US20110251602A1 - Method and apparatus for tissue expansion - Google Patents

Abstract

Exemplary embodiments of the present disclosure provide method and apparatus for facilitating stretching of a bio-logical tissue by forming a plurality of micro-slits in the tissue. Each micro-slit can be less than about 2 mm or less than about 1.5 mm long, or even less than about 1 mm, such that small gaps that can heal quickly can be formed when the tissue is stretched. The micro-slits can be formed using a plurality of cutting arrangements or an ablative laser. The micro-slits can be formed in various patterns, including staggered rows, circular or spiral patterns, or random patterns.

Description

CROSS REFERENCE TO RELATED APPLICATION
• The present application claims priority from U.S. Provisional Patent Application Ser. No. 61/041,591 filed Apr. 1, 2008, the disclosure of which is incorporated herein by reference in its entirety.
FIELD OF THE DISCLOSURE
• The present disclosure relates to an expansion of biological tissue, and in particular to exemplary embodiments of method and apparatus which can provide such expansion.
BACKGROUND INFORMATION
• Expansion of connective tissue, especially skin, fascia, cartilage and tendon, is often desirable for cosmetic or functional purposes. Achieving tissue expansion without damaging, impairing, or aesthetically harming the tissue is a common concern in reconstruction after surgery, trauma, and for various medical and congenital disorders.
• Tissue expansion can be used for tension relief of contracted surgical, traumatic, and burn scars. For example, burn victims often suffer through many painful surgeries performed to relieve the tension and contraction of hypertrophic scars. After excision of skin cancer on the forehead and scalp, large defects are often left to heal openly because the surrounding skin cannot be moved enough to close the wound. On the legs, skin healing can be poor and the skin is relatively inelastic, such that surgical wounds and ulcers on the legs are difficult to close. Scalp reduction surgery can be limited by the rigidity of scalp skin. In addition to a need for tissue stretching of skin in these examples, tissue stretching can also be useful for lengthening tendons, re-shaping cartilage, and for expanding other connective tissues.
• Conventional techniques for stretching tissue include, e.g., (a) subcutaneous implantation of saline-filled balloons to expand the skin prior to surgery, (b) using incisions to create various artful flaps that move skin from one location to another without removing it entirely, such that tension is relieved and/or missing tissue is replaced by mobilizing the surrounding tissue, and (c) tissue grafts, which involve removal of skin or other connective tissue from one location and placing it on another location.
• Tissue grafts can be used to replace skin or other tissue that has been removed by surgery or trauma. For example, split-thickness skin grafts can be used to cover a wound in burn and skin ulcer patients. A conventional split-thickness graft can be made, e.g., by harvesting a sheet of epidermis and upper dermis tissue from a donor site, much like peeling an apple, which can then be placed on the burn or ulcer location. The skin tissue can then grow back on the donor site following a generally extended healing time.
• Split thickness grafts may often be “meshed” for expansion, so they can cover a larger area than the donor site. Conventional tissue meshing includes formation of an array of many slits, typically several millimeters in length or longer, which can open into diamond-shaped or lens-shaped holes when the meshed graft is subjected to tension and expanded. These holes can facilitate an overall expansion of the graft. The expanded meshed tissue sheet generally may have an appearance of a chain-link fence, with large holes that can remain visible after the graft is placed and the tissue is healed. Thus, meshed grafts may save a burn victim's life by expanding the usable area of skin available from donor sites, but they also can contribute to life-long aesthetic disfigurement.
• Conventional full-thickness grafts generally include a removal of epidermal tissue and the complete thickness of the dermis from a donor site to be used as a graft, with the edges of skin adjacent to the removed tissue being re-opposed at the donor site. Meshing may not be ideal for expanding full-thickness grafts because, for example, (a) the lens-shaped holes left by gross meshing and expansion of full-thickness skin can be even more disfiguring than in split-thickness grafts because they are much deeper, and may look like an array of acne scars after healing, and (b) the large, full-thickness holes can take weeks to heal because cells from the surrounding dermis have to build new fibrotic tissue to fill in the substantial volume of each hole. Similarly, meshing of flaps may not be appropriate because skin incisions within a flap can sever some of the blood supply to the flap, thus impairing the viability of the flap tissue. For these reasons, conventional tissue meshing may generally not be suitable for expansion of skin grafts or flaps during surgery, and not for relief of tension on scars, nor to modify the scar tissue itself.
• Accordingly, there can be a need to address and/or overcome at least some of the deficiencies or issues described herein above.
SUMMARY OF EXEMPLARY EMBODIMENTS
• Embodiments of the present disclosure are directed to method and apparatus for facilitating an expansion of a portion of tissue, while reducing a presence or likelihood of noticeable holes or scars after healing of the expanded tissue. The exemplary method and apparatus can be applied in situ for releasing local skin tension, to cover damaged or removed regions of tissue using adjacent healthy tissue, and other tissue expansion applications, or ex vivo for expansion of split-thickness and/or full thickness grafts while providing an improved outcome.
• According to one exemplary embodiment of the present disclosure, a method can be provided for facilitating tissue expansion that includes a formation of a plurality of micro-slits in the tissue to be stretched. The length of extension of the micro-slits can be less than about 2 mm, or less than about 1.5 mm, or less than about 1 mm, or even less than about 0.8 mm. The length of each micro-slit can be greater than about 0.1 mm to allow sufficient expansion of the tissue. The width of the gap formed by a micro-slit when the tissue is expanded can be less than about 1 mm, or preferably less than about 0.5 mm.
• Such micro-slits may extend through an entire depth of the tissue (e.g., in a full-thickness graft or a split-thickness graft), or to a particular depth such as, e.g., the depth of the dermis (e.g., for in situ meshing and stretching). A force can then be applied to the tissue to expand it, which can widen the micro-slits to form lens-shaped or rounded gaps therefrom. The small dimensions of the micro-slits—and the gaps formed therefrom after stretching—can facilitate rapid regrowth and filling of these gaps, which can be facilitated by adjacent functional tissue. A shallower depth can also be formed, e.g., a depth of about 0.6 mm in skin tissue, or about one-third (⅓) of the skin thickness, which can assist in avoiding formation of scars after the tissue is stretched and allowed to heal. Accordingly, the use of such micro-slits can reduce healing times and result in an aesthetically pleasing appearance of the stretched tissue.
• In certain exemplary embodiments of the present disclosure, micro-slits can be provided in a form of z-shaped incisions, such that triangular flaps formed by these incisions can be repositioned to allow expansion of the tissue with little or no gap being formed.
• For example, micro-slits can be formed in a pattern of alternating lines of staggered micro-slits, where the gap between adjacent micro-slits in a line can be greater than about one-tenth ( 1/10) of the length of an adjacent micro-slit, and where the spacing between adjacent lines of micro-slits can be between about ⅓ and 3 times the length of a micro-slit. Micro-slits can also be provided in other patterns, such as random arrays, circular or spiral patterns, or arrays containing orthogonal lines of micro-slits.
• According to another exemplary embodiment of the present disclosure, an apparatus can be provided which is configured to form micro-slits in a tissue. The exemplary apparatus can include one or more blades, where each blade can further include one or more extensions or protrusions, with each having a sharp cutting edge. For example, the width of the extensions can correspond to the approximate width of the micro-slits formed when each extension is pressed into the tissue.
