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BACKGROUND
Applications exist, particularly in the field of neurosurgery, for
mechanisms capable of effecting accurate positioning of an implement, such
as the working end of a surgical instrument, an electrode, a needle, or
the like. Because the implement must be spatially moved to any desired
position over the skull of the patient, the mechanism for effecting this
positioning must be capable of multiple movements in a three dimensional
coordinate system. Consequently, sliding movements with respect to a fixed
rail over the operating table, coupled with rotational movements, tilting
movements and the like, all must be precisely controlled in order to place
the implement at the desired position and angle at which it is to be used.
Mechanisms for positioning such implements typically require a number of
separate adjustments, with separate locking of each of the different
movements necessary to effect and hold the three-dimensional positioning.
As a result, such mechanisms are difficult and cumbersome to use and
require substantial skill and considerable manipulation on the part of the
physician or other user.
Three surgical instrument positioning devices, capable of multiple movement
in a three dimensional coordinate system, are disclosed in the U.S.
patents to Mocarski No. 3,073,310; Moore No. 4,723,544; and Carol No.
4,955,891. The devices disclosed in each of these patents are relatively
complex arrangements of rotational and sliding members, requiring multiple
clamps to secure and release the different movements of various levers
comprising the components of the positioning devices in order to effect
the desired positioning. All of these devices are cumbersome to use,
because of the multiple clamps or cams which must be operated in order to
lock the different motions of the different parts in place. Since all of
these parts and motions are separately locked or released, the
manipulation of the components and the accurate positioning of the
instrument, with which they are designed for use, requires a substantial
amount of skill and experience.
An effort to reduce the complexity of operation of a spatial positioning
implement for positioning an electrode in a precise manner is disclosed in
the U.S. patent to Pfeiffer No. 3,196,875. This patent is directed to a
manipulating device, which is slidably mounted on a carriage on a
semi-circular track. The carriage may be moved to different positions
along the track and rotated or tipped about the track. Once the location
of the carriage has been selected, it is locked in place on the track by a
threaded locking handle.
In the Pfeiffer device, the instrument itself is carried on the tip of an
extension of an elongated rod, which is slidably and rotatably mounted in
a bore through a split compressible sphere. The sphere is held in a clamp
having a split through it, which may be drawn together or released by
means of a clamping lever. When the clamping lever is released, a handle
on the end of the positioning rod may be used to move the rod back and
forth through the bore in the sphere, and to rotate it until the
instrument is located in the desired position. Once this has been
effected, clamp jaws are contracted by manipulation of a lock lever to
squeeze the compressible sphere. This holds the sphere in place, so that
it cannot be rotated. The sphere also compresses against the bore through
it to prevent further rotation and sliding of the rod extending through
it.
Thus, two different mechanisms are required in Pfeiffer to complete the
positioning of the device; and two different clamping members must be
operated in order to effect that positioning. Manipulation of the two
together effects the proper position of the instrument. Then two separate
operations by the person utilizing the positioning device are necessary to
lock it into place, and, subsequently, to release it.
Accordingly, it is desirable to provide a positioning device capable of
positioning an implement in a three-dimensional coordinate system quickly
and accurately, and in which the position of the implement then may be
secured by means of the operation of a single locking member or control
member.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved position control
mechanism.
It is another object of this invention to provide an improved implement
positioning mechanism.
It is an additional object of this invention to provide an improved
implement positioning mechanism for positioning an implement in a
three-dimensional coordinate system.
It is a further object of this invention to provide an improved implement
positioning system capable of positioning an implement in a
three-dimensional coordinate system and in which operation of a single
control member releaseably locks all of the movements of said device in a
single operation.
