Patent Publication Number: US-2022211356-A1

Title: Device for skin biopsy

Description:
FIELD OF INVENTION 
     The present invention relates broadly, but not exclusively, to devices for skin biopsy. 
     BACKGROUND 
     Skin biopsy is a biopsy technique in which a skin lesion is removed and sent to a pathologist or dermatologist to render a microscopic diagnosis. Skin biopsy not only helps in diagnosis in cases of dilemma but also provides an opportunity to find something unusual in routine practice. As skin biopsy is typically done in a setting of localised anaesthesia, a dermatologist may face the challenge of choosing the correct lesion and adapting the right technique for performing biopsy in order to ensure a good interpretation of the biopsy. It is a classical dictum in skin biopsy to choose the classical, well-formed, non-modified (by scratching or any topical application) lesion. 
     One of three types of skin biopsies is performed in order to evaluate the nature of the lesion. The first type of skin biopsy is the shave biopsy where a physician manually removes a thin layer of the lesion to be viewed under a microscope by a pathologist. This procedure is done using a circular punch that cuts a circle around the skin lesion and the required section of the skin is subsequently removed and stitched up. The second type of biopsy procedure is called an excision biopsy, where a physician (typically a cosmetic surgeon or a dermatologist) uses a scalpel to surgically remove the area of interest, again to be viewed by a pathologist. However, depending on the skill of the surgeon and the size of the lesion, this procedure can leave large and unsightly scars requiring multiple stitches to heal properly. The third type of biopsy is called punch biopsy, where a device with a circular cutting head is pushed into the lesion and rotated, removing a core section of the skin to be evaluated again by histology. Punch biopsy has become the preferred method of biopsy in recent times as it does not require the skill of a specialist and can be done in little time and minimal discomfort during a normal visit to the physician. 
     A typical circular punch biopsy device is shown in  FIG. 1 . The simplicity of the tubular cutting blade on a modified scalpel handle of the typical punch biopsy device makes it inexpensive to manufacture and easy to operate. However, a disadvantage of the device of  FIG. 1  is that the patient is left with a more noticeable scar. By removing a circular section of skin around a lesion, closing the wound becomes difficult because there are no edges to be joined. In closing such wounds, raised edges, known as “dog-ears”, appear at either edge of the closed circle. “Dog-ears” can be defined as an upward formation of excess skin as a result of a suture. Furthermore, “dog-ears” are the result of the closure of a circular or asymmetric wound which causes surrounding skin to create pressure on the wound site and force the flaps of skin upward and outward. 
     Skin biopsy may also be performed during scar revision surgery. Scar revision surgery takes approximately one to three hours, depending on the scar length and complexity. During the procedure, the surgeon makes precise and small incisions of approximately 5 mm to 7 mm each while excising the scar. However, commercial blades that are currently used in scar revision are often large and unwieldly. Further, the design and incision process take a large portion of the operative time and closure of the scar and healing of the wound typically takes approximately five to seven days for scars on the face. Therefore, incisions and incision designs that are imprecise may cause unfavourable results and can delay operative time and wound healing. 
     Accordingly, a need exists to provide a device for skin biopsy that seeks to address some of the above problems. 
     SUMMARY 
     According to a first aspect of the present invention, there is provided a skin biopsy device comprising: a base member configured to be placed onto a skin surface; an cutting member configured to be received by the base member and to be movable relative to the base member in a direction substantially orthogonal to the skin surface; and an actuation member configured to drive the cutting member to travel a predetermined distance at a predetermined velocity in said direction. 
     In an embodiment, the base member may be made of a transparent material. 
     In an embodiment, the base member may have an alignment element to align the cutting member with a shape of an incision on the skin surface. 
     In an embodiment, the base member may be movable relative to the skin surface, and wherein the base member is configured to generate a tension on the skin surface. 
     In an embodiment, the cutting member may be mounted to a cartridge, and wherein the cartridge is received by the base member. 
     In an embodiment, the cutting member may comprise a fusiform profile having a length to width ratio of about 3 to 1. 
     In an embodiment, the fusiform profile may comprise an apical angle of about 30 degrees. 
     In an embodiment, the cutting member may comprise a profile having a pair of matching zig-zag lines separated by a pre-determined gap. 
     In an embodiment, the cutting member may comprise a profile having at least one zig-zag line, and wherein the at least one zig-zag lines comprises a segment defining an obtuse angle. 
