Note: Descriptions are shown in the official language in which they were submitted.
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POWER OPERATED ROTARY EXCISION TOOL
CROSS-REFERENCE TO RELATED APPLICATIONS
[gm] This application claims the benefit of U.S. Provisional Application
No. 62/012,707 filed June 16, 2014. U.S. Patent Application No.
14/725,303 filed May 29, 2015 is hereby incorporated by reference.
TECHNICAL FIELD
[00021 The present invention reiates generally to power operated
dermatomes, such as rotary knife dermatomes and rotary disc
dermatomes.
BACKGROUND OF THE INVENTION
[00031 Power operated dermatomes, such as rotary knife dermatomes,
are hand-held surgical instruments used by a physician or
medical professional to cut thin layers or sections of skin tissue.
Dermatomes are used in hospitals and other medical facilities for
excising or removal of skin tissue from patients in connection with
various medical procedures including split-thickness and full-
thickness skin grafting, skin debriding (e.g., removal of burned
skin tissue), tumor/lesion removal, and breast reduction, among
other procedures. Dermatomes are also used to remove skin tissue
from deceased human or animal donors for skin grafting
purposes.
[0004] Prior power operated dermatomes typically included a
reciprocating cutting blade disposed at a front or leading edge of
the dermatome with a guard or depth gauge to allow the operator
to set a depth of cut to remove a desired thickness of skin tissue.
The handle of prior dermatomes was disposed rearward of the
cutting direction of the blade. Such dermatome configurations
required the operator to move the dermatome away from the his
body while cutting, resulting in reduced visibility of the area of
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skin to be removed, less precise control of the dermatome and
increased force required to operated the dermatome.
SUMMARY
[00051 Exemplary methods of operating powered dermatomes are
disclosed herein.
[0006] In one exemplary embodiment, a power operated dermatome
comprises a blade housing assembly, a skin deflector, an annular
rotary knife blade, a cutting plane and a depth gauge. The rotary
knife blade has an inner region, an upper body portion, and a
lower cutting portion. The lower cutting portion has an inner
surface, an outer surface, and a bottom surface. A cutting edge of
the rotary knife blade is formed by the intersection between the
inner surface and the bottom surface of the lower cutting portion.
The cutting plane of the dermatome is defined by the cutting edge
of the rotary knife blade, and the depth gauge is disposed within
the inner region of the rotary knife blade. The dermatome is
pulled across a skin surface.
[00071 In an exemplary method, a dermatome having a blade is pulled
with a force applied against a skin surface while maintaining an
acute angle between the blade and skin surface of about 30 to 45
degrees, which requires at least 30 percent less force than
pushing a standard oscillating flat-plane dermatome across a skin
surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[00081 These and other features and advantages of the present invention
will become better understood with regard to the following
description and accompanying drawings in which:
[0009] Figure 1 is a perspective view of an exemplary dermatome;
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[0010] Figure 2 is a cross-section of the exemplary dermatome of
Figure 1;
[0011] Figure 3 is an enlarged view of a cross-section of annular blade
housing 410;
[00121 Figure 4 is an enlarged view of a cross-section of lock ring 450;
[0013] Figure 5 is an enlarged view of a cross-section of rotary knife
blade 300;
[0014] Figure 5A is a schematic diagram of a portion of the cross-section
of rotary knife blade 300 of Figure 5;
[0015] Figure 5B is a perspective view of the cross-section of rotary knife
blade 300 of Figure 5;
[13016] Figure 6 is an enlarged view of a cross-section of blade housing
assembly 400; and
[00r] Figure 7 is an enlarged view of a cross-section of depth gauge
assembly 600.
[0018] Figure 8 is a plot of force over time for a first technician to
operate 1) a dermatome as described herein using the method
described herein, and 2) a standard oscillating flat-plane
dermatome operated using standard methods.
[00191 Figure 9 is a plot of force over time for a second technician to
operate 1) a dermatome as described herein using the method
described herein, and 2) a standard oscillating flat-plane
dermatome operated using standard methods.
