U.S. patent number RE40,914 [Application Number 09/827,252] was granted by the patent office on 2009-09-08 for orthopaedic fixation plate.
This patent grant is currently assigned to Smith & Nephew, Inc.. Invention is credited to Harold S Taylor, J. Charles Taylor.
United States Patent |
RE40,914 |
Taylor , et al. |
September 8, 2009 |
Orthopaedic fixation plate
Abstract
A plate for use in fixating the position of a first bone segment
relative to a second bone segment, the plate comprising a body
portion having a plurality of attachment mechanisms located
therein, wherein the attachment mechanisms include: a first group
of three attachment mechanisms substantially positioned within
90.degree.-150.degree. of one another about a circle, and
preferably within substantially 120.degree. of one another, whereby
the first group of attachment mechanisms is designed to facilitate
attachment of a plurality of adjustable length struts to the plate;
and a second group of attachment mechanisms substantially
positioned about the circle that are designed to facilitate
attachment of accessories to the plate, wherein the total number of
the attachment mechanisms is a multiple of three.
Inventors: |
Taylor; J. Charles (Memphis,
TN), Taylor; Harold S (Memphis, TN) |
Assignee: |
Smith & Nephew, Inc.
(Memphis, TN)
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Family
ID: |
25494812 |
Appl.
No.: |
09/827,252 |
Filed: |
April 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
08954003 |
Oct 20, 1997 |
05891143 |
Apr 6, 1999 |
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Current U.S.
Class: |
606/56; 606/53;
606/54 |
Current CPC
Class: |
A61B
17/62 (20130101); A61B 17/66 (20130101) |
Current International
Class: |
A61B
17/56 (20060101) |
Field of
Search: |
;606/52,53,54-61 |
References Cited
[Referenced By]
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WO |
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WO |
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WO 96/26678 |
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Sep 1996 |
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WO |
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Primary Examiner: Erezo; Darwin P
Attorney, Agent or Firm: Kilpatrick Stockton LLP
Claims
We claim:
1. An orthopaedic spatial fixation system for holding bone parts
comprising a plurality of fixation plates wherein each plate
includes a body portion having n .[.holes.]. .Iadd.attachment
structures .Iaddend.positioned therein, whereby said .[.holes.].
.Iadd.attachment structures .Iaddend.are substantially positioned
along an arc of .alpha..degree. of a circle defined by a diameter
d, and .[.the cord.]. .Iadd.a chord .Iaddend.length between
adjacent .[.holes.]. .Iadd.attachment structures .Iaddend.is
.[.substantial.]. .Iadd.substantially .Iaddend.equal to .[.1.].
.Iadd.and is substantially equal between all attachment
structures.Iaddend., and .times. .function..alpha..times.
##EQU00009## .[.and.]. whereby .[.the diameter d for each plate
within the system is unique, and.]. the value for n(360/.alpha.)
.[.for each consecutive plate diameter d.]. in the system is a
multiple of 3.Iadd., and wherein at least two of the fixation
plates are connected to each other by at least six substantially
rigid, adjustable length struts, wherein each of the struts is
disposed substantially diagonally with respect to its adjacent
struts.Iaddend..
2. The orthopaedic spatial fixation system of claim 1 further
comprising bone pins for interfacing the bone parts and plates;
and, .[.a plurality of.]. .Iadd.wherein the .Iaddend.struts
.[.that.]. extend between the plates to hold the plates in a
selected position relative to one another and relative to the bone
parts; wherein the struts are attached to the plates at the
.[.holes.]. .Iadd.attachment structures.Iaddend.; and, wherein .[.a
plurality of.]. the struts have adjustable length sections for
varying the length of the strut to adjust the relative position of
the plates.
3. The orthopaedic spatial fixation system of claim 2 wherein the
.[.holes.]. .Iadd.attachment structures .Iaddend.on at least one of
the plates are one hundred twenty degrees (120.degree.) apart.
4. The orthopaedic spatial fixation system of claim 1 wherein
rotation of one plate one hundred twenty degrees (120.degree.)
relative to an adjacent plate results in the same alignment of
adjacent .[.holes.]. .Iadd.attachment structures .Iaddend.as before
such rotation of the plates.
5. The orthopaedic spatial fixation system of claim 1 wherein the
plates are symmetrically configured so that if one plate is placed
over an adjacent plate, the .[.holes.]. .Iadd.attachment structures
.Iaddend.in each plate can be aligned.