     In an embodiment, the cutting member may be made of stainless steel. 
     In an embodiment, the actuation member may comprise a spring-loaded mechanism. 
     In an embodiment, the spring-loaded mechanism may comprise a dampener. 
     In an embodiment, the actuation member may comprise a gas-powered mechanism. 
     In an embodiment, the actuation member may be configured to provide a force of about 130N. 
     In an embodiment, the actuation member may have a pistol and trigger form. 
     In an embodiment, the predetermined distance may be at least 6 mm. 
     According to a second aspect of the present invention, there is provided a method of operating a skin biopsy device comprising a base member, a cutting member and an actuation member, the method comprising: placing the base member onto a skin surface; disposing the cutting member in the base member such that the cutting member is movable relative to the base member in a direction substantially orthogonal to the skin surface; and operating the actuation member to drive the cutting member to travel a predetermined distance at a predetermined velocity in said direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings, in which: 
         FIG. 1  shows a plan view of a typical circular punch biopsy device. 
         FIG. 2  shows a side view of a skin biopsy device, according to an example embodiment. 
         FIG. 3  shows a perspective view of the base member of the device of  FIG. 2 , according to an example embodiment. 
         FIG. 4  shows a perspective view of the cutting member of the device of  FIG. 2 , according to an example embodiment. 
         FIG. 5A  shows a plan view of a blade end of the blade of  FIG. 4  used for W-plasty procedure, according to an example embodiment. 
         FIG. 5B  shows a plan view of a mid-blade of the blade of  FIG. 4  used for W-plasty procedure, according to an example embodiment. 
         FIG. 5C  shows a plan view of a mid-blade of the blade of  FIG. 4  used for Z-plasty procedure, according to an example embodiment. 
         FIG. 5D  shows a plan view of a blade end of the blade of  FIG. 4  used for Z-plasty procedure, according to an example embodiment. 
         FIG. 5E  shows a plan view of an alternative mid-blade used for Z-plasty procedure, according to an example embodiment. 
         FIG. 6  shows a perspective view of the cutting member received by the base member, according to an example embodiment. 
         FIG. 7A  shows a plan view of the actuation member, according to an example embodiment. 
         FIG. 7B  shows a side view of the actuation member, according to an example embodiment. 
         FIG. 8  shows a flow chart illustrating a method for skin biopsy, according to the example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. Herein, devices for skin biopsy are presented in accordance with present embodiments which may have the advantages of providing a high-velocity punch and delivering momentum onto an elliptical blade to puncture an elliptical wound onto the skin, thereby using minimal manual force to penetrate the skin during operation. It may also minimise scarring during a punch biopsy process and may also produce a clean cut biopsy specimen with minimal collateral tissue injury. The device may also be used easily, can be sterilisable and reusable, thus minimising wastage. 
       FIG. 2  shows a side view of a skin biopsy device  100 , according to an example embodiment. The device  100  includes a base member  102 , a cutting member  104  and an actuation member  106 . The base member  102  is configured to be placed onto a skin surface while the cutting member  104  is configured to be received by the base member  102  and to be movable relative to the base member  102  in a direction substantially orthogonal to the skin surface. The actuation member  106  is configured to drive the cutting member  104  to travel a predetermined distance, e.g. 6 mm or more, at a predetermined velocity in the direction substantially orthogonal to the skin surface. A detailed view of the base member  102 , the cutting member  104  and the actuation member  106  are shown in  FIGS. 3-7B  and will be explained in more detail below. 
       FIG. 3  shows a perspective view of the base member  102  of the device  100  of  FIG. 2 , according to an example embodiment. The base member  102  may be a jig that is made of a transparent material, e.g. polyethylene plastic, as shown in  FIG. 3 . By being transparent, the base member  102  may provide visual aid of the cut area such that a user of the skin biopsy device  100  may be able to see the area of cut before the cutting member  104  makes the cut using energy that is released from the actuation member  106 . This may increase the accuracy of the cut as the user may be able to position the actuation member  106  accurately. The base member  102  may include a blade receiver  302  to receive the cutting member  104 . The base member  102  may also include a support  304  such that a bottom surface of the support  304  is placed on the skin surface. 