DETAILED DESCRIPTION
[0020] Figures 1 through 7 illustrate an exemplary embodiment of a
head assembly 200 of a hand-held, power operated dermatome
100. The power operated dermatome 100 comprises a handle
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assembly (not shown), a drive assembly (not shown), and a head
assembly 200. The head assembly 200 includes a frame body 202,
an annular rotary knife blade 300, a blade housing assembly 400,
and a depth gauge 600. The cross-section of Figure 2 is taken
through the above components to more clearly indicate their
relative position inside of the head assembly 200 of the
dermatome 100.
[0021] During operation of the dermatome 100, the rotary knife blade
300 is driven around an axis of rotation 700 at high rotational
speed (on the order of about 500-1,500 RPM) by the drive
assembly. As shown in Figure 6, the cutting edge 360 of the rotary
knife blade 300 forms a cutting plane 702 that is substantially
orthogonal to axis of rotation 700. A lower blade portion 304 of the
rotary knife blade 300 is generally frustoconical in shape, defining
a cutting angle 704 with the cutting plane 702. During operation
of the dermatome 100, the cutting edge 360 cuts into the skin of a
patient at the cutting angle 704 until a bottom surface 624 of the
depth gauge plate 622 of the depth gauge assembly 600 contacts
the patient's body. An axial distance between the bottom surface
624 and the cutting plane 702 defines a depth of cut 706 that
corresponds to a maximum thickness skin excised during use of
the dermatome 100. An adjustment knob 650 of the depth gauge
assembly 600 allows the user to quickly and precisely set and
adjust the axial position of the bottom surface 624, thereby
adjusting the depth of cut 706. The depth of cut 706 can be
adjusted during a cutting operation to vary the thickness of the
portion of skin excised from the patient.
[0022] The dermatome 100 operates in a manner similar to that of the
power operated dermatome disclosed in U.S. Pat. Appl. No.
13/842,224 (hereinafter "the '224 application") filed on March 15,
2013 and entitled Power Operated Dermatome With Shielded
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Rotary Knife Blade, which is incorporated herein by reference in
its entirety.
[0023] The frame body 202 connects a handle assembly (not shown) to
the blade housing assembly 400 of the head assembly 200. The
frame body 202 comprises a generally cylindrical body 205 and
includes a rearward handle attachment portion 204 and a forward
interface portion 206. The interface portion 206 of the frame body
202 includes an end portion 210. The end portion 210 and the
body 205 include an opening 214 configured to receive the
interface portion 420 of the annular blade housing 410. The
rearward attachment portion 204 includes a threaded outer
surface 230 located in the handle attachment portion 204 to
attach the frame body 202 to the handle assembly. The head
assembly 200 can be attached to the handle assembly by any
releasable means, such as with a flange and fasteners, a quarter-
turn collar, latches, a compression fit, or the like.
[0024] The frame body 202 also includes a gear box housing 208 that
houses a gear train (not shown) of the drive assembly. The drive
assembly is disposed within the handle assembly and gear box
housing 208. The rear opening 234 in the frame body 202 allows
the drive assembly to be inserted into the gear box housing 208 of
the frame body 202 when the handle assembly is attached to the
frame body 202. Exemplary handle and drive assemblies are
disclosed in the '224 application.
[0025] The blade housing assembly 400 includes an annular blade
housing 410 and a lock ring 450. The annular blade housing 410
is generally cylindrical in shape and includes a rear interface
portion 420 and a forward skin deflector portion 440. The housing
410 has an inner wall 411 radially spaced apart from an outer
wall 413. An outer lower end 414 is axially spaced apart from an
upper end 412 and intersects with the outer wall 413. An inner
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=
lower end 415 is axially spaced apart from the upper end 412 and
intersects with the inner wall 411. An annular blade channel 416
is disposed between the outer and inner lower ends 414, 415. An
arcuate bearing surface 417 is located where the outer lower end
414 meets the annular blade channel 416. The outer wall 413
includes a threaded portion 418 for assembly with the lock
ring 450.
[00261 The interface portion 420 of the annular blade housing 410
includes a gear interface opening 424 that intersects the upper
end 412, inner wall 411, and outer wall 413 to expose the driven
gear 330 of the rotary knife blade 300 disposed within the annular
channel 416. The forward interface portion 206 of the frame body
202 attaches to the interface portion 420 of the housing 410 in the
location of the openings 424, 214. The gear interface opening 424
in the blade housing 410 and the opening 214 in the frame body
202 allow the drive train (not shown) within the frame body 202
to interface with the driven gear 330 of the rotary knife blade 300.
