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Claims  |
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What is claimed is:
1. A screw an driver combination comprising:
an elongate screw including
(a) first and second ends,
(b) an axial bore coupled with said first end, said axial bore having a
circular cross section of selected diameter, and
(c) a counterbore coupled with said first end and coaxial with said axial
bore, said counterbore having a selected length and a polygonal cross
section of selected configuration and dimension; and
a driver including
(a) an elongate shaft having a front end,
(b) an elongate intermediate portion having first and second ends, said
second end of said intermediate portion being fixedly attached to said
front end of said shaft, said intermediate portion having a polygonal
cross section configured and dimensioned (i) so that said intermediate
portion can be inserted into said counterbore of said screw with a sliding
fit and (ii) so that when said intermediate portion is inserted in said
counterbore said intermediate portion drivingly engages said counterbore
so that rotational drive can be transmitted from said driver to said
screw, and
(c) a cylindrical front portion having a back end and a front end, said
back end of said front portion being fixedly attached to said first end of
said intermediate portion, said front portion comprising compression means
for permitting said front portion to be compressed radially into a
compressed state, the design and diameter of said cylindrical front
portion being chosen (i) so that insertion of said front portion into said
bore of said screw causes said front portion to be compressed into said
compressed state, and (ii) so that when said front portion is inserted in
said bore said front portion engages said bore with a spring interference
fit, whereby said front portion cannot be removed from said bore except
when a selected axial force is applied to said front portion.
2. A combination according to claim 1 wherein said compression means
comprises:
an axial bore in said front portion coupled with said front end of said
front portion and extending substantially the entire length of said front
portion; and
a plurality of axially-extending slots in said front portion coupling said
axial bore of said front portion with the exterior surface of said front
portion.
3. A combination according to claim 2 wherein said plurality of slots
comprises three slots.
4. A combination according to claim 2 wherein said plurality of slots
comprises four slots.
5. A combination according to claim 1 wherein the length of said
intermediate portion is greater than the length of said counterbore and
the length of said front portion is less than the length of said axial
bore minus the length of said counterbore.
6. A combination according to claim 1 wherein said intermediate portion is
attached to said shaft and said front portion is attached to said
intermediate portion so that the axes of elongation of said shaft, said
intermediate portion and said front portion are coaxial.
7. A combination according to claim 1 wherein said second end of said screw
is pointed.
8. A combination according to claim 1 wherein said cylindrical front
portion comprises a central portion and a tip portion, the outside
diameter of said tip portion being slightly greater than the inside
diameter of the portion of said axial bore of said screw having a circular
cross section when said front portion is not in said compressed state, and
the outside diameter of said central portion being less than the outside
diameter of said tip portion regardless of whether or not said front
portion is in said compressed state.
9. A combination according to claim 1 wherein the outside diameter of said
front portion is slightly greater than the inside diameter of the portion
of said axial bore of said screw having a circular cross section when said
front portion is not in said compressed state.
10. A combination according to claim 1 wherein a screw thread is disposed
on the exterior surface of said screw extending along the entire length of
said screw.
11. A combination according to claim 1 wherein the configuration of the
cross section of said intermediate portion of said drive and said
counterbore of said screw is hexagonal.
12. A combination according to claim 1 wherein said screw comprises a
central bore extending through the entire length of said screw, and said
driver comprises a central bore extending through the entire length of
said driver.
