WO2008006156A1

WO2008006156A1 - Improved method and apparatus for taking a split-thickness skin graft

Info

Publication number: WO2008006156A1
Application number: PCT/AU2007/000959
Authority: WO
Inventors: Comus John Whalan
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-07-11
Filing date: 2007-07-11
Publication date: 2008-01-17
Anticipated expiration: 2009-01-11

Abstract

The invention relates to a method and apparatus for taking a split-thickness skin graft (STSG). The apparatus is a STSG testing plate (10) including at least one surface sized (10A) so that a test graft (12) can be taken from the surface (10A) by a dermatome (5) and wherein said at least one surface (10A) of the plate (10) is made from a material having at least one characteristic emulating skin. The invention enables a surgeon to take test grafts from the testing plate to establish an appropriate dermatome setting prior to taking the actual STSG from the patient's donor site.

Description

Improved Method and Apparatus for Taking a Split-Thickness Skin Graft

Cross References

This application claims priority from Australian Provisional Patent Application 2006903704 filed on 11 July 2006 and Australian Provisional Patent Application 2007900833 filed on 15 February 2007, the contents of which are to be taken as incorporated herein by this reference.

Field of the Invention

The present invention relates to a method and apparatus for taking a split- thickness skin graft.

Background of the Invention

A skin graft is a very common surgical procedure in which a piece of skin is transplanted from one area of a patient to another. Typically, skin is taken from an unaffected area of the patient (known as the donor site), and used to cover an area from which the skin has been lost, such as a burn. Rarely, skin is taken from one individual and grafted onto another.

Skin grafts are of two major types. These are full-thickness skin grafts (FTSGs)₁ and split-thickness skin grafts (STSGs). STSGs contain the epidermis (top skin layer) with only a portion of the underlying dermis. In a STSG, the donor site heals by migration of epithelial cells from within the oil and sweat glands within the remaining dermis. This is similar to the healing that occurs after a common abrasion.

A wide variety of surgical instruments exists for taking STSGs. Such instruments are generally referred to as dermatomes, and may be operated freehand, or powered by some external means such as compressed air. Typically, they have a flat blade which slices a thin layer of skin, in a way that may be likened to a carpenter's plane shaving a thin layer of wood.

Irrespective of the type of instrument used to take a STSG, it is very important for the graft to be of the correct or desired thickness. To enable the surgeon to achieve the desired thickness of graft, dermatomes are adjustable. This adjustment is typically done "by eye". This means that the surgeon examines the distance between the blade of the dermatome and an adjacent edge and increases or reduces that distance depending on the desired graft thickness. Once the surgeon decides that the dermatome is correctly set, the skin graft is taken from the donor site. However, even once the dermatome is adjusted, the resulting skin graft will vary slightly in thickness depending on the pressure and angle at which the surgeon applies it to the patient's skin.

If the graft is too thick, the donor site will be left with a defect that heals poorly or not at all. This results in new problems for the patient, additional to the original defect sought to be repaired by the graft. On the other hand, grafts that are too thin are difficult to handle, are prone to tearing and are often ragged and contain holes. Holes occur when the dermatome blade merely scrapes over the donor site without actually taking any skin. Furthermore, grafts that are too thin usually have poor long-term cosmetic appearance and function.

It can be difficult to take a STSG of the desired thickness. A typical STSG is only 10 - 15 thousands of an inch (about 0.3 mm) thick. Therefore, the difference between a satisfactory graft and an unsatisfactory one, can be a difference of only 5 one-thousandths of an inch (about 0.1 mm). Such small differences are difficult to judge "by eye" when adjusting the dermatome. This difficulty is exacerbated when the patient has very thin skin, such as elderly patients or when the patient has a history of taking corticosteroids. Considerable technical expertise is required to obtain consistent thickness over a large STSG. The present invention seeks to provide a method and apparatus for ensuring STSGs of desirable thickness are taken from the donor site.

The discussion of the background to the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of this application.

Summary of the Invention

According a first aspect of the invention there is provided a method of taking a

STSG including the steps of: a) selecting a dermatome for taking the STSG from a donor site; b) taking a test graft from a STSG testing plate; c) examining the test graft so as to determine whether it has a desired thickness; and d) if the test graft is of the desired thickness, taking the STSG from the donor site using the dermatome without any adjustment thereto; or e) if the test graft is not of the desired thickness, adjusting the dermatome and taking a further test graft from a STSG testing plate.

Preferably, the steps of examining the test graft, adjusting the dermatome and taking a further test graft are repeated until the test graft is of the desired thickness.