The interface slot 220 in the forward interface portion 206 of the
frame body 202 receives the upper end 412 of the interface portion
420 of the blade housing 410. In one particular embodiment, the
frame body 202 is secured to the annular housing 410 with
fasteners 222 threaded into threaded openings 422 in the
interface portion 420 of the housing 410. The frame body 202 may
be attached to the housing 410 by any releasable means, such as
with pins, clamps, or the like.
[0027] The skin deflector portion 440 of the annular blade housing 410
includes: a blade shield 444 comprising an inner wall 411 and an
inner lower end 415; and a rounded guide surface 442 comprising
an inner wall 411 and an upper end 412. The blade shield 444
covers the body portion 302 of the rotary knife blade 300 so that
the driven gear 330 disposed within the blade channel 416 is not
exposed during operation of the dermatome 100. The rounded
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guide surface 442 is formed at the intersection of the inner wall
411 and upper end 412 and prevents excised skin from tearing as
it is removed from the dermatome 100 during operation.
[00281 The blade housing assembly 400 further includes a depth gauge
support portion 430. The depth gauge support 430 includes one or
more ribs 432 that connect the depth gauge assembly 600 and the
blade housing assembly 400 to align the center of the depth gauge
assembly 600 with the axis of rotation 700. The gauge support
portion 430 is integrally part of the blade housing 410, but the
gauge support 430 may comprise separate components attached to
the blade housing 410 by any means, such as with threaded
fasteners, clamps, pins, a welded connection, or the like. The
gauge support 430 may also attach to the blade housing 410 in
one or more locations, provided that room is left between the ribs
432 in the skin deflector portion 440 of the annular housing 410
for excised skin to be extracted from the dermatome 100 during
operation, and provided that the depth gauge assembly 600 is
adequately supported during operation of the dermatome 100.
[0029] The lock ring 450 is generally cylindrical in shape and includes an
upper end 454, an axially spaced apart lower end 456, a lower
inner surface 451, an upper inner surface 453, and an outer
surface 455. The upper and lower inner surfaces 453, 451 are
radially spaced apart from the outer surface 455. The lower inner
surface 451 is disposed inward of the upper inner surface 453,
forming a shoulder 452. An arcuate bearing surface 457 is formed
at the intersection of the lower inner surface 451 and the shoulder
452. The upper inner surface 453 includes a threaded portion 458
to assemble the lock ring 450 to the threaded portion 418 of the
annular blade housing 410. The outer surface 455 includes
peripherally spaced cavities 459 so that the lock ring 450 can be
held securely during assembly with the blade housing 410.
Though the lock ring 450 is attached to the blade housing 410
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with a threaded connection, the lock ring 450 may be attached to
the blade housing 410 by any releasable means, such as with
threaded fasteners, pins, clamps, or the like.
[0030] The rotary knife blade 300 includes an upper body portion 302
and a lower blade portion 304. The upper body portion 302
extends between an upper end 306 and a lower end 308, and
includes an inner wall 310 and an outer wall 312. The outer wall
310 includes a bearing race 320 and an arcuate bearing surface
322 that extend radially inward into the outer wall 312 to receive
a continuous rolling bearing structure 370. When assembled
within the bearing race 320, the bearing structure 370 defines a
convex outer surface 380 of the rotary knife blade 300 that
projects radially outward from the outer wall 312. The continuous
rolling bearing structure 370 supports the rotary knife blade 300
within the blade housing assembly 400. Specific details
concerning the structure and configuration of the continuous
rolling bearing structure 370 are disclosed in the '224 application
and U.S. Pat. No. 8,806,761 (hereinafter "the '761 patent") filed on
July 25, 2011 and entitled Power Operated Rotary Knife, which is
incorporated herein by reference in its entirety.
