ETE – A Device for External Tissue Extensions

Author: M.D. Ph.D. Gunnar Blomqvist, Department of Plastic Surgery,
Sahlgrenska Sjukhuset Göteborg, Sweden

Tissue expansion is a well established method in Plastic and Reconstructive Surgery. It was first described by Neuman 1957 (Ref. no 1) but did not become a routine procedure until Radovan 1976 (Ref. no 2) described a similar technique using a subcutaneous tissue expander made of silicone.

Indications and contraindications have since been established. Morbidity has gradually been reduced, but is still relatively high.

The technique is costly as it mostly has to be performed under general anesthetics and the expansion has to be done at the clinic once or twice a week. On average the final surgery can be done after 80 - 90 days. The expanders do also intervene both cosmetically and functionally with the possibility to live a normal life during the treatment.

We have developed an alternative method – utilizing the extension properties of a tissue - which is a cost effective, fast and versatile way will be able to replace or complement other expanders.

External Tissue Extension

A few years ago we started by using simple prototypes made of two holding bars with several straps placed between them. Each strap had a stopper at one end and a one-way locking device at the other end. After local infiltration anesthesia, each strap was placed subcutaneously under the skin defect through small incisions on each side of the defect. The straps were placed parallel to each other. On each side of the skin defect the holding bars were attached to the straps.

After tension was applied, the patient was instructed to push the one-way locker slightly twice a day to ensure optimal stretching tissue. After one to two weeks the stretching was completed, the whole device was removed, the defect excised, and the wound primarily sutured.

The indications were the same as for tissue expanders, e.g. scars, naevi and previous skin grafts.
These initial studies gave encouraging results. The average treatment time was eight days and the complication rate was 8% (Ref. no 4) which is far less than what we see with ordinary tissue expanders (Ref. no 4).

However, the first primitive prototypes had some drawbacks we wanted to eliminate. We wanted, for example, to control the tension applied. The one-way locking system in the prototypes did not allow us to loosen the tension and could therefore lead to both local irritation and rupture of skin bridges. We also wanted to facilitate the application by having a more flexible solution, allowing the device to follow the contour of the skin defect.

ETE Blomqvist

The device now consists of a needle and two friction stoppers mounted on a silicone string. The friction stoppers will allow tension not exceeding 3.5N, thus minimizing the risk of overstretching, which may lead to rupture of skin bridges. When connected the stoppers will form ball-to-socket joints allowing the device to follow the contours of skin defects.

Application

After preparation of the surgical site according to clinical practice, we mark the places for the application of the ETE units on both sides of the surgical site - 18 mm apart and approx. 5 mm from the edge of the site.

Each unit is applied by piercing the skin with the needle pulling it across the defect and piercing the skin on the opposite side of the defect. This is repeated with every ETE unit needed and the stoppers are finally connected.

Treatment and Excision

When the application is completed every string is pulled until optimal tension is achieved (=3.5N). The tension is optimized by pulling the strings generally twice a day, until sufficient tissue to cover the defect has been achieved. In most cases the patient can do this at home.

The applied ETE device does not interfere with the patient's normal life. The excision of the defect and closure of the wound can most often be done after 5-6 days. The suturing is preferably done with Z-plasty which will not only strengthen the scar but may also allow incorporation of the incision holes and thus eliminate scars from the application sites.

Why ETE?

We find the use of ETE advantageous to other established techniques as:

It can mostly be performed under local anesthetic.
It is comparably faster.
It can be used polyclinically.
The total treatment is inexpensive. Compared to the use of silicone balloons the treatment cost is less than 1/5th.
The technique is very simple.
Low complication rate.

Other Indications

The commercially available ETE has been used in our clinic for around a year for reconstructive plastic surgery. However, very soon after the introduction it was realized that the ETE could replace different suturing techniques for closure of large wounds. Thus, it has been frequently used for closure of acute fasciotomies.

In these cases the application of ETE follows the same procedure as for removal of skin defects. An essential advantage of using ETE is that it minimizes the cases where skin grafts are needed. Another very important factor to consider when closing fasciotomies is the internal tissue pressure, as too high a pressure can lead to vascular stenosis and necrosis, which ETE does not (Ref. no 5).
A few studies have been done with other techniques. In one study it has been shown that the internal tissue pressure will not exceed 20 mm Hg, which is well below damaging levels. The advantages in this indication are:

It is fast - you may close a fasciotomy in 4-5 days.
The internal tissue pressure will not exceed the critical point for tissue necrosis.
It is cost-effective.

Other studies conclude it is safe to use ETE for secondary wound closure following fasciotomy after acute compartment syndrome (Ref no 6). The following advantages were listed:

It is a simple, convenient and fast speed procedure;
Skin graft is not needed, forming a line-like scar after healing etc
The procedure us also suitable for those cases with exposure of bone or tendon

Conclusion

ETE is a versatile, safe, and cost-effective device, which in the case of reconstructive plastic surgery may replace and sometimes complement established techniques and in the case of closure of large wounds will give us a good and fast result without jeopardizing the internal tissue pressure. In both indications it is a very cost-effective alternative to established techniques.

References

Neumann CG. The expansion of an area of skin by the progressive distension of a subcutaneous balloon. Plastic Reconstructive Surgery 1957; 19:124-130, 1957.
Radovan C. Adjacent flap development using an expandable silastic implant. Presented at the Annual Meeting of the American Society of Plastic and Reconstructive Surgeons, Boston, Mass. Sept. 30, 1976.
Steenfos H, Tarnow P, Blomqvist G. Skin expansion. Long term follow up of complications and costs of care. Scandinavian Journal Plastic Reconstructive Hand Surgery; 27:179-182, 1993.
Blomqvist G, Steenfos H. A new partly external device for extension of the skin before excision of skin defects. Scandinavian Journal Plastic Reconstructive Hand Surgery; 27: 179-182, 1993.
Wiger, Per et.al.:Wound Closure By Dermatotraction After Fasciotomy For Acute Compartment Syndrome. Scandinavian Journal Plastic Reconstructive Hand Surgery 34: 315-320, 2000.
WEI, Xiaochun, ZHANG, Zhiqiang, WANG Dong et.al.: Secondary Wound Closure Following Fasciotomy With the External Tissue Extender. Chin J Orthop, January 2001, Vol. 21, No.1.

Quality System

The Production Quality Assurance System at Höjmed AB has approved the product External Tissue Extender – ETE - and holds the EC Certificate No 41314152 (Annex V of the Directive 93/42/EEC on Medical Devices). Notified Body is SEMKO (Id. No. 0413).