of interference at P3 and P4 comprising 1 to 2 millimeters of interference, preferably 1 to 1.5 millimeters, the amount of interference at P5 and P6 comprising 3/4 to 1.5 --ll--millimeters of interference, preferably 3/4 to 1 millimeter, the maximum amount of interference comprising 11 to 30 percent interference, preferably 11 to 20 percent, the amount of interference at P3 and P4 comprising 11 to 18.7 percent interference, preferably 11 to 14 percent, and the amount of interference comprising 7.5 to 13.8 percent interference, preferably 7.5 to 9.2 percent.
The present invention further comprises such an apparatus further comprising a broach, the broach configured and dimensioned so as to be inserted into and removed from the bone canal so as to prepare the bone canal so as to provide the appropriate interference press-fit with the body member.
The present invention further comprises a method comprising inserting and removing a first body member into a bone cavity, t~e first body member configured and dimensioned so as to prepare the bone cavity so as to provide a nonuniform interference press-fit with a second body member, and placing the second body member into the bone cavity, the second body member configured and dimensioned so as to form a nonuniform interference press-fit with the bone cavity, the bone cavity being an intramedullary canal of a femur, the method further comprising the second body member having an anterior side, a posterior side, a lateral side and medial side, the second body member defining a circumference, a centerline and a central axis, the bone cavity comprising an intramedullary canal of a femur, the nonuniform press-fit comprising an interference press-fit at Pl comprising an amount of interference equal to the maximum amount present between the second body member and the bone cavity, a predetermined amount of interference at P3 and P4 which is less than the maximum amount, and a predetermined amount of interference occurring at P5 and P6 which is less than the amount occurring at P3 and P4.