[0031] The bearing structure 370 is disposed in an annular gap 708
defined between opposing faces of the rotary knife blade 300,
blade housing 410, and blade lock ring 450 of the blade housing
assembly 400, in the region of the rotary knife blade bearing race
320. Specifically, the plurality of ball bearings (not shown) of the
bearing structure 370 are disposed within an annular passageway
710, which is generally circular in cross section and defined by the
opposing arcuate bearing surfaces 322, 417, and 457 of the rotary
knife blade 300, blade housing 410, and lock ring 450,
respectively.
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[0032] The lower blade portion 304 of the rotary knife blade 300 extends
from an upper end 350 to a lower end 352, and includes an inner
wall 354 and a radially spaced apart outer wall 356. The inner
and outer walls 354, 356 are generally frustoconical, converging
in a direction proceeding downwardly toward the cutting edge 360
of the rotary knife blade 300. The inner wall 310 of the body
portion 302 and the inner wall 354 of the blade portion 304 are
connected by a shoulder surface 314 and combine to define an
inner region 301 of the rotary knife blade 300. A bottom surface
362 defines the lower end 352 of the blade portion 304, connecting
the inner and outer walls 354, 356. The cutting edge 360 is
defined by the intersection of the bottom surface 362 and the
inner wall 354 and is generally circular in nature. A plane aligned
with the cutting edge 360 of the rotary knife blade 300 defines the
cutting plane 702 of blade 300. The cutting angle 704 is defined as
the acute angle between the inner wall 354 of the blade portion
304 and the cutting plane, 702.
[0033] The relationship between the various surfaces of the lower blade
portion 304 is illustrated in Figure 5A. Before the lower blade
portion 304 of the rotary knife blade 300 is formed by a grinding
operation, the thickness of the material W may range from about
0.005" to about 0.1". In one particular embodiment, the thickness
of the material W is about 0.034". A height distance H from the
cutting plane 702 to the lower end 308 of the upper body portion
302 of the rotary knife blade 300 may range from about 0.01" to
about 1". In one particular embodiment, the height distance H is
about 0.03".
[0034] A blade angle X between the inner wall 354 of the lower blade
portion 304 and a vertical line extending from the cutting edge
360 may range from about 20 degrees to an angle approaching 90
degrees. In one particular embodiment, the blade angle X is about
60 degrees. The lower blade portion 304 is ground to bring the
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bottom surface 362 within a desirable range for a chisel grind
width C, which may be up to about 0.106". In one particular
embodiment, the chisel grind width C is about 0.037". In some
other embodiments, the inner and outer walls 354, 356 are joined
at the cutting edge 360 so that there is no bottom surface 362. To
the extent that a bottom surface 362 exists in these other
embodiments, the chisel grind width C is at most 0.001".
[0035] After these grinding operations, a taper angle A between the
inner and outer walls 354, 356 is an acute angle, that is, it is
greater than 0 and less than 90 degrees. In one particular
embodiment, the taper angle A is about 10 degrees. The bottom
surface 362 is then ground to a sharpened edge angle Y to create
the cutting edge 360 and provide a bottom surface 362 that is
more suitable for sliding over the skin of a patient during a
cutting operation. The sharpened edge angle Y between the
bottom surface 362 and the inner wall 354 is greater than 0
degrees and up to about 70 degrees. In one particular
embodiment, the sharpened edge angle Y is about 29 degrees.
[0036] As can be seen from Figure 5A, the surfaces of the lower blade
portion 304 form a quadrilateral shape 500 without any parallel
sides that is bounded by the inner and outer walls 354, 356 of the
lower blade portion 304, the bottom surface 362, and a line
extending from the lower end 308 of the upper body portion 302.
This shape is swept through a full revolution around the axis of
rotation 700 to create the rotary knife blade 300. A partially
swept shape is shown in Figure 5B to illustrate how the surfaces
of Figure 5B form the blade 300. The dimensions noted above are
maintained throughout the blade to ensure that all portions of the
blade 300 are consistent in their cutting performance.
[00371 The depth gauge assembly 600 includes a cylindrical depth gauge
support 610 and the depth gauge 620. The depth gauge support
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610 further includes a flange 612, a cylindrical support 602, and a
stop plate 670. The depth gauge 620 includes a depth gauge plate
622, a shaft 640, and an adjustment knob 650. The depth gauge
plate 622 is disposed within an inner region 301 of the blade 300.