     The base member  102  may have an alignment element (not shown) to align the cutting member  104  with a shape of an incision on the skin surface. An example of an alignment element may be a collagen line aligner. The base member  102  may be movable relative to the skin surface and may also be configured to generate a tension on the skin surface. The base member  102  may hold the cutting member  104  in position while the actuation member  106  (e.g. a gun) is aimed at the base member  102  to release an actuation momentum to puncture into the skin. Further, the base member  102  may also work as a depth-control tool such that the cutting member  104  does not penetrate too deep into the skin when making the incision. 
       FIG. 4  shows a perspective view of the cutting member  104  of the device  100  of  FIG. 2 , according to an example embodiment. The cutting member  104  may include a blade  402  having a straight and pointed blade profile which can provide a clean and sharp cut. The straight and pointed blade profile may reduce scarring associated with traditional punch biopsy as the incision made by the straight and pointed blade profile can have two even edges which can meet to form a straight line during stitching of the wound. 
     Healing of a closed wound is affected by factors such as size and geometry of incision and the distribution and magnitude of the stresses on the wound. The circular wound has the worst healing, with maximum stresses ranging from 40% to 62% greater than the other shapes. The elliptical excisions have the least adverse maximum stresses, while the fusiform excision has minimum stress. High adverse stresses adversely affect the microcirculation in the area around the wound, slowing the healing of the wound. It was found that aligning the incision along Langer lines (i.e. topological lines on a human body) results in lower stresses when closing the wound, thereby assisting in the healing and reducing scarring of the skin. In addition, surgical techniques can play a role in “dog-ear” formation. For example, improper surgical techniques can cause excess tissue to be present at the wound site, which may occur due to the tendency of surgeons deferring from the 90° proper cutting angle. According to an embodiment, the blade  402  may also be of a fusiform profile having a length to width ratio of approximately 3:1. The fusiform profile may have an apical angle of about 30 degrees. 
     The blade  402  may be made of stainless steel. In one embodiment, the stainless steel blade  402  may be made using 304 stainless steel. For example, to make the blade, plates measuring 2.64 cm in length and 4 cm in width are cut out from a larger plate using a water jet. The edges of the blade  402  are initially grinded to a preliminary bevel. A Lansky 5 stone deluxe sharpening system is subsequently used for finer grit sharpening. Various grits may be used, starting from 70, 120, 280, 600 to 1000 grit. After reaching 1000 grit, different stones can be used to improve sharpness and surface finish of the blade  402 . In an alternative embodiment, the blade  402  may be made of high carbon steel. The high carbon steel blade  402  is hard and may be able to hold a grinded edge for a longer period of time than normal steel blades. This may result in sharper blades that do not dull after a single use. The high carbon steel blade  402  may be sharpened until it is able to push cut paper and then bent into an elliptical shape. It can also be appreciated that alternative manufacturing and bending methods can provide blades that can maintain the sharp edge, achieve precise geometry and do not rust. In an example implementation, heat treatment on the blade  402  may be carried out using a blowtorch. More specifically, the blade  402  is heated up, bent, cooled and the process is repeated. Such a method of heat treatment may allow the blade&#39;s edge to be maintained longer. The cutting member  104  may include a blade holder  404  made up of multiple (e.g. four) layers of clear acrylic in which the blade  402  is mounted. The acrylic pieces of the blade holder  404  are cut with slots that provide a compression fit for the blade  402 . The clear acrylic blade holder  404  may also act as a viewing window for the user. In addition, the blade holder  404  is dimensioned to fit into the blade receiver  302  of the base member  102 . 
       FIG. 5A  shows a plan view of a blade end  500  of the blade of  FIG. 4  while  FIG. 5B  shows a plan view of a mid-blade  550  of the blade of  FIG. 4  used in a W-plasty procedure, according to an example embodiment. The blade as shown in the Figures can be used in the W-plasty technique of scar revision (or scar healing). In an embodiment, the blade may consist of a zigzag, geometric broken line with the blade end  500  having dimensions of 6 mm, 120° and 60°, representing numerals  504 ,  506  and  508  respectively in  FIG. 5A . The mid-blade  550  may have dimensions of 6 mm, 9.24 mm, 60° and 21.63 mm, representing numerals  512 ,  514 ,  516  and  518  respectively in  FIG. 5B . In an embodiment, the blade may include a profile having a pair of matching zig-zag lines separated by a pre-determined gap. The blade may also include a profile having a pair of zig-zag lines joining at their respective ends to form an obtuse angle. 
