U.S. patent number 3,641,590 [Application Number 05/003,353] was granted by the patent office on 1972-02-15 for acetabular replacement prosthesis and method of assembling.
Invention is credited to Arthur A. Michele.
United States Patent |
3,641,590 |
Michele |
February 15, 1972 |
ACETABULAR REPLACEMENT PROSTHESIS AND METHOD OF ASSEMBLING
Abstract
A selective individualized technique for acetabulum socket
replacement per se, or in conjunction with a hip replacement
prosthesis (Michele U.S. Pat. No. 3,228,393) for a total hip
replacement, designed for all ages including the very young. A
selective anchorage for a cup prosthesis of a size selected from
the limited number of differently sized cups is made available.
Anchorage of the acetabular socket replacement conforms to
variations in dimensions, shapes and positions of the (medullary)
canals of the acetabulum pelvis of the individual patient and
includes at least two elongated and convergent or divergent
fasteners. The bone is preferably drilled for a main pin fastener
of the appropriate length at the proper inclination and site. There
is then arranged in the acetabulum socket a selected cup prosthesis
having a preformed hole determined by and corresponding to the
drilled hole, into which the main pin is driven after passing
through the prosthesis hole. The spherical cup is quite thick and
has generally keyhole or T-shaped slots penetrating its rim and its
outer surface at various inclinations but avoiding penetration of
its inner surface. A relatively wide fastener drift of T-shaped or
other appropriate cross-sectional shape, designed to be inserted
with part of its width in the slot and the remaining part
projecting transversely as well as longitudinally beyond the cup
and out of the slot is driven into and through a selected slot at
the inclination and site most advantageous to the recipient
patient.
Inventors: |
Michele; Arthur A. (Montclair,
NJ) |
Family
ID: |
21705452 |
Appl.
No.: |
05/003,353 |
Filed: |
January 16, 1970 |
Current U.S.
Class: |
623/22.37 |
Current CPC
Class: |
A61F
2/32 (20130101); A61F 2002/3401 (20130101); A61F
2002/3631 (20130101) |
Current International
Class: |
A61F
2/32 (20060101); A61F 2/34 (20060101); A61F
2/36 (20060101); A61f 001/24 () |
Field of
Search: |
;3/1
;128/83,92R,92B,92BA,92BB,92C,92CA,92D,92E,92EB,92F,92G |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,126,961 |
|
Sep 1968 |
|
GB |
|
948,690 |
|
Jan 1949 |
|
FR |
|
124,585 |
|
Jan 1960 |
|
SU |
|
Other References
Gaenslen Acetabulum Caps, Vitallium Surgical Appliances Catalog,
Howmet Corp. p. 30 (No. 6937 relied upon). .
"Replacement of Arthritic Hips by the McKee-Farrac Prostheses" by
G. K. McKee et al., Journal of Bone & Joint Surgery, Vol. 48B,
No. 2, May 1966 pp. 245-246. relied upon..
|
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Frinks; Ronald L.
Claims
I claim:
1. In a hip replacement prosthesis, a cup having continuous
spherical inner and outer surfaces and an annular rim surface and
having circumferentially disposed slots therein penetrating the rim
surface and the outer surface and in sufficient spaced relation
outwardly of the inner surface to provide a closing inner wall on
each slot and to avoid penetration by said slots of said inner
surface, the slots extending through the material of the cup in the
general direction of the central longitudinal axis of the cup.
2. The prosthesis of claim 1, the slots being of the keyhole type,
fastening elements each having a part of the length and part of the
width thereof in a selected slot, the corresponding remainder of
the width of each of said elements projecting tranversely beyond
the slots.
3. The prosthesis of claim 1, the cup having a pin receiving hole
therethrough in predetermined inward spaced relation to the rim of
the cup and in predetermined angular relation to the axis of the
cup, said relations being determined by the bony structure of the
recipient.
4. The prosthesis of claim 3 and a corrugated main pin passing
through said hole.
5. The prosthesis of claim 3, drifts retained in the slots and a
main pin passing through the hole.
6. The hip replacement prosthesis of claim 1, selected slots being
enlarged along the lengths thereof and the widths thereof at the
inner parts of the slots to receive part of the width and a
substantial part of the length of a fastening drift with the
remaining part of the width of the drift projecting transversely
out of the slot to enter the bone of the recipient.
7. The prosthesis of claim 6, and fastening drifts associated with
selected slots for securing the cup in the acetabulum socket, the
drifts being longer than the slots and projecting transversely
therefrom.