A depth of cut 706 is defined by the axial distance between the
cutting plane 702 and the bottom surface 624 of the depth gauge
plate 622. The depth of cut 706 determines the thickness of the
skin excised by the dermatome 100 during use. As with the depth
gauge of the '224 application, the depth gauge assembly 600
allows the operator to quickly and accurately change the depth of
cut 706 during operation of the dermatome 100 by rotating the
adjustment knob 650.
[0038] The depth gauge flange 612 extends from and is supported by the
one or more ribs 432 of the blade housing support portion 430 and
is generally rectangular, though it may be any shape. The
cylindrical support 602 extends below the flange 612 to the lower
end 606. The central bore 608 extends from the upper surface 604
of the flange 612 through the flange 612 and the cylindrical
support 602 to the lower end 606. The depth gauge 620 includes
the depth gauge plate 622. and the depth gauge shaft 640. The
shaft 640 is slideably disposed within the central bore 608 and
includes an outer surface 641, a lower end 642, a middle portion
644, and an upper end 648. The outer surface 641 of the shaft 640
includes a threaded adjustment portion 643 at the upper end 648
and an axially oriented slot 646. The upper end 648 includes a
threaded opening 645 to receive a stop screw 680.
[0039] The stop plate 670 is generally rectangular and assembles to the
depth gauge flange 612. The stop plate 670 includes an
adjustment knob opening 678 that is configured to receive an
adjustment knob 650 and limit vertical movement of the
adjustment knob 650 when the depth of cut 706 is adjusted by an
operator. The stop plate 670 further includes two openings 672
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that are aligned with the threaded openings 614 in the depth
gauge flange 612. Threaded fasteners 676 are inserted through
the openings 672 and into the threaded openings 614 to secure the
stop plate 670 to the flange 612. The stop plate 670 may be
attached to the depth gauge flange 612 in any way, such as with
clamps, pins, a welded connection, or the like.
[0040] The adjustment knob 650 is generally cylindrical and extends
from the top surface 652 to the bottom surface 654. Upward
movement of the adjustment knob 650 is limited by contact of the
top surface 652 with the opening 678 in the stop plate 670, and
downward movement of the adjustment knob 650 is limited by
contact of the bottom surface 654 with the upper surface 604 of
the flange 612. The knob 650 includes a threaded opening 656 for
receiving a threaded adjustment portion 643 of the shaft 640. A
peripheral surface 658 of the knob 650 includes a plurality of
indentations to provide the operator with a better grip of the knob
650 when making adjustments to the depth of cut 706. An
opening 618 in the cylindrical support 602 receives a dowel pin
660 that slideably engages the slot 646 of the shaft 640,
preventing the shaft 640 from rotating as the adjustment knob
650 is rotated during adjustment of the depth of cut 706. As a
result, rotational motion of the adjustment knob 650 is translated
to linear vertical motion of the shaft 640 within the bore 608. The
rotation of shaft 640 may be prevented by any means, such as
with a keyed slot, using a non-circular shaft and bore, or the like.
The top surface 652 of the knob 650 and the stop plate 670 include
markings or indicia 653, 673 that indicate the current setting of
the depth of cut 706, similar to those disclosed in the '224
application.
[0041] The stop plate 670 also includes a central opening 674 that is
aligned with a stop screw opening 645 of the shaft 640. The stop
screw 680 is inserted through the opening 674 and threaded into
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the threaded opening 645. The stop screw 680 includes a screw
head 682 that engages a washer 684 placed on top of the stop
plate 670. The position of the stop screw 680 sets the lower limit
of the vertical movement of the depth gauge 620, and also
prevents the threaded adjustment portion 643 of the shaft 640
from unthreading from the threaded portion 656 of the knob 650
during adjustment of the depth of cut 706. Compression of the
washer 684 during downward adjustment of the knob 650 reduces
backlash in the threaded connection between the knob 650 and
the shaft 640. Alternatively, a biasing spring (not shown) like that
shown in the '224 application may be used to limit thread
backlash during adjustment of the depth of cut 706.