6. The orthopaedic spatial fixation system of claim 5 wherein the
plates are symmetrically configured so that one plate can be
flipped over without affecting the alignment of adjacent
.[.holes.]. .Iadd.attachment structures.Iaddend..
7. The orthopaedic spatial fixation system of claim 2 wherein there
are two plates and each plate includes 3 .[.holes.].
.Iadd.attachment structures.Iaddend..
8. The ort.Iadd.h.Iaddend.opaedic spatial fixation system of claim
7 wherein .[.there are.]. .Iadd.the struts comprise only
.Iaddend.six struts each having a first end and a second end; the
first end of each strut is attached to one of the plates and the
second end of each strut is attached to the other plate; the ends
of the struts are attached to the plates at the .[.holes.].
.Iadd.attachment structures.Iaddend.; and, each .[.hole.].
.Iadd.attachment structure .Iaddend.accommodates two strut ends,
one from each of two adjacent struts.
.Iadd.9. The orthopaedic spatial fixation system of claim 1,
wherein the attachment structures are holes..Iaddend.
.Iadd.10. The orthopaedic spatial fixation system of claim 1,
wherein the circle comprises a groove and the attachment structures
are clamps attached to the groove..Iaddend.
.Iadd.11. The orthopaedic spatial fixation system of claim 1,
further comprising markings or etches to designate the attachment
structure positions..Iaddend.
.Iadd.12. The orthopaedic spatial fixation system of claim 1,
further comprising one or more plates being multiple diameter
plates having a second set of attachment structures..Iaddend.
.Iadd.13. The orthopaedic spatial fixation system of claim 12,
wherein the second set of attachment structures is not spaced
according to the diameter equation and chord length
limitations..Iaddend.
.Iadd.14. The orthopaedic spatial fixation system of claim 1,
wherein the chord length between adjacent attachment structures is
between about 0.48 inches and about 0.52 inches..Iaddend.
.Iadd.15. An orthopaedic spatial fixation system, comprising a
plurality of arcuate shaped fixation plates, wherein each plate
comprises a plurality of attachment structures, at least some of
which have substantially uniform sizes and a geometrical
arrangement defined whereby the attachment structures are: (a) in
sets of three, (b) spaced substantially 120 degrees apart from each
other along an arc of the fixation plate, and (c) substantially
equally spaced apart; wherein rotating a first one of the fixation
plates substantially 120 degrees from a starting position in a
plane substantially parallel to another one of the fixation plates
causes the first fixation plate to present the same geometrical
arrangement of attachment structures as the geometrical arrangement
of the attachment structures of the another plate, and wherein at
least two of the fixation plates are connected to each other by at
least six substantially rigid, adjustable length struts, wherein
each of the struts is disposed substantially diagonally with
respect to its adjacent struts..Iaddend.
.Iadd.16. The orthopaedic spatial fixation system of claim 15,
whereby rotating the first fixation plate substantially 60 degrees
from the starting position in a plane substantially parallel to
another one of the fixation plates presents the same geometrical
arrangement of attachment structures as the geometrical arrangement
of the attachment structures of the another plate..Iaddend.
.Iadd.17. The orthopaedic spatial fixation system of claim 15,
wherein the number of attachment points is a multiple of six,
providing 2.times.3 symmetry..Iaddend.
.Iadd.18. The orthopaedic spatial fixation system of claim 15,
wherein at least one of the fixation plates is ring
shaped..Iaddend.
.Iadd.19. The orthopaedic spatial fixation system of claim 15,
wherein the plurality of attachment structures is positioned such
that in use, at least some of the attachment structures on one of
the plates move into alignment with at least some of the attachment
structures on another plate as adjustment is effected..Iaddend.
.Iadd.20. The orthopaedic spatial fixation system of claim 15,
wherein the attachment structures are positioned along an arc of
.alpha..degree. of a circle defined by a diameter d, and a chord
length between adjacent attachment structures is substantially
equal to l, and the defined relationship comprises .times.
.function..alpha..times. ##EQU00010## .Iaddend.
.Iadd.21. The orthopaedic spatial fixation system of claim 15,
wherein the orthopaedic spatial fixation system is adapted to be
positioned on a patient..Iaddend.