In accordance with a preferred embodiment of this invention, a device for
positioning an implement consists of a main body member. This main body
member, in turn, includes a base portion and an upper portion, which is
rotatably mounted on the base portion. The upper portion has a hollow
chamber in it; and an elongated slot extends through the upper portion to
communicate with this chamber. A compressible sphere is located in the
hollow chamber for rotational movement about the center of the sphere,
which also has a bore through it. An elongated cylindrical shaft then is
slidably and rotatably mounted in the bore through the sphere, and passes
through the slot in the upper portion of the main body member. A single
control member is used to releaseably lock the base portion and upper
portion of the main body member together, simultaneously, with the locking
of the sphere and the cylindrical shaft in preselected positions.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a preferred embodiment of the invention;
FIG. 2 is a cross-sectional view taken along the line 2--2 of FIG. 1;
FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG. 1; and
FIG. 4 is an exploded view of the embodiment shown in FIG. 1.
DETAILED DESCRIPTION
Reference now should be made to the drawings, in which the same reference
numbers are used throughout the different figures to designate the same
components. The embodiment illustrated in the four figures of the drawings
is a device which is particularly suitable for use in a variety of
neurosurgical applications for positioning an implement quickly and
precisely at a predetermined selected area of the skull or the brain of a
patient. The device is capable of five different simultaneous movements
for effecting a precise three-dimensional positioning of an instrument
quickly and effectively. Once the positioning has been accomplished, all
five of the different motions, which the device is capable of performing,
are secured or locked in place by means of the manipulation of a single
control lever. Consequently, the positioning quickly and easily is
accomplished; and once that has been effected, the locking of all of the
different motions in place easily may be effected, since no multiple lever
or multiple cam locking devices are used.
To accomplish the foregoing, the device consists of a unique arrangement
and interrelationship of parts. Typically, a positioning device for
surgical instruments, particularly used for neurosurgery, is mounted on a
support rail 10. The support rail 10 is placed in a fixed location
relative to an operating table (not shown) and forms the base reference
for the location of the surgical instrument or other implement carried by
the device.
The positioning device itself comprises a main body having a lower or base
portion 12 and an upper portion 14, rotatably mounted on the base portion
12. The base portion 12 is slidably placed on the rail 10, which passes
through a slot 13 through the base portion perpendicular its central axis.
The slot 13 has inwardly turned legs on it to engage the opposite side of
the rail 10 from the side on which the remainder of the device of FIG. 1
is located. These inwardly turned legs are shown most clearly in FIGS. 2
and 4. When the device is released, the base portion 12 may be moved back
and forth along the rail 10 in the direction of the arrow to any desired
position.
As illustrated in FIGS. 2, 3 and 4, the base portion 12 has a central
cylindrical extension 36 on it, which is of less diameter than the outer
diameter of the portion 12. This extension 36 is externally threaded, and
terminates in a spherically concave upper surface 37. In the assembly of
the device, the upper portion 14 is placed over the extension 36 to abut
the shoulder on the base portion 12. The upper portion 12 is hollow, and
has an inwardly turned flange 34 around its lower end, with the diameter
of the opening of the flange selected to pass freely over the extension 36
on the base portion 12.
When the upper portion 14 is in place, as shown in FIGS. 2 and 3, a
threaded retaining ring or locking shoulder 33 is turned in place to the
position shown in FIGS. 2 and 3 to rotatably secure the upper portion 14
onto the base portion 13. The threaded portion 33 is moved into close
proximity to the inwardly turned flange 34; but sufficient clearance is
provided to permit free axial rotation of the portion 14 with respect to
the base 13 when the ring or shoulder 33 is in place.
After placement of the ring 33, a compressible sphere, made of an upper
part 24A and a lower part 24B, is placed into the hollow chamber in the
upper portion 14, in the location shown most clearly in FIGS. 2 and 2. As
is readily apparent from an examination of FIG. 4, this compressible
sphere is split horizontally in a plane located above a plane passing
through the center of the sphere; so that the section 24A is smaller than
the section 24B. Together, however, the two sections comprise a complete
sphere. Also, as is clearly shown in FIGS. 2, 3 and 4, there is a central
bore through the sphere, in which an elongated split cylindrical bushing
26 is placed.