[0042] The depth gauge 620 includes a depth gauge plate 622 attached to
the lower end 642 of the shaft 640. The gauge plate 622 includes a
generally cylindrical center portion 632 and an annular ring
portion 630 connected to the center portion 632 by one or more
ribs 634. Openings 636 between the one or more ribs 634 allow an
operator to view the skin below the dermatome 100 during a
cutting operation. The center portion 632 includes a bore 628 that
receives the lower end 642 of the shaft 640. The center portion
632 of the depth gauge plate 622 may be connected to the shaft
640 by any means, such as a threaded connection, a welded
connection, a pinned connection, or the like. The bottom surface
624 of the annular ring portion 630 rests on the cutting surface
during operation of the dermatome 100 to help an operator
maintain the set depth of cut 706. Upward movement, and
therefore maximum depth of cut, is limited by contact between
the upper end 626 of the center portion 632 of the gauge plate 622
and the lower end 606 of the cylindrical support 602. Further
details of the cutting operation of the dermatome 100 are
disclosed in the '224 application.
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[00431 Successful skin excising operations depend on precision
equipment and operator skill. These variables are inversely
related: the less precise the dermatome, the more skill and
training an operator must have to perform the operation
successfully. Skin removed from the patient for a typical skin
grafting operation can be as thin as about 0.005 inches and as
thick as about 0.043 inches. Dermatome 100 allows the operator
to accurately excise skin at a desired thickness in a way that is
less dependent on the operator's skill than prior dermatomes,
resulting in more reliable results from operation to operation.
[0044] The position and size of the depth gauge relative to the cutting
edge and depth of cut improves the precision and consistency of
the depth of the cut. The relationship of the surfaces of the
cutting portion of the blade also improve consistency and ease of
cutting. For example, the sharpened edge angle between the
bottom surface of the blade and the inner wall of the lower blade
portion provides relief behind the cutting edge of the blade,
thereby reducing friction between the blade and the skin of the
patient, helping to separate the excised skin from uncut skin. The
angle of the bottom surface improves movement of the dermatome
during a cutting operation so that the dermatome can be moved at
a consistent and predictable speed across the body of the patient
while removing an excised portion of skin with substantially
uniform thickness at a given setting. The movement of the cutting
edge is countered by the depth gauge pressing against the body of
the patient, resulting in a precise and repeatable cutting of the
skin during an excision operation. That is, the same setting of the
adjustment knob will result in the same thickness of excised skin
between operations.
[0045] Additionally, features of dermatome 100 critical to precision
cutting can be machined during a single manufacturing operation,
improving alignment of critical features and components. This is
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accomplished by the generally cylindrical shape of key
components of dermatome 100.
[0046] Components of the power operated dermatome disclosed in the
'224 application that are similar to the upper body portion 302 of
the rotary knife blade 300, blade housing 410, and lock ring 450
are generally frustoconical in shape. In the power operated
dermatome 100, however, these components have a generally
cylindrical shape. Consequently, manufacturability of the blade
300, blade housing 410, and lock ring 450 is improved compared
to similar components of the dermatome of the '224 application.
For example, the generally cylindrical shape of the blade housing
410 allows features critical to the operation of the dermatome
100, such as the annular blade channel 416 and arcuate bearing
surface 417, to be machined in a single operation resulting in
more precise positioning of these features relative to each other. A
skin deflector 444 can also be integrally formed into the blade
housing 410 because of the blade housing's 410 generally
cylindrical shape. Forming the skin deflector 444 during the same
operation as the blade channel 416 results in improved alignment
of the rotary knife blade 300 and the skin deflector 444, allowing
excised skin to more smoothly transition from the surface of the
blade 300 to the skin deflector 444.
[00471 The generally cylindrical shape of these components also
increases their stiffness relative to generally frustoconical
components. This increased stiffness provides blade 300 with
greater resistance to warping during heat treatment of cutting
edge 360, thereby improving the quality of the component and
manufacturing yield.
[00481 Manufacturing advantages of generally cylindrical parts extend to
the time and cost of manufacturing the components as well. For
example, blade 300 can be machined from a blank formed with a
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stamping process that is closer to the final dimensions of the part
and does not require a special chuck during machining. As a
result, blade 300 is produced in less time and for lower cost than
the generally frustoconical blade of the dermatome of the '224
application. Integrally forming skin deflector 444 as part of blade
housing 410 also reduces manufacturing time and cost by
reducing the number of components of dermatome 100.
