US 3426364 A
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Description (OCR text may contain errors)
Feb. 11, 1969 w. v. LUMB 3,425,364
PROSTHETIC APPLIANCE FOR REPLACING ONE OR MORE NATURAL VERTEBRAE Filed Aug. 25, 1966 o O O OO INVENTOR. WILLIAM V. LUMB United States Patent O 3,426,364 PROSTHETIC APPLIANCE FOR REPLACING ONE OR MORE NATURAL VERTEBRAE William V. Lumb, Fort Collins, Colo., assignor to Colorado State University Research Foundation, Fort Collins, Colo., a nonprofit corporation of Colorado Filed Aug. 25, 1966, Ser. No. 575,065 U.S. Cl. 3-1 10 Claims Int. Cl. A61f1/00, /04; A61b 17/04 This invention relates to a prosthetic appliance and, more particularly, to a prosthesis in the form of an artificial vertebra to be used singly or in combination to bridge the gap left in the spinal column when one or more of the natural vertebrae have to be removed because they are diseased, broken or malformed.
Occasions sometimes arise in the treatment of the higher vertebrates, both man and animal, when it becomes desirable to remove one, and possibly several, vertebra from the spinal column. Removal of a diseased section may, for example, be necessary to check the spread of the disease to adjacent portions of the spinal column and the surrounding tissues. Accidents and birth defects may, likewise, produce conditions that necessitate removal of part of the vertebral column.
Notwithstanding the need for some form of prosthesis to completely replace one or more vertebra, up to the present time none has been available. Accordingly, both the surgeon and veterinarian have been forced to leave some portion of the natural diseased or broken vertebra in the body to provide a bridge or link between adjoining healthy vertebra on either side thereof. In many instances, this is a highly unsatisfactory solution and may, in the case of cancerous or otherwise diseased bone, enable the disease to spread.
The present state of the art is such that little can be done insofar as substituting a prosthetic appliance for the centrum, or body portion, of the vertebra, the latter being required to maintain the continuity of the vertebral column. About all that can be done is to bridge across a broken neural spine and, in rare instances, substitute a metal arch bridging the natural neural spines for an entire neural arch.
It has been found in accordance with the teachings of the instant invention that it is, in fact, possible to replace one or more entire vertebra by substituting therefor the prosthesis forming the subject matter hereof. The appliance includes an inverted generally Y-shaped element that corresponds to and replaces the natural neural arch and spine. The stem of the Y-shaped element performs the function of the neural spine and includes provision for fastening thereto a pair of apertured metal arches that bridge across the appliance and connect to the natural neural spines of adjoining vertebra. If, perchance, the centrum is intact, the above-described Y-shaped element can be fastened directly thereto leaving a spinal foramen for the passage of the spinal cord.
In the event that natural centrum must also be removed, it is replaced by an arched member that passes in front of the spinal cord and connects to the divergent arms of the Y-shaped member. Ears projecting from this arched member into position alongside the centra of adjoining vertebra are pivotally attached to the latter to produce an articulated joint.
It is, therefore, the principal object of the present invention to provide a novel and improved prosthesis to replace vertebra(e) in the higher vertebrates.
A second objective of the invention herein disclosed and claimed is to provide a device of the type aforementioned that can be substituted for an entire natural vertebra or even a series thereof.
3,426,364 Patented Feb. 11, 1969 ICC Another object is to provide a prosthetic appliance that is nontoxic and otherwise compatible with body tissue and one.
Still another objective is the provision of a prosthetic vertebra that is separable into parts corresponding to both the natural centrum and neural arch, either portion of the artificial appliance being usable with its natural companion part.
An additional object is to provide a prosthesis of the type abovementioned that is readily adaptable for use as a replacement for any of the vertebra(e) of the human or animal spinal column.
Further objects are the provision of artificial vertebra(e) that are of relatively simple construction, easy to install, versatile, rugged, virtually unbreakable, compact and even somewhat decorative in appearance.