13. A screw and driver combination designed for use with an elongate guide
wire, the combination comprising:
an elongate screw including
(a) first and second ends,
(b) an axial bore extending through the entire length of said screw, with
the diameter of said axial bore being greater than the diameter of a guide
wire adapted for insertion into the material into which the screw is to be
implanted,
(c) a counterbore coupled with said first end and coaxial with said axial
bore, said counterbore having an inner axial portion with a circular cross
section of selected diameter, and an outer axial portion coupled with said
first end and having a polygonal cross section of selected configuration
and dimension; and
a driver including
(a) an elongate shaft having a front end,
(b) an elongate intermediate portion having first and second ends, said
second end of said intermediate portion being fixedly attached to said
front end of said shaft, said intermediate portion having a polygonal
cross section configured and dimensioned (i) so that said intermediate
portion can be inserted into said outer axial portion of said counterbore
of said screw with a sliding fit and (ii) so that when said intermediate
portion is inserted in said outer axial portion of said counterbore said
intermediate portion drivingly engages said outer axial portion of said
counterbore so that rotational drive can be transmitted from said driver
to said screw,
(c) a cylindrical front portion having a back end and a front end, said
back end of said front portion being fixedly attached to said first end of
said intermediate portion, said front portion comprising compression means
for permitting said front portion to be compressed radially into a
compressed state, the design and diameter of said cylindrical front
portion being chosen (i) so that insertion of said front portion into said
inner axial portion of said counterbore of said screw causes said front
portion to be compressed into said compressed state, and (ii) so that when
said front portion is inserted in said inner axial portion of said
counterbore said front portion engages said inner axial portion of said
counterbore with a spring interference fit, whereby said front portion
cannot be removed from said inner axial portion of said counterbore except
when a selected axial force is applied to said front portion, and
(d) an axial bore extending through the entire length of said driver, said
axial bore having a diameter greater than the diameter of said guide wire.
14. A system for use in implanting a screw into selected material, the
system comprising:
an elongate guide wire adapted to be inserted into selected material in
which said screw is to be implanted;
an elongate screw including
(a) first and second ends,
(b) an axial bore extending through the entire length of said screw, with
the diameter of said axial bore being greater than the diameter of said
guide wire,
(c) a counterbore coupled with said first end and coaxial with said axial
bore, said counterbore having an inner axial portion with a circular cross
section of selected diameter, and an outer axial portion coupled with said
first end and having a polygonal cross section of selected configuration
and dimension; and
a driver including
(a) an elongated shaft having a front end,
(b) an elongate intermediate portion having first and second ends, said
second end of said intermediate portion being fixedly attached to said
front end of said shaft, said intermediate portion having a polygonal
cross section configured and dimensioned (i) so that said intermediate
portion can be inserted into said outer axial portion of said counterbore
of said screw with a sliding fit and (ii) so that when said intermediate
portion is inserted in said outer axial portion of said counterbore said
intermediate portion drivingly engages said outer axial portion of said
counterbore so that rotational drive can be transmitted from said driver
to said screw,
(c) a cylindrical front portion having a back end and a front end, said
back end of said front portion being fixedly attached to said first end of
said intermediate portion, said front portion comprising compression means
for permitting said front portion to be compressed radially into a
compressed state, the design and diameter of said cylindrical front
portion being chosen (i) so that insertion of said front portion into said
inner axial portion of said counterbore of said screw causes said front
portion to be compressed into said compressed state, and (ii) so that when
said front portion is inserted in said inner axial portion of said
counterbore said front portion engages said inner axial portion of said
counterbore with a spring interference fit, whereby said front portion
cannot be removed from said inner axial portion of said counterbore except
when a selected axial force is applied to said front portion, and
(d) an axial bore extending through the entire length of said driver, said
axial bore having a diameter greater than the diameter of said guide wire.