[00491 The generally cylindrical shape of blade 300, blade housing 410,
and lock ring 450 also improves handling and performance of
power operated dermatome 100. The cylindrical shape of these
components allows head assembly 200 to be smaller than the
head assembly of the dermatome disclosed in the '224 application
without reducing the diameter of cutting edge 360 of blade 300.
The smaller overall size of dermatome 100 as compared to the
dermatome of the '224 application provides many benefits. For
example, head assembly 200 of dermatome 100 weighs less than
that disclosed in the '224 application, allowing for improved
maneuverability during operation. Also, the radial distance
between cutting edge 360 and outer surface 455 of lock ring 450
allows an operator to excise skin closer to joints or transitions in
the body than the dermatome of the '224 application.
[00501 An exemplary method of operating a hand-held, power operated
dermatome, for example dermatome 100, includes supplying
power to the dermatome to rotate a blade of the dermatome and
pulling the dermatome with a force applied against a skin surface
while maintaining an acute angle between the blade and skin
surface of between about 30 and 45 degrees. In an experiment,
explained more fully below, the present invention was used
according to this method and compared to a standard oscillating
flat-plane dermatome used according to traditional methods. The
experiment conclusively proves the benefits of the present device
and method over prior devices and methods.
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Experimental Example
[0051] A experiment was designed and run to measure force needed to
recover "good" or "excellent" skin grafts, using both a standard
oscillating flat-plane dermatome and a rotary-blade dermatome
as disclosed herein. Two experienced technicians, unrelated to
each other and with neither personal nor business affiliation to
either device, were asked to recover skin on two cadavers. The use
of "good" or "excellent" ratings simulated and leveraged the
technicians' skill and expertise with each device without over-
defining or constricting technique or device settings. A tactile
pressure system was used to record forces transferred from the
operators' hands to the instrument. Gloves with 18 different
positions simultaneously recorded 349 independent force
measurements per hand in areas most likely to see the highest
grip forces when holding onto a generally cylindrical object.
[00521 The data collected through the tactile sensors was recorded for
each individual point of contact on the glove (698 total) and all
positions on the hands (36 total). Maximum forces per section
along with overall average force through the users' hands were
evaluated.
[0053] Figure 8 illustrates a resulting plot of force required over time
during which a first technician operated first, an embodiment of
the powered rotary dermatome described herein, using the
method described herein, and second a standard oscillating flat-
plane dermatome, while removing a set amount of skin from a
cadaver. The first technician exerted an average of 30.60 percent
=
less force while operating the rotary dermatome as compared to
the standard model. Further, in 20 of 22 trials, the first
technician was able to complete the skin removal in noticeably
less time with the rotary device¨on average 36 percent less time.
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[00541 Figure 9 illustrates a resulting plot of force required over time
during which a second technician operated first, an embodiment
of the powered rotary dermatome described herein, using the
method described herein, and second a standard oscillating flat-
plane dermatome, while removing a set amount of skin from a
cadaver. The second technician exerted an average of 33.58
percent less force while operating the rotary dermatome as
compared to the standard model. The second technician was able
to complete the skin removal in noticeably less time with the
rotary device¨on average 54 percent less time
[0055] The above experiment conclusively proves the benefits of the
invention disclosed herein. Pulling a rotary dermatome as
disclosed herein, as opposed to pushing a flat blade oscillating
dermatome, requires both less force and time to recover split
thickness skin, especially when the dermatome blade is at about a
30 to 45 degree angle with respect to the skin surface.
[0056] While the present invention has been illustrated by the
description of embodiments thereof, and while the embodiments
have been described in considerable detail, it is not the intention
of the applicants to restrict or in any way limit the scope of the
appended claims to such detail. Additional advantages and
modifications will readily appear to those skilled in the art.
Moreover, elements described with one embodiment may be
readily adapted for use with other embodiments. Therefore, the
invention, in its broader aspects, is not limited to the specific
details, the representative apparatus and illustrative examples
shown and described. Accordingly, departures may be made from
such details without departing from the spirit or scope of the
applicants' general inventive concept.
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