Skin incising device

A device for making skin incisions for bleeding time determinations in accordance with Ivy's method has a cutter guide on which an incising cutter is movable from a retracted position to an advanced position under the action of spring bias. A base surface adapted to be pressed against the patient's skin has a depression of a length corresponding to the desired length of the skin incision. A slot in the base surface extends across the depression and accommodates the tip of the cutter. When the cutter is released from the retracted position the spring bias displaces it along the slot and as it traverses the depression it makes a skin incision of predetermined constant depth.

BACKGROUND OF THE INVENTION 
1. Field of the Invention: 
This invention relates to a device for making a skin incision of 
predetermined depth and predetermined length. 
2. Prior Art: 
Determination of a patient's bleeding time in accordance with the method 
devised by Ivy includes making a skin incision on the palm side of the 
patient's forearm and measuring the time that elapses until the bleeding 
has crease. On each occasion two such determinations are made with the 
incisions parallel and separated about 2 cm. The mean value of the 
measured bleeding times is taken. 
In order that the determination may produce a correct result, the skin 
incision must have a certain standardized depth and it should also have a 
certain standardized length. In practice it is necessary therefore to use 
some form of mechanical device for making the incision. 
Skin incision devices for use in the determination of bleeding time 
according to the method of Ivy are known in the art. Examples of known 
embodiments of such devices are shown in U.S. Pat. Nos. 3,712,293 and 
3,902,475 and French Patent Publication No. 2,327,755. The prior art 
devices are disadvantageous in some respects, e.g. by being unhandy and/or 
expensive. 
SUMMARY OF THE INVENTION 
The general object of the present invention is to provide an improved skin 
incision device. A more specific object is to provide an inexpensive skin 
incising device which is simple to use and which reproducibly produces an 
incision having a predetermined, constant depth throughout the length 
thereof. 
According to the invention, these and other objects are realized in a skin 
incising device constructed in accordance with the claims. 
The device includes a guide which guides a cutter having a cutting tip. In 
a retracted position, the cutter is latched against biasing means, and on 
release of the latching means, the biasing means moves the cutting tip 
through a space of predetermined length and depth adapted to be disposed 
against the skin. 
For a full understanding of the invention, three embodiments thereof are 
described with reference to the drawings.

DETAILED DESCRIPTION 
The skin incising device shown in FIGS. 1 to 4 comprises three main 
elements: a tubular body or blade guide 11 which also forms a housing or 
case of the device, a cutter in the form of a blade assembly 12 which is 
axially displaceable in the blade guide, and a compression spring 13 
acting between the blade guide and the blade assembly. The blade assembly 
12 comprises two parts, a blade holder 14 and a flat steel blade 15 firmly 
held in a recess 16 of the blade holder. The blade guide 11 and the blade 
holder 14 are made of acetal plastic (Delrin, a registered trademark of E. 
I. Du Pont de Nemours and Company). 
The blade guide 11 is generally cylindrical exteriorly and has a flat base 
surface 17 which is parallel to the blade guide axis and extends 
throughout the length of the blade guide. Approximately halfway between 
the ends of the blade guide the base surface 17 has an intermediate 
portion 17A which is offset towards the longitudinal axis of the blade 
guide a distance at least equal to the predetermined or desired depth of 
the incision to be made. The offset base surface portion 17A is parallel 
to the adjoining front and rear portions 17B, 17C of the base surface 17, 
and its length is approximately equal to the predetermined standardized or 
desired length of the skin incision. 
A cylindrical bore 18, the axis of which is parallel to, but slightly 
spaced from, the axis of the cylindrical outer surface of the blade guide 
17, extends from the front end 11A of the blade guide to the vicinity of 
the rear end 11B. A pair of lower and upper longitudinal slots 19 and 20 
formed in a common plane perpendicular to the base surface 17 extend from 
the front end 11A of the blade guide 11. The lower slot 19 opens into the 
end portion 17C of said base surface 17. The upper slot 20 is slightly 
shorter. The slots are sufficiently wide to slidably accommodate the blade 
15. Approximately halfway between the ends of the upper slot 20 the blade 
guide 17 also has a transverse slot 21. 