• In yet another exemplary embodiment, the apparatus can include a stack of such blades that can be spaced apart from one another by a particular distance, e.g., using spacer elements between the blades. Such exemplary apparatus can be used to form a plurality of micro-slits simultaneously using a ‘stamping’ procedure, whereby the ends of the blades having sharp cutting edges are pressed into the tissue and then withdrawn. This exemplary stamping procedure can be repeated in different locations on the tissue to provide micro-slit meshing for a larger tissue area.
• In a further exemplary embodiment of the present disclosure, a roller apparatus can be provided that includes a plurality of extensions provided on one or more circular blades, where the circular blades are configured to rotate around an axle in a roller configuration. The exemplary roller apparatus can optionally include a handle coupled to the axle. The circular blades can be rolled over the tissue, and the extensions around the perimeter of the circular blades penetrate the tissue to form a plurality of micro-slits.
• According to still another exemplary embodiment of the present disclosure, an apparatus can be provided which is configured to form micro-lines in tissue using optical energy such as, e.g., an ablative laser apparatus. The exemplary apparatus can include, for example, a laser source, a controller, and an optical arrangement. The laser source can be an ablative laser such as a CO₂laser or the like. The controller circuitry can be configured to control parameters of the laser source and of the optical arrangement, for example, to form a plurality of micro-slits in the tissue by direct energy from the laser source to ablate thin regions of the tissue to a particular depth.
• According to yet another exemplary embodiment of the present disclosure, an apparatus for facilitating an expansion of a biological tissue can be provided. In particular, a plurality of cutting arrangements can be provided, with each cutting arrangement comprising at least one cutting edge structured to cut at least one respective micro-slit in the tissue. For example, a length of extension of the cutting edge(s) of at least one of the cutting arrangements can be less than about 2 mm or less than about 1.5 mm (or possibly less than about 1 mm or 0.8 mm). In addition, each of the cutting edge(s) of each of the cutting arrangements can comprises a plurality of cutting edges that have a length of extension that is less than about 2 mm or less than about 1.5 mm (or possibly less than about 1 mm or 0.8 mm).
• These and other objects, features and advantages of the present disclosure will become apparent upon reading the following detailed description of exemplary embodiments of the invention, when taken in conjunction with the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
• Further objects, features and advantages of the present disclosure will become apparent from the following detailed description taken in conjunction with the accompanying figures showing illustrative embodiments, results and/or features of the exemplary embodiments of the present disclosure, in which:
• FIG. 1A is an illustration of a first exemplary pattern of micro-slits that can be used to expand tissue in accordance with the present disclosure;
• FIG. 1B shows an illustration of the pattern of the micro-slits ofFIG. 1A after the tissue has been expanded to form a plurality of small gaps in the tissue;
• FIG. 2 is an illustration of a portion of the micro-slit pattern shown inFIG. 1A;
• FIG. 3 is an illustration of a second exemplary pattern of the micro-slits that can be used to facilitate the tissue expansion;
• FIG. 4 is an illustration of a third exemplary pattern of the micro-slits that can be used to facilitate the tissue expansion;
• FIG. 5A is an illustration of a fourth exemplary pattern of the micro-slits that can be used to facilitate tissue expansion;
• FIG. 5B illustrates a fifth exemplary pattern of the micro-slits that can be used to facilitate the tissue expansion;
• FIG. 6A is an illustration of an exemplary z-shaped micro-incision that can be used to facilitate the tissue expansion;
• FIG. 6B shows an illustration of the exemplary z-shaped micro-incision ofFIG. 6A after two triangular flaps have been transposed to provide a net lengthening of the tissue in a particular direction;
• FIG. 7A is an illustration of a first exemplary array of z-shaped incisions that can be used to facilitate tissue expansion;
• FIG. 7B is an illustration of a second exemplary array of z-shaped incisions that can be used to facilitate the tissue expansion;
• FIG. 7A is an illustration of a third exemplary array of z-shaped incisions that can be used to facilitate the tissue expansion;
• FIG. 8A is an illustration of a first exemplary blade configuration that can be used to form the micro-slits;
• FIG. 8B is an illustration of a second exemplary blade configuration that can be used to form the micro-slits;
• FIG. 8A is an illustration of a third exemplary blade configuration that can be used to form the plurality of micro-slits;
• FIG. 9 is an illustration of an exemplary stack of blades that can be used to form a plurality of micro-slits;
• FIG. 10 is an illustration of an exemplary spiral blade configuration that can be used to form the micro-slits;
• FIG. 11A is an illustration of a first exemplary roller apparatus that can be used to form the micro-slits;
• FIG. 11B is an illustration of a second exemplary roller apparatus that can be used to form the micro-slits;
• FIG. 12A is an illustration of a first exemplary square pattern of cutting edges that can be used to form the micro-slits in a tissue;
• FIG. 12B is an illustration of a second exemplary square pattern of the cutting edges that can be used to form the micro-slits in the tissue;
• FIG. 12C is an illustration of an exemplary pattern of the micro-slits that can be formed in a tissue using the square patterns of cutting edges shown inFIGS. 12A and 12B;
• FIG. 13A is an illustration of an exemplary hexagonal pattern of cutting edges that can be used to form the micro-slits in the tissue;
• FIG. 13B is an illustration of an exemplary pattern of the micro-slits that can be formed in the tissue using the hexagonal pattern of the cutting edges shown inFIG. 13A;
• FIG. 14 is a schematic illustration of an exemplary laser apparatus that can be used to form the micro-slits in accordance with exemplary embodiments of the present disclosure;
• FIG. 15A is an image of an exemplary blade that can be used to form the micro-slits;
• FIG. 15B is a further image of the exemplary blade shown inFIG. 15A;
• FIG. 16A is a first image of an exemplary apparatus that can be used to form the micro-slits to facilitate tissue stretching in accordance with embodiments of the present disclosure;
• FIG. 16B is a second image of a portion of the apparatus shown inFIG. 16A;
• FIG. 16C is a third image of a portion of the apparatus shown inFIG. 16A;
• FIG. 16D is a fourth image of a portion of the apparatus shown inFIG. 16A, showing the pattern of the cutting edges;
• FIG. 17A is an image of a piece of graft skin tissue that includes the micro-slits provided therein in accordance with the exemplary embodiments of the present disclosure;
• FIG. 17B is an image of the piece of the graft skin tissue shown inFIG. 17A after such skin tissue has been stretched;
• FIG. 18A is an illustration of an exemplary pattern of the micro-slits that can be used to expand tissue in situ in accordance with the present disclosure; and
• FIG. 18B is an illustration of the in situ tissue shown inFIG. 18A after such tissue has been stretched.
• Throughout the drawings, the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components, or portions of the illustrated embodiments. Moreover, while the present disclosure will now be described in detail with reference to the figures, it is done so in connection with the illustrative embodiments and is not limited by the particular embodiments illustrated in the figures. It is intended that changes and modifications can be made to the described embodiments without departing from the true scope and spirit of the present disclosure as defined by the appended claims.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