The method of the present invention further comprising the maximum amount of interference comprising 1 to 3 millimeters of interference, preferably 1 to 2 millimeters, the amount of interference at P3 and P4 S comprising 1 to 2 millimeters of interference, preferably 1 to 1.5 millimeters, the amount of interference at P5 and P6 comprising 3/4 to 1.5 millimeters of interference, preferably 3/4 to 1 millimeter, the maximum amount of interference comprising 11 to 30 percent interference, preferably 11 to 20 percent, the amount of interference at P3 and P4 comprising 11 to 18.7 percent interference preferably 11 to 14 percent, and the amount of interference at P5 and P6 comprising 7.5 to 13.8 percent interference, preferably 7.5 to 9.2 percent.
An implant according to the present invention can be forged, machined or cast utilizing any biologically inert material, such as Vitallium~, titanium, stainless steel, ceramics, polymers or plastics, and may be multi-layer combinations thereof.
Referring to FIG. 1, the hip implant according to the present invention includes a body member or stem 2 which tapers in the proximal to distal direction. As used hèrein, distal refers to the portion of the prosthesis positioned farthest within the bone canal.
Furthèr, the cross-section of the stem 2 preferably changes from circular at the distal end 3 of the stem to substantially greater medial-lateral dimensions as compared with anterior-posterior dimensions at the proximal end 4 of the stem 2. Also, the anterior-posterior width of the stem 2 gradually becomessubstantially greater adjacent the lateral side 5 of the implant than the corresponding length adjacent the medial side 6 nearer the proximal end 4 of the stem.
In a preferred embodiment of the present invention, the stem 2 has an outside diameter of .406 in.
at point 30 near distal end 3 of FIG. 1 where the stem is -13- 1 32~953 circular in cross-section. As illustrated in FIG. 4, the cross-sectional diameter of stem 2 at line D-D of FIG . 1 is .492 in., and the stem is circular in cross-section.
As shown in FIG. S the cross-sectional view along line c-c of FIG. 1 is not circular. Here the stem 2 hasdimensions of .597 in. in the medial-lateral direction and .579 in. in the anterior-posterior direction.
Referring to FIG. 6, at line B-B of FIG. 1 the cross-section of stem 2 has dimensions of .913 in. in the medial-lateral direction and .672 in. in the anterior-posterior direction. Also the dimensions as shown in FIG. 7 along line A-A of FIG. 1 are preferably 1.5 in. in the medial-lateral direction and .832 in. in the anterior-posterior direction on the lateral side.
With reference to the curvature of the radius of the cross-sections of the stem 2, these gradually transform from a circular shape at the distal end 3 to a substantially greater anterior-posterior length on the lateral side than a corresponding length on the medial side.
As used herein the term "radial curvature" will designate a measure of the radius from a corresponding center of the circumference or portion of the cross-section of the stem, and the number given for the radial 2S curvature will correspond to the radius which a circle drawn possessing that degree of curvature would possess.
For example, referring to FIG. 6 at point 14 the radial curvature is .25 which indicates that if a circle were drawn beginning at point 14 and possessing the same degree of curvature as is shown at point 14, the radius of the circle would be .25.
According to a preferred embodiment, FIG. 4 illustrates that the cross-section of the stem 2 is circular at line D-D of FIG. 1 and has the cross-section at line C-C of FIG. 1 possesses a radial curvature of .41 at point 31, .36 at point 7 and .34 at point 8. Since the stem 2 is symmetrical about the medial-lateral axis, ~ 328953 thus the radial curvat~re is also .36 at point 9. The symmetry of the stem about the medial-lateral axis continues in the proximal direction up to point lo on the medial side of line A-A of FIG. 1. FIG. 6 illustrates a s cross-section at line B-B of FIG. 1 which has a radial curvature of l.oO at point 11, .22 at point 12, .67 at point 13 and . 25 at point 14. Figure 7 illustrates a cross-section along line A-A of FIG. 1 preferably a radial curvature of 1.00 at point 15, .22 at point 16, 1.25 at point 17 and .30 at point 18. Line A-A of FIG. 1 bends 30 towards the distal end 3 of the stem at point 19 .
The proximal end 4 of the stem 2 is provided with a neck 20 extending at a 45 angle in the medial direction. The proximal end of the neck 20 is provided with a peg or spigot 21 which is designed to receive a joint head as shown in FIG. 1.
The neck 20 preferably is . 865 in. in length from point 22 on line A-A of FIG. 1 to the distal end of 20 peq 21. The neck 20 has a circular cross-section taken along line F-F of FIG. 1 and preferably has an outside diameter of . 512 in. Neck 20 narrows toward the proximal end at a slope of 1 25 , and is provided with a radial curvature of .09 at point 23 where neck 20 meets peg 21.
At its distal end, peg 21 is circular, and has an outside diameter of . 536 in. Peg 21 narrows toward its proximal end at a slope of 1 25 ~ 15~ resulting in an outside diameter of . 506 in. at point 24 with a length of .659 in. between the distal end of peg 21 and point 24.
At its proximal end, peg 21 iS provided with a .06 in. by 45 bevel.
Referring to FIG. 9, the implant has a perpendicular length of 2.12 in. from the proximal end of peg 21 to the lateral side of the proximal end of stem 2.
Stem 2 is provided with a threaded cavity 25 on the top side of its proximal end, designed to threadedly engage a 1 328~53 drive which may be used for insertion or removal of the implant into or out of a bone. Threaded cavity 25 has an inner diameter of .25 in. and a depth of .30 in. A
second cavity 26 may be provided adjacent cavity 25 at its lateral end. Second cavity 26 extends .13 in. from the lateral side of cavity 25, and .100 in. deep and .094 in. wide.
The length of stem 2 can be 5.80 in. on its lateral side from the proximal end to the distal end.
Referring to Figs. 1-3, the stem 2 is provided with horizontal grooves 27 on its proximal end. The grooves 27 are uniformly spaced vertically and are positioned at the edges, i.e., the stem's antero-lateral, postero-lateral, antero-medial and postero-medial edges.
Referring to FIG. 3, the antero-medial and postero-medial edges of stem 2 are preferably provided with five uniformly vertically spaced horizontal grooves.
Each groove is .06 in wide and .04 in. deep, with center to center spacing of .18 in. between each pair of parallel adjacent grooves. A distance of .20 in. is maintained between the anterior edges of the postero-medial edge grooves and the posterior edges of the antero-medial edge grooves on the medial side of the stem 2. The horizontal centerline of the grooves is .15 in.
from the closest portion of the proximal edge of stem 2.
Referring to FIG. 2, the antero-lateral and postero-lateral edges of stem 2 are each preferably provided with four uniformly spaced horizontal grooves.
A distance of .30 in. is maintained between the anterior edges of the postero-lateral edge grooves and the posterior edges of the antero-lateral edge grooves on the lateral side of the stem. Referring to FIG. 1, on the anterior and posterior sides the antero-medial and postero-medial edge grooves extend approximately .25 in., and the antero-lateral and postero-lateral edge grooves extend approximately .317 in.