15. A screw and driver combination comprising:
an elongate screw including
(a) a first end and a pointed second end,
(b) an axial bore coupled with said first end, said axial bore having a
circular cross section of selected diameter, and
(c) a counterbore coupled with said first end and coaxial with said axial
bore, said counterbore having a selected length and a hexagonal cross
section of selected dimension, wherein a screw thread is disposed on the
exterior surface of said screw extending along the entire length of said
screw; and
a driver including
(a) an elongate shaft having a front end,
(b) an elongate intermediate portion having first and second ends, said
second end of said intermediate portion being fixedly attached to said
front end of said shaft so that said shaft and said intermediate portion
are coaxially aligned, said intermediate portion having a hexagonal cross
section configured and dimensioned (i) so that said intermediate portion
can be inserted into said counterbore of said screw with a sliding fit and
(ii) so that when said intermediate portion is inserted in said
counterbore said intermediate portion drivingly engages said counterbore
so that rotational drive can be transmitted from said driver to said
screw, and
(c) a cylindrical front portion having a back end and a front end, said
back end of said front portion being fixedly attached to said first end of
said intermediate portion so that said intermediate portion and said front
portion are coaxially aligned, said front portion comprising compression
means for permitting said front portion to be compressed radially into a
compressed state, the design and diameter of said cylindrical front
portion being chosen (i) so that insertion of said front portion into the
section of said bore of said screw having a circular cross section causes
said front portion to be compressed into said compressed state, and (ii)
so that when said front portion is inserted in said section of said bore
having a circular cross section said front portion engages said section
with a spring interference fit, whereby said front portion cannot be
removed from said section except when a selected axial force is applied to
said front portion,
said compression means comprising
(a) an axial bore in said front portion coupled with said front end of said
front portion and extending substantially the entire length of said front
portion and
(b) a plurality of axially-extending slots in said front portion coupling
said axial bore of said front portion with the exterior surface of said
front portion, and further wherein said front portion comprises a central
portion and a tip portion, the outside diameter of said tip portion being
slightly greater than the inside diameter of said section of said axial
bore of said screw having a circular cross section when said front portion
is not in said compressed state, and the outside diameter of said central
portion being somewhat less than the outside diameter of said tip portion
regardless of whether or not said front portion is in said compressed
state.
16. A combination according to claim 1 wherein said driver further
comprises:
expansion means movable between a first position and a second position for
coacting with said front portion of said driver so as to cause said front
portion to expand radially when said expansion means is moved toward said
second position; and
actuation means coupled to said expansion means for causing said expansion
means to move between said first position and said second position.
17. A combination according to claim 16 wherein said actuation means
comprises:
an axial bore in said driver extending through said front portion, said
intermediate portion, and at least a front section of said handle, said
bore being open to said front end of said front portion, said bore
comprising a radially-inwardly tapering section adjacent said front end of
said front portion;
a shaft disposed in said axial bore and sized to be freely slidable along
the entire length of said axial bore except for within said
radially-inwardly tapering section of said axial bore, said shaft having a
front end, said shaft being additionally sized so that when said front end
of said shaft is urged into said radially-inwardly tapering section of
said axial bore said shaft coacts with said radially-inwardly tapering
section in cam-like fashion so as to cause said front portion to expand
radially.
18. A combination according to claim 17 wherein said actuation means
comprises lever means mounted adjacent said front section of said handle
and coupled to said shaft for causing said shaft to move axially between a
first position wherein said front end of said shaft is not disposed within
said radially-inwardly tapering section of said axial bore and a second
position wherein said front end of said shaft is disposed within the
portion of said radially-inwardly tapering portion having the smallest
inside diameter.
19. A combination according to claim 17 wherein said axial bore extends
through the entire length of said handle and is open to a rear end of said
handle, and said shaft comprises a central axial bore extending through
the entire length of said shaft.