.Iadd.22. The orthopaedic spatial fixation system of claim 15,
wherein the struts comprise only six adjustable struts, a first end
of each of the struts connected to one of the attachment structures
on one of the fixation plates and a second end of each of the
struts connected to one of the attachment structures on another one
of the fixation plates, wherein the attachment structures connected
to the struts are each connected to two struts..Iaddend.
.Iadd.23. The orthopaedic spatial fixation system of claim 15,
wherein the struts comprise only six adjustable struts, each strut
connected at a first end to one of the attachment structures of one
of the fixation plates and each strut connected at a second end to
one of the attachment structures of another one of the fixation
plates, wherein each attachment structure that is connected to a
strut is only connected to one strut..Iaddend.
.Iadd.24. The orthopaedic spatial fixation system of claim 15,
wherein a chord length between adjacent attachment structures is
between about 0.48 inches and about 0.52 inches..Iaddend.
.Iadd.25. An orthopaedic spatial fixation system, comprising a
plurality of fixation plates wherein each plate comprises a
plurality of attachment structures, at least some of the attachment
structures being in sets of three attachment points, each plate
having a geometrical arrangement defined whereby the three
attachment points in a set are spaced substantially 120 degrees
apart from each other along an arc of the fixation plate; wherein
at least two of the fixation plates are connected to each other by
at least six substantially rigid, adjustable length struts, wherein
each of the struts are disposed substantially diagonally with
respect to its adjacent struts, and the number of attachment
structures on each plate being a multiple of 3, whereby rotating
the first fixation plate substantially 120 degrees from a starting
position in a plane substantially parallel to another one of the
fixation plates presents the same geometrical arrangement of
attachment points as the geometrical arrangement of attachment
points presented to the struts when the first fixation plate is in
the starting position..Iaddend.
.Iadd.26. The orthopaedic spatial fixation system of claim 25,
further comprising an accessory adapted to be attached to one or
more of the fixation plates..Iaddend.
.Iadd.27. The orthopaedic spatial fixation system of claim 25,
wherein the orthopaedic spatial fixation system is adapted to be
positioned on a patient..Iaddend.
.Iadd.28. The orthopaedic spatial fixation system of claim 25,
wherein the struts comprise only six struts, a first end of each of
the struts connected to one of the attachment structures on one of
the fixation plates and a second end of each of the struts
connected to one of the attachment structures on another one of the
fixation plates, wherein the attachment structures connected to
struts are each connected to two struts..Iaddend.
.Iadd.29. The orthopaedic spatial fixation system of claim 25,
wherein a chord length between adjacent attachment structures is
between about 0.48 inches and about 0.52 inches..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plate for use as part of an
external fixation device, and more particularly to a unique hole
pattern within the plate.
2. General Background and Description of the Prior Art
Traditional circular ring external fixation devices consist of
Ilizarov-type devices that are based on a circumferential external
fixator system disclosed by G. A. Ilizarov during the early 1950's.
The Ilizarov system includes at least two rings or "halos" that
encircle a patient's body member (e.g., a patient's leg),
connecting rods extending between the two rings, transfixion pins
that extend through the patient's boney structure, and connectors
for connecting the transfixion pins to the rings. Use of the
Ilizarov system to deal with angulation, translation and rotation
is disclosed in "Basic Ilizarov Techniques," Techniques in
Orthopaedics.RTM., Vol. 5, Nov. 4, December 1990, pages 55-59.
The Ilizarov system provides an external fixation frame that allows
for gradual correction along and about six axes; however such
frames require many parts and are relatively complicated to build
and use in a clinical situation. In addition, often orthopedic
external fixators such as Ilizarov frames must be modified after
their initial application. Such modification may be necessary to
convert from one correctional axis to another. Alternatively, such
modifications may allow conversion from an initial adjustment type
of frame to a weight bearing type frame, since some of the
correctional configurations are not stable enough for weight
bearing.
The rings used in the Ilizarov devices include a plurality of
spaced apertures or holes that allow for the attachment of various
accessories to the device. The pattern of Ilizarov ring holes is
primarily determined as a function of the diameter of the ring.
Conventional wisdom teaches that for any given diameter, the ring
should include the maximum number of equally spaced arcuately
positioned holes. Those skilled in the art believe that such hole
positioning provides the surgeon with the greatest degree of
flexibility in constructing the often times complicated and
elaborate Ilizarov frame configuration. The Ilizarov ring holes,
although equally spaced about a circle, are positioned such that
the location of any given hole relative to another hole on
additional rings attached thereto, is completely irrelevant.