Other objects will be in part apparent and in part pointed out specifically hereinafter in connection with the description of the drawings that follow, and in which:
FIGURE 1 is a side elevation showing one of the prosthetic vertebra elements attached in place between two natural vertebrae of a higher vertebrate;
FIGURE 2 is an end elevation of the prosthetic appliance by itself, portions of the inverted Y-shaped element having been broken away and revealed in section;
FIGURE 3 is a section taken along line 3-3 of FIG- URE 1;
FIGURE 4 is a top plan view of the appliance;
FIGURE 5 is a side elevation showing one of the appliances of the type revealed in FIGURES l-4 used in conjunction with two slightly modified versions thereof to bridge a gap left upon removal of three adjoining natural vertebrae, a portion of one of the modified versions having been broken away and shown in section;
FIGURE 6 is a bottom plan view of one of the modified appliances having a corner broken away and shown in section to reveal the interior construction;
FIGURE 7 is a side elevation similar to FIGURE 5 except all three of the prosthetic elements have been further modified to eliminate the rigid bridge and accept as a substitute therefor a springable hinge member that leaves the joint articulate;
FIGURE 8 is a section taken along line 88 of FIG- URE 7; and
FIGURE 9 is a longitudinal section taken along the centerline of the FIGURE 7 body portions, the Y-shaped elements and connectors having been removed therefrom.
Referring now to the drawings for a detailed description of the present invention and, initially, to FIGURES 1-4, inclusive, for this purpose, reference numeral 10 has been employed to designate the prosthetic appliance in a general way and it will be seen to include an inverted generally Y-shaped element 12 detachably connected to a body-forming portion 14 that has a semi-cylindrical trough 16 cut in its connecting surface 18 that, when joined to the divergent arms 20 of the Y-shaped element, cooperates therewith to define a cylindrical bore 22 adapted to receive the patients spinal cord. As aforementioned, the divergent arms 20 of the Y-shaped member 12 function in much the same manner as the neural arches 24 of the patients natural vertebrae that have been generally referred to by reference numeral 26; whereas, the stem portion 28 of said member takes the place of the neural spine 30 of the real bone. Body 14 of the prosthesis, on the other hand, replaces the centrum 32.
Elements 12 and 14 of the appliance are both preferably fabricated from some type of plastic material compatible with the internal tissues and bone of the body, several such materials being commercially available for use in the fabrication of prosthetic appliances. The material must, of course, be non-toxic, able to withstand the compression and bending loads to which a vertebrates spine is subjected without breaking, and be workable through either machining or direct moulding techniques to produce a smooth surface which will not chafe or otherwise irritate the patients spinal cord or the pads of cartilaginous tissue that separate same from the adjacent natural vertebrae. Thermoplastic vinylidene fluoride manufactured by Pennsalt Chemicals Corporation and marketed under the trademark Kynar has proven quite satisfactory although there are probably several other materials that will do as well.
Dimensionally, the prosthetic device of the present invention closely approximates in overall height, width and thickness that of the vertebra it is to replace although, for a given animal species, these dimensions remain much the same so that the units can be manufactured in standard sizes. The various screws, nuts and connecting braces which will be described presently may also be fabricated from plastic materials although, from the standpoint of strength, it is desirable to make them from metal. Stainless steel is satisfactory for this purpose although these elements are preferably made from a special steel alloy containing chromium, molybdenum and nickel sold under the trademark Vitalium that is widely used in the fabrication of metal fittings for internal applications.
The Y-shaped member 12 is joined to the body portion 14 by means of four screws 34 (Figure 3) that pass into countersunk threaded openings 36 that extend from the arms 20 down into the body alongside spinal cord passage 22. The body must, of course, be passed in front of the patients spinal cord into the space left vacant by removal of the natural vertebra before the arms of the Y-shaped element can be screwed thereto from the back through an incision made for this purpose. In those instances where the centrum 32 remains intact and only the neural arch and spine must be replaced, Y-shaped element 12 may be screwed directly to the centrum after the latter has been separated from the neural arch.