     In an alternate embodiment, the blade may be used for Z-plasty procedure. In this example, the blade may have mid-blade  570  dimensions of 60°, 6 mm and 17 mm, representing numerals  522 ,  524  and  526  respectively as shown in  FIG. 5C . A blade end  575  of the blade used for Z-plasty procedure is shown in  FIG. 5D  while an alternative mid-blade  580  can be used for Z-plasty procedure is shown in  FIG. 5E . It will be appreciated that the dimensions and number of zig-zag lines forming the blades as described with reference to  FIGS. 5A-5E  may vary in alternate embodiments. 
     The blade profiles as described with reference to  FIGS. 5A-5E  can be selectively used in a scar revision (or scar healing) surgery to improve or reduce the appearance of scars. The following techniques are commonly used during the formation of unfavourable scars in various locations on the body, particularly the face, due to its conspicuous location. Scar revision can be performed using W-plasty technique or geometric broken line closure, which is a surgical procedure to irregularize an unfavourable scar for cosmesis. Irregularizing a linear scar causes light to scatter in an irregular manner and shortens the limbs of individual limbs of the scar to less than 7 mm, making it less conspicuous during examination by the human eye. Z-plasty technique may also be used to perform scar revision, which lengthens a contracted (shortened) scar in addition to irregularizing it. The Z-plasty technique can be used to release and lengthen scars that are causing distortion and restriction of function to surrounding structures. It can also improve scar appearance through irregularization. 
     The blade having the dimensions and designs in embodiments shown in  FIGS. 5A-5E  may economize the surgical process by allowing the design and excision of the scar to take place with a single cut of the device  100 . The blade may be used in a sequential fashion, such that one blade is used to cut the ends of the design and one blade is used for the body. The body-cutting blade can be used serially to lengthen the design in order to suit the length of the scar. The blade may also allow for excision of the scar and is held in place by the base member  102 . The base member  102  may allow for accurate placement of the blade while limiting the depth of the cut at the same time. The actuation device  106  may then deliver an instantaneous driving force to allow the blade to cut the skin cleanly. This may save operative time used for the design and incision phase of the surgery, and may remove human error in the design and incision portion of the surgery. The base of the wound is cut with tissue scissors and the scar excised. The wound can then be closed by using routine methods. 
       FIG. 6  shows a perspective view  600  of the cutting member  104  received by the base member  102 , according to an example embodiment. The blade  402  may be mounted to the blade holder  404  such that it snugly fits into the blade receiver  302  of the base member  102 . The transparent material of the blade holder  404  and the base member  102  may provide visual aid to the user before firing the actuation device  106 . This may result in greater accuracy of the cut during the incision process. 
       FIG. 7A  shows a plan view of the actuation member  106  while  FIG. 7B  shows a side view of the actuation member, according to an example embodiment. As shown in the Figures, the actuation member  106  may be a pistol and trigger form, such as a gun. The actuation member  106  may include a linear guide  702 , a viewing window  704  for visual aid, a trigger  710  and a handle grip  712 . The actuation member  106  may include a spring-loaded mechanism, including a dampener (not shown), a hammer rod  706  and/or a linear cocking rod  708 . The spring-loaded mechanism may provide energy storage before releasing the cutting member  104  as springs are more cost efficient in achieving functional requirements for punch biopsy. The spring-loaded mechanism may also have a lower margin of error, does not require air-tight design and removes the need to reload the punch with an external fluid. 
     A lock-and-load mechanism may be used for the release of the cutting member  104 . This may have the advantage of a controlled release by the user as punch biopsy requires only a single attempt. The cocking of the spring only requires the hammer rod  706  to be pushed back into a catch (not shown) of the actuation member  106 . The handle grip  712  may be ergonomic to the user which may result in better aiming and higher accuracy of the punch. Moreover, the trigger  710  can be positioned such that minimal force is required to depress the trigger  710 . 
     In an alternate embodiment, the actuation member  106  may include a gas-powered mechanism instead of a spring for energy storage, which may make it easier for users without the need to load. The spring-loaded mechanism and/or the gas-powered mechanism may be configured to provide a force of about 130N. The energy storage can also be a hydraulic piston and/or a pressured air mechanism. Release of the cutting member  104  may be a continuous motion mechanism, which includes a single action to load and release; and/or a direct release mechanism, which includes loading the punch and release. In alternative embodiments, the handle grip  712  can be a palm down grip, a pencil grip or an ice pick grip. 