The blade holder 14 comprises a slightly conical body the circular large 
end 25 of which faces the rear blade guide end 11B and forms an abutment 
for the spring 13. A cylindrical projection 26 on the large end 25 serves 
to keep the spring 13 in position. The small end of the blade holder body 
has a circular rim 27 the thickness of which is slightly smaller than the 
width of the transverse slot 21. Both the large end 25 and the rim 27 have 
a loose sliding fit with the straight guideway defined by the bore 18 of 
the blade guide 11 so that the blade holder body can readily be displaced 
axially along the guideway without any substantial radial play. 
The flat blade 15 is wedged or secured in any other suitable manner to the 
blade holder 14 in a plane containing the axes of the blade holder and the 
blade guide 11. More particularly, when the blade holder 14 is inserted in 
the blade guide bore 18 as shown in FIG. 2, the tip 15A of the blade 15 is 
accommodated in the lower blade guide slot 19 and extends past the level 
of the intermediate base surface portion 17A a distance equal to the 
predetermined desired depth of the incision to be made. Since the 
intermediate base surface portion 17A is offset from the front and rear 
end portions 17B, 17C a distance at least equal to the just-mentioned 
distance, the tip portion 15A projects from the base surface 17 only when 
it is at the intermediate portion 17A. The upper end portion 15B of the 
blade 15 extends through the upper slot 20 and projects upwardly from the 
blade guide to form a finger grip. 
The skin incising device of the invention can advantageously be produced as 
a disposable item. It is then supplied in a sterile package ready for use 
in the blade assembly 12 in the retracted and cocked position shown in 
FIG. 2. In this position the front portion of the blade assembly 12 is 
slightly lifted and the upper portion of the rim 27 is engaged in the 
transverse blade guide slot 21 with the compressed spring 13 urging the 
front face 27A of the rim against the front rearwardly facing wall 21A of 
the slot. The friction between the rim and the wall of the slot is 
sufficient to retain the blade assembly 12 in the retracted and cocked 
position during shipping and handling. As shown in FIG. 2, the tip 15A of 
the blade 15 is concealed in the portion of the lower blade guide slot 19 
which extends into the rear end base surface portion 17C. 
When a skin incision is to be made using the device shown in FIGS. 1 to 4 
the nurse or other person making the incision grips the ends of the blade 
guide 11 between the thumb and the middle finger of one hand. The index 
finger is allowed to rest against the upper portion of the blade guide 
rearwardly of the upwardly projecting finger grip portion 15B of the blade 
15. The base surface 17 of the blade guide 11 is engaged with the area of 
the patient's skin to be incised--typically the palm side of the 
forearm--and firmly pressed against the skin so that the skin is flattened 
against substantially the entire intermediate base surface portion 17A. In 
FIG. 2 the skin area to be incised is indicated at P. Using the index 
finger the nurse then presses against the upwardly projecting blade 
portion 15B, either forwardly as indicated by an arrow 30 or downwardly as 
indicated by an arrow 31. The finger pressure will cause the blade holder 
14 to pivot about the large end 25 until the rim 27 clears the wall 21A of 
the slot 21. When the latch formed by the rim 27 and the slot wall 21A has 
thus been released, the compressed spring 13 displaces the blade holder 14 
with the blade 15 to the advanced position shown in FIG. 3 in which the 
blade tip 15A, having traversed the intermediate base surface portion 17A, 
is concealed in the portion of the slot 19 opening into the front end base 
surface portion 17B. As the blade tip 15A traverses the intermediate base 
surface portion 17A it produces a skin incision the length of which is 
closely related to the length of the intermediate base surface portion 
17A. For practical purposes the length of the skin incision may be 
considered to be equal to the length of the intermediate base surface 
portion; the exact length is dependent on the shape and dimensions of the 
transitions from the intermediate base surface portion to the front and 
rear base surface portions. The depth of the incision is constant 
throughout the length thereof and equal to the distance by which the blade 
tip 15A projects past the intermediate base surface portion 17A. 
If two consecutive incisions are to be made on each patient as is common 
practice, the nurse may easily make the device ready for the second 
incision by gripping the upper blade portion 15B between the thumb and 
index finger and pulling it rearwardly toward the retracted position as 
indicated by an arrow 32 in FIG. 3 until the rim 27 snaps into the 
transverse slot 21 under the action of the turning moment about the large 
end 25 produced by the pulling force applied to the blade portion 15B. 