In the preferred embodiment the distal-most antero-lateral and postero-lateral edge grooves are on the same medial-lateral plane as the proximal-most antero-medial and postero-medial edge grooves.
S The above-described grooves are preferably formed by forging the device.
Referring to Figs. 1 and 15, at least one and preferably both of the anterior and posterior sides of the proximal end of the stem are provided with a substantially randomly patterned array of multiple curved-line surface unevenness, such as indentations or protrusions, defining a random texture ("EDM"). The cancellous texture is preferably formed by forging the device to a depth of .020 in.
The macro cancellous texture covers an area of the anterior and posterior sides of the stem defined at its lateral edge by a line beginning distally 1.5 in.
from the proximal end of the lateral side of the device, and extending substantially to the proximal end of the stem while maintaining .030 in. clearance with the medial edges of the antero-lateral or postero-lateral edge grooves. The proximal and distal sides of the macro cancellous texture extend at 30- angles with the lateral-medial axis in the medial-distal direction. The medial border of the texture maintains a .030 in. clearance with the lateral edges of the antero-medial and postero-medial edge grooves.
Before the prosthetic device is implanted, a broach 80 is inserted into the bone canal to form the proximal endosteal envelope by exposing strong cancellous bone in the metaphysis. The broach also indicates the final level of the femoral neck osteotomy and the correct position of the stem.
The broach has a shape which corresponds to the shape of stem 2 of the present invention such that the bone canal may be prepared in a manner which assures that ~ 3~89~3 the side or sides of the bone cavity which possess a relatively substantial layer of cancellous bone will form an interference press-fit with a portion of the ~tem of the prosthesis. The side or sides of the bone cavity which do not possess a relatively substantial layer of cancellous bone but rather possess a layer substantially of cortical bone will not interfere with the stem but will maintain a substantially line-to-line fit with a portion of the stem.
As illustrated in FIG. 14, when the preferred embodiment of the present invention is implanted into a human femur, the proximal end of the stem 2 will maintain an interference press-fit with the lateral side and adjacent portions of the anterior and posterior sides of the bone envelope and a substantially line-to-line fit with the medial side and adjacent portions of the anterior and posterior sides of the bone cavity or envelope. It is preferred that an interference press-fit will be maintained at least along the entire lateral side of the proximal end of the stem, and a line-to-line fit will be maintained at least along the entire medial side of the proximal end of the stem.
The distal end of the stem is provided with a distal sleeve illustrated in FIG. 12, prior to implantation to assure proper alignment of the device within the bone canal.
The distal sleeve 32 is substantially cylindrical and hollow, and provided with an interior conical slope of 430' in the proximal-distal direction such that the distal sleeve can securely engage the distal end of stem 2 when forced thereon. The distal end of the distal sleeve is provided with a 9 taper on a portion of the outside diameter such that the distal sleeve can be more easily inserted into the bone canal.
The dimensions of the distal sleeve vary according to the stem size utilized as well as according to the size of the bone canal. Such distal sleeve 32 also aids in ....

controlling micromotion of the stem 2 within the canal as discussed in P.C. Noble et al., "Distal Stem Centralization Affects The Acute Fixation Of Cementless Femoral Stems"

The preferred embodiment of the present invention can be implanted according to typical surgical techniques further incorporating methods according to the present invention as diæclosed herein. Several aspects of a typical technique embod~ing the present invention are noted below.
The medullary canal is reamed and the O.D. size of the last flexible reamer used is noted, as this approximates the diameter of the distal sleeve necessary for correct positioning of the tip of the femoral component. The close distal fit restricts implant/bone micromotion and centralizes the distal stem to provide optimal implant stability. Distal sleeves may be provided in OD sizes from 11 to 20 mm, all in 1 mm increments.
Preoperative sizing from templates provides a startinq point for selecting the appropriate femoral broach. This instrument forms the proximal endosteal envelope by exposing strong cancellous bone in the metaphysis, and provides for a nonuniform interference, press-fit between the body member and the bone cavity, in accordance with the present invention. It also indicates the final level of the femoral neck osteotomy and the correct position of the femoral component.
Femoral broaches may be provided in a number of sizes corresponding to the dimensions of each implant and to the configurations and dimensions necessary in order to provide a press-fit in accordance with the present invention. Each broach comes with a detachable handle to allow impacting and extracting. The cutting teeth are located in the proximal section only, and this instrument cuts bone only when driven distally into the bone. The broach is driven down the canal With a mallet, keeping it aligned With the femoral aXis. After the broach is properly inserted into the bone cavity, and a fit in accordance with the present invention is obtained, the broach is removed from the bone cavity.
Prior to implantation, the appropriate size distal sleeve is placed on the stem and an appropriate stem impactor/extractor is placed in the proximal threaded hole 25. This assembly is placed in an appropriate distal sleeve impactor. The stem impactor is tapped with a mallet. The assembly is removed from the sleeve impactor and placed in the prepared femoral canal.