Applicants have recently developed a new external fixation device
known as the Taylor Spatial Frame.TM. external fixator. This device
is described and claimed in the allowed U.S. patent application
Ser. No. 08/782,731 entitled "Orthopaedic Fixation Device." In
addition, applicants have developed a unique method of using the
Taylor Spatial Frame.TM. fixator that is the subject of allowed
U.S. patent application Ser. No. 08/726,713 entitled "Method of
Using An Orthopaedic Fixation Device." Both of these patent
applications are incorporated herein by reference. As disclosed in
these prior patents, the Taylor Spatial Frame.TM. fixator, in its
preferred embodiment, consists of two ring plates interconnected by
six adjustable length struts. This device can be configured to
correct virtually an infinite number of deformities, each of which
would have otherwise required the construction of a specific custom
Ilizarov frame.
As with the prior art Ilizarov fixator, the Taylor Spatial
Frame.TM. fixator plates include a plurality of spaced apertures or
holes therethrough for attaching accessories to the device. In
addition, the plates include plurality of cavities or holes for
attachment of the struts to the rings. Applicants have now
developed a unique hole placement scheme for the Taylor Spatial
FRAME.TM. fixator rings. This unique hole placement scheme takes
advantage of the unique nature of the Taylor Spatial Frame.TM.
fixator and the unique method of using the same, and provides
substantial advantages over the unsystematically placed hole
patterns utilized in Ilizarov rings.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a novel
external fixation plate that can be used as part of the Taylor
Spatial FRAME.TM. fixator, and facilitates the unique method of
using the Taylor Spatial Frame.TM. fixator.
It is a further object of the present invention to provide a novel
external fixation plate that easy to manufacture, and simplifies
the fixator construction process.
It is a further object of the present invention to provide a novel
external fixation plate that offers various clinical advantages
over prior art designs by providing a convenient frame of reference
to aid a surgeon in preoperative planning and surgical application
of the device.
It is a further object of the present invention to provide a system
of plates, wherein each plate within the system offers unique
symmetrical properties and common hole spacing.
It is a further object of the present invention to provide a hole
scheme for an external fixation plate that provides a clear
geometric relationship between the holes on such plate relative to
other holes on the same plate or holes on attached plates.
These and other objects are realized by a fixation plate that
includes a plurality of attachment mechanisms located thereon. The
attachment mechanism preferably consists of a plurality of equally
spaced and symmetrically positioned holes. In accordance with a
preferred embodiment, the present invention includes a plate having
a body portion that includes a plurality of substantially equally
spaced apertures or holes positioned arcuately therein. The holes
are designed to facilitate attachment of a plurality of adjustable
length struts that interconnect one or more plates, and the
attachment of various accessories to the plates. The strut holes
and the accessory holes may be indistinguishable or they may be
different. The arrangement of the holes provides triple symmetry,
and preferably 2.times.3 symmetry. Based on a defined geometric
relationship between plate holes, a system of plates can be
designed that offer triple symmetry or 2.times.3 symmetry.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of a plate in accordance with one embodiment
of the present invention.
FIG. 2 is a perspective view of an external fixation device
incorporating one embodiment of the novel plate of the present
invention.
FIG. 3 is an enlarged view of a portion of one of the plates shown
in FIG. 2.
FIG. 4 is a perspective view of an external fixation device
incorporating an alternative embodiment of the novel plate of the
present invention.
FIG. 5 is an enlarged view of a portion of a plate of the present
invention, and illustrates the geometric relationship between two
adjacent holes.
FIG. 6 is a top view of a plate in accordance with an alternative
embodiment of the present invention.
FIG. 7 is a top view of a plate in accordance with an alternative
embodiment of the present invention.
FIG. 8 is a top view of a plate in accordance with an alternative
embodiment of the present invention.
FIG. 9 is a top view of a plate in accordance with an alternative
embodiment of the present invention.
FIG. 10 is a top view of a plate in accordance with an alternative
embodiment of the present invention.
FIG. 11 is a perspective view of an external fixation device
incorporating an alternative embodiment of the novel plate of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
Because of the unique nature of the Taylor Spatial FRAME.TM.
fixator and the unique method of using the Taylor Spatial FRAME.TM.
fixator, the position of a given hole relative to another hole,
either on the same plate or a different plate, is very important.