The body 14, in the particular form illustrated in FIG- URES 1-4, has a pair of integrally-formed ears 38 projecting longitudinally in transversely-spaced relation from both ends thereof adapted to lap the centrum 32 of the adjacent natural vertebrae to which they are fastened by screws 40. As revealed most clearly in FIGURES 2 and 4, the opposed inside surfaces of the ears 38 are curved to conform with the shape of the natural centrum to which they attach.
The stem portion 28 of the Y-shaped element 12 is provided with an elongated vertical slot 42 adapted to receive a screw fastener 44 that attaches metal braces 46 to opposite sides thereof. As shown in FIGURE 1, braces 46 include a plurality of apertures 48 to receive the screws 44 and are slightly curved. In the forms shown in FIG- URE 1 where the prosthetic appliance is used to bridge the gap left upon removal of only one natural vertebra, the braces are fastened on opposite sides of the stem 28 at approximtaely their mid-point. The extremities thereof thus project longitudinally beyond the stem in position to lap the adjacent neural spines 30 of the natural vertebrae in much the same manner as the ears 38 of the body 14 lap the centrum. These extremities are fixedly attached to the spines by screws 50 that pass through holes drilled in the latter.
As shown in FIGURE 1, the connection thus formed is a rigid one and no hinged or articulate movement takes place between the artificial vertebra and the adjacent natural vertebrae. Slot 42 in the brace 46 merely makes it possible to raise and lower the latter so that its extremities are properly located to be fastened onto the adjacent spines. The resulting rigid connection is much the same as would occur if two or more of the patients natural vertebrae were fused, the latter being a fairly common surgical procedure for back injuries.
Next, reference will be made to FIGURES and 6 wherein a slightly modified structure has been shown by means of which two or more missing natural vertebrae may be replaced by artificial ones. The prosthetic device 10a shown on the left is much the same in construction as the one identified by numeral 10 in the previouslydescribed figures. The inverted Y-shaped member 12 is substantially identical except that it has slightly different dimensions. Brace 46a is straight and shorter but performs the selfsame function as brace 46, namely, to rigidly fasten the appliance 10a to the adjacent natural vertebra 26. The body 14a has, however, been modified slightly in that the ears 38a on the right-hand end thereof that fasten onto the second of the three prosthetic devices 1012 are straight and parallel to one another like those shown in FIGURE 6 rather than being curved to fit the centrum as are the cars 38 on the left-hand end of the unit 10a.
The middle unit of the three (10b) again carries the identical Y-shaped element 28 but has a further modified base 14b. This modification, however, comprises nothing more than the elimination of ears 38 from the 10a unit and substituting therefore sockets 52 adapted to receive the parallel ears 38a for limited pivotal movement about screw pivot 40.
The third element of the three on the right-hand end of the assembly is still different in that the base instead of being equipped with the parallel ears 38a as is the middle element 10b, it has the curved ears 38 to fit the centrum of the natural vertebras. In all other respects, units 10b and 10c are identical and the latter fastens onto the adjacent natural vertebra with modified brace 46a in the same manner as unit 10a to form a rigid connection therewith. While not illustrated, it is obvious that an appliance like 10:: could be used on both extremities of the assembly with the one occupying the position of present unit 100 being reversed end-for-end. This would necessitate altering the form of the middle unit 10b slightly by replacing the ears 38a with sockets 52 and fitting the ears 38a on the unit 10a therein. Obviously, the abovedescribed construction would be simpler than that illus trated because only two, rather than three, different forms of the appliance would be required. From another standpoint, however, the assembly shown in FIGURE 5 is preferred, namely, because it is adaptable for use in any situation requiring a chain of two or more artificial prosthetic vertebrae while the one described previously is limited to a three unit assembly. For example, in the construction shown, unit 10a can be connected directly to 10 eliminating 10b altogether and producing a two-unit chain. On the other hand, several units like 10b can be linked together between a 10a and a 100 unit to form a longer chain where needed.