20. A screw and driver combination comprising:
an elongate screw including
(a) first and second ends,
(b) an axial bore coupled with said first end, said axial bore having a
circular cross section of selected diameter, and
(c) a counterbore coupled with said first end and coaxial with said axial
bore, said counterbore having a selected length and a polygonal cross
section of selected configuration and dimension; and
a driver including
(a) an elongate shaft having a front end,
(b) an elongate intermediate portion having first and second ends, said
second end of said intermediate portion being attached to said front end
of said shaft, said intermediate portion having a polygonal cross section
configured and dimensioned (i) so that said intermediate portion can be
inserted into said counterbore of said screw with a sliding fit and (ii)
so that when said intermediate portion is inserted in said counterbore
said intermediate portion drivingly engages said counterbore so that
rotational drive can be transmitted from said driver to said screw, and
(c) a cylindrical front portion having a back end and a front end, said
back end of said front portion being attached to said first end of said
intermediate portion, said front portion comprising compression means for
permitting said front portion to be compressed radially into a compressed
state, the design and diameter of said cylindrical front portion being
chosen (i) so that insertion of said front portion into said bore of said
screw causes said front portion to be compressed into said compressed
state, and (ii) so that when said front portion is inserted in said bore
said front portion engages said bore with a spring interference fit,
whereby said front portion cannot be removed from said bore except when a
selected axial force is applied to said front portion,
wherein said driver further comprises:
expansion means movable between a first position and a second position for
coating with said front portion of said driver so as to cause said front
portion to expand radially when said expansion means is moved toward said
second position; and
actuation means coupled to said expansion means for causing said expansion
means to move between said first position and said second position,
wherein said actuation means comprises:
an axial bore in said driver extending through said front portion, said
intermediate portion, and at least a front section of said handle, said
bore being open to said front end of said front portion, said bore
comprising a radially-inwardly tapering section adjacent said front end of
said front portion; and
a shaft disposed in said axial bore and sized to be freely slidable along
the entire length of said axial bore except for within said
radially-inwardly tapering section of said axial bore, said shaft having a
front end, said shaft being additionally sized so that when said front end
of said shaft is urged into said radially-inwardly tapering section of
said axial bore said shaft coacts with said radially-inwardly tapering
section in cam-like fashion so as to cause said front portion to expand
radially.
21. A combination according to claim 10 wherein said actuation means
comprises lever means mounted adjacent said front section of said handle
and coupled to said shaft for causing said shaft to move axially between a
first position wherein said front end of said shaft is not disposed within
said radially-inwardly tapering section of said axial bore and a second
position wherein said front end of said shaft is disposed within the
portion of said radially-inwardly tapering portion having the smallest
inside diameter.
22. A screw and driver combination comprising:
an elongate screw including
(a) first and second ends,
(b) an axial bore coupled with said first end, said axial bore having a
circular cross section of selected diameter, and
(c) a counterbore coupled with said first end and coaxial with said axial
bore, said counterbore having a selected length and a non-circular cross
section of selected configuration and dimension; and
a driver including
(a) an elongate shaft having a front end,
(b) an elongate intermediate portion having first and second ends, said
second end of said intermediate portion being fixedly attached to said
front end of said shaft, said intermediate portion having a non-circular
cross section configured and dimensioned (i) so that said intermediate
portion can be inserted into said counterbore of said screw with a sliding
fit and (ii) so that when said intermediate portion is inserted in said
counterbore said intermediate portion drivingly engages said counterbore
so that rotational drive can be transmitted from said driver to said
screw, and
(c) a cylindrical front portion having a back end and a front end, said
back end of said front portion being fixedly attached to said first end of
said intermediate portion, said front portion comprising compression means
for permitting said front portion to be compressed radially into a
compressed state, the design and diameter of said cylindrical front
portion being chosen (i) so that insertion of said front portion into said
bore of said screw causes said front portion to be compressed into said
compressed state, and (ii) so that when said front portion is inserted in
said bore said front portion engages said bore with a spring interference
fit, whereby said front portion cannot be removed from said bore except
when a selected axial force is applied to said front portion.