The step of examining the test graft may only include making a visual examination of the thickness of the test graft. Additionally or alternatively, it may include some other step, for example meshing the test graft and then conducting a visual examination of the meshed test graft.

The method may also include an additional step prior to step b) of selecting a STSG testing plate having characteristics similar to the characteristics of the patient's skin. According to the present invention there is also provided a STSG testing plate including a surface sized so that a test graft can be taken from the surface by a dermatome and wherein at least the surface of the testing plate is made from a material having at least one characteristic emulating skin.

Preferably, said at least one characteristic of the testing plate is the opacity or translucency of the material and/or the flexibility of the material.

The material of the testing plate is preferably further arranged so that it behaves in such a way when it is cut, that the thickness of the test graft is substantially similar to the thickness of a graft taken from a donor site using that dermatome at the same adjustment.

Preferably, the testing plate is formed from a block of material having at least one characteristic emulating skin. The block of material may adopt a variety of different shapes. The block is preferably configured to allow multiple test grafts to be taken therefrom.

Preferably, the material of the testing plate is sterilised.

The invention further provides a STSG testing plate including at least one surface sized so that a test graft can be taken from the surface by a dermatome and wherein said at least one surface of the plate is made from a material having at least one characteristic emulating human skin and is such that the thickness of the test graft taken from the testing plate is substantially similar to the thickness of a graft that would be taken from a human patient using that dermatome at the same adjustment.

Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic illustration of a STSG being taken from a donor site;

Figure 2 is a schematic side view of a testing plate in accordance with an embodiment of the invention showing after a first test graft has been taken (but still being partially connected); and

Figure 3 is a side view of the testing plate shown in Figure 2 after a second test graft has been taken (the first and second grafts still being partially connected).

Detailed Description of the Preferred Embodiments

Figure 1 schematically illustrates a STSG being taken from a donor site using a manual dermatome 5. The dermatome 5 has a blade which is set by the surgeon so that the skin graft 7 taken from the donor site has a thickness T. As explained above, by adjusting the blade setting it is possible to vary the thickness T of the skin graft 7.

Figure 2 illustrates a testing plate 10 in accordance with an embodiment of the invention. The testing plate 10 is made from a rectangular shaped block of material having at least one characteristic emulating skin. In accordance with this embodiment, the material of the testing plate 10 has an opacity or translucency similar to that of human skin. Accordingly, a very thin test graft from the testing plate 10 will appear almost translucent. Additionally, in accordance with this preferred embodiment, the material of the testing plate 10 also has a flexibility emulating skin. It will be appreciated by those skilled in the art that a very thin skin graft readily folds or crinkles. In contrast, a thicker graft crinkles less readily and when it does, the folds or crinkles are coarser. The material of the testing plate 10 should preferably be made of a substance that is similar in flexibility to human dermis so that it crinkles in a similar way to skin when cut to a similar thickness. As will be appreciated from the following description, the material of the testing plate 10 is intended to act as an imitation of the patient's skin.

Although the dimensions of the testing plate 10 may vary, it is envisaged that it would be desirable for the testing plate 10 to be approximately 10cm wide, 20cm long and 0.5cm thick.

The illustrated testing plate 10 has an upper surface 10A that is substantially rectangular. However, it will be appreciated that a testing plate in accordance with an embodiment of the invention may adopt other shapes. For example, the testing plate could be shaped as an oval, square etc.

In preparation for taking a SPSG from a donor site using a particular dermatome 5, the surgeon uses that dermatome 5 to take a test graft from the upper face 10A of the testing plate 10. In order to take such a test graft, the surgeon applies the dermatome 5 to the upper face 10A of the testing plate 10 as if the upper face 10A was the patient's actual donor site.

Figure 2 illustrates the testing plate 10 with a first test graft 12 still partially connected to the testing plate 10. It will of course be appreciated that the surgeon can and may use the dermatome 5 or other cutting instrument to completely remove the test graft from the testing plate 10.

The surgeon then examines the first test graft 12 to ensure that it is of the required thickness. This examination and assessment is one typically done "by eye" and by "feel". For example, he may examine the test graft for holes, check its flexibility and examine its translucency. The surgeon may, optionally and additionally, mesh the test graft to satisfy himself/herself that the resultant meshed STSG will be satisfactory for the patient's needs. If the surgeon is satisfied that the test graft meets his requirements, then the surgeon can proceed, using that dermatome 5 without any adjustment thereto, to take the required skin graft from the donor site. When taking the skin graft from the donor site the surgeon must be careful to apply the same pressure and angle as he did when taking the test graft from the testing plate 10.