The remaining feature of the modification of FIG- URES 5 and 6 that requires description is arch 54. Two such arches 54 are fastened at their mid-points through elongate central slot 56 to slot 42 in the stem 28 of the middle unit 10b in the same manner as brace 46 in FIG- URE 1. The extremities of these arches are similarly attached to the stems 28 of units 10a and 100 on opposite sides thereof through elongate end slots 58. By tightening fastener 44 in the central slot 56 so as to prevent any relative movement between the arches 54 and the middle appliance while leaving the screws a little loose that pass through the end slots 58, limited articulated movement between the end units 10a and 100 along with the natural vertebrae rigidly connected thereto and middle unit 1012 is possible. If one were to make all of the aforementioned connections rigid, no less than five vertebrae (2 natural and 3 artificial) would be fuse-d together and, perhaps, limit the patients freedom of movement unduly.
Finally, with reference to the remaining Figures of the drawing, specifically FIGURES 7, 8 and 9, a further modified three-unit assembly has been shown wherein the metal arches 54 have been eliminated altogether and the bases 14d, e and f of the altered units 10d, e and f modified to include provision for carrying spring member 60. With the exception of the fact that units 10d and 10f have their bases modified to include a slightly conical socket 62 adapted to receive the extremities of spring member 60 in spaced parallel position beneath opening 22, these elements are identical to the previously-described members a and 100, respectively as is their manner of connecting to the adjacent natural vertebrae. Likewise, middle unit 10e corresponds closely to unit 10b except that the former has an opening 64 therethrough adapted to loosely receive the middle section of spring element 60. Specifically, opening 64 comprises two opposed conical counterbores that intersect at the center of base Me and flare as they emerge through the ends in axial alignment with the conical sockets 62.
The conical sockets and conical counterbored opening produce oblique conical surfaces wherein the elements thereof that lie closest to the pivots 40 are all colinear and tangent to the spring member 60 when the segments of the appliance occupy the straight line relation shown in FIGURE 9. Any flexion in a direction to open the gap 66 between the segments will, of course, be immediately resisted by the spring which biases them back to their straight line relation. Now, when the segments are flexed in the opposite direction to close gap 66, the elements of the conical surfaces diametrically opposite those pre viously mentioned assume a colinear relationship and lie tangent to the spring element. Thus, the latter type of flexion takes place independent of the spring which does not bend or otherwise resist such movement. For purposes of illustration, the slope of these conical surfaces has been exaggerated in FIGURE 9 because, as shown, with the Y-shaped members mounted atop the bases, the gap would close before the elements in the conical surfaces assumed a colinear relation.
Having thus described the several useful and novel features of the prosthetic vertebra of the present invention, it will be seen that the several worthwhile objectives for which it was developed have been achieved. Although but a few specific embodiments of the invention have been disclosed and described, I realize that certain changes and modifications therein may well occur to those skilled in the art within the broad teaching hereof; hence, it is my intention that the scope of protection afforded hereby shall be limited only insofar as said limitations are expressly set forth in the appended claims.
What is claimed is:
1. The prosthetic appliance which comprises: at least one body member sized for insertion into the gap left in the spinal column of a higher vertebrate following removal of one or more natural vertebrae therefrom, each of said body members having at least one relatively flat surface extending between its ends that includes a longitudinal substantially semi-cylindrical trough; generally Y-shaped elements having a stem-portion merging at one extremity into divergent leg-portions that fasten onto the flattened surfaces of each of the body members astride the trough and cooperate therewith to define a passage sized to loosely receive said vertebrates spinal cord; first connecting means attached to the stem-portion of each Y-shaped element located adjacent a natural vertebra adapted for attachment to the neural spine of the latter; and, second connecting means attached to each base member located adjacent a natural vertebra adapted for attachment to the centrum thereof, said first and second connecting means cooperating with one another to hold said adjacent natural vertebra in fixed relation to said appliance.