8. In a hip replacement prosthesis, a cup having rim slots
therethrough, selected slots being inclined to the axis of the cup
and each other, the slots being of the keyhole type, each of a
number of selected slots having a pair of substantially parallel
outer walls extending inwardly from the outer surface of the cup
and terminating in an inner cylindrical wall of greater diameter
than the distance between the parallel walls and spaced outwardly
of the inner surface of the cup.
9. The method of assembling a hip replacement prosthesis having a
spherical cup provided with slots passing generally longitudinally
through only the rim surface and the outer surface of the cup and
having fastening drifts in the slots said slots having an inwardly
spaced first portion connected to an outwardly spaced second
portion of lesser width which intersects said outer surface to
define an open side, the cup having a hole therethrough in spaced
relation to the rim surface and having a pin passing through the
hole, the method comprising determining the position of said hole
to correspond to a pin-receiving hole in the acetabulum of the
recipient, aligning the holes, driving the pin into the aligned
holes, arranging the inner part of the width of a drift wider than
the selected slot second portion in said selected slot in inward
spaced relation to the outer surface of the cup, and driving the
outer part of the drift and the leading end part thereof into the
acetabulum of the recipient.
10. The method of claim 9, the step of determining the position of
the hole in the cup comprising rotating a guide jig having
therethrough a number of guide holes for a drill after inserting
the jig into the acetabulum socket of the recipient, the jig being
rotated to carry a selected guide hole into alignment with a
selected part of the bone of the recipient, drilling the hole in
the bone guided by the selected hole and replacing the jig in the
socket by a cup having a hole arranged correspondingly to the
selected guide hole and rotating the cup to align the cuphole with
the drilled hole.
11. The assembling method of claim 9, the slots in the cup being
inclined to the axis of the cup and to each other, the hole in the
cup being angularly related to said axis, the pin being corrugated,
the drift having the same cross-sectional shape at the inner part
thereof as said selected slot, the pin and the drift being
nonparallel, the position of a hole in the acetabulum being
determined by rotating a guide jig having a number of drill guide
holes therethrough after inserting the jig in the acetabulum
socket, the guide holes being at different distances from the axis
of the jig, rotation of the jig through the proper angle carrying a
selected hole thereof into alignment with the deepest and strongest
cortical or medullary bone, drilling a hole in said bone guided by
the selected hole, then replacing the jig in the socket by a cup
having a hole corresponding to the selected hole of the jig, and
aligning the cup hole with the drilled hole before driving the main
pin into the cup and the drilled hole.
Description
The invention relates to total hip replacement prosthesis but more
so to the acetabular socket as well as to the combination of an
acetabular cup prosthesis with a biomechanical femoral head
replacement prosthesis (Michele U.S. Pat. No. 3,228,393)
constituting a total hip replacement including the femoral
head.
Prior acetabular sockets or cups have not generally been firmly and
permanently anchored. The anchoring screws employed to fasten
certain sockets tend ultimately to loosen under the severe forces
acting on the joint. Those cups with integral and hence necessarily
parallel spikes cannot be adequately anchored to suit the
particular individual. For many patients the spikes may extend in
the wrong direction or may be of the wrong length or shape or at
the wrong location. The spikes cannot be adjusted or changed in any
attempt to prevent loosening of the cup and consequent
deterioration of the bony structure under the resulting excessive
stresses. The spikes, instead of the convex surface of the cup,
receive and transmit the pressure exerted upon the concave surface
of the cup by the femoral head or the ball head of a hip prosthesis
and resist the transmission of sufficient pressure upon the
acetabulum socket to result in the filling of voids which might be
present between the cup and said socket. Such pressure is necessary
to induce or encourage the growth of filling fibros-osseous tissue
which ultimately becomes hard bone in contact with a smooth outer
convex surface of the cup. A maximum entry into cortical or
medullary bone is needed for permanent anchorage and cannot be
adequately provided by prior screws or spikes.
Prior hip joint replacement prostheses, further, do not permit the
surgeon enough leeway or choice to conform the anchorage to the
normal and expected natural variations in the bones of different
patients, nor have such prostheses been adapted to attain the
proper rotational angle to withstand effectively the eccentric
weight loads to which they are subjected when in use, except for a
femoral head replacement prosthesis such as is disclosed in U.S.
Pat. No. 3,228,393 to which reference is hereby made and which is
incorporated herein.