23. A driver for use in conjunction with a screw of the sort comprising (a)
first and second ends, (b) an axial bore coupled with said first end, said
axial bore having a circular cross section of selected diameter, and (c) a
counterbore coupled with said first end and coaxial with said axial bore,
said counterbore having a selected length and a polygonal cross section of
selected configuration and dimension,
said driver comprising:
(a) an elongate shaft having a front end,
(b) an elongate intermediate portion having first and second ends, said
second end of said intermediate portion being fixedly attached to said
front end of said shaft, said intermediate portion having a polygonal
cross section configured and dimensioned (i) so that said intermediate
portion of said driver can be inserted into said counterbore of said screw
with a sliding fit and (ii) so that when said intermediate portion of said
driver is inserted in said counterbore of said screw said intermediate
portion of said driver will drivingly engage said counterbore of said
screw so that rotational driver can be transmitted from said driver to
said screw, and
(c) a cylindrical front portion having a back end and a front end, said
back end of said front portion being fixedly attached to said first end of
said intermediate portion, said front portion comprising compression means
for permitting said front portion to be compressed radially into a
compressed state, the design and diameter of said cylindrical front
portion being chosen (i) so that insertion of said front portion of said
driver into said bore of said screw will cause said front portion of said
driver to be compressed into said compressed state, and (ii) so that when
said front portion of said driver is inserted in said bore of said screw
said front portion of said driver will engage said bore of said screw with
a spring interference fit, whereby said front portion of said driver
cannot be removed from said bore of said screw except when a selected
axial force is applied to said front portion of said driver.
24. A method of installing a screw into a bone, said method comprising the
steps of:
(1) providing a screw and a driver wherein:
said screw comprises:
(a) first and second ends,
(b) an axial bore coupled with said first end, said axial bore having a
circular cross section of selected diameter, and
(c) a counterbore coupled with said first end and coaxial with said axial
bore, said counterbore having a selected length and a polygonal cross
section of selected configuration and dimension, and
said driver comprises:
(a) an elongate shaft having a front end,
(b) an elongate intermediate portion having first and second ends, said
second end of said intermediate portion being fixedly attached to said
front end of said shaft, said intermediate portion having a polygonal
cross section configured and dimensioned (i) so that said intermediate
portion of said driver can be inserted into said counterbore of said screw
with a sliding fit, and (ii) so that when said intermediate portion of
said driver is inserted in said counterbore of said screw said
intermediate portion drivingly engages said counterbore of said screw so
that rotational drive can be transmitted from said driver to said screw,
and
(c) a cylindrical front portion having a back end and a front end, said
back end of said front portion being fixedly attached to said first end of
said intermediate portion, said front portion comprising compression means
for permitting said front portion to be compressed radially into a
compressed state, the design and diameter of said cylindrical front
portion being chosen (i) so that insertion of said front portion into said
bore of said screw ill cause said front portion of said driver to be
compressed into said compressed state, and (ii) so that when said front
portion of said driver is inserted in said bore of said screw said front
portion will engage said bore with a spring interference fit, whereby said
front portion of said driver cannot be removed from said bore of said
screw except when a selected axial force is applied to said front portion
of said driver;
(2) attaching said screw to said driver by inserting said front portion of
said driver into said bore of said screw and said intermediate portion of
said driver into said counterbore of said screw;
(3) installing said screw into said bone by pressing said second end of
said screw against said bone and rotating said driver so that said screw
is driven into said bone; and
(4) detaching said driver from said screw by moving said driver away from
said bone.