2. The prosthetic appliance as set forth in claim 1 in which: two body members are disposed in end-to-end relation having an overall length adapted to fit within the gap left after removal of two adjacent natural vertebrae; and in which, a third connecting means is carried by one of the two body members connecting same to the other of said body members for pivotal movement about a transverse axis.
3. The prosthetic appliance as set forth in claim 2 in which: the two body members include elongate sockets in their adjacent ends arranged in aligned opposed relation paralleling the semi-cylindrical trough in spaced relation thereto; and in which, an elongate spring-member is positioned within the sockets bridging between the body members, said spring member normally biasing said body members into straight-line relation.
4. The prosthetic device as set forth in claim 3 in which: the third connecting means interconnects the two body members so as to leave a gap therebetween when they are arranged in straight-line relation to one another; and in which, the sockets are shaped to immediately flex the spring element upon an application of forces to the body members adapted to open the gap therebetween while allowing said gap to close without flexing same.
'5. The prosthetic appliance as set forth in claim 2 in which: at least one longitudinally-slotted rigid brace is connected between the stem-portions of the two Y-shaped elements, said brace cooperating with said third connecting means to limit the extent of relative pivotal movement between the body members.
6. The prosthetic appliance as set forth in claim 1 in which: at least three body members are disposed in endto-end relation having an overall length adapted to fit within the gap left after removal of a corresponding number of adjacent natural vertebrae; and in which fourth connecting means apertatively interconnect each of the intermediate body members with the adjacent body members on both ends thereof for pivotal movement about longitudinally-spaced substantially parallel axes.
7. The prosthetic appliance as set forth in claim 6 in which: at least one longitudinally-extending rigid brace is attached intermediate the ends thereof to the stem-portion of the Y-shaped element mounted upon one of the intermediate body members, the extremities of said brace extending longitudinally therefrom in opposite directions into position for attachment to the stem-portions of the Y-shaped elements adjacent the ends thereof, each of said brace extremities having a longitudinally-extending slot therein; and in which, fastener means mounted within the slots attach said brace extremities to the corresponding stem-portions so as to permit relative slidable movement therebetween as the body elements are pivoted about their parallel axes.
8. The prosthetic appliance as set forth in claim 6 in which: each of the intermediate body members has a longitudinal opening therethrough paralleling the semicylindrical trough in spaced relation thereto and in aligned relation to one another; both of the end body members include elongate sockets arranged in opposed aligned relation to the openings in the intermediate body members; and in which an elongate spring member is located within the openings in the intermediate body members with the extremities thereof extending into the sockets in the end body members, said spring member normally biasing said body members into straight-line relation.
9. The prosthetic appliance as set forth in claim 1 in which: a single base member is employed of a length adapted to fit in the gap left after removal of a single natural vertebra; the first connecting means comprises at least one brace member attached intermediate the ends thereof to the stem-portion of the Y-shaped element with its remote extremities extending longitudinally therebeyond into position for attachment to the neural spines of both natural vertebra adjacent thereto on opposite ends; and in which, the second connecting means comprises a pair of longitudinally-extending transverselyspaced ears projecting from opposite ends of the body member into bracketing relation alongside the centra of the adjacent natural vertebrae.
10. The prosthetic appliance as set forth in claim 1 in which: the first connecting means comprises a pair of rigid braces fastened to opposite faces of the stem-portion that project longitudinally therefrom in spaced substantially parallel relation to one another into position bracketing the neural spine.
(References on following page) 7 8 References Cited OTHER REFERENCES UNITED STATES PA Vitallium Spin-a1 Fusion Plates and Bolts, Catalog Of Zimmer Mfg. Co., Warsaw, Ind., Feb. 1947, page 40. 2,545,452 3/1951 Fletcher 3-12-7 copy in Group 335 2,677,369 5/1954 Knowles 128-92 5 RICHARD A. GAUDET, Primary Examiner.
FOREIGN A S RONALD L. FRINKS, Assistant Examiner.
1,037,262 4/1953 France. i28 92, 334