A systematic review of the various surgical techniques used for correction of post-burn contracture of joints.


Abstract
Major skin burns can have a large impact on a patient's life. They do not only have psychological implications, but can also give functional problems. Skin contracture in joints is a common problem of burn injury, because they limit the range of motion in a joint. This reduces the quality of life for the patient. There are different surgical techniques to improve the range of motion. Z-plasty is one of the most used surgical techniques for burn contracture. This technique is often described as a quite simple, incredible effective and very versatile. V-Y plasty also uses the laxity of skin left near the contracture. Future techniques for releasing burn contracture will also be discussed in this review. Techniques like tissue expanding, artificial skin grafting and Matriderm(r). These techniques can be very important in improving surgical techniques mentioned before or releasing burn contracture by itself. 


Introduction 

Major skin burn can have a large impact on a patient's life. They do not only have psychological implications, but can also give functional problems. These functional problems are caused by burn contracture. Burn contracture in major burns limits range of motion in a joint and hinders the patient in his daily activities. 
A scar is a result of the repair mechanism after injury. The healing process starts with the formation of a clot that is created to reduce the damage. This process results in a temporarily matrix, also known as the provisional matrix. In the first 24 to 72 hours of repair the injured body tissue expresses fibroblasts and vascular endothelial cells in the provisional matrix to create granulation tissue. The amount of granulation tissue that is formed depends on the size of the tissue deficit. Contraction of the wound helps to close the gap between its dermal edges and reduces the wound surface area. Myofibroblasts contribute to the contraction. The size of the skin burns correlates with the limited range of motion.1 
Management of these contractures by surgical reconstruction can be very important in functional restoration. There are many ways to improve the range of motion of burn contracture. In this systematic review I will discuss the benefits, difficulties and complications of two major surgical techniques for correcting burn contractures: Z-plasty and V-Y plasty. Finally I will discuss future techniques. 
Z-plasty is one of the most used surgical techniques for burn contractures. This technique is often described as a quite simple, incredible effective and very versatile. 2 The reason why it is so versatile is the way it can be repeated and modified. Commonly used modifications are the four-flap, five-flap, six-flap and double opposing Z-plasties.
V-Y plasty also uses the laxity of skin left near the contracture. The margin of the incision is like a Y with on top of that a V. When the incisions are made, the tip of the V will be pushed in the stem of the Y. In this way you will create the gain length in the contracture as in Z-plasty. 4
Future techniques for releasing burn contracture will also be discussed in this review. Techniques like tissue expanding, artificial skin grafting and matri-derm. These techniques can be very important in improving surgical techniques mentioned before or releasing burn contracture by itself. 5


Methods

Case studies that describe the surgical methods to release contraction of skin burns were included.  Studies for review were found through computerized search in PubMed. Patients of all ages who have had a burn injury and needed a surgical intervention because of contracture of only the the joints, for example the ankle, knee, elbow, hands or neck, were included. Excluded were people who needed a surgical intervention for contraction of the skin without a burn injury. The following surgical techniques were described: the Z-plasty, V-Y plasty and future techniques. PubMed search terms included the next words: burn scar, reconstruction, Z-plasty, V-Y plasty, Propellor flap, contractures, joints, motion, comparison, comparing, release and extremities. 