If the surgeon determines that the first test graft 12 is not as required, he adjusts the blade of the dermatome 5 so that either a thinner of thicker graft can be taken. Alternatively, the surgeon may elect to apply more or less pressure

(or angle) on the dermatome 5 when taking the graft. The surgeon then performs a second test graft 14 on the testing plate 10. Such a second test graft 14 is depicted in Figure 3. This process is reiterated by the surgeon until he/she is satisfied that the test graft is of the desired thickness.

It will be appreciated that the testing plate 10 should be sterile so that the sterilised dermatome 5 used to take the test graft(s) can then be used on the actual patient without risk of contamination. It is preferable that once the correct blade setting of the dermatome 5 has been established using the testing plate 10, that the dermatome 5 promptly be used to take the actual STSG from the patient. This reduces the likelihood of any inadvertent adjustment of the dermatome 5 which may result in a STSG of the incorrect thickness being taken from the patient's donor site.

It will also be appreciated that the material of the testing plate 10 should ideally have characteristics closely emulating the skin of the actual patient. This enables the surgeon to assess the test graft on the basis that when he subsequently takes the skin graft from the donor site, that skin graft will have the same characteristics (for example, thickness, flexibility, translucency) as the test graft. It will also be appreciated by those skilled in the art that the desired thickness of the skin graft may vary depending on the characteristic of the skin of the donor site and/or the nature of the repair being attempted with the skin graft.

Testing plates with material of varying characteristics would preferably be available for use by the surgeon. Accordingly, the surgeon would, as part of their surgical preparation, select the testing plate that most closely emulates the particular patient's skin type. For example, the material of the testing plates could vary to reflect differences between the skin characteristics of young patients, very old patients and patient's taking medications that affect the dermis. This will optimise the likelihood of the STSG being of the same thickness as the test graft taken from the testing plate 10. Additionally, the material of the testing plate 10 should preferably be such as to not have any negative affects on a patient in the event that such material inadvertently comes into contact with the patient.

It is envisaged that the material of the testing plate 10 would have a colour similar to human skin. As skin colour varies considerably between racial groups, it may not be practical to have testing plates that match the exact skin colour of every patient. However, a variety of different colour testing plates 10 could be available for selection by the surgeon.

In human skin, the layer that gives the characteristic pigmentation distinguishing different racial groups is very superficial (i.e. very close to the surface of the skin). Therefore, when a STSG is taken, this pigmented layer is entirely removed. This is particularly noticeable when taking STSGs from patients with very dark skin, as even a thin STSG will leave a white (or off-white) donor site. Thus, a STSG test plate that includes a very shallow layer of pigment on or near its surface will be a more realistic imitation of a real STSG taken from such a patient. It follows that the surgeon will find it easier to assess the suitability of a test graft from such a test plate.

It is envisaged that the material of the testing plate 10 may be a plastics material or rubber compound having at least one characteristic that emulates that of the patient's skin. Alternatively, the material of the testing plate may be an artificial skin.

It is envisaged that each testing plate 10 would only be used for a single patient.

Example A An example of a material suitable for making a testing plate in accordance with an embodiment of the invention is as follows:-

The material should, as far as practical, resemble skin in the way it behaves when cut like a conventional STSG. In particular, when cut with a dermatome, the resulting test graft from the testing plate should be of a very similar thickness to a graft taken from real skin using the same dermatome adjusted to the same setting. Such a test graft preferably has a similar translucency to a graft of real skin.

A suitable material is a silicone rubber with a Shore A hardness of about 10 and a tensile strength of about 475 psi. Furthermore, the translucency of such a silicone rubber can be adjusted with pigment (preferably resembling the colour of normal human skin), so that it has the following translucency characteristics when cut in thin layers:

Text written in standard black-on-white Times New Roman print in size 12-point, is easily legible through a layer 0.35 mm (0.014 inches) thick.

Text written in standard black-on-white Times New Roman print in size 12- point, is readable with difficulty through a layer 0.54 mm (0.021 inches) thick.

Text written in standard black-on-white Times New Roman print in size 12-point, is visible, but not legible, through a layer 0.67 mm (0.0265 inches) thick.

Text written in standard black-on-white Times New Roman print in size 12-point, is barely visible, but not legible, through a layer 0.83 mm (0.033 inches) thick.