This invention is therefore directed to the provision of a hip
joint (acetabular) cup prosthesis which when once implanted, is
held securely and permanently in place, being effectively resistant
to movement relative to the bone in any direction; which has a
smooth convex outer surface unconstrained by fastening means from
exerting pressure upon the concave surface of the socket in order
to cause the formation of filling fibros-osseous tissue and thereby
resulting in a firm concentric placement and secure foundation for
the cup; which is adapted for standardization in few sizes without
significant variation in shape but entirely capable of being fitted
to individuals whose bones differ substantially in shape,
dimensions, density and adaptive changes; which is anchored in two
or more places by fasteners of the same or of different
cross-sectional shapes, lengths, inclinations and sites and which
are chosen from a variety of fasteners each designed to enter
deeply into the strongest part of the pelvis whether it be cortical
or medullary bone; which can be used with several types of femoral
ball shaped head prostheses for total hip joint replacement; which
when used with the "MICHELE" head replacement is adequate to
withstand vibrational, eccentric, compressive, tensile and other
otherwise destructive stresses as well as all normal stresses and
to impart the proper rotational axis to the joint; which is adapted
for implantation in its miniature size in the young, without the
need for substitution of a larger size for relatively long periods;
which is adapted for implantation in an unusually large acetabulum
socket by the mere use of a standard-type cup of larger thickness
than the usual cup and of standard inner diameter; which can be
withdrawn in emergencies by the deliberate retraction of the
fasteners; which can be readily secured in place by a simple
technique and which remedies the defects of the prior orthodox
prostheses above mentioned.
The above and other objects of the invention will be clear from the
description which follows and from the drawings in which
FIG. 1 is a front elevational view of the implanted total hip
replacement prosthesis, showing outlines of the main parts of the
receiving bones in dash-dot lines and showing the cup in cross
section.
FIG. 2 is a side elevational view of a typical one of the cups of a
set of such cups, showing typical pin receiving holes and
drift-receiving slots.
FIG. 3 is a front elevational view of FIG. 2 partly in section to
expose some of the slots for the drifts.
FIG. 4 is a side elevational view of the jig or tool employed for
drilling the hole in the bone at the proper angle and position for
the reception of the main pin.
FIG. 5 is a front elevational view of FIG. 4 partly in section.
FIG. 6 is an elevational view, partly in section, of a typical main
pin fastener.
FIG. 7 is a similar view of one of the various types of drift
fasteners.
FIG. 8 is a fragmentary side elevation view of the cup and of a
modified form of drift fastener inserted into one of the rim slots
of the cup.
FIG. 9 is a horizontal sectional view of FIG. 8.
FIG. 10 is a view similar to FIG. 8 of a modified form of drift
fastener.
FIG. 11 is a horizontal sectional view of FIG. 10.
FIGS. 12 and 13 are cross-sectional views respectively of other
forms of drift fasteners.
Briefly, in practice a set of about four or more standard cups 15
(FIGS. 1-3) all of the same size, are provided. A smaller set
seldom needed and a third thicker set take care respectively of
youngsters and of patients having unusually large acetabulum
sockets. In each cup of a set, a main pin receiving hole is
positioned at an inclination and location differing from those of
the holes in the other cups. Should it be found that the main pin
for the cup is advisable, then after the usual surgical
preparation, the jig or tool 16 of FIGS. 4 and 5 is employed to
determine where and at what inclination the hole for the main pin
is to be drilled in the bone to attain the maximum degree of
fixation of the cup as by the greatest penetration into the pelvis.
The jig is rotated in the joint socket until one of the guide
holes, 17, 18, 19 or 20 is directed toward a suitable deep and
strong part of the bone, whereafter the hole 21 in the bone is
drilled through said guide hole. The proper cup of the set of
otherwise identical cups except for the cup hole and with a
corresponding hole 22 then replaces the jig and the main pin 23 is
driven into the holes 21 and 22. One or more drifts or auxiliary
pins (FIGS. 7-13) of the proper shape and length are driven through
the proper rim slot as 24, 24a or 24b in the cup and into the bone.
The natural femoral head or its equivalent prosthesis as shown in
FIG. 1 is finally inserted into the cup and surgery completed. When
advisable, the main pin and the drilled hole in the bone may be
omitted and reliance had upon suitable drifts to secure the cup in
place.