The general structure and operation of the embodiment shown in FIGS. 5 to 8 
is similar to the embodiments of FIGS. 1 to 4. The case or housing forming 
the blade guide 40 is made of acetal plastic (Delrin) and comprises two 
molded channel elements 40A, 40B held together by a pair of short 
transverse pegs 41 integral with the channel element 40A and inserted in 
recesses in the channel element 40B. 
The channel element 40A has a longitudinal recess 42 the walls of which 
define a straight guideway for the blade assembly together with the 
adjacent flat face of the other channel element 40B. 
The blade assembly 43 comprises a blade holder 44 of acetal plastic and a 
flat steel blade 45. The blade 45 is held in oblique position on the blade 
holder 44 by a pair of short pegs 46, 47 integral with the blade holder 
44. The pegs 46 protrude through a pair of longitudinal slots 48A, 48B of 
the channel elements 40A, 40B so that the blade assembly 43 can be 
manipulated from outside the blade guide 40. 
A compression spring 49 is interposed between the rear end of the blade 
holder 44 and a transverse rear wall of the recess 42. 
Along its bottom portion the blade guide 40 has an elongated, generally 
flat cantilevered segment 50 which is separated from the body of the blade 
guide by a longitudinal slot 51 having a rounded rear or inner end 51A. 
The upper side 52 of the cantilevered segment 50 defines a portion of the 
straight guideway for the blade assembly 43, and its bottom side forms a 
base surface 53 comprising intermediate, front end, and rear end portions 
53A, 53B, 53C, all of which are flat and generally parallel to each other 
and to the longitudinal axis of the guideway. The intermediate base 
surface portion 53A is offset from the front and rear end portions 53B, 
53C toward the guideway a distance at least equal to the predetermined 
standardized or desired depth of the skin incision to be made and its 
length is approximately equal to the predetermined standardized or desired 
length of the incision. 
A longitudinal vertical slot 54 through the cantilevered segment 50 extends 
throughout the intermediate base surface portion 53A and partly through 
the adjoining portions of the segment and slidably receives the tip 45A of 
the blade 45. The upper portion 45B of the blade is slidably received in a 
longitudinal slot 55 formed in the upper portion of the blade guide 40. 
In the retracted and cocked position of the blade assembly 43 shown in FIG. 
6, a transverse shoulder 44A on the lower side of the blade holder 44 
abuts a confronting transverse face 56 on the blade guide 40 adjacent the 
free end of the cantilevered segment 50 under the action of the compressed 
spring 49. In this position, in which the blade assembly is thus latched 
against forward movement, the tip 45A of the blade 45 is concealed in the 
rear portion of the slot 54. 
The latch formed by the shoulder 44A of the blade holder 44 and the 
transverse face 56 of the blade guide 40 can be released by displacing the 
cantilevered member 50 upwardly against the resistance produced by the 
friction between the shoulder 44A and the face 56 and by the resilience of 
the ligament 50A joining the cantilevered segment 50 to the body of the 
blade guide 40. In use of the incising device, such displacement is 
brought about by pressing the device against the patient's skin after the 
cantilevered segment 50 has been engaged with the skin area to be incised. 
As soon as the front portion of the blade holder 44 has been displaced 
upwardly sufficiently for the shoulder 44A to clear the face 56, the 
spring 49 displaces the blade holder with the blade to the advanced 
position shown in FIG. 7. During its movement over or through the 
intermediate base surface portion 53A, the tip 45A of the blade 45 
protrudes from the surface portion a distance equal to the predetermined 
standardized or desired depth of the incision to be made. 
Since the blade holder latch 44A, 56 is released in response to exerting a 
predetermined pressure on the patient's skin through the cantilevered 
segment 50, the incising device of FIGS. 5 to 8 eliminates any errors in 
the bleeding time determinations which may be caused by varying pressure 
on the skin. The pressure required to release the latch is determined 
primarily by the force of the spring 49 and the resiliency of the ligament 
50A, and since these parameters are fairly easy to control with sufficient 
accuracy during manufacture, the release pressure will not vary 
significantly from one device to the other. 