The bushing 26 has an elongated solid cylindrical shaft 16 passing through
it for slidable movement and for rotational movement, as indicated most
clearly in FIG. 1. The shaft 16 typically is bent at right angles to
terminate in a projection 17. The projection 17 then may have any suitable
implement or surgical instrument attached to it for positioning by the
device. It is to be noted that the shaft 16, passing through the bushing
26 in the bore through the sphere 24A/24B, also passes through elongated
slots 15A and 15B, located on diametrically opposite sides of the
cylindrical upper portion 14, and aligned with the axis of the cylindrical
upper portion 14.
To facilitate accurate assembly and disassembly of the device if the shaft
16 ever is completely removed after assembly, the sphere 24A/24B also has
a pair of partial bores located on an axis through the center of the
sphere 24A/24B for receiving a pair of locating pins 28 and 39. These pins
respectively extend into short elongated slots 25 and 38 on opposite sides
of the upper portion 14 of the device. These locating pins 28 and 39
permit rotation of the sphere 24A/24B freely about a line passing through
the center of the sphere and the slots 15A and 15B.
Some longitudinal movement of the sphere 24A/24B parallel to the axis of
portion 14 also is permitted by the elongated slots 26 and 38. The slots
25 and 38 are shown in exaggerated proportion to the diameter of the
circular pins 28 and 39 for the purposes of illustration of the operation
of the device. Typically, these slots are only slightly elongated to
permit a small amount of movement of the sphere 24A/24B along the
longitudinal axis of the upper portion 14.
Next in the assembly of the device, a plug or top 18 is placed in the open
upper end of the upper portion 14. This plug 18 then may be held in place
by means of pins 19, as illustrated in FIGS. 2 and 4; or it may be keyed
by means of other suitable keys, or secured by means of brazing, welding
or the like. It is to be noted from an examination of FIGS. 2 and 3 that
the lower end of the plug 18, used to close the top of the cylinder for
the upper portion 14, has a spherically concave surface on it, which is
complementary to the outer surface of the upper portion 24A of the sphere
24A/24B. Similarly, the surface 37 on the extension 36 is a complementary
mating surface for the outer surface of the spherical section 24B of the
compressible sphere.
The device described thus far is capable of five different independent or
simultaneous movements, indicated by the various double-ended arrows in
FIG. 1. As mentioned previously, the base portion 12 may be moved anywhere
desired along the rail 10. Similarly, a 360.degree. rotation of the part
14, with respect to the base portion 13, may be effected. In addition, the
rod 16 may be moved to the limits of its length back and forth in a
sliding motion through the bushing 26 in the sphere 24A/24B, and also may
be rotated 360.degree. to pivot the end 17, as desired. The final motion
is a rocking motion on the sphere 24A/24B. The extent of this motion is
limited by the relative dimensions of the sphere 24A/24B, the rod or shaft
16 and the length of the slots 15A and 15B.
Once the position of the implement-carrying end 17 on the shaft or rod 16
is effected, all of the above motion is locked in place by turning a
single handle 22 to rotate a threaded shaft 20, which is threaded through
a center opening in the plug 18 in the top of the upper portion 14 of the
main body of the device. As shown in FIG. 2, the shaft 20 is in its
released position to permit all of the above five different positioning
movements to take place. When the shaft is turned clockwise to tighten it,
the lower end of the shaft 20 engages the top 24A of the compressible
sphere, pushing it downwardly against the split cylindrical bushing 26,
causing the bushing 26 to squeeze together as it presses onto the bottom
portion 24B of the compressible sphere, which in turn is pressed into
engagement with the surface 37 of the extension 36. The bottom portion 24B
of the sphere also presses downwardly on a rod 31 terminating in a
circular flange 32, which presses onto the upper surface (as viewed in
FIGS. 2, 3 and 4) of the rail 10 to clamp it tightly into the slot 13
against the inwardly turned edges of the housing 12 located on the
opposite side of the rail 10, as most clearly shown in FIGS. 2 and 4. The
rod 31 passes through an opening 30 in the extension 36, and it is held in
place; so that it does not drop out of the apparatus, by means of a rubber
O-ring bushing 35, which may be located anywhere along the length of the
bore 30 through the extension 36. As illustrated in FIGS. 2 and 3, the
O-ring 35 is located near the upper end of the bore 30; but this location
is not critical.