Indeed, we have found that the correct positioning of the holes
simplifies the manufacturing and device construction processes,
simplifies the method of using the device by simplifying the
geometric analysis of the system, and provides a number of clinical
advantages.
FIG. 1 illustrates a fixator plate in accordance with a preferred
embodiment of the present invention. The plate 2 includes a circuit
body portion 4 fabricated from a suitably strong and rigid material
such as a metal, alloy, plastic, composite, or ceramic. The body
portion 4 includes a plurality of substantially equally spaced
apertures or holes 8 positioned arcuately therein. In the specific
embodiment shown in FIG. 1, the center of the holes 8 form a
complete circle as illustrated by the broken line 10, wherein the
circle has a center c and a radius of r. It is important to note
that each hole 8 may have a different diameter or shape as long as
the center of the hole substantially intersects with the circle
10.
As illustrated in FIG. 2 and FIG. 4, the holes 8 are designed to
facilitate attachment of a plurality of adjustable length struts 20
that interconnect one or more plates 2. In accordance with the
preferred embodiment of the present invention, six struts 20 are
used to interconnect two plates 2. In addition, the holes 8 are
designed to facilitate attachment of various accessories to the
plate 2, such as for example, wires (not shown), clamps 24, pins
26, additional plates, etc. In accordance with the embodiment shown
in FIG. 1 and FIG. 4, the strut holes and the accessory holes are
indistinguishable, i.e. any hole 8 can be selected to serve as a
strut hole or an accessory hole. In accordance with an alternative
embodiment, as shown in FIG. 2, the accessory holes 14 and the
strut holes 12 are different.
As illustrated in FIG. 2, in accordance with one embodiment of the
present invention, each plate 2 has three actual strut attachment
positions 16. In addition, each plate 2 includes three additional
strut positions 18 that are not actually used. The unused strut
positions 18 are included to provide a 2.times.3 symmetrical
design, which is discussed in greater detail below. In the
preferred embodiment of the invention as shown in FIG. 2, the used
strut attachment holes 16 should be positioned approximately
120.degree. from one another so as to form a substantially
equilateral triangle. Similarly, the unused strut attachment holes
18 should be positioned approximately 120.degree. from one another
so as to form a second substantially equilateral triangle. The two
overlapping triangles are illustrated by broken lines in FIG. 1,
and are designated triangle A and triangle B. Alternatively, one or
more strut attachment holes 16, 18 can deviate slightly from its
ideal 120.degree. position. Such deviation, however, should be less
than 30.degree., but preferably no more than 15.degree., and
ideally less than 6.degree..
Unlike the unsystematically positioning of prior art Ilizarov ring
holes, the holes 8 in the present device are preferably
strategically positioned within plate 2 to provide 2.times.3
symmetrically throughout a complete system of plates. 2.times.3
symmetry is achieved when the holes are positioned such that the
plate can be rotated in increments of 180.degree. about a first
axis and increments of 120.degree. about a second axis, and each
time maintain identical hole positions. For example, the plate 2
can be rotated 180.degree. about an axis passing through center c
and within the plane of the plate 2, i.e. the x axis shown in FIG.
2. Such a rotation would essentially flip plate 2 over. For both of
the two possible positions, the hole pattern within plate 2 would
be identical. This characteristic represents the "2" of the
2.times.3 symmetry. Similarly, plate 2 can be rotated in increments
of 120.degree. about an axis perpendicular to the plate and passing
through center c, i.e. the y axis shown in FIG. 2. There are three
possible positions that the plate 2 could assume by making
120.degree. rotation about the y axis. Following each rotation,
however, the resulting hole positions will remain unchanged. This
characteristic represents the "3" of the 2.times.3 symmetry. In
accordance with the present invention, a system of plates is
provided, as described hereinbelow, wherein each plate within the
system offers at least triple symmetry (i.e., the "3" symmetry),
and preferably each plate offers complete 2.times.3 symmetry.
In order to obtain the 2.times.3 symmetry, as noted above, plate 2
should include two sets of three strut holes with each strut hole
12 positioned about 60.degree. apart in a circle. In addition,
2.times.3 symmetry requires that the total number of holes 8
(including both strut holes 12 and accessory holes 14) be a
multiple of six (6). For triple symmetry alone, however, the total
number of holes 8 need only be a multiple of three (3).