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Claims

1. A bone implant comprising a neck and stem, said stem defining a longitudinal axis and a circumference, said stem having a distal portion, a proximal portion with a proximal end, an anterior side, a posterior side, a lateral side, a medial side, an antero-medial corner, an antero-lateral corner, a postero-medial corner and a postero-lateral corner, said stem being provided with at least one groove along each of the antero-lateral, postero-lateral, antero-medial and postero-medial corners, each of said grooves extending transverse to the longitudinal axis of said stem and each said groove terminating adjacent each said corner, wherein on the medial side of the stem approximately 0.2 inch is maintained between a vertical line drawn parallel to the longitudinal axis and tangent to the anterior edge of each postero-medial groove and a vertical line drawn parallel to the longitudinal axis and tangent to the posterior edge of each antero-medial corner groove; and on the lateral side of the stem approximately 0.3 inch is maintained between a vertical line drawn parallel to the longitudinal axis and tangent to the anterior edge of each postero-lateral corner groove and a vertical line drawn parallel to the longitudinal axis and tangent to the posterior edge of each antero-lateral corner groove.

2. A bone implant according to claim 1 wherein the lateral side is wider than the medial side, the anterior-lateral corner and the posterior-lateral corner are each provided with four grooves, the anterior-medial corner and the posterior-medial corner are each provided with five grooves, each groove extending parallel to each other groove and perpendicular to the longitudinal axis, each groove on each corner spaced from each adjacent groove on said corner by 0.18 inch, the distal most groove on each of the anterior-lateral corner and the posterior-lateral corner extending in the same horizontal plane as the proximal most groove on each of the anterior-medial corner and the posterior-medial corner, the proximal most groove on each of the anterior-lateral corner and the posterior-lateral corner extending in a horizontal plane which is spaced from the proximal end of the lateral side by 0.15 inch, and the proximal most groove on each of the anterior-medial corner and the posterior-medial corner extending in a horizontal plane which is spaced from a line drawn perpendicular to the longitudinal axis and through the midpoint of the proximal end of the medial side by 0.15 inch.

3. A bone implant kit comprising a broach and an implantable body member, said broach having a proximal portion configured and dimensioned so as to prepare a bone cavity with a proximal region having a portion of the side walls consisting of cancellous bone and a portion of the side walls consisting of cortical bone;
said body member comprising a neck and a stem;
said stem having a proximal portion with predetermined dimensions relative to the proximal portion of said broach so as to provide a nonuniform interference press-fit with said prepared bone cavity upon insertion;

said nonuniform interference press-fit comprising an interference press-fit with those portions of the side wall consisting of cancellous bone and a line-to-line fit with those portions of the side wall consisting of cortical bone, wherein the proximal portion of said stem has an anterior side, a posterior side, a medial side and a lateral side, an anterior-lateral corner, an anterior-medial corner, a posterior-lateral corner and a posterior-or-medial corner;
said proximal portion of said stem having at least one groove on each of the anterior-lateral, anterior-medial, posterior-lateral and posterior-medial corners; and each said groove terminating adjacent each said corner.