The incising device shown in FIGS. 9 to 13 is the presently preferred 
embodiment of the invention. It only comprises two parts: a cutter guide 
or blade guide in the form of a generally plate-shaped body 61 integrally 
molded from acetal plastic, such as Delrin, and a cutter 62 which is 
supported by the body and formed by a bent length of spring wire. 
The lower surface of the plate-shaped body 61 has, on the body portion 61A 
or segment that is to the left in FIGS. 9 and 10 and that is here regarded 
as the front body portion, a base surface 63 which is engageable with the 
area of a patient's skin where the incision is to be made. The base 
surface 63 comprises three substantially flat portions, two end portions 
63A of relatively small extension laterally (up-down direction in FIG. 9 
and left-right direction in FIG. 11) and an intermediate portion 63B 
bounded by the outer portions and having a length, i.e. lateral extension, 
corresponding to the desired length of the incision. The intermediate 
portion 63B is offset parallel to itself upwardly relative to the two 
coplanar outer end portions 63A by a distance almost the same as but 
slightly larger than the desired depth of the incision. 
The front body portion or segment 61A is united with the rear body portion 
61B by an integral resilient joint 61C enabling the front portion 61A and 
the rear portion or segment 61B to flex upwardly relatively to one another 
against the resilience of the joint 61C; the flexing takes place about a 
transverse axis 61H extending through the joint. 
The front portion 61A of the body 61 has a slot 64 extending across the 
intermediate portion 63B of the base surface 63 and into the outer or end 
base surface portions 63A. The top face of the front body portion 61A is 
flat and parallel to the intermediate base surface portion 63B at least 
within the region that is situated directly rearwardly of the slot 64; 
this region of the top face forms a guideway for the cutter 62. 
The cutter 62, which is made from spring wire of circular cross-section to 
serve also as a biasing means, is generally V-shaped and is secured to the 
body 61 near the rear or right-hand (as viewed in FIGS. 9 and 10) end of 
the body. One limb or blade holder 62A of the cutter extends forwardly 
along the top face 61F of the body. The front end of the limb 62A merges 
with a bent end portion 62B which is pointed to form a cutting tip or 
blade. The end portion 62B extends through the slot 64 substantially 
normal to the guideway 65 the base surface 63. The other limb 62C 
resiliently engages a lateral part of the body 61. 
As best shown in FIG. 9, the cutter 62 extends about a circular upstanding 
projection 66 on the body 61 near the rear end thereof. More particularly, 
the cutter is arranged such that the limb 62A with the end portion 62B 
forming the cutting tip is pendulously movable relative to the body 61 
about a point on or near the projection 66. Because of the illustrated 
mounting of the cutter 62, the limb 62A is biassed so as always to tend to 
move towards an advanced position which is indicated in dash-dot lines in 
FIG. 9. In addition, the limb 62A is biassed against the guideway 65 so 
that the limb tends to maintain the portion 62D thereof which is adjacent 
the end portion 62B in sliding engagement with the guideway. To this end, 
the body 61 is provided with a tongue 67 overlying the limb 62A and 
exerting a downward force on it. The tongue 67 and a similar tongue 67A 
also assist in retaining the cutter 62 in place on the body 61 so that no 
separate fastening elements are required to secure the cutter to the body. 
When the cutter 62 is in the retracted, cocked position shown in full lines 
in FIG. 9 with the limb portion 62D in engagement with the guideway 65, 
the extreme end of the end portion 62B forming the cutting tip is slightly 
above the plane containing the outer end portions 63A of the base surface 
63 and slightly below the plane containing the intermediate base surface 
portion 63B; the distance by which the end portion protrudes from the 
plane containing the intermediate base surface portion 63B is equal to the 
controlled depth of the incision to be made. 
In order that the cutter 62 may be releasably retained in the retracted, 
cocked position shown in full lines in FIG. 9 against the action of the 
bias of the limb 62A tending to move the limb to the advanced position, 
releasable latching means are provided acting between the blade guide and 
the blade holder. To this end the top face of the front body portion 61A 
has an upstanding lug 68, the shape of which is best shown in FIG. 12. 