Furthermore, the accessory holes should be equally spaced. One
skilled in the art will appreciate that asymmetrical "dummy" holes
can be added to the plate 2. Such a plate would nonetheless fall
within the scope of the present invention.
As illustrated in FIG. 3, the spacing between the accessory holes
14 can be measured in terms of the arc length l.sub.arc along
circle 10 or in terms of the chord length l.sub.chord. In
accordance with the preferred embodiment, the distance between
holes 14 is measured by the chord length I.sub.chord, and such
lengths are equal. Furthermore, the distance between each strut
hole 12 and its adjacent accessory hole 14 need not be the same as
the distance between two adjacent accessory holes 14. As
illustrated in FIG. 3, this distance can be measured along arc as
d.sub.arc or along the chord as decor. In accordance with the
preferred embodiment of the present invention, the chord lengths
between every accessory hole 14 and its adjacent accessory hole 14
or strut hole 12 are equal, that is d.sub.chord=l.sub.chord. In
addition, the chord length is should be greater than about 0.475
inch, but preferably is between about 0.48-0.52 inch, and most
preferably equal to about 0.5 inch.
In accordance with the specific embodiment of the present invention
illustrated in FIG. 2, the exact positions of the holes 8 are
determined as follows. The process is very different from the
unsystematic positioning of the holes in prior art Ilizarov
devices, which starts with determining the ring diameter. The
Taylor Spatial Frame.TM. fixator hole positions are determined by
first determining the hole spacing, and then determining the number
of holes that will be used. The present hole positioning scheme
starts with the number of holes because it is important that the
number be a multiple of three to maintain the requisite symmetry.
Once the distance between the holes and the number of holes is
determined, the diameter of the ring is defined by the formula:
.times. .function. ##EQU00001## where l is the chord distance
between holes 8, and N is the total number of holes.
As illustrated in FIG. 5, for any given two adjacent holes 8, the
angle between the holes is .theta., and the chord between the holes
is 1. An isosceles triangle T is formed by connecting the two
adjacent plate holes 8 and the center c of the circle 10. If a line
28 having length b is formed in the middle of the isosceles
triangle T, two right triangles are formed, and the following
relationships exists:
.times..times..times..function..times..theta..times. ##EQU00002##
where r represents the radius of the circle 10. If for convenience
we define v=1/2l and Q=tan (1/2.theta.), the following
relationships can be derived from the above equations:
From Equation (1) ##EQU00003##
From Equation (2) ##EQU00004##
Combining (4) and (5) ##EQU00005## solving for the radius r gives:
.function. ##EQU00006## Therefore, for any plate having N holes and
a chord distance of 1 between adjacent holes, the diameter of the
circle that defines the hole locations can be expressed
mathematically as .times. .times..times..function..times..theta.
.times..function..times..theta. ##EQU00007## If the total number of
holes in the ring will be N, then .theta.=360.degree./N, and
.times. .function. ##EQU00008## Using the relationship defined in
equation 10, a system of rings including a variety of ring
diameters can be developed wherein each ring has triple symmetry
and the hole spacing for each ring is the same. The following table
illustrates such a system wherein the hole spacing in 0.5 inch:
TABLE-US-00001 TABLE I Chord Length (l) Number of Diameter angle
(.theta.) (inches) Holes (N) (inches) (degrees) 0.5 3 0.5776 130
0.5 6 1.0030 60 0.5 9 1.4519 40 0.5 12 1.9319 30 0.5 15 2.4049 24
0.5 18 2.8794 20 0.5 21 3.3548 17.143 0.5 24 3.8306 15 0.5 27
4.3069 13.333 0.5 30 4.7834 12 0.5 33 5.2601 10.939 0.5 36 5.7369
10 0.5 39 6.2138 9.281 0.5 42 6.6907 8.571 0.5 45 7.1678 8 0.5 48
7.6449 7.5 0.5 51 8.1220 7.059 0.5 54 8.5992 6.657 0.5 57 9.0764
6.316 0.5 60 9.5537 6 0.5 63 10.0309 5.714286 0.5 66 10.5082
5.454545 0.5 69 10.9855 5.217391 0.5 72 11.4628 5 0.5 75 11.9401
4.8 0.5 78 12.4174 4.615385 0.5 81 12.8948 4.444444 0.5 84 13.3721
4.285714 0.5 87 13.8497 4.137931 0.5 90 14.3269 4 0.5 93 14.8042
3.870968 0.5 96 15.2816 3.75 0.5 99 15.7590 3.635364 0.5 102
16.2364 3.529412 0.5 105 16.7138 3.428571 0.5 108 17.1912 3.333333
0.5 111 17.6686 3.243243 0.5 114 18.1460 3.157895 0.5 117 18.6234
3.076923 0.5 120 19.1008 3 0.5 123 19.5782 2.826829 0.5 126 20.0556
2.857143 0.5 129 20.5330 2.790698
The triple symmetry for the complete system is realized by only
including rings where the numbers of holes in each plate is a
multiple of three. Similarly, a system with complete 2.times.3
symmetry can be designed by using plates where the number of holes
in each plate is a multiple of six.