4. A hip prosthesis kit comprising a broach and an implantable body member;
said body member having a neck and a stem;
said broach and said stem each having a distal portion, a proximal portion with an anterior side, a posterior side, a lateral side, a medial side, an anterior-lateral corner, an anterior-medial corner, a posterior-lateral corner and a posterior-medial corner;
said broach having on its circumference means for cutting bone tissue upon insertion of the broach into a bone cavity in the proximal femur;
the proximal portion of said broach having predetermined dimensions so as to expose substantially all cortical bone on the medial side of the proximal portion of the bone cavity and substantially all cancellous bone on the lateral side of the proximal portion of the bone cavity upon singular insertion into and removal from the bone cavity;
the proximal portion of said stem having predetermined dimensions which are greater than the corresponding predetermined dimensions of the proximal portion of said broach so as to produce an interference press-fit with cancellous bone along the lateral side of the bone cavity and a line-to-line fit with cortical bone along the medial side of the bone cavity upon insertion of said stem into a bone cavity in the proximal femur prepared by the insertion and removal of said broach.

5. The hip prosthesis kit as claimed in claim 4, wherein the proximal portion of the broach has predetermined widths between the anterior side and posterior side so as to expose substantially all cortical bone along the anterior and posterior sides adjacent the medial side and to expose substantially all cancellous bone along the anterior and posterior sides adjacent the lateral side upon said singular insertion into and removal from the bone cavity;
the proximal portion of said stem having predetermined widths between the anterior and posterior sides which are greater than the corresponding widths of the proximal portion of said broach adjacent the lateral side and which are approximately equal to the corresponding widths of the proximal portion of said broach adjacent the medial side so as to produce an interference press-fit along the anterior and posterior sides adjacent the lateral side and a line-to-line fit along the anterior and posterior sides adjacent the medial side upon insertion of the stem into a bone cavity in the proximal femur prepared by the insertion and removal of said broach.

6. A hip prosthesis kit comprising a broach and an implantable body member;
said body member having a neck and a stem;
said broach and said stem each having a distal portion, a proximal portion with a proximal end, an anterior side, a posterior side, a lateral side, a medial side, an anterior-lateral corner, an anterior-medial corner, a posterior-lateral corner and a posterior-medial corner;
said broach having on its circumference means for cutting bone tissue upon insertion of the broach into a bone cavity in the proximal femur;
the proximal portion of said broach having predetermined widths between the medial side and the lateral side and having predetermined circumferential curvature along the medial side and the lateral side so as to expose substantially all cortical bone along the medial side and substantially all cancellous bone along the lateral side upon singular insertion into and removal from the bone cavity;
the proximal portion of said stem having widths between the medial side and the lateral side greater than the corresponding widths of said broach and having circumferential curvature identical to said broach along the medial side so as to produce an interference press-fit along the lateral side and a line-to-line fit along the medial side upon insertion of said stem into a bone cavity in the proximal femur prepared by the insertion and removal of said broach.

7. A hip prosthesis kit according to claim 6 wherein the proximal portion of said broach has predetermined widths between the anterior side and the posterior side and has predetermined circumferential curvature along the anterior-medial corner, the anterior-lateral corner, the posterior-medial corner and the posterior-lateral corner so as to expose substantially all cortical bone along the anterior-medial and posterior-medial corners and along the anterior and the posterior sides adjacent the medial side and substantially all cancellous bone along the anterior-lateral and posterior-lateral corners and along the anterior and posterior sides adjacent the lateral side upon singular insertion into and removal from the bone cavity;
the proximal portion of said stem having predetermined widths between the anterior and posterior sides adjacent the medial side approximately equal to the corresponding widths of said broach and having predetermined widths between the anterior and posterior sides adjacent the lateral side greater than the corresponding widths of said broach; and the proximal portion of said stem further having circumferential curvature along the anterior-medial and posterior-medial corners approximately equal to the corresponding circumference curvature of the proximal portion of said broach and having circumferential curvature along the anterior-lateral and posterior-lateral corners wider than the corresponding circumferential curvature of the proximal portion of said broach so as to produce a line-to-line fit along the anterior-medial and posterior-medial corners and along the anterior and posterior sides adjacent the medial side and an interference press-fit along the anterior-lateral and posterior-lateral corners and along the anterior and posterior sides adjacent the lateral side.