In detail and referring particularly to FIGS. 2 and 3, the
generally spherical hollow cup is of nonuniform thickness, having
two surfaces 25 and 26 nonconcentric with each other to provide the
greatest thickness at the planar surface 27 constituting the rim of
the cup. The diameter of the smooth outer convex surface 26 is
approximately that of the socket most likely to be encountered in
hip socket replacements. The diameter of the smooth inner concave
surface 25 is precisely that of the femoral head or prosthesis
coacting with the cup. For unusually large acetabulum sockets, a
set of cups is provided otherwise standard but employing for each
cup a greater outer cup diameter than standard. Should the socket
be too small in diameter, it may usually be reamed out to fit the
cup. For the young, a third set of cups is provided and if
necessary, a femoral head prosthesis of less than standard
size.
The slots 24, 24a and 24b for the drifts in the planar cup rim 27
pass through the cup's outer surface 26 and the rim surface 27 only
and do not penetrate the cup's inner surface 25, said inner surface
remaining unmutilated by the slots and preserving its full bearing
area except for any cup hole optionally made through both inner and
outer surfaces. Said slots extend longitudinally in the general
direction of, but are respectively at different angles to the
central axis of the cup to permit a choice of sites for the drifts
and to insure that the drifts are not parallel when in place,
better to resist unwanted relative movement of the cup and bone.
Each cup 15 of the set has its own main hole 22 in radial spaced
relation to the cup axis and at a different angle to said axis,
than the spacing and angle of the holes of the remaining otherwise
identical cups of the set. In the example shown in FIGS. 2 and 3,
the hole 22 corresponds to the hole 18 in the jig and is marked
similarly to the jig hole 18, with the identifying numeral "2."
(See reference numeral 30). The other holes in the jig are marked
"1," "3" and "4," there being four standard cups in the set, each
having one hole corresponding to a hole in the jig. Should it be
found that a main pin is not required in any particular case, there
should be a fifth cup in the set devoid of a main pin hole.
The cup hole 22 is shallowly countersunk as at 31 to receive the
short conical head 32 of the main pin 23, said head limiting the
entrance of the pin into the bone and determining the fully driven
position of the pin. At its leading end 33, the otherwise
corrugated pin is preferably rounded. Parallel annular grooves 34,
for the reception of cancellous bone or for receiving growing bone
and for easy reading of its length on X-ray pictures in which the
length may appear foreshortened, are made along the shank of the
pin. Since the pin is driven deeply into well-defined medullary or
cortical bone, it is relatively long.
For ease in withdrawing the pin if and when required, the recess 35
in the trailing end of the pin is provided. The reduced entrance to
the enlarged bulbous part 36 of the recess is preferably
substantially cylindrical. A suitable collapsible tool similar to
an inside ball hole gage is used to exert a pull on the spherical
wall of the recess to extract the pin, if necessary. In addition
to, or in place of the main pin, one or more drifts are used for
anchoring the cup. The inner marginal portions of the drifts of
FIGS. 7-11 are generally cylindrical and are adapted to enter and
to fit the corresponding cylindrical inner portions of the key
slots 24, 24a and 24b. Like any other kind of nail-type fastener,
there should be a considerable range of cross-sectional shapes,
proportions, dimensions and other characteristics in a supply of
drifts to meet the varied conditions presented in different
individuals.
In the form shown in FIG. 7 the drift 37 is of the cylindrical nail
type, headed at its trailing end and pointed at its leading end. To
permit said nail drift to be driven to a point in which its conical
head is slightly below the surface 25, the rim slots of the cup are
countersunk somewhat as at 38, the head limiting the extent to
which the drift may be driven. The remaining drifts illustrated are
preferably unheaded for reasons of economy, but are driven by a
suitable impact tool, not shown, engaging the rim surface 27 of the
cup to halt further drive when the drift is fully driven.
Referring to FIGS. 8 and 9, the drift 40 has a relatively thin
outer flange 41, a web 42 and a cylindrical inner marginal part 43
keyed with part of the web width projecting transversely beyond the
cup, into a selected rim slot of the cup. The projecting part of
the web 42 together with the flange 41 are driven into the bone of
the recipient. Suitable closely spaced fenestras 44 are formed in
the web. A withdrawal hole 45 is positioned in the web close to the
tailing end of the drift for the reception of a pulling tool if
withdrawal of the drift should be required. The leading edge 46 of
the drift, is sharpened for easy driving into the bone. A quite
shallow countersink 47 in the trailing end of the marginal portion
43 is adapted to receive the end of a driving tool. The drift 48 of
FIGS. 10 and 11 is similar to the drift 40 excepting for the
omission of the flange 41 and the substitution therefor of the
sharp side edge 49.