• Exemplary embodiments of the present disclosure provide method and apparatus for facilitating tissue expansion by forming a plurality of micro-slits in the tissue, where each micro-slit is sufficiently small such that it may not be easily seen by the human eye without magnification. By providing a plurality of such small micro-slits in a tissue, it is possible to utilize a procedure that can be referred to as “micro-meshing,” such that the gross appearance of the tissue (e.g., skin) when expanded may remain substantially normal after healing. Accordingly, such exemplary micro-meshing procedure can be used in situ, for example, in place of other conventional techniques, such as advancement flaps or skin tension release operations, which can be more problematic. Exemplary embodiments of the present disclosure can also provide ways to eliminate a need for a tissue graft in certain applications by facilitating a stretching of adjacent tissue in situ that can exhibit a substantially normal appearance after healing.
• According to a first exemplary embodiment of the present disclosure, a method can be provided for facilitating tissue stretching by forming a plurality of micro-slits in full or partial thickness tissue such as, e.g., skin or other connective tissue. The size, orientation, density, and configuration of the micro-slits can be selected to facilitate a certain amount of tissue expansion for a particular application as described herein. Such micromesh tissue expansion can be accomplished in situ, e.g. by providing micro-slits in skin tissues adjacent to or at some distance from a local wound that needs to be closed, to facilitate stretching of the skin tissue over the wound. Such exemplary method can also be used, e.g., to facilitate the expansion of graft tissues, such as a piece of skin harvested from a donor site that can be used to cover a wound.
• An exemplary array100 of micro-slits is shown inFIG. 1A. This exemplary micro-slit array100 has a form of staggered rows of collinear slits. Such array can be used, e.g., to facilitate a substantially unidirectional expansion of the tissue in the direction of arrow110.FIG. 1B illustrates the exemplary array100 after it has been stretched. Each micro-slit has widened to form a small lens-shaped gap that facilitates the overall tissue length to increase in the direction of the arrow110 without significant contraction in the perpendicular direction along the tissue surface. These small gaps may rapidly fill in with the regrown tissue as the stretched tissue heals.
• For example, the length of the micro-slits can be less than about 2 mm, or less than about 1.5 mm, to avoid a likelihood of forming visible scars and/or to allow a rapid regrowth of the gaps formed in the expanded micro-slits. The length of the micro-slits can be less than about 1 mm, or less than about 0.8 mm. The length of each micro-slit can be greater than about 0.1 mm to facilitate a sufficient expansion of the tissue using a reasonable number of slits. In general, a maximum width of the gap formed by each micro-slit when the tissue is expanded is preferably less than about 1.5 mm. This width of the gaps can also be less than about 1.0 mm, or less than about 0.5 mm.
• Small micro-slits as described herein can provide several advantages over conventional meshing techniques. For example, each of the micro-slits can be a tissue wound that forms a gap when the tissue is expanded. This gap may eventually be filled in by a wound healing process. Clinical experience indicates that very small wounds may heal by regrowth of healthy tissue, a process that can be referred to as remodeling, with little or no scar tissue formation. During tissue remodeling, local structures such as hair follicles, sebaceous and sweat glands are capable of local regeneration when injured on the scale of the structure itself, e.g., at distances of less than about 1 mm. Examples of tissue injury that can be healed by remodeling include, e.g., tattoo placement (which may involve a healing of thousands of microscopic puncture wounds), and healing of single puncture wounds created by insertion of hypodermic needles or the like.
• In contrast, large wounds may heal by replacement of damaged or lost tissue with undesirable scar tissue. Scar tissue can re-establish physical integrity, but it often can be dysfunctional. In skin, scar tissue lacks hair follicles, sweat glands, and normal dermal and dermo-epidermal junction structure. Scar tissue can also be mechanically stiff as compared with healthy tissue. Over time, scars subjected to tension may react by contraction. This response can be observed after burn trauma and surgery, and can be debilitating. Accordingly, using micro-slits having a size smaller than that used in conventional tissue meshing, e.g., less than about 2 mm or less than about 1.5 mm in length, can facilitate a prevention of a formation of significant amounts of scar tissue after the stretched tissue heals.
• Further, generating micro-slits having a length that is smaller than that of a diameter or typical spacing of major skin arteries can facilitate a meshing of the tissue that may not fully or substantially sever its blood supply. Healing of the gaps created in the expanded tissue after micro-meshing can also occur more rapidly than healing of larger gaps created using conventional meshing techniques, because of the smaller distances and areas of regrowth that occur, supported by adjacent healthy tissue.
• Using a small micro-slit size for tissue expansion, especially in skin, can provide further advantages, e.g., in the appearance of the tissue after expansion and healing. Even if a small amount of scar tissue forms in each micro-mesh incision, a grossly visible scar can be avoided. Such micro-slits can create small “dells” in the skin surface after healing that can effectively disappear among normal dermatoglyphics (e.g., permanent skin surface texture features). An ability to visually resolve a skin feature can depend on a size of the feature, and a distance from which it is viewed. The micro-meshing procedure performed in accordance with the exemplary embodiments of the present disclosure can be performed using a plurality of micro-slits, each of which can be approximately at or below the resolution of human vision under typical viewing conditions, e.g., from a distance of about 0.5 meter.
• As an example of this visual effect, newsprint photographs can be composed using individual ink spots having feature sizes that are below the resolution limit of the naked eye when viewed at typical distances. Such photographs can be formed, for example, using small dots of ink spaced about 0.5 mm apart in a simple array. Although all points on the photograph can be either white (e.g., spaces between ink dots) or black (e.g., points within an ink dot), the photograph may appear as a full gray-scale range to the naked eye because the ink dots are not individually resolved. The size of each ink dot can be varied from zero to completely intersecting with its neighbors, which can produce white and black regions, respectively. A full gray scale can be obtained for portions of the array containing intermediate-sized dots.
• An appearance of such newsprint photographs as apparently continuously varying shades of gray can be analogous to skin appearance after micro-meshing, in which a uniform appearance can be obtained despite the presence of very small regions of the regrown tissue. An exemplary size range for micro-slits cut into tissue to facilitate tissue expansion can be somewhat greater than that for typical newsprint photographs, because there can be a lower contrast between the original and the regrown tissue as compared to the contrast between the white paper and black ink dots.
• Using small micro-slit and gap sizes as described herein for tissue expansion facilitated by the exemplary micro-meshing procedure can also facilitate rapid healing after the tissue is stretched. The healing time for a gap in the tissue can be approximately proportional to the size of the gap. For example, during fractional laser ablative resurfacing of skin, a large number of small holes (e.g., each hole being about 0.2 mm diameter and 2 mm deep) can be produced, removing up to about 50% of the skin tissue. Within several days the epidermis can cover each hole, and within a week the holes can be filled in by remodeling without scarring. Similar rapid healing can be obtained in tissue stretching by forming a plurality of micro-slits in the tissue, such that the size of the gap formed by each micro-slit after stretching remains small.
• The depth of the micro-slits can be sufficiently large to pass through an entire thickness of a tissue graft (e.g., for an ex vivo tissue sample) or the tissue layer or structure (e.g., for in situ applications) to be expanded. For example, split-thickness skin grafts can typically be about 0.2 mm thick, and micro-slits used for expanding such grafts can be sufficiently deep to pass entirely through this thickness. The micro-slits can also be formed in full-thickness grafts, e.g., that pass through the entire thickness of such grafts. The micro-slits having a shallower depth can also be formed. For example, the micro-slits can be formed that have a depth of less than about 0.6 mm in skin tissue, or less than about ⅓ of the total skin thickness. The micro-slits having such depths can facilitate healing of the tissue after such tissue is stretched while avoiding significant scar formation as described, e.g., in Plastic Reconstructive Surgery, vol. 119, pp. 1722-32 (2007).