Text written in standard black-on-white Times New Roman print in size 12-point, is not visible through a layer 1.17 mm (0.046 inches) thick. A testing plate made in accordance with an embodiment of the invention is made from a block of material having at least one characteristic emulating skin. However, it is envisaged that the testing plate may only include a surface or upper face of material that has at least one characteristic emulating skin. In accordance with such an embodiment, the surface may form part of a layer of material mounted on or attached to a body. The body may be made of any suitable material that is capable of supporting the layer. Alternatively, the body may have two or more layers of material mounted or attached thereon. Those layers may have the same or different characteristics. It may be preferable for the layers to have different characteristics so that the surgeon can take the test graft from the layer on the testing plate that most closely emulates the characteristics of the particular patient's skin. The material of the block is most preferably such that when it is cut, that the thickness of the test graft is substantially similar to the thickness of a graft taken from a donor site using that dermatome at the same adjustment.

Although the embodiments of the invention have been described in relation to a graft made on a human patient, the invention is not so restricted.

The embodiments have been described by way of example only and modifications within the spirit and scope of the invention are envisaged.

Claims

1. A method of taking a STSG including the steps of: a) selecting a dermatome for taking the STSG from a donor site; b) taking a test graft from a STSG testing plate; c) examining the test graft so as to determine whether it has a desired thickness; and d) if the test graft is of the desired thickness, taking the STSG from the donor site using the dermatome without any adjustment thereto; or e) if the test graft is not of the desired thickness, adjusting the dermatome and taking a further test graft.

2. A method according to claim 1 wherein the steps of examining the test graft, adjusting the dermatome and taking a further test graft are repeated until the test graft is of the desired thickness.

3. A method according to claim 1 or claim 2 wherein the step of examining the test graft includes making a visual examination of the thickness of the test graft.

4. A method according to any one of claims 1 to 3 wherein the step of examining the test graft includes meshing the test graft and then conducting a visual examination of the meshed test graft.

5. A method according to any one of the preceding claims including an additional step prior to step b) of selecting a STSG testing plate having at least one characteristic similar to the characteristics of the patient's skin.

6. A STSG testing plate including at least one surface sized so that a test graft can be taken from the surface by a dermatome and wherein said at least one surface of the plate is made from a material having at least one characteristic emulating skin.

7. A STSG testing plate according to claim 6 wherein the material of the surface of the testing plate is such that the thickness of the test graft taken from the testing plate is substantially similar to the thickness of a graft that would be taken from a patient using that dermatome at the same adjustment.

8. A STSG testing plate including at least one surface sized so that a test graft can be taken from the surface by a dermatome and wherein said at least one surface of the plate is made from a material having at least one characteristic emulating human skin and is such that the thickness of the test graft taken from the testing plate is substantially similar to the thickness of a graft that would be taken from a human patient using that dermatome at the same adjustment.

9. A STSG testing plate according to any one of claims 6 to 9 wherein the material is a silicone rubber.

10. A STSG testing plate according to any one of claims 6 to 9 wherein the material has a Shore A hardness of about 10 and a tensile strength of about 475 psi.

11. A STSG testing plate according to any one of claims 6 to 8 wherein the characteristic of the material emulating skin is translucency.

12. A STSG testing plate according to claim 11 wherein the translucency of the material is such that text written in standard black-on-white Times New

Roman print in size 12-point: a) is easily legible through a layer 0.35 mm (0.014 inches) thick ;

b) is readable with difficulty through a layer 0.54 mm (0.021 inches) thick;

c) is visible, but not legible, through a layer 0.67 mm (0.0265 inches) thick; d) is barely visible, but not legible, through a layer 0.83 mm (0.033 inches) thick; and

e) is not visible through a layer 1.17 mm (0.046 inches) thick.

13. A STSG testing plate according to any one of the claims 6 to 8 wherein the characteristic of the material emulating skin is flexibility.

14. A STSG testing plate according to any one of claims 6 to 13 wherein the material of the testing plate is sterilised.

15. A STSG testing plate according to any one of claims 6 to 14 wherein the material includes a pigmented layer.

16. A STSG testing plate according to any one of claims 6 to 15 including a block of material having at least one characteristic emulating skin and said at least one surface is a top surface of said block of material.

17. A STSG testing plate according to claim 16 wherein the block of material is supported on a supporting layer.

18. A STSG testing plate according to claim 16 wherein more than one block of material is supported on said supporting layer and the characteristics of the respective blocks of material are different.

19. A STSG testing plate according to any one of claims 6 to 18 for use with the method of any one of claims 1 to 5.

20. A STSG testing plate substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.

21. A STSG testing plate substantially as hereinbefore described with reference to the Example.

22. A method substantially as hereinbefore described with reference to the accompanying drawings.