8. A hip prosthesis kit comprising a broach and an implantable body member;
said body member having a neck and a stem;
said broach and said stem each having a distal portion, a proximal portion with a proximal end, an anterior side, a posterior side, a lateral side, a medial side, an anterior-lateral corner, an anterior-medial corner, a posterior-lateral corner and a posterior-medial corner;
said broach having on its circumference means for cutting bone tissue upon insertion of the broach into a bone cavity in the proximal femur;
the proximal portion of said broach having predetermined widths between the medial side and the lateral side and having predetermined circumferential curvature along the medial side and the lateral side so as to expose substantially all cortical bone along the medial side and substantially all cancellous bone along the lateral side, the proximal portion of said stem having widths between the medial side and the lateral side greater than the corresponding widths of said broach and having circumferential curvature identical to said broach along the medial side and so as to produce an interference press-fit along the lateral side and a line-to-line fit along the medial side upon insertion of said stem into the bone cavity, wherein the proximal portion of said stem defines a longitudinal axis and has at least one groove on each of the anterior-lateral, posterior-lateral, anterior-medial and posterior-medial corners, each groove extending transverse to the longitudinal axis of the femoral component and terminating adjacent each said corner.

9. A hip prosthesis kit as set forth in claim 7 wherein the proximal portion of said stem is provided with multiple curved-line surface unevenness on a portion of each of the anterior side and posterior side.

10. A hip prosthesis kit as set forth in claim 7 wherein the proximal portion of said broach has predetermined widths between the anterior and posterior sides so as to expose substantially all cancellous bone along a majority of the anterior and posterior sides extending continuously from adjacent the lateral side upon singular insertion to and removal from the bone cavity; and the proximal portion of said stem has predetermined widths between the anterior and posterior sides along a majority of the anterior and posterior sides extending continuously from adjacent the lateral side which are greater than the corresponding predetermined widths of said broach so as to produce an interference press-fit along a majority of the anterior and posterior sides extending continuously from adjacent the lateral side upon forced insertion of the stem into the bone cavity.

11. A hip prosthesis kit comprising a broach and an implantable body member;
said body member comprising a neck and a stem and said broach comprising a stem;
the proximal portions of said broach stem and said body member stem being configured and dimensioned relative to each other so that any cross section of said body member is larger in area than a corresponding cross section of said broach;
the medial side of said cross section of said body member has curvature and dimensions which are the same as the corresponding curvature and dimensions of the medial side of said cross section of said broach; and the medial to lateral widths of said cross section of said body member are greater than corresponding medial to lateral widths of said cross section of said broach.

12. A hip prosthesis kit according to claim 11 wherein the anterior to posterior width of said cross section of said body member adjacent the medial side is the same as the corresponding anterior to posterior width of said cross section of said broach;
and the anterior to posterior width of said cross section of said body member adjacent the lateral side is greater than the corresponding anterior to posterior width of said cross section of said broach.

13. A hip prosthesis kit according to claim 11 wherein a cross section of said body member at the proximal end of said stem has a width between the midpoints of the medial and lateral sides which is 1 to 3 mm larger than the corresponding width of said cross section of said broach at the proximal end of the stem.

14. A hip prosthesis kit according to claim 13 wherein said cross section of said body member at the proximal end of the stem has widths between the medial and lateral side which are 1 to 3 mm larger than the corresponding widths of said cross section of said broach at the proximal end of the stem.

15. A hip prosthesis kit comprising a broach and an implantable body member;
said body member comprising a neck and a stem and said broach comprising a stem;
the proximal portions of said broach stem and said body member stem being configured and dimensioned relative to each other so that:
a cross section of said body member at the proximal end of said stem is larger in area than a corresponding cross section of said broach;
the medial side of said cross section of said body member has curvature and dimensions which are the same as the corresponding curvature and dimensions of the medial side of said cross section of said broach; and the medial to lateral widths of said cross section of said body member are greater than corresponding medial to lateral widths of said cross section of said broach.

16. A hip prosthesis kit according to claim 15 wherein the anterior to posterior width of said cross section of said body member adjacent the medial side is the same as the corresponding anterior to posterior width of said cross section of said broach;
and the anterior to posterior width of said cross section of said body member adjacent the lateral side is greater than the corresponding anterior to posterior width of said cross section of said broach.

17. A hip prosthesis kit according to claim 15 wherein said cross section of said body member has a width between the midpoints of the medial and lateral sides which is 1 to 3 mm larger than the corresponding width of said cross section of said broach at the proximal end of the stem.

18. A hip prosthesis kit according to claim 17 wherein said cross section of said body member has widths between the medial and lateral side which are 1 to 3 mm larger than the corresponding widths of said cross section of said broach at the proximal end of the stem.