As noted above, the arc length, as opposed to the chord length,
between adjacent holes 8 can be fixed. If the arc length between
the holes 8 is fixed, for a given arc length k and holes N, the
circumference of the circle 10 will equal k.times.N. Therefore the
diameter would be: diameter=kN/.pi. Using this relationship, a
plate system such as following can be made:
TABLE-US-00002 TABLE II Arc Length Number Diameter (inches) of
Holes (inches) 0.5 6 0.9549 0.5 9 1.4324 0.5 12 1.9099 0.5 15
2.3873 0.5 18 2.8648 0.5 21 3.3423 0.5 24 3.8197 0.5 27 4.2972 0.5
30 4.7746 0.5 33 5.2521 0.5 36 5.7296 0.5 39 6.2070 0.5 42 6.6845
0.5 45 7.1620 0.5 48 7.6394 0.5 51 8.1169 0.5 54 8.5944 0.5 57
9.0718 0.5 60 9.5493 0.5 63 10.0268 0.5 66 10.5042 0.5 69 10.9817
0.5 72 11.4592 0.5 75 11.9366 0.5 78 12.4141 0.5 81 12.8916 0.5 84
13.3690 0.5 87 13.8465 0.5 90 14.3239 0.5 93 14.8014 0.5 96 15.2789
0.5 99 15.7563 0.5 102 16.2338 0.5 105 16.7113 0.5 108 17.1887 0.5
111 17.6662 0.5 114 18.1437 0.5 117 18.6211 0.5 120 19.0986 0.5 123
19.5761 0.5 126 20.0535 0.5 129 20.5310
FIG. 4 illustrates an alternative embodiment of the present
invention. Unlike the embodiment illustrated in FIG. 2, the
adjoining struts 20 in FIG. 4 do not connect to the plates 2 at a
single common hole 8. As a result, each plate 2 in FIG. 4 includes
six (6) strut holes 32 that are connected to a strut 20. As
illustrated, the adjacent connecting strut holes 32 are separated
by a single unused hole 30. In other embodiments of the present
invention, the adjacent connecting strut holes 32 may be separated
by no holes or by more than one unused hole 30. When adjacent
struts 20 do not terminate at a common hole a theoretical strut
hole should be determined. As illustrated in FIG. 6, the
theoretical strut hole 34 is positioned along the arc of circle 10
half way between the two actual strut holes 32, i.e. along the
circle 10 at the bisector of the two actual strut holes. When
adjacent struts terminate at a single strut hole as in FIG. 2, the
theoretical strut hole is the actual strut hole. In accordance with
the present invention, the theoretical strut holes 34 on plate 2
should form two overlapping triangles A, B in the same manner
described above regarding the embodiment illustrated in FIG. 2. As
with the actual strut holes, the chords connecting the theoretical
strut holes 34 preferably form two substantially equilateral
triangles. The theoretical strut holes 34, however, may deviate
from their ideal 120.degree. positions to the same extent described
above with regard to actual strut holes.
The extent to which an actual strut hole 32 can deviate from its
theoretical strut hole is limited. As this deviation increases, the
range of movement between the two plates 2 is reduced. The reduced
range limits the various configurations that the device can assume,
and therefore, limits the types of deformities that can be
corrected with the device. As a result, the deviation of an actual
strut hole 32 from its theoretical strut hole should be less than
about 30.degree., but can be less than 12.degree., and preferable
no more than about 6.degree..
The hole spacing scheme of the present invention can be utilized to
design plates having holes that do not form a complete circle. For
example, a half plate or a 1/6 plate, as illustrated in FIGS. 7 and
8 respectively, can be designed. In addition, the plate itself need
not be circular, as illustrated in the embodiment shown in FIG.
9.