• Micro-mesh expansion of other connective tissue such as tendon, ear cartilage, etc., can be done using various micro-slit depths that can be selected based on mechanical properties of the tissue and the amount of stretching desired. Tissue expansion can also be accomplished in three dimensions for organ tissues such as kidney, heart, and liver by forming appropriate micro-slits in various orientations, e.g., in at least one of the xy, yz, and/or xz planes.
• The exemplary micro-slit array100 shown inFIG. 1A can be used to facilitate tissue expansion that can be substantially unidirectional. The exemplary array100 can be provided as a plurality of substantially parallel dashed lines, where each dash can represent a micro-slit formed in the tissue. The micro-slits can be in a staggered alignment, such as that shown inFIG. 1A, which may facilitate a substantially uniform unidirectional expansion of the tissue when an appropriate force is applied, as shown inFIG. 1B. Some staggering or offset of the micro-slits in some rows of slits, e.g., in adjacent rows, can be provided such that any imaginary line drawn across the tissue substantially in the direction of expansion110 can intersect a plurality of micro-slits that can widen by forming gaps in a direction substantially parallel to the arrows. Such staggering or offset of slit lines can thereby help to avoid formation of continuous regions of un-slit tissue along the elongation direction, where such regions would lack gap-forming slits to accommodate the overall expansion and thereby can be undesirably strained.
• Aportion200 of the exemplary micro-slit array100 is shown inFIG. 2. Parameters which can be used to describe the exemplary micro-slit array include, e.g., amicro-slit length210, a gap length betweenadjacent micro-slits220, a spacing230 between adjacent lines of micro-slits, and anoverlap240 between neighboring micro-slits in adjacent rows.
• Thegap length220 can be at least about 1/10 of themicro-slit length210. This exemplary ratio can provide sufficient tissue between adjacent micro-slits to maintain integrity of the tissue when it is stretched. The spacing230 between adjacent lines of micro-slits can be between about ⅓ and 3 times the length of the adjacent micro-slits.Spacings230 that are smaller than this ratio range can reduce the mechanical integrity of the tissue when stretched, and spacings larger than this ratio range may not facilitate a sufficient expansion of the tissue.
• Theoverlap240 between neighboring micro-slits in adjacent rows can be between about 1/10 and 8/10 of the length of adjacent micro-slits. The larger overlap can provide agap length220 of at least about 1/10 of the adjacentmicro-slit length210 to be maintained between adjacent micro-slits in a line. An overlap240 of, e.g., at least 1/10 of the adjacentmicro-slit length210 can be effectuated so that there are no extended regions of tissue in the direction of the tissue expansion that are free of any expandable micro-slits. Such extended micro-slit-free regions, if present, can be subjected to excessive strains and possibly tear because there are no micro-slits available locally to form gaps and accommodate the overall tissue expansion.
• In addition to the exemplary micro-slit array100 shown inFIG. 1A, which can provide unidirectional expansion of tissue, other slit arrangements can be provided to facilitate various expansion behaviors while maintaining small micro-slit and gap sizes as described herein. For example, micro-slit configurations similar to the array100 shown inFIG. 1A can be used, where the slit lengths, the spacing between adjacent lines, and/or the spacing between slits in a single line can be varied. Generally, a portion of tissue having closely-spaced lines of micro-slits can be stretched more than a portion having similar lines of slits spaced further apart. Line spacings can thus be varied in such an array to provide portions of tissue that can be stretched to varying degrees within a single graft or skin region. Certain further portions of the tissue being stretched can also be free of any micro-slits to inhibit stretching in these portions. Such variations in a local expandability can be used to provide improved cosmetic appearance of the stretched tissue or applied graft, e.g., based on such factors as hair follicle density, pigmentation, etc.
• Exemplary embodiments of the present disclosure can also facilitate for a use of tissue having an exemplary configuration or array ofmicro-slits300 such as that shown inFIG. 3, which includes intersecting lines of micro-slits that lie substantially along one of two substantially orthogonal directions. Such array ofslits300 can be capable of facilitating expansion of the tissue in any direction. For example, an arbitrary direction for stretching can generally be expressed as a vector combination of two orthogonal stretching components that can be perpendicular to the two orthogonal slit directions. Stretching of the tissue in a direction orthogonal to each line of micro-slits can be accommodated by facilitating the micro-slits to form gaps in that direction as shown in the exemplary embodiment ofFIGS. 1A and 1B. Thus, regular micro-slit arrays, such as theexemplary array300 shown inFIG. 3, can be used to provide grafts or regions of in situ tissue that can be more easily expanded in any direction.
• The exemplary micro-slits described herein can also be used to stretch skin in situ, e.g., to cover certain wounds or damaged skin regions with tissue from adjacent healthy regions. An exemplary illustration of such in situ stretching procedure is shown inFIGS. 18A and 18B. For example, a plurality of micro-slits1220 can be formed in ahealthy tissue1800 that is adjacent or proximal to awound1810. For example, thewound1810 can be a portion of the tissue where an outer layer of the skin is missing, e.g., a portion of the skin surface that may have been burned or abraded. Thewound1810 can be cleaned to remove any remaining portions of the damaged tissue and/or to provide a uniform and sterile base of tissue capable of receiving an overlayer of stretched tissue.
• The exemplary micro-slits1220 shown inFIG. 18A can be formed such that a surface direction of the micro-slits1220 is substantially perpendicular to the direction that thehealthy tissue1800 is to be stretched. A local density of the micro-slits1220 can also be higher in regions of thehealthy tissue1800 that is to be stretched further, e.g., those regions that are to undergo a greater areal expansion to cover thewound1810.FIG. 18B shows an exemplary illustration of thehealthy tissue1800 shown inFIG. 18A after such tissue has been stretched to cover thewound1810. The micro-slits1220 can be formed as described herein, and can be provided in a sufficient density that agap1820 formed by each stretched micro-slit is small, e.g., less than about 1.5 mm in width, or less than about 1 mm in width. Suchsmall gaps1820 can facilitate a rapid healing of the stretchedtissue1800, and can avoid a formation of visible scars.
• Thehealthy skin tissue1800 can be about 1-3 mm thick. The micro-slits1220 that are formed to facilitate the expansion of thisskin tissue1800 in situ can be provided at least to a depth so as to extend through substantially the entire local dermal layer. For example, the dermal layer of theskin1800 may not be strongly attached to the fatty layer below, such that theskin1800 can more easily separate from the underlying fatty layer, and be stretched to widen thegaps1820 in the micro-slits1220. The micro-slits1220 formed in situ may, e.g., not extend into the underlying tissue below the dermis to any significant depth, to avoid damaging blood vessels and/or other structures underlying theskin tissue1800.
• In further exemplary embodiments, micro-slit arrays can be formed using micro-slits oriented in a plurality of directions, such as in the exemplarymicro-slit array400 shown inFIG. 4. The micro-slits can be formed in a pattern which may repeat at some distance, or their positions and/or orientations can be random. Theexemplary array400 shown inFIG. 4 can be used to facilitate the expansion of portions of the tissue in different directions. The micro-slits can be provided in a substantially non-intersecting pattern to reduce or avoid a formation of wide gaps and/or pointed flaps of tissue after expansion is achieved by applying appropriate tension to the micro-meshed tissue.
