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Tissue expansion offers the advantages of supplying tissue similar in texture and colour to the defect to be covered. However, to maximise the result, the expanded tissue must be used in the most efficient way possible. Rectangular expanders have been shown to yield the most available tissue. A technique to maximise the use of expanded tissue with a rectangular tissue expander is described. The technique is one of an advancement flap that maximises the use of expanded tissue in both a vertical and horizontal direction by adding backcuts to the sides (and interposing triangles of local tissue into these backcuts) as well as the base of the flap. This technique has been successfully applied to 11 children (17 expanders) undergoing tissue expansion during a 19 month period.
Additionally, there is minimal donor site morbidity.
However, in order to achieve the best possible result, the expanded flap must be mobilised maximally. Inability to perform this may impair the final result.
A technique is described to use maximally the rectangular expanded flap. It is based on the concept that a fully expanded tissue expander creates a three-dimensional structure, which has to be converted to a two-dimensional sheet for skin resurfacing. This technique has been used in 11 children (17 expanders) over a 19-month period.
1. Technique
Only rectangular expanders are used, and these are inserted adjacent to the defect to be resurfaced. In all cases the incision is made adjacent to the skin defect which is to be resurfaced with tissue expanded skin.
The area to be resurfaced and adjacent tissue expanded flap are cleaned and prepped in the usual manner. At this stage, it is prudent to look for triangles of local tissue adjacent to the area which is to be resurfaced with the tissue expanded skin flap, which may be used as triangles of tissue to interpose into the defects created as the tissue expanded flap advances (see later). In Fig. 1(A) and (B), for example, two triangles (marked in white) on the left and one on the right have been identified.
Fig. 1Preop view. Six-year-old girl with anterior scalp burn alopecia. The patchy alopecia anterior to the tissue expander was discarded. A 400 ml rectangular tissue expander had been inserted and inflated to 800 ml. (A) Bird's eye view. Two triangles of adjacent local tissue were identified (marked with white arrows) on the left side, and one on the right side of the defect as ‘potential’ sources of adjacent tissue to be advanced into the defects created by backcutting the tissue expanded flap. (B) Left lateral view. Lateral view showing two triangles of adjacent local tissue which will be advanced into the backcuts which were used to allow the tissue expanded flap to flatten and advance.
Step (i). Three of the four sides (Diagram 1) of the rectangular tissue expanded flap are incised at the base of the expander. The fourth side is the pedicle.
Diagram 1Rectangular (three-dimensional) box. The thickened black line diagrammatically indicates the site of the initial incision at the base of the box (flap) (i.e. along lines A to X to Y to B). If this is performed on a cardboard box it would remain a three-dimensional structure. It is only when the side walls of the box are cut and flipped outwards that the front wall can move forward and flattening can occur.
Note. A capsulectomy is not performed, but commonly at the perimeter (edge) of the rectangular flap just created, a ‘band’ of thickened capsule is present. This capsule band only is divided (‘scored’) in a radial fashion to release the constriction it has caused, and to enhance ‘spread’ of the flap and increase its surface area. This is not always required, but is commonly necessary in the scalp, as the periphery of the rectangular flaps develops thickened edges (Fig. 5(A)).
Skin hooks are placed in the advancing (anterior) edge of the flap and the flap advanced as far as possible. Relatively little flap advancement is achieved and a large amount of excess tissue is evident in the vault (middle) of the expanded flap. In fact, on the scalp, the expanded flap at this stage now resembles a plastic ball which has been cut in the middle.
Step (ii). To achieve further (i.e. anterior or forward) flap advancement, full thickness backcuts are required. These are made in the lateral walls (sidewalls) of the flap and enable a sizeable forward/anterior advancement of the flap. In addition, some horizontal (lateral) flap advancement also accrues from this manoeuvre.
The sites of these backcuts are determined by the configuration of local tissues, as triangles of local tissue adjacent to the area to be resurfaced are advanced into the triangular defects created by the backcuts (Diagram 3, Diagram 4, Fig. 1, Fig. 2, Fig. 4, Fig. 5, Fig. 7) . This is an important component of this technique.
Fig. 2Intraop view: patient 1. Three backcuts were made on the flap—two on the left and one on the right (these are shown as white, off/spickled white and black arrows). Three triangles of adjacent local tissue had been identified (again marked with arrows of complimentary colours to those on the flap) which would be advanced into these backcuts. The flap after backcuts now forms a two-dimensional (flat) ‘sheet’. The defect covered measured 14 cm×12 cm.