     In other embodiments, the interface between the hammer rod  706  and the cartridge holding the cutting member  104  can also be improved by increasing the surface area and dampening the impact slightly to remove the relatively loud sound of the hammer rod  706  hitting the cartridge, while also improving the force distribution onto the cartridge to increase the accuracy of firing. 
     There are different methods for skin biopsy. One method for skin biopsy is a mounted cut, which includes releasing a barrel-mounted blade onto the skin surface. Such a method may provide the advantage of having a moderate accuracy of aim and a single-hand operation by the user. Another method for skin biopsy is an external cut, where an externally-placed blade is used. The external cut method may provide a high accuracy of aim as the area to be cut is visual to the user. A third method for skin biopsy is a direct cut, where the blade is directly used to cut the skin. This may provide the advantage of having a simple design of the device used in such a method. In a preferred embodiment, the external cut configuration is used. This can be implemented in the form of a jig (or base member  102 ) and blade cartridge (or cutting member  104 ). 
     The typical method for the external cut is to apply the jig on the area to be cut, insert the blade, and shoot it with the gun. Depth control of the external cut can be achieved by constraining the geometry of the front barrel of the gun and the height of the jig and blade. Further, having a rotational degree of freedom while the jig is being pressed down onto the patient&#39;s skin, the oval blade can be rotated along with the jig to align the apical angles with the skin collagen lines. This may further improve scar revision (or scar healing) at the later stage. 
       FIG. 8  shows a flow chart  800  illustrating a method for skin biopsy, according to the example embodiments. At step  802 , the method includes positioning the base member  102  such that the area to be incised is clearly visible in the centre. At step  804 , the method includes aligning and positioning the cutting member  104  into the base member  102 . The user may also ensure that the cutting member  104  is properly aligned by looking through the acrylic piece of the base member  102 . At step  806 , the method includes positioning the actuation member  106  vertically on top of the base member  102  and the cutting member  104  while holding on to the base member  102 . The user may ensure a constant downward force on the base member  102  such that there is constant tension on the skin, which may allow for an even, accurate cut. At step  808 , the method includes loading the actuation member  106  and releasing the energy stored in the actuation member  106 , which can be performed by one person. The cutting member  104  may move a distance of at least 6 mm in the above step. At step  810 , the method includes removing the base member  102  and the cutting member  104 . The user can then cut out the skin specimen as required using a forcep and a scalpel and remove the specimen to proceed with suture of the wound. 
     In an alternative embodiment, a method of skin biopsy is described as follows. At the first step, the method includes positioning the base member  102  such that the area to be incised is clearly visible in the centre. At the second step, the method includes aligning and positioning the cutting member  104  into the base member  102 , while ensuring that the cutting member  104  is properly aligned by looking through visual aids in the base member  102 . At the third step, the method includes holding on to the base member  102  to ensure there is a constant downward force on the base member  102  so that there is constant tension on the skin. This may allow for an even, accurate cut. At the fourth step, the method includes positioning the actuation member  106  vertically on top of the base member  102  and the cutting member  104 . At the fifth step, the method includes releasing the trigger of the actuation member  106  to release the energy stored. This step can be achieved by a single person and the cutting member  104  may move a distance of at least 6 mm in the above step. At the sixth step, the method includes removing the base member  102  and the cutting member  104 . At the seventh step, the method includes using a forceps and a scalpel/or scissors to complete the cut on the deep surface of the specimen. At the eighth step, the method incudes removing the specimen and proceeding with suture. 
     The device for skin biopsy as described herein may be used to excise suspicious growths on the skin surface. The device may also be able to create a 30° elliptical corner at the edge of the biopsy allowing for direct edge-to-edge closure and minimise the causation of “dog-ears”. The device may be manufactured easily, cost effective, sterilisable, disposable, and ergonomically sound and easy to use. Embodiments of the present invention may provide a high velocity punch that is able to consistently produce an elliptical cut of ratio 1:3 on the skin. In addition, the sutured extracted skin area shows less “dog-ears” formation using the above high-velocity cut concept. 
     While exemplary embodiments have been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. 
     It should further be appreciated that the exemplary embodiments are only examples, and are not intended to limit the scope, applicability, operation, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements and method of operation described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims. 
     It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.