• In still further exemplary embodiments, a circular micro-slit pattern such as anexemplary pattern500 shown inFIG. 5A can be used to facilitate a particular expansion behavior of the tissue. The round slit pattern shown inFIG. 5A can be used, for example, to facilitate the expansion of a nominally flat piece of tissue over a rounded surface such as, e.g., a chin or a shoulder. A micro-slit pattern that includes one or more spiral-shaped lines of slits, such as theexemplary pattern510 shown inFIG. 5B, can also be used to facilitate a similar tissue expansion geometry.
• Several exemplary parameters associated with the micro-slit arrays can be varied for particular applications including, for example, average micro-slit length, variation of micro-slit lengths, slit density (e.g., number of micro-slits per unit area of tissue), micro-slit orientations, spacing between micro-slits or lines of micro-slits (which can be related to the overall micro-slit density), and/or randomness of micro-slit staggering. A mean orientation of a group or pattern of the micro-slits can be selected to better facilitate tissue expansion in one or more particular directions. For example, if an expansion of the tissue is desired along a given vector, e.g., a primarily one-dimensional expansion, most or all of the micro-slits can be oriented substantially perpendicular to that vector, as shown inFIG. 1. An omnidirectional tissue expansion can be facilitated, e.g., by providing a plurality of micro-slits having a mean orientation vector that is nearly zero, e.g., as shown inFIGS. 3 and 4.
• In further exemplary embodiments of the present disclosure, micro-slits can be provided to form a plurality of z-shaped micro-incisions600, such as that shown inFIG. 6A. Such z-shaped micro-incisions can be similar in shape to incisions used, e.g., in a conventional z-plasty procedure as described, e.g., in Salam et al., American Family Physician, vol. 67, no. 11 (Jun. 1, 2003), pp. 2329-2332. The exemplary z-shapedmicro-incisions600 can include, e.g., two opposingmicro-slits610, which can be substantially parallel or at some small angle relative to each other, and adiagonal micro-slit620 connecting near ends of the opposingmicro-slits610 to form twotriangular flaps630,640.
• The relative positions of theflaps630,640 can be switched across thediagonal micro-slit620, e.g., as shown inFIG. 6B, which can facilitate a net expansion of the tissue in the direction650 and a slight contraction of the tissue in a direction substantially orthogonal to such direction650. The micro-slits610,620 can be approximately the same length to facilitate the alignment of theflaps630,640 after they are repositioned as shown inFIG. 6B. Further, similar to conventional z-plasty procedures, thediagonal micro-slit620 may intersect each of the twomicro-slits610 at substantially the same angle, which can also facilitate the alignment of theflaps630,640 when they are repositioned. This angle of intersection can be about 60 degrees or less, to avoid excessive local deformation of the tissue and to facilitate repositioning of theflaps630,640. Smaller angles can also be used, and they may provide a smaller amount of expansion when theflaps630,640 are repositioned.
• A plurality of such z-shapedmicro-incisions600 can be provided in various arrays, such as the exemplary arrays shown inFIGS. 7A-7C. The size, orientation and/or spacing of the z-shapedmicro-incisions600 can be varied to provide different local expansion behavior of the tissue. Each of the micro-slits610,620 can be less than about 2 mm in length, or optionally less than about 1 mm. These micro-slit lengths of the z-shaped micro-incisions can be larger than corresponding lengths of single micro-slits, such as those shown inFIG. 1. This is because much of the effective tissue expansion can be accomplished geometrically with a z-shaped micro-incision, such that smaller gaps can be formed when the tissue is stretched.
• The micro-slit lengths described herein can be smaller than typical slit sizes used in conventional z-plasty techniques, and they can provide several advantages. For example, using themicro-slits610,620 to form a small z-shapedmicro-incision600 can facilitate the repositioning of theflaps630,640 when applying a local tension to the tissue containing themicro-slits610,620. Theflaps630,640 are likely smaller relative to their thickness than larger conventional flaps, and therefore they can be comparatively rigid and easier to reposition properly.
• Theflaps630,640 can also be repositioned with little or no undermining of the tissue beneath them. In contrast, conventional z-plasty techniques can require significant undermining of tissue beneath the relatively large triangular flaps to provide them with sufficient mobility to be moved with respect to adjacent tissue and be repositioned. Further, the small z-shapedmicro-incisions600 can produce relatively small markings of the tissue after the tissue is expanded and healed that may not be apparent to the naked eye, and thereby likely avoid a formation of larger, more visible scars or tissue discontinuities. Theflaps630,640 formed by themicro-slits610,620 can also avoid the use of stitches to hold them in place after repositioning, in contrast to some large flaps used in conventional z-plasty procedures. In addition, the alignment of theflaps630,640 does not have to be precise to obtain tissue expansion without formation of undesirable scars. For example, any gaps formed by themicro-slits610,620 after the tissue expansion can also be small (for example, less than about 0.5 mm). As described herein, functional tissue can preferentially regrow in such small gaps rather than scar tissue.
• A general pattern of slits can produce the same relative expansion (expressed as a percentage or fraction of the original tissue lengths) at any size scale based on geometric similarity. For example, a particular array of large slits may provide approximately a 30% expansion in a certain direction by formation of lens-shaped gaps. If the size and spacings of the slits in the particular array are uniformly decreased by half (e.g., by 50%), the resulting array can also produce a 30% expansion by forming lens-shaped gaps having a similar shape. In this example, four times as many of the smaller slits can be provided per unit area (as compared with the large slits) to obtain this exemplary 30% expansion in a particular portion of tissue. The larger number of smaller slits is based on the 50% reduction in size scale, which doubles the number of slits per unit distance in each of two orthogonal directions parallel to the tissue surface. These particular exemplary percentages merely illustrate the effect of changing the size scale of a slit pattern. In general, miniaturizing a given pattern of mesh slits can provide substantially the same degree of tissue expansion as a larger slit pattern when forming gaps from the slits which have a geometrically similar shape.
• Reducing the size scale of a slit pattern also proportionally can reduce the physical width of the gaps formed by the slits for a particular amount of overall tissue expansion. Thus, by using a pattern of micro-slits to expand tissue as described herein, the width of each gap formed when the tissue is expanded can be small. In general, the gap width used in tissue expansion can be less than about half the micro-slit length, or less than about one-quarter of the micro-slit length. Larger gap widths can also be used. For example, greater expansion can be achieved using a particular micro-slit pattern if the gap width approaches the length of the micro-slits. This can lead to formation of gaps that are more equiaxed in shape. Such wider gaps can also be useful for tissue expansion, particularly if the micro-slit length and gap width are small enough to allow tissue to regrow and fill in the gap without producing significant amounts of scarring or nonfunctional tissue.
• In general, reducing the micro-slit size (or an average micro-slit size in an array or pattern of micro-slits having different sizes) can reduce the size of the gaps formed when the tissue is expanded. The micro-slits can be larger than some minimum size that are selectable, e.g., based on the type of tissue, the thickness of the tissue layer being expanded, the ease of forming small micro-slits, etc. The micro-slits can extend through substantially the entire thickness of the tissue being expanded. This can lead to larger aspect ratios of depth to length if very short micro-slits are formed in relatively thick tissue layers. Such narrow, deep micro-slits may not readily facilitate the uniform tissue expansion because of possible non-uniformities in the depth direction. Accordingly, a length-to-depth ratio of a micro-slit can be greater than about 1:10, or possibly greater than about 1:5. Length-to-depth ratios of about 1:2 can also be used, as can larger ratios.