The mathematical relationships between hole spacing, the number of
holes and the diameter that are set forth above specifically relate
to a hole pattern that forms a complete circle and includes equally
spaced hole around the entire circle. These mathematical
relationships, however, can be adapted to describe the hole pattern
for a partial circle. For example, assume that you wanted n holes
positioned about a partial ring that has an arc length of
.alpha..degree., i.e. 180.degree. for a half ring, 90.degree. for a
quarter ring, etc. The number of such partial rings required to
form a complete circle would be 360/.alpha.. The number of holes in
such a theoretical circle (N) equals n(360/.alpha.). One would then
use the number of holes for the theoretical complete ring (N) in
the equations set forth above to define the hole positions needed
to form the requisite partial plate.
In accordance with another embodiment of the present invention, a
plate can include holes corresponding to more than one diameter
within a given system. As noted above each system is defined by the
hole spacing. An example is illustrated in FIG. 10 using the system
defined above in Table I. The plate 2 includes two sets of holes 8.
The first set 38 includes sixty (60) holes equally spaced
(l.sub.chord-0.5 inch) along circle 10. As indicated above in Table
I, the diameter of circle 10 is 9.5537 inches, and the radius
r.sub.1=4.7769 inches. The second set of holes 40 consists of six
groups of three holes, i.e. six partial plates. These hole are
spaced along the next highest diameter within the system.
Therefore, the diameter of circle 36 is 10.5082 and the radius
r.sub.2=5.2541. Multiple diameter plates, such as shown in FIG. 10
are very useful. In such plates, the struts can be attached at one
diameter, using for example hole set 40, and the accessories can be
attached using the other diameters, using for example hole set
38.
It is important to emphasize that although the present invention is
described in terms of accessory holes and strut holes, other
attachment mechanisms can be used and still fall within the scope
of the present invention. For example, each hole could be replaced
with a peg that would facilitate attachment of a strut or
accessory. Alternatively, an illustrated in FIG. 11, the plate 42
could include one continuous circular grove 44 that traces circle
10. Clamps 46 could be provided that attach to the groove 44 at any
location. Such clamps 46 can easily be positioned to mimic the hole
patterns described above. Indeed, such a plate 42 could included
indicia such as markings 48 or etches 50 within the plate, that
designate the hole positions described above.
The unique hole placement scheme described herein provides a number
of advantages over the prior art. In particular, a ring that has
2.times.3 symmetry substantially simplifies the manufacturing
process and the fixator construction process. With 2.times.3
symmetrical rings, one ring can serve as either the upper ring or
the lower ring. As a result, a manufacturer need only make half as
many ring designs for a system. In addition, if a surgeons using
the device want to attach additional rings to the base Taylor
Spatial Frame.TM. fixator, they need not overly concern themselves
with having the proper ring, nor the proper orientation of the
ring.
Key advantages also result from having a defined relationships
between the various holes on a plate, and a defined relationship
between various holes on different plates. In general, this
facilitates the use of mathematical methods to analyze a fixation
system, and determine the proper mode for correcting a deformity.
From a clinical standpoint, it gives a surgeon a great deal of
flexibility and aids in preoperative planning and surgical
application of the device. For example, in cases of sever
deformities the various bone fragments are completely out of
alignment. In such cases it is difficult for a surgeon to place
various plates with the same orientation on the various fragments.
With the current invention, a surgeon when attaching the device can
place reference wires at the same predetermined anatomical position
on each unaligned bone fragment. One the surgeon determines the
appropriate positioning of the first plate on the first bone
fragment, the first plate is secured to the reference wire.
Subsequent plates can then be easily positioned on the remaining
bone fragments. A surgeon would attached the subsequent plates to
the reference wires on the remaining fragments using the accessory
holes at the same locations used with the first plate. The various
plates would then be aligned after the correction is made. Such
strategic placement of plates relative to one another facilitates
the use of the unique method of using the Taylor Spatial FRAME.TM.
fixator. Moreover, this provides an easy gauge during the course of
the correction that allows the surgeon to judge if the correction
is accurate or needs adjustment. Indeed, if the plate holes are not
moving into alignment, the surgeon knows that an adjustment is
needed. Furthermore, once the plates have returned to their neutral
positions, with the holes in the upper and lower plates are
perfectly aligned, and a surgeon can simply insert horizontal rods.
Such rods could provide accessory stabilization if required.
* * * * *