Inspite of newer advances split thickness skin grafts (STSG) still have an important place in many areas of plastic surgery. Though the technique of skin grafting is more or less standardized the treatment of the donor site differs greatly and has been a topic of debate. The STSG donor site usually receives little attention and is often a source of delayed healing with considerable pain and discomfort to the patient. Thus it is not uncommon for patients to complain more about the pain at the donor site than at the site of surgery. To overcome this various dressing materials have been used.

Skin is natural barrier that prevents penetration of pathogens and escape of interstitial fluid. The harvest of a split thickness skin graft causes a partial thickness injury and an outflow of blood and protein rich exudate from the wound. This exudate and coagulated blood combine to form an eschar which provides a temporary cover to the wound and underlying regenerating epithelium. However the eschar does not prevent tissue desiccation and infection at the donor site which can thus convert a partial thickness injury to a full thickness loss.¹ After the harvest of STSG, the new epidermis arises from proliferation of the remaining epithelial cell layer at the donor site periphery and reserve cells in the remaining hair follicles, sebaceous glands and sweat glands. This is the first phase in the healing of a donor site. The process of cell proliferation is followed by migration of the cells outward until the wound is reepithelialised.² Complete re-epithelialisation occurs in 10-14 days, although the rate may be affected by the local wound environment.³

Split thickness skin graft donor sites have been treated with open or closed dressings.⁵ The open technique of donor dressing has been long abandoned in favour of the closed method since occlusive dressings have shown better results with shorter healing time, superior quality of the regenerated epithelium and more patient comfort. It has also shown the added advantage of protecting the donor site from desiccation, mechanical trauma and contamination.⁵ A more traditional method is dressing the donor site with a fine mesh gauze beneath a closed absorbent dressing. The gauze may be dry but is usually impregnated with bismuth, scarlet red or petroleum jelly. Though the gauze initially provides a moist environment it gradually becomes desiccated and an eschar forms which acts as a mechanical barrier and impairs cellular migration. However these dressings