• Visible disfigurement associated with scars can result from a lack of dermatoglyphics, e.g., the scar tissue can have a smooth, often glossy surface. A pattern or array of micro-slits as described herein can be formed on a visible scar to disrupt the surface texture of the scar after healing, which can result in a dermatoglyphic appearance that is more similar to that of normal skin.
• In another exemplary embodiments of the present disclosure, a tissue expansion apparatus can be provided that is configured to form a plurality of micro-slits in a layer of tissue to be expanded. For ex vivo meshing of split thickness skin grafts, for example, the apparatus can have a configuration similar to that of a conventional meshing device, except that the cutting surfaces are configured to form micro-slits as described herein that are much shorter than the slit lengths produced by the conventional meshing devices.
• In certain exemplary embodiments, the expansion apparatus can include one or more micro-blades that can be pushed through a skin surface to a desired predetermined depth to form micro-slits.Exemplary micro-blades800,810,820 that can form such micro-slits are shown inFIGS. 8A-8C. The micro-blades800,810,820 can include a plurality ofextensions830 coupled at their proximal ends to ablade body840. Acutting edge850 can be provided at a distal end of eachextension830 to facilitate a penetration of theextensions830 into the tissue to form the micro-slits. For example, the micro-blade800 can be produced by cutting away portions of a conventional razor blade or the like to form the plurality ofextensions830. Other manufacturing procedures can also be used. Theextensions830 can be very thin and thecutting edge850 can be very sharp, for example, similar to a razor blade or a scalpel.
• The length of theextensions830 can be approximately the same as the depth of the tissue being expanded. For example, if tissue (such as a half-thickness graft) is being expanded ex vivo, the length of theextensions830 can be about the same as or greater than the tissue thickness to facilitate the formation of the micro-slits that can pass through the entire thickness of the tissue. Theblades800,810,820 can be formed of stainless steel and/or any other suitable material, such as another metal, a polymer, or silicon, and they may optionally be disposable. The approximate depth of the micro-slits formed can correspond to the length of theextensions830, because theblades800,810,820 can only penetrate the tissue until the lower edge of theblade body840 contacts the tissue surface. Alternatively or in addition, theextensions830 that are longer than the desired depth of the micro-slits can be provided. The depth of the micro-slits formed can be controlled, e.g., by providing one or more hilts or stops on theblades800,810,820 located a particular distance above thecutting edge850 corresponding to the desired micro-slit depth. Such hilt or stop can be fixed to theblades800,810,820, or alternatively it can be adjustable to facilitate the formation of the micro-slits having different depths with a single blade arrangement. Theblades800,810,820 can be pressed into the tissue to form a single line of the micro-slits, and this exemplary procedure can be repeated to form an array containing a plurality of such lines of micro-slits, such as the array100 shown inFIG. 1A.
• According to further exemplary embodiments, an apparatus for forming micro-slits can be provided that includes astack900 ofblades910 as shown, e.g., inFIG. 9. Thestack900 of theblades910 may include a plurality ofblades910 such as those described herein, withspacers920 provided between theblades910. Theblades910 can be staggered such that theextensions830 with cuttingedges850 are configured to create a micro-slit pattern, such as that shown inFIG. 1A or the like, when the lower portion of thestack900 is pressed into the tissue. Thestack900 ofblades910 can also be pressed onto a particular portion of tissue for a second time, with theblades910 oriented in a second direction that is substantially orthogonal to a first direction of theblades910, to produce a pattern of micro-slits, e.g., similar to that shown inFIG. 3.
• Other blade configurations can be used to create particular micro-slit patterns. For example,FIG. 10 shows a plan view of aspiral blade1000 which can be formed by bending theblade910 into a spiral shape, and which may further includespacers920 between portions of the spiral. Thespiral blade1000 can be used to form a spiral pattern of micro-slits such as that shown inFIG. 5B. Various micro-slit patterns can be obtained by using different combinations and configurations of blades as described herein.
• According to another exemplary embodiment of the present disclosure, an exemplary roller apparatus1100 (such as that shown inFIG. 11A) can be provided. For example, theroller apparatus1100 can include around blade body1110, with a plurality of substantiallycoplanar extensions830 provided around a perimeter of thecircular blade body1110. Acutting edge850 can be provided on an outer portion of eachextension830, and may optionally extend along a portion or all of the sides of theextensions830. Theblade body1110 can be configured to rotate around anaxle1140 that can be attached to ahandle1150. Theexemplary roller apparatus1100 can be rolled over a portion of tissue to produce a line of micro-slits. Theexemplary roller apparatus1100 can be used, for example, to easily form a large number of micro-slits over a large area of tissue by rolling theapparatus1100 across the tissue.
• A further exemplary embodiment of aroller apparatus1120 is shown inFIG. 11B. Theexemplary roller apparatus1120 can include acircular blade body1110. A plurality ofextensions830 can be provided around the perimeter of thecircular blade body1110, for example, in a staggered configuration. Acutting edge850 can again be provided on an outer portion of eachextension830, and may optionally extend along to the sides of theextensions830. Theblade body1110 can be configured to rotate around theaxle1140, which can be attached to ahandle1150. Theroller apparatus1120 can then be rolled over the tissue to produce a plurality of lines of micro-slits at the same time, for example, similar to the array of micro-slits100 shown inFIG. 1A.
• The ease with which an exemplary cutting apparatus can form the micro-slits by cutting through tissue may depend on factors such as, e.g., a sharpness of eachcutting edge850, a width and/or thickness of eachextension830, a rigidity of the tissue, an applied pressure, a number and/or density of theextensions830, etc. It can be difficult to force a high density ofsmall extensions830 into the tissue simultaneously. Various modifications to the exemplary embodiments of the apparatus as described herein can be provided to facilitate an easier formation of the micro-slits. For example, theextensions830 and/or cuttingedges850 can be coated with a lubricant or other low-friction coating. Theextensions830 can be inserted sequentially into the tissue rather than simultaneously, such as with theroller apparatus1100.
• Theextensions830 can also be driven into the tissue using force impulses, e.g., by tapping or hammering using piezoelectric elements, solenoids, pneumatics, hydraulics, etc. In certain embodiments, a vibrating arrangement such as, e.g., a transducer can be mechanically coupled to the apparatus to induce vibrations in theextensions830 and facilitate their penetration into the tissue. For example, the vibration can be provided at frequencies up to about 100 kHz. Certain advantages of the cutting devices over other techniques for forming slits in the tissue can include disposability, low cost, simplicity, ease of use, and eye-safe operation.
• In further exemplary embodiments of the present disclosure, a micro-slit pattern can be formed that includes different parameters (e.g., slit length, orientation, density, etc.) can be provided in different regions of a single portion of tissue. For example, the micro-slit patterns such as those shown inFIG. 1A can be provided at different orientations in different regions of the tissue. The local expansion of the tissue in each region can be utilized in a direction substantially orthogonal to the local micro-slits, as shown inFIG. 1B. Accordingly, a variation in micro-slit parameters in a tissue portion can be used to further accommodate variations in local expansion behavior of the stretched tissue. For example, by varying micro-slit parameters, a particular section of graft tissue can be expanded to better fill a wound area having a shape different than that of the unexpanded graft tissue. Such a variation in micro-slit parameters can also be used to expand tissue in situ to better cover and conform to the shape of an adjacent wound area.