The backcut must not exceed about one quarter of the width of the flap. One or two backcuts are usually performed per side of the flap: the configuration of the local tissue (available triangles of tissue which is available to be advanced into the defects so created) determines the number and the sites of the backcuts (Diagram 3, Diagram 4, Fig. 1, Fig. 2, Fig. 5, Fig. 6).
Step (iii). Further flap advancement can be achieved by making backcuts at the base of the flap (pedicle). These should not exceed a quarter of the base of the flap. The length of the backcuts can be made asymmetrically which enables a limited amount of flap rotation to occur, as may be necessary when the defect is trapezoid in shape for example, where one edge of the flap needs to advance more than the other edge i.e. this backcut is dictated by the configuration of the defect. However, it is emphasised that the major movement of the flap is that of direct advancement.
1.1 Clinical cases
This technique has been used in the 11 children (8 boys and 3 girls with age range 5–17 years) who underwent tissue expansion (17 expanders) between 1 January 2001 and 31 July 2002. The sites include scalp (9 expanders), back (2 expanders), thigh (1 expander) and neck (5 expanders). There were performed for burn reconstruction (9) and excision of a giant hairy nevus (2). One child who had 3 expanders inserted for a giant hairy nevus had 3 expanders removed and 3 flaps advanced using the described technique, at the same sitting. Four children who each had 2 expanders inserted also had both expanders removed and flaps advanced. The other children each had only one expander inserted.
1.2 Results
There have been no instances of flap loss. One scalp flap developed some epidermolysis that healed with dressings.
2. Discussion
Tissue expansion has been described as an effective manoeuvre for reconstruction after trauma, burns and in the management of giant hairy nevi.
Except when (unplanned) major complications occur, the only long term sequalae of tissue expanders should be the scars.
It is the policy of this unit always to use rectangular expanders (except in breast reconstruction where tissue is expanded, but not transposed). Rectangular expanders have been shown to yield the most available tissue compared to round or crescent shaped expanders.
In this study, the expanders are always placed subcutaneously, except in the scalp where the subgaleal plane is used.
Tissue expansion creates a three-dimensional structure. On most occasions, this tissue must be converted to a flat sheet or two-dimensional flap. Hence the ‘excess’ tissue present in the three dimensions must be maximally converted to a two-dimensional flap, so that all the additional tissue available is utilised rather than ‘wasted’.
A simple analogy is to compare the tissue expanded tissue to a (three-dimensional) cardboard rectangular box, which has to be made completely flat (Diagram 1, Diagram 2, Diagram 3, Diagram 4) . The first manoeuvre is to divide three sides at the base of the rectangular cardboard box (Diagram 1). This allows access (to the inside of the box) at its base, but the box remains a three-dimensional structure. It is only when the side (walls) of the box are cut and then flipped outwards that the box could be converted into a flat structure (Diagram 2, Diagram 3, Diagram 4). As the box flattens, the (anterior) front wall advances forward. When the box is flat, it is no longer rectangular in shape, but is now shaped a bit like an aeroplane (Fig. 4). To convert it to a rectangle, the four triangles adjacent to the flattened box (the black arrows in Fig. 4) need to be filled. In the clinical situation, this is done by advancing triangles of adjacent tissue into these defects. In this way, the expanded tissue is used maximally and none is discarded. These two concepts are the basis of this article.
Diagram 2For the box to flatten, the two side walls of the box need to be flipped/rotated outward. This is achieved by making two cuts per side up the whole length of each side wall. In the clinical situation this represents a backcut.
Diagram 3Shows the box starting to flatten, as the two side walls flip outwards (a1 and x1, and b2 and y2) and the anterior wall (x2 and y1) advances forward.
Diagram 4Rectangular box which has been converted into a two-dimensional flat structure. When completely flat, the box has the configuration of an aeroplane. The areas where triangles of local tissue are required can be seen (four black arrows). In the clinical situation a2 to b1 represents the pedicle of the expanded flap.
Hence, the first step in maximising the use of tissue expanded tissue is to divide the base of the flap on three sides (anterior and each lateral side). This allows access to the tissue expander, which is removed (step i). Once the expander is removed, little flap advancement is obtained, and that which is possible occurs due to tissue elasticity, and the expanded tissue remains a ‘three-dimensional structure’. As the aim of the procedure is usually advancing the flap as much as possible, the base/pedicle of the flap can also be backcut to allow a little more advancement (step iii). This should not be more than about 25% of the length of the base of the flap so as not to impair the blood supply. However, it has been shown that tissue expanded flaps are very robust and survived by 117% more than control flaps in an experimental study.