25. A method of installing a screw into a bone, said method comprising the
steps of:
(1) providing a guide wire, a screw and a driver wherein:
said guide wire comprises first and second ends and has a circular cross
section of a selected diameter,
said screw comprises:
(a) first and second ends,
(b) an axial bore extending through the entire length of said screw, said
axial bore having a circular cross section of a selected diameter, wherein
said selected diameter of said axial bore is greater than said selected
diameter of said guide wire, and
(c) a counterbore coupled with said first end and coaxial with said axial
bore, said counterbore having an inner axial portion with a circular cross
section of selected diameter, and an outer axial portion coupled with said
first end and having a polygonal cross section of selected configuration
and dimension, and
said driver comprises:
(a) an elongate shaft having a front end,
(b) an elongate intermediate portion having first and second ends, said
second end of said intermediate portion being fixedly attached to said
front end of said shaft, said intermediate portion having a polygonal
cross section configured and dimensioned (i) so that said intermediate
portion of said driver can be inserted into said outer axial portion of
said counterbore of said screw with a sliding fit, and (ii) so that when
said intermediate portion of said driver is inserted in said outer axial
portion of said counterbore of said screw said intermediate portion
drivingly engages said outer axial portion of said counterbore of said
screw so that rotational drive can be transmitted from said driver to said
screw, and
(c) a cylindrical front portion having a back end and a front end, said
back end of said front portion being fixedly attached to said first end of
said intermediate portion, said front portion comprising compression means
for permitting said front portion to be compressed radially into a
compressed state, the design and diameter of said cylindrical front
portion being chosen (i) so that insertion of said front portion into said
inner axial portion of said counterbore of said screw will cause said
front portion of said driver to be compressed into said compressed state,
and (ii) so that when said front portion of said driver is inserted in
said inner axial portion of said counterbore of said screw said front
portion will engage said inner axial portion of said counterbore with a
spring interference fit, whereby said front portion of said driver cannot
be removed from said inner axial portion of said counterbore of said screw
except when a selected axial force is applied to said front portion of
said driver, and
(d) an axial bore extending through the entire length of said driver, said
axial bore having a circular cross section of a selected diameter, wherein
said selected diameter of said axial bore is greater than said selected
diameter of said guide wire, and
(2) installing said guide wire in said bone by inserting said second end of
said guide wire into said bone so that said first end of said guide wire
is disposed remote from said bone, and attaching said screw to said driver
by inserting said front portion of said driver into said inner axial
portion of said counterbore of said screw and said intermediate portion of
said driver into said outer axial portion of said counterbore of said
screw;
(3) loading said screw and said driver onto said guide wire by passing said
first end of said guide wire through said axial bore of said screw and
said axial bore of said driver,
(4) installing said screw into said bone by moving said screw and said
driver along said guide wire toward said bone until said second end of
said screw is pressed against said bone and then rotating said driver so
that said screw is driven into said bone; and
(5) detaching said driver from said screw by moving said driver along said
guide wire from said bone.
26. An elongate screw for use in conjunction with a driver of the sort
comprising (a) an elongate shaft having a front end, (b) an elongate
intermediate portion having first and second ends, said second end of said
intermediate portion being fixedly attached to said front end of said
shaft and said intermediate portion having a polygonal cross section, and
(c) a front portion having a back end and a front end, said back end of
said front portion being fixedly attached to said first end of said
intermediate portion, and said front portion comprising compression means
for permitting said front portion to be compressed radially into a
compressed state, said elongate screw comprising:
(a) a shaft having first and second ends and a threaded exterior surface;
(b) an axial bore adapted to receive a guide wire therethrough, said axial
bore extending through said shaft and coupled with said first and second
ends respectively, said axial bore having a substantially constant
transverse cross section;
(c) a blind axial bore coaxial with said axial bore, said blind axial bore
having an outer portion coupled with said first end of said shaft and an
inner portion terminating in a shoulder, said inner portion of said blind
axial bore having a cross section larger than the cross section of said
axial bore and selected (i) so that insertion of said front portion of
said driver into said inner portion of said blind axial bore in said screw
will cause said front portion of said driver to be compressed into said
compressed state, and (ii) so that when said front portion of said driver
is inserted in said inner portion of said blind axial bore in said screw,
said front portion of said driver will engage said inner portion of said
blind axial bore with a spring interference fit, whereby said front
portion of said driver cannot be removed from said inner portion of said
blind axial bore of said screw except when a selected axial force is
applied to said front portion of said driver; and
(d) a counterbore disposed about said outer portion of said blind axial
bore, coupled with said first end of said shaft and coaxial with said
axial bore, said counterbore having a constant polygonal cross section
chosen (i) so that when said front portion of said driver is fully
inserted into said inner portion of said blind axial bore, said
intermediate portion of said driver engages said counterbore of said screw
with a sliding fit, and (ii) so that when said intermediate portion of
said driver engages said counterbore of said screw, said intermediate
portion of said driver is in driving relation to said counterbore so that
rotational drive can be transmitted from said driver to said screw. |
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Claims |
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Description |
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FIELD OF THE INVENTION
The present invention relates to screw and driver assemblies, and more
particularly to surgical screw and driver assemblies designed so that the
driver is releasably couplable to the screw.