• For example, an exemplary apparatus for facilitating tissue expansion can be provided that includes theextensions830 arranged in anexemplary array1200 that has an overall square or rectangular shape, as shown inFIG. 12A. A furtherexemplary array1210 that can include theextensions830 arranged in a diagonal direction is shown inFIG. 12B. For example, suchexemplary arrays1200,1210 ofextensions830 can be formed using thestack900 of theblades910 as shown inFIG. 9. Eachextension830 can include, e.g., acutting edge850 provided on a distal portion thereof to facilitate the insertion of theextension830 into the tissue to form a micro-slit.
• One or more apparati that includes such anarray1200,1210 can be pressed into a plurality of regions of the tissue, for example, to form a pattern of the micro-slits such as the exemplary pattern(s) shown inFIG. 12C. The exemplary pattern(s) of micro-slits1220 shown inFIG. 12C can include several regions outlined by dashedlines1230, where each region can have a particular local orientation of the micro-slits. The exemplary pattern(s) shown inFIG. 12C can thereby provide a substantially uniform distribution of the micro-slits1220 over a portion of tissue that includes a variation in local stretching directions (e.g., directions substantially orthogonal to the length of a micro-slit1220). Providing thearrays1200,1210 in a substantially square or rectangular shape, e.g., as shown inFIGS. 12A and 12B, can facilitate the formation patterns of the micro-slits1220 that are substantially uniformly spaced over a portion of tissue to be stretched.
• In a further exemplary embodiment, an apparatus for facilitating tissue expansion can be provided that can include a plurality ofextensions830 arranged in anarray1300 that can have an approximately hexagonal shape, as shown inFIG. 13A. As described above with respect to thearrays1200,1210 ofFIGS. 12A and 12B, theexemplary array1300 can also be formed, e.g., using thestack900 of theblades910 similar to that shown inFIG. 9. The lengths of theblades910 can be selected to provide thehexagonal array1300 shown inFIG. 13A.
• The apparatus that can includesuch array1300 can be pressed into a plurality of regions of a tissue, for example, to form a pattern of micro-slits1220 that can cover a portion of tissue to be stretched with a substantially uniform density of such micro-slits.
• For example, the exemplary pattern of micro-slits1220 shown inFIG. 13B can include several regions outlined by dashedlines1310, where the micro-slits1220 in each region can be formed by pressing thearray1300 of theextensions830 into the tissue, and withdrawing it. The exemplary pattern shown inFIG. 13B can be used to facilitate stretching of tissue (e.g., skin) over a rounded surface (e.g., an elbow, a chin, or the like), similar to the circular pattern shown inFIG. 5A. Other uniform distributions of the micro-slits1220 having variations in local preferred stretching directions can also be formed using the apparatus that can include theexemplary array1300 of theextensions830 shown inFIG. 13A.
• In a further exemplary embodiment, an apparatus that includes an array of theextensions830 can be provided, e.g., in a form of a triangle or another geometric shape, to facilitate formation of a pattern of the micro-slits1220 that can have various local orientations thereof, and which can be used to provide a substantially uniform density or distribution of the micro-slits1220 over a portion of the tissue as described above.
• In still another exemplary embodiment, anoptical apparatus1400 as shown inFIG. 14 can be used to form a plurality of micro-slits as described herein. The exemplaryoptical apparatus1400 can include anoptical energy source1410, anoptical arrangement1420, and acontrol arrangement1430. Theoptical energy source1410 can be, e.g., an ablative laser that is configured to produce minimal thermal injury, such as a pulsed CO₂laser, an Erbium (Er) laser, an excimer laser, or any one of various conventional femtosecond lasers. Other sources of optical energy that are configured to ablate or cut thin regions of the tissue can also be used.
• For example, pulsed CO₂lasers and pulsed Er lasers that are commonly used in dermatology and plastic surgery for tissue removal can generate a residual thermal damage layer in tissue next to an ablated region that can be between about 50 and about 200 micrometers in thickness. Excimer lasers, including a 193 nm excimer laser, can also be used and are capable of cutting tissue with almost no observable residual thermal damage. Such lasers are commonly used for LASIK procedures in corneal tissue. Femtosecond lasers, for example, having a pulse energy of greater than about 1 microjoule, when focused appropriately, can also sever or ablate tissue while generating a negligible amount of thermal damage in adjacent tissue. Such ablative lasers can operate at wavelengths and/or power densities for which the tissue exhibits strong optical absorption. Exemplary advantages of using optical energy, e.g., a laser, to form micro-slits in tissue as compared with blades or other material cutting devices can include speed, precision, depth control, arbitrary micro-slit pattern design, sterility, and non-contact operation.
• Theoptical arrangement1420 can include one or more waveguides, beam splitters, and/or mirrors, and can be configured to direct energy from theoptical energy source1410 towards thetissue layer1440 to form a plurality of the micro-slits1220 therein. Thecontrol arrangement1430 can be configured to adjust parameters of theoptical energy source1410 and theoptical arrangement1420 to affect and/or determine a position, length, and depth of the micro-slits1220. The exemplaryoptical apparatus1400 can be provided in a fixed position relative to thetissue layer1440. Alternatively, at least a portion of theoptical apparatus1400 can be provided in or as a handpiece or the like, which can be translated or moved over thetissue layer1440 to create larger regions of the micro-slits1220.
EXAMPLE
• Images of an exemplary blade in accordance with embodiments of the present disclosure are shown inFIGS. 15A and 15B. The exemplary blade illustrated inFIG. 15A can be similar to theexemplary blade800 illustrated inFIG. 8A. A close-up view of the extensions provided on theblade800, each with a cutting edge at a distal end thereof, is shown inFIG. 15B.
• Images of the exemplary apparatus in accordance with certain exemplary embodiments of the present disclosure are shown inFIGS. 16A-16D. The exemplary apparatus shown inFIG. 16A can include a handle attached to plurality of blades, where each blade is similar to the blade shown inFIG. 15A.FIGS. 16B and 16C are close-up images of the stack of blades having spacers between them, similar to the stack of theblades900 shown inFIG. 9.FIG. 16D provides an image of the array of cutting edges provided by the exemplary apparatus, which can be used to form a pattern of micro-slits that is similar, e.g., to the pattern of the micro-slits shown inFIG. 1A.
• A piece of human graft skin tissue is shown inFIG. 17A. A portion of this tissue can include a pattern of micro-slits formed therein using the exemplary apparatus shown inFIGS. 16A-16D, in accordance with the exemplary embodiments of the present disclosure. The pattern of micro-slits can be similar to the exemplary pattern shown inFIG. 1A.
• FIG. 17B illustrates an image of the skin tissue shown inFIG. 17A after it has been stretched sideways. Each micro-slit can be widened to form a small gap, and the portion of tissue that includes the pattern of micro-slits appears to have expanded substantially uniformly in a left-right direction. This stretched pattern of gaps is similar to that shown inFIG. 1B. A maximum dimension of each gap is small, e.g., on the order of about a millimeter or less as described herein. Accordingly, the graft tissue may regrow to rapidly fill in these small gaps, e.g., when the graft tissue is applied to a recipient site, and the healed graft tissue may appear substantially normal because of the small size scale of the plurality of healed gaps.
• The foregoing merely illustrates the principles of the invention. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous techniques which, although not explicitly described herein, embody the principles of the invention and are thus within the spirit and scope of the invention. All patents, patent applications, and other publications cited herein are incorporated herein by reference in their entireties.