To allow flap advancement really to occur, ‘backcuts’ (analogous to cutting the side walls of the box and flipping out these two side walls outwards) are required (step ii). However, before this is done, it is first necessary to seek triangles of tissue which will be advanced into the triangular spaces created by these incisions on the tissue expanded flap; this is a most important step in allowing the flap to advance (see Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, in which the triangles of adjacent tissue which is to be advanced into the defects created by making backcuts on the tissue expanded flap are identified with arrows). These incisions (backcuts) can be performed anywhere along the side walls of the flap, but are designed where local tissue is available so that the defect created by the backcuts can be filled (Diagram 3, Diagram 4 and Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8). Expanded flaps are very robust from a vascular viewpoint. However, in order not to compromise flap vascularity, the incisions should not exceed 1/4 of the width of the flap. Unlike a rigid box, tissue elasticity allows the flap to flatten without creating squares of tissue representing the side walls of the box. Furthermore, unlike a cardboard box, which is rigid, and therefore requires two backcuts per side, skin elasticity allows one or two (or more) backcuts per side. Because the scalp is more rigid than other tissues, this technique has been particularly effective for scalp defects (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8).
Fig. 3Patient 1 postop at 2 weeks. Postop result at 2 weeks with staples still in situ to show the backcuts on the tissue expanded flap and triangles of local tissue to be advanced. (A) Left lateral view. The two triangles of local tissue, which was advanced into the triangular defects created by backcutting, the flap (which permitted the tissue expanded flap to advance and flatten) is shown by white arrows. (B) Right lateral view. Only one backcut was used on this side of the tissue expanded flap (Fig. 2) and only one triangle of local tissue was needed to be advanced into this backcut (shown by white arrow). (C) Bird's eye view again highlighting the two triangles of local tissue needed to fill the two backcuts on the tissue expanded flap.
Fig. 4Preop right-sided view: patient 2. 12-year old boy with burn alopecia. Again the patchy alopecia anterior to the tissue expander was discarded. A 160 ml rectangular expander was inflated to 450 ml. A triangle of adjacent local tissue has been identified (white arrow).
Fig. 5Intraop view: patient 2. (A) Bird's eye view. In this patient, two backcuts were used on the right side and one was performed on the left side. The one backcut on the flap is marked by a white arrow and the triangle of local tissue which will be advanced into this backcut (see also (B)) is also marked with a white arrow. The five black arrows indicate radial ‘scoring’ at the periphery of the flap. Note flap after scoring and backcuts forms a flat sheet which measured 14 cm×8 cm. (B) Lateral view. Lateral view showing triangle of local tissue (white arrow and also dissecting scissors) which will be advanced into the backcut. See Fig. 6.
Fig. 6Patient 2, postop right-sided view. Result at 2 weeks with staples in situ to show flap backcut and triangle of local tissue advanced into the backcut.
Fig. 7Preop view: patient number 3. Posterior scalp burn alopecia. The two triangles of local tissue which will be advanced into the backcuts after the tissue expanded flap has been identified (white arrows).
Fig. 8Postop view, patient number 3. Postop result at 2 weeks with staples in situ. The sites of the backcuts on the flap as well as the triangles of local tissue advanced into the backcuts can be seen.
It is contended that flap advancement is the most effective method of using expanded skin from rectangular expanders, especially when closing rectangular or square defects. Another advantage of rectangular expanders is that the base (site of the pedicle) of the flap is well defined. Rotation flaps are better suited to triangular defects but require very large expanders to achieve this (which is seldom possible in the clinical situation), so that the outer circumference of the expanded flap can be five times the length of the defect, as is recommended.
In my experience this has seldom been possible. This technique requires that the expander size be similar in size or (slightly larger) than that of the defect.
A further advantage of dividing the flap along its length and interposing triangles of tissue, is that this effectively breaks up a long straight scar and limits scar contraction. Not only does this improve the scar appearance, but it may also play a role in limiting flap retraction. Also, no tissue is discarded: this compares to other techniques where the lateral wings of the expanded tissue is discarded.
Another advantage of an advancement flap is that the amount of advancement expected to be obtained can be roughly calculated. This is done by measuring the distance beginning at the base of the flap (in cm) passing over the height/top of the expander to the base at the other side, and subtracting this distance from the known width of the base of the tissue expander.
This simple technique has proved to be effective in the use of flaps after rectangular tissue expander removal. It is similar to the technique described by Zide et al.
As the technique is really that of a flap advancement, it is preferably suited to rectangular, round and square defects rather than triangular defects.
References
Manders E.K.
Reconstruction using soft tissue expansion.
in: Cohen M. Mastery of plastic and reconstructive surgery. Little Brown,
Boston1994: 201-215
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