It will be understood that the cross-sectional shapes of the drifts
may be many and varied. Obviously, for example, by combining parts
of the drifts 40 and 48 and changing the shape of the corresponding
inner part of the key slots in the rim of the cup, drifts of a
number of different cross-sectional forms would result. By varying
the length of the drifts and the disposition of the fenestras
therein, a still greater variety is obtained. In the examples
illustrated herein, the respective drifts 50 and 51 of the FIGS. 12
and 13 each have an inner marginal portion 52 of rectangular,
instead of circular, cross section. Consequently, the inner parts
of those key slots in the cup rim intended to receive such drifts
are enlarged and obstructed by the constricted outer parts and are
also made of rectangular cross section to fit the drifts, though
such slots are not specifically illustrated. The relatively thin
and wide web 42 of the drifts 40 and 48 is retained and is
substantially the same in both drifts 50 and 51 and the sharpened
outer side edge 49 is kept in the drift 50. In the drift 51, the
flange 41 is retained as the outer side edge portion.
Because of the differences in the inclinations of many of the rim
slots, which receive the fastener elements or drifts, from each
other and from the main pin hole 22, it will be noted from FIG. 1
for example, that the fastening elements are not parallel in the
bone when driven, but converge or diverge. Consequently, they are
dependably secured and cannot work loose though they can be
individually withdrawn deliberately as herein before described.
However, neither the drifts nor the main pin are fitted so tightly
in the respective slots or main hole as to prevent the cup from
being pressed under the required pressure against the acetabulum
socket. It has also been pointed out that only one main pin hole,
differing in position from the corresponding holes in the other
cups of the same set, is made in each cup, and that a suitable jig
is used to guide the drill boring the main pin hole 21, in the
bone, which hole may be smaller than the diameters of the pin and
of the holes in the cup.
Reference is now made to FIGS. 4 and 5 showing the hollow
hemispherical drilling guide jig 16 for the purpose mentioned. The
outer convex surface 55 of the jig is of the diameter and shape to
fit into the acetabulum socket which is suitably reamed by means of
a surgical ballend reamer, while the inner surface 56 is of
sufficiently large diameter to permit about four or more guide
holes as 17, 18, 19 and 20, marked with the identifying numerals
30, to be made through the thickness of the jig at different
inclinations to and at different distances from the axis of the
jig. Said thickness is greater than that of the cup 15 and enough
to guide the drill adequately. Extending outwardly from the flat
rim 57 of the main body of the jig and secured thereto as by the
screws 58 are the circumferentially spaced apart flat supports 59,
the extensions 60 of which are intended to be held on the rim of
the acetabulum socket during the drilling operation. The drill jig
is rotated until one of the holes, as 18 is opposite the strongest
and longest cortical or medullary bone extending from the socket,
whereupon the main pin hole is drilled and the hole identifying
numeral as for Example "2" is noted. The jig is then replaced by
that cup of the set perforated with a hole marked "2" and the cup
is rotated to bring its hole into alignment and registration with
the drilled hole, the cup being set into the socket with its rim 27
substantially flush with the planar rim of the acetabulum (FIG. 1)
or slightly below. The main pin of the proper length is driven into
the aligned holes. There is a sufficient number of rim holes 24,
24a and 24b, which alternate around the cup rim, to allow a wide
choice of sites and inclinations for the drifts to be driven
therethrough to the best advantage.
It is advisable that a variety of drifts as 37, 40, 48, 50 and 51
and possibly others be prepared in several lengths so that few
restrictions are put upon the selection of the correct number and
types of drifts needed for complete dependability on the
implantation of the cup in the socket.
It will now be seen that there has been provided a prosthesis and
an assembling technique adapted for either total hip joint
replacement or for acetabulum socket replacement and designed to
meet the severe conditions involved in such replacements because of
the different shapes, proportions and dimensions of the bones of
different individuals and the unpredictable effect disease may have
had upon them; that the difficulties of impermanence present in
most prior prostheses for the same purpose have been adequately
resolved and that the various objects of the invention have been
attained.
While certain specific embodiments of the invention have been
herein shown and described, various obvious changes may be made
therein without departing from the spirit of the invention defined
by the appended claims.
* * * * *