Results

Flap techniques compared to skin grafting

Flap techniques are very desirable for reconstructing burn contracture. Unlike skin grafts, flap surgery will use healthy skin near the contracture. Characteristics of the skin, colour and thickness are more the same using flap technique than if skin graft is used.  Skin grafts rely on revascularisation from the wound bed. Factors like shearing forces, infection, seromas, hematomas and poor contact with the skin graft can prevent revascularisation. Grafting will fail if there is no revascularisation.
Skin grafts need to be acquired from another place of the patient his body (autologous) or from a donor (allogeneic). When a graft is gained, the donor site needs to be closed or covered.  Sometimes ultra thin split-thickness grafts are used to cover donor sites. 8 Split-thickness grafts consist of epidermis and a part of the dermis, therefore the donor site can be reepithelialised. When the entire dermis is used for the graft it is called full-thickness skin graft. The amount of dermis used for the graft determines the survival chance and the contracture risk of the graft.  Split-thickness grafts result more often in contractures then full-thickness grafts, but full-thickness grafts requires a better vascular wound bed for survival. 7
Because skin grafting gives an extra scar elsewhere on the body, aesthetics results must be mentioned in the patient his interest. At the same time grafts cannot be too large because closure of the donor site will be too difficult. If the laxity degree or health of the skin around large contractures is too poor skin graft is sometimes necessary. 

Z-plasty: a transposition flap technique

The primary function of a Z-plasty is to lengthen a scar in a specific direction. When the Z is designed on the skin (Fig. 1) before surgery, the diagonal limb is the direction of lengthening (Fig. 1). The diagonal limb, also called common or central limb, is positioned in the direction of the scar or contracture.  The reason why Z-plasty is called a transposition flap technique is very clear. The triangular flaps created in flap plasty will be transposed from each other in the direction of the scar. This creates direct lengthening in the direction of the drawn common limb and it needs laxity of the surrounding skin along this limb (Fig. 2).  Z-plasty also relocates the scar into a new more desirable or less conspicuous position 8. That's why Z-plasty is also used for realignment of tissue or shifting topographical structures. The classic Z-plasty is designed with 60-degree angles and equal limbs. In general this gives the most proper length gain, with the least difficulty.
 In theory more length is gained with large angles. A 30-degree angle gives 25% length gain, a 60-degree angle 75% and a 90-degree angle 120%. 9 Unfortunately this theory is no reality because skin tension varies within each region of the body. 10 Depending on the size of the triangular flaps and the region the flaps are made skin tension will differ. Leading to unequal amounts of tension for closure and distortion of flaps. The length gained in the contracture will differ between each patient. In reality the length gain is 55 to 84 percent of the mathematical predicted length gain. The same research showed that angle enlargement leads to more tension. 11     A 90-degree Z-plasty gives ten times more tension then a 30-degree Z-plasty. 

Figure 1 - Z-plasty

 
  Figure 2 - Z-plasty transposed

In Z-plasty it is important to consider increasing of the angle wisely. Examination of quality and quantity of the skin before surgery is on that account very important. Nevertheless, as the angle increases the vascular safety also increases. An angle less then 60 degrees creates a triangular flap with a small base compared to its length, leading to precarious blood supply. If a Z-plasty is constructed with an angle of less then 45 degrees, vascularisation of the flap is tenuous. Poor blood supply leads to tip necrosis of the flap. Careful surgery is desirable and elevation of skin in the tip region of the flap is not desirable. 
When Z-plasty is used and the flaps are transposed tension, space and forces will create dog-ears (fig. 3).  These dog-ears are cosmetically not desirable and creates some elevation of the skin especially on flat surface. A solution to this problem is excision of these dog-ears. This modification is called the planimetric Z-plasty. 12

If Z-plasty is used, the following things have to be taken into account:
- Skin tension is different within each region of the body; theoretical length gain is not actual length gain.
- Flap and angle enlargement give more length gain in theory.
Increasing the angle increases the tension. Closure will be more difficult and flap distortion is more likely. Large flaps are more difficult to transpose and gives the same difficulties as angle enlargement.
- Small flaps and angles give less safety for blood supply. 
- Small z-plasties give insufficient lengthening.
- Z-plasty has a three-dimensional effect on tissue and creates dog-ears or elevation of skin. Planimetric Z-plasty may be a solution.
- Examination of quality and quantity of the skin is very important before choosing a Z-plasty design. 
There are many types of Z-plasty: the multiple Z-plasty in serie, the double opposing Z-plasty, three flap Z-plasty, four, five, six, seven, nine plasty and many more.2 Planning and examining are important on choosing a Z-plasty. Multiple Z-plasty in serie might have the advantage of spreading the tension along the contracture. In theory one single classic Z-plasty and two series of Z-plasty half the size will gain the same length but in reality another outcome is seen. A serie of Z-plasties gains less lengthening then one single Z-plasty of the same length. However, choosing a serie z-plasties can have its advantage if laxity of skin is poor around the contracture. Multiple Z-plasty in serie needs less laxity skin perpendicular of the common designed limb. 