Claims (22)

1-50. (canceled)

51. An apparatus for facilitating an expansion of a biological tissue, comprising:

a plurality of cutting arrangements structured to form a plurality of spaced-apart micro-slits in the tissue, wherein each of the micro-slits has a length of extension along a surface of the tissue that is less than about 2 mm.

52. The apparatus ofclaim 51, wherein the length of extension of each of the micro-slits is less than about 1.5 mm.

53. The apparatus ofclaim 51, wherein the length of extension of each of the micro-slits is less than about 1 mm.

54. The apparatus ofclaim 51, wherein the cutting arrangements are provided on a plurality of blades.

55. The apparatus ofclaim 51, wherein the cutting arrangements are provided in a staggered pattern.

56. The apparatus ofclaim 51, wherein the cutting arrangements are provided in at least one of a circular pattern and/or a spiral pattern.

57. The apparatus ofclaim 51, wherein the cutting arrangements are provided in a random pattern.

58. The apparatus ofclaim 51, wherein a distance between proximal ends of adjacent ones of the micro-slits is greater than about 1/10 the length of the micro-slits.

59. The apparatus ofclaim 51, wherein the cutting arrangements are configured to form the micro-slits in a form of a plurality of substantially parallel lines of micro-slits, and wherein a distance between the lines of the micro-slits is between about ⅓ and about 3 times the length of the micro-slits.

60. The apparatus ofclaim 51, wherein the cutting arrangements are provided on a substrate that has a shape that is at least one of circular and/or cylindrical, and wherein the substrate is structured to be rolled over a portion of the tissue to form the micro-slits.

61. The apparatus ofclaim 51, wherein at least one micro-slit has a form of a z-shaped incision in the tissue.

62. The apparatus ofclaim 51, wherein the cutting arrangements are structured to form micro-incisions that extend substantially through an entire thickness of a portion of ex vivo tissue.

63. The apparatus ofclaim 51, wherein the tissue comprises skin and the cutting arrangements are structured to form micro-incisions that extend substantially through an entire dermal layer of the tissue.

64. The apparatus ofclaim 51, wherein the cutting arrangements are structured to form micro-incisions that extend through less than about one-third of the thickness of the tissue.

65. The apparatus ofclaim 51, wherein the cutting arrangements comprise an optical arrangement configured to direct optical energy onto the tissue to form the plurality of micro-slits in the tissue.

66. The apparatus ofclaim 65, further comprising an optical energy source configured to provide the optical energy.

67. The apparatus ofclaim 65, wherein the optical energy source comprises an ablative laser.

68. A method for facilitating expansion of biological tissue, comprising:

forming a plurality of spaced-apart micro-slits in the tissue, wherein a length of extension of each of the micro-slits along a surface of the tissue is less than about 2 mm.

69. The method ofclaim 68, wherein at least some of the micro-slits are provided in a form of a z-shape.

70. The method ofclaim 68, wherein the micro-slits are formed using a plurality of blades.

71. The method ofclaim 68, wherein the micro-slits are formed using optical energy.

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