BACKGROUND OF THE INVENTION
In certain situations, it is desirable that a screw be both rotationally as
well as axially releasably couplable with a driver. For instance, in
limited-access work applications, e.g., in arthroscopic or other "closed"
surgeries, where a screw is to be inserted into a hole which is not
readily accessible, it is advantageous to axially couple the screw with
the driver before inserting the screw into the surgical site. Such axial
coupling is also beneficial where the screw implantation site is
accessible, e.g. where the screw is inserted in a downwardly facing hole.
With such screw and driver combinations, the screw is first attached to the
driver and then the driver is manipulated until the screw contacts the
implantation site, whereupon the driver is rotated until the screw is
fully implanted. Then, the driver is disengaged from the screw by pulling
it axially away from the screw.
Such screw and driver combinations are known in the art, as illustrated by
U.S. Pat. Nos. 2,329,398, 2,511,051, 2,775,913, 3,463,209, 3,695,321, and
3,888,144. Known screw and driver combinations typically suffer from one
or more problems which limit their utility and acceptance in certain
situations. For instance, known screw and driver assemblies when designed
to provide sufficient axially locking engagement can be difficult to
operate, inasmuch as the driver must be inserted with an unacceptably
large axial force to overcome the frictional interference between screw
and driver. With some screw and driver combinations, the rotational
engagement between the screw and driver is not sufficiently positive,
i.e., there often is an unacceptably large amount of play between the
screw and driver. Other screw and driver combinations (1) tend to be
relatively expensive to produce due to the relatively complex shapes of
the screw and driver and (2) can permit some axial wobble between screw
and driver, i.e., the combination is not designed to ensure the driver is
always perfectly co-axially aligned with the screw.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a screw and driver
combination designed (a) to provide positive rotational engagement between
screw and driver, (b) to permit the driver to be securely attachable to
the screw so that the driver is restrained from moving axially relative to
the screw while at the same time permitting the driver to be relatively
easily attachable to and detachable from the screw, and (c) to ensure the
screw and driver when engaged remain co-axially aligned with one another.
Another object of the present invention is to provide a screw and driver
combination achieving the foregoing objects which is adapted for use with
a "K-wire" or other guide wire insertion system.
These and other objects are achieved by a screw and driver combination
comprising a screw and a driver designed to rotatably drive the screw. The
latter is preferably, although not necessarily, threaded along its entire
length, comprises an axial bore of circular cross section which is open to
the top end of the screw and a counterbore of polygonal, preferably
hexagonal, cross-section which is also open to the top end of the screw.
The driver comprises an elongate shaft terminating in a
radially-compressible cylindrical front portion. The latter is sized and
configured so that when the front portion is inserted through the
counterbore into the axial bore of the screw, the front portion will
compress radially. When the front portion is fully inserted, it snugly
engages the wall of the axial bore with a minor spring-biased
interference, whereby the driver is releasably coupled in an axial sense,
to the screw.
The driver also comprises an elongate intermediate portion having a
polygonal, preferably hexagonal, cross-section with the cross-sectional
configuration and dimension of the intermediate portion being
substantially equal to the cross-sectional configuration and dimension of
the counterbore of the screw. The intermediate portion is attached to the
rear end of the front portion and the front end of the shaft. Thus, when
the front portion is inserted in the axial bore of the screw and the
intermediate portion is inserted in the counterbore, by rotating the shaft
rotational drive is transmitted, via the engagement of the intermediate
portion and the counterbore, to the screw.
BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the nature and objects of the present
invention, reference should be made to the following detailed description
which is to be considered together with the accompanying drawings.
FIG. 1 is a side elevation view, partially broken away, of the screw of the
present invention;
FIG. 2 is an end view of the screw taken along line 2--2 in FIG. 1;
FIG. 3 is a side elevation of the driver of the present invention;
FIG. 4 is an enlarged view of the front portion of the driver illustrated
in FIG. 3;
FIG. 5 is an enlarged cross-sectional view taken along line 5--5 in FIG. 4;
FIG. 6 is a cross-sectional view of the driver taken along line 6--6 in
FIG. 5;
FIG. 7 is an enlarged side elevation view of an alternative version of the
front portion of the driver;
FIG. 8 is an enlarged cross-sectional view of the front portion illustrated
in FIG. 7 taken along line 8--8 in FIG. 7;
FIG. 9 is a cross-sectional view of the front portion illustrated in FIG. 8
taken along line 9--9 in FIG. 8;
FIG. 10 is a plan view showing the screw of the present invention inserted
into a gap between a bone plug and the wall of the hole in the bone in
which the bone plug is inserted;
FIG. 11 is a side elevation, partially broken away, of the screw of the
first alternative embodiment of the present invention;
FIG. 12 is a side elevation of the driver of the first alternative
embodiment of the present invention;
FIG. 13 is a schematic side elevation view showing the screw and driver of
the first alternative embodiment, the material in which the screw of the
first alternative embodiment is to be implanted, and the guide wire used
with the screw and driver of the first alternative embodiment;
FIG. 14 is a side elevation, taken in cross section, of the front portion
of one version of the driver of the second alternative embodiment;
FIG. 15 is a side elevation of the driver of the second alternative
embodiment; and
FIG. 16 is a side elevation, taken in cross section, of the front portion
of another version of the driver of the second alternative embodiment.
In the drawings, like reference numerals refer to like parts.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIGS. 1-3, the present invention is a screw and driver
combination consisting of screw 20 and driver 50.
Screw 20 comprises an elongate shaft having a flat back end 22 and a
pointed front end 24. Screw 20 is preferably cylindrical along the
majority of its length, with the front portion of the screw tapering down
to pointed front end 24. Thus, screw 20 preferably does not comprise a
distinct head having a diameter which is greater than the diameter of the
shaft of the screw. Alternatively, where the application so requires, a
head (not shown) may be attached to back end 22.
Screw 20 is threaded along the entire length of its outside surface. The
specific thread pitch will, of course, vary with application and screw
size, although for a screw designed for use in arthroscopic or other
closed surgeries and having a length of about one inch (1") a thread pitch
of about 0.110 inches/thread is satisfactory.
Screw 20 comprises a blind axial bore 26 which is open to back end 22.
Axial bore 26 has a circular cross-section, with the diameter of the axial
bore preferably being equal to roughly one-third the outside diameter of
screw 20. The length of axial bore 26 is preferably equal to about
two-thirds the overall length of screw 20.
Screw 20 also comprises a blind counterbore 28 which is co-axial with axial
bore 26 and is open to back end 22. Counterbore 28 has a polygonal,
preferably hexagonal, cross-section with the result that the counterbore
comprises a plurality of flat elongate adjoining faces 28'. Counterbore 28
is dimensioned so that the diameter of a circle contacting simultaneously
all of the flat faces 28' of the counterbore is at least as large as the
diameter of axial bore 26, and in most cases is larger than the diameter
of axial bore 26. As a result of this dimensioning, a seat 30 is formed at
the base of counterbore 28. The length of counterbore 28 relative to the
portion of axial bore 26 having a circular cross section may vary based on
known design parameters, although in an exemplary screw 20 the portion of
bore 26 having a circular cross section is approximately one-and-a-half
times as long as counterb | | |