        
Figure 3 - Dog-ear


V-Y plasty an advancement flap technique.

In V-Y plasty skin is recruited from the sides of the contracture. Before surgery a Y is designed perpendicular to the contracture. If the Y is designed the incision can be made along these designed lines creating a V-flap and a straight incision upon the tip of the V-flap. The incision in the skin and the fascia has to be made separately to avoid retraction of the flap. Incision deep through the fascia makes sliding of the flaps more easy. 13 Next the tip of the V-flap will be moved to the end of the former Y's pedicle (the straight incision upon the V-flap and basic limb of the designed Y). Note that the V-flap and this pedicle will form a Y together. In V-Y plasty a lot of skin is recruited along the sides of the contracture, therefore laxity of skin is very important. Less laxity leads to more tension, less contracture release and difficult wound closure. If a large contracture needs to be released these Y's can be designed in series. The Y's pedicle will change from side to side every time an extra Y is designed. This is called the multiple V-Y plasty. 
The mathematical theory of the V-Y plasty is as follows: In V-Y plasty the angles of the Y doesn't play any role in the amount of scar lengthening. So if multiple V-Y plasties are used, angle between Y's can be different. Every Y can be customized for the available laxity of skin. The size of advancement the flap undergoes is the determinant. So limb length is important. Length gain in V-Y plasty is 100%. 
Increase of advancement leads to increase of tension, so in reality examination of the patient is very important. In V-Y plasty blood supply is more protected and tip perfusion is safer compared to Z-plasty regarding.14 An advantage in V-Y plasty is that the patient is able to commence mobilization directly after the operation.


Figure 4 - V-Y plasty

Artificial skin- Matriderm(r)

As mentioned before the amount of dermis used for the graft determines the survival chance. A full-thickness graft requires a good vascular wound bed for survival and makes management of full-thickness burns difficult. Therefore, improvement in this technique is necessary.
Skin grafting gives an extra scar elsewhere on the body, aesthetics results must be mentioned in the patient his interest. At the same time grafts cannot be too large because closure of the donor site will be too difficult. If the laxity degree or health of the skin around large contractures is too poor skin graft is sometimes necessary.
The survival rate of people with massive burn wounds has increased. These large wounds are difficult to close with standard autografting techniques, which are the golden standard. 16 Poor skin quality and scar contraction are disadvantages of autologous split skin grafting. Joints are strained regions that require a lot of elasticity, pliability and stability for a good functionality is important after reconstruction of burn wounds. Dermal substitutes can be an appropriate way to minimize scar contraction and to optimize the quality of the grafted area. 17

This substitute covers the skin after removing the destroyed tissue by a severe burn and leaves it here for two or four weeks. The own cells of the patient


Tissue expander 

Sometimes skin is poor of laxity and actually needs to be stretched. When more skin is needed the tissue expander can offer a solution. The tissue expander is an inflatable balloon under the skin. Once or possibly twice a week the expander is injected with saline, approximately 10% of the expander. 8
When skin is stretched beyond his physiological limit, cell growth and new cell formation are created.
The excessive skin that is obtained can be used for reconstruction of burn wounds.



Figure 6 - Tissue expander 


Conclusions

It is difficult to compare the different surgical techniques. Not every burn contracture is the same. The shape, severity and location vary by person. This makes comparison very difficult.
In order to be able to compare this, more data is needed. To achieve this, all the data must be well documented and classified.

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