This lug 68 is positioned well behind the slot 64, namely, adjacent to the 
resilient joint 61C, see FIG. 9. The lug 68 has an end face 68A which is 
normal to the guideway 65 and forms a latching abutment for the cutter 
limb 62A. The limb is released by moving the limb 62A upwardly from the 
front body portion 61A in the region of the lug 68 until it is disengaged 
from the lug and thus allowed to move towards the advanced position under 
the action of its bias. 
Finally, the body 61 is provided with a pair of forwardly directed arms 61D 
disposed on opposite sides of, and spaced from, the front body portion 61A 
and having finger grip projections 61E. As shown in FIG. 10, the bottom 
side of each arm is flush with the flat bottom face 61G of the rear body 
portion 61B, that is, slightly higher than the base surface 63. 
The skin incising device of the invention can advantageously be produced as 
a disposable item. It is then supplied in a sterile package ready for use 
with the cutter 62 in the retracted, cocked position shown in FIG. 9. In 
this position, the cutting tip 62B is concealed in the end portion of the 
slot 64 extending into the lower (as viewed in FIG. 9) end portion 63A of 
the base surface 63, see also FIG. 11. Thus, the cutting tip is held away 
from the intermediate base surface portion 63B. 
When a skin incision is to be made using the device shown in FIGS. 9 to 13, 
the nurse or other person making the incision grips the body 61 at the 
projections 61E between the thumb and index finger of one hand. The base 
surface 63 is engaged with the area of the patient's skin to be incised 
and firmly pressed against the skin so that the skin is flattened against 
substantially the entire intermediate base surface portion 63B. In FIGS. 
11 and 13 the skin is indicated by a dash-dot line at P. 
When the base surface 63 is pressed against the skin, the joint 61C will 
allow the front body portion 61A and the rear body portion 61B to flex 
upwardly relative to one another as shown in FIG. 13. As a consequence, 
the limb 62A will be lifted sufficiently from the top face 61F in the 
region of the latch lug 68 to clear the lug and move to the advanced 
position under the action of the bias. The limb portion 62D will slidably 
engage the flat area 65, namely, the region of the area 65 which is 
adjacent to the slot 64 and forms the aforesaid guideway, throughout the 
movement to the advanced position. 
As the cutting tip 62B of the cutter traverses the intermediate portion 63B 
of the base surface 63, it protrudes from the intermediate base surface 
portion a distance equal to the desired depth of the incision. Thus, as 
the cutting tip 62B moves across the intermediate base surface portion 
63B, it makes a skin incision the length of which corresponds to the 
length of the intermediate base surface portion and the depth of which is 
constant and equal to the distance by which the cutting tip 62B protrudes 
downwardly from the intermediate base surface portion 63B. 
If two consecutive incisions are to be made on each patient, the nurse may 
make the device ready for the second incision by moving the cutter 62 back 
to the cocked position shown in FIG. 9 by a finger. 
The cutter 62 preferably is made of round spring wire, and in order that 
the limb 62A, upon release of the latch formed by the lug 68, may not be 
thrown upwardly by camming action between the lug and the curved surface 
of the wire, the cross-section of the wire is modified in the region of 
the limb 62A which engages the lug. The modified cross-section is shown in 
FIG. 12 and may advantageously be produced by grinding. In practice, the 
grinding of the modified cross-section is effected simultaneously with the 
grinding of the cutting tip formed by the cutter end portion 62B. 
As shown in FIG. 9, the slot 64 is arcuate, and because of the curvature of 
the cutter limb 62A and its pendulous movement from the retracted, cocked 
position to the advanced position, the incision will be curved. However, 
the curvature of the incision may be reduced by a suitable choice of the 
ratio of the length of the cutter limb to the length of the incision and a 
suitable choice of the shape of the slot. Besides, unless the curvature of 
the incision is very sharp, it has no significant adverse effect; the 
important points are that the length and depth are within the prescribed 
limits and that the depth is constant throughout the incision. 
The invention is not limited to the embodiments specifically illustrated 
and described by way of example. It should be understood, therefore, that 
other embodiments may be considered as coming within the spirit and scope 
of the invention as defined by the claims. A feature common to such 
embodiments is that the cutter performs an incising movement at a 
controlled depth in parallel with the skin under the action of an 
accumulated force after a cutter latch has been released to allow the 
accumulated force to displace the cutter along a guideway.