It is to be noted that when the handle 22, attached to the shaft 20, is
rotated approximately one-quarter turn, all of the different relative
motions of the different parts of the device are clamped in place. When
the lower end of the rod 20 presses on the top portion 24A of the split
collapsible sphere 24A/24B, the bottom portion presses against the surface
37, as described previously. This causes the upper portion 14 of the
housing to move relatively upwardly to the position shown in FIG. 3; so
that the inwardly turned flange 34 tightly engages the lower side of the
locking shoulder formed by the ring 33 to clamp the upper portion 14
against rotation relative to the base portion 12 of the housing.
When the two sections of the sphere 24A/24B are pressed together, the split
bushing 26 is tightly squeezed onto the rod or shaft 16. The shaft 16
cannot be rotated, and cannot be slidably moved in the bushing 26. When
the top portion 24A and the bottom portion 24B of the sphere are clamped
tightly by means of the end of the shaft 20 and the surface 37 on the
extension 36, the sphere 24A/24B cannot be rotated; so that the rod or
shaft 16 cannot be rocked in the slots 15A/15B. Finally, the downward
force of the lower sphere portion 24B on the upper end of the rod 31
causes the flange 32 to tightly press onto the upper surface of the rail
10 to clamp the entire device against sliding movement on the rail 10. All
of this is effected by a single control member, namely the shaft 20
operated by the handle 22.
Release of all of the different movements, to which the device is capable,
is effected simply by turning the handle 22 counterclockwise approximately
one quarter turn. This releases all of the compressive forces which have
been described above; so that the various motions which have been
described, once again, may be effected.
Preferably, all of the various parts, which have been shown and described
above, are made of metal, such as steel or aluminum. The bushing 26 is a
spring-like bushing, which expands to its original shape upon release of
the locking pressure, when the shaft 20 is rotated counterclockwise to the
position shown in FIG. 2, to unlock all of the different motions.
Consequently, the bushing 26 effectively functions as the return mechanism
for releasing the different parts to permit the different motions which
have been described above. The device is illustrated in FIG. 1 in
approximately full size. A typical positioning device, suitable for use
with instrument positioning for a variety of different neurosurgery
techniques is approximately four inches long, with a diameter of the
cylindrical portion 14 of approximately one inch. Thus, it is readily
apparent that the device is a very compact mechanism. It should be noted
that while the discussion of the preferred embodiment has been made in
conjunction with the spatial positioning of an instrument on the end 17 of
the rod 16, particularly suited for neurosurgery, any application which
requires accurate positioning of an implement in a spatial or
three-dimensional location may be effected by means of this device.
The foregoing description of the preferred embodiment of the invention is
to be considered as illustrative, and not as limiting. Various changes and
modifications will occur to those skilled in the art without departing
from the true scope of the invention. For example, the use of a threaded
shaft 20, operated by a lever 22 for effecting the release and locking of
the mechanism, may be replaced by a cam operation for some applications,
if desired. So long as the downward pressure, which is effected by the end
of the shaft 20 relative to the housing sections 12 and 14, is
accomplished, other mechanisms may be used. Also, it should be noted that
the locating pins 28 and 39, which hold the sphere 24A/24B in position
even when a shaft 16 is completely removed from the sphere, may be
eliminated if desired. If they are eliminated, it is possible for the
sphere to rotate in the chamber of the housing 14; so that the bushing 26
is not aligned with the slots 15A and 15B. It then would be necessary to
reach through the slots 15A or 15B to rotate the sphere until proper
alignment of the bushing 26 was attained, to permit re-insertion of a
shaft 16. The pins 28 and 39, however, are not essential for the clamping
and release operation which has been described.
Different techniques for assembling the various parts together may be used,
so long as the relative motions and the manner of clamping or locking
those motions simultaneously with a single operating lever or control
member may be used. Other changes and modifications will occur to those
skilled in the art, without departing from the true scope of the invention
as defined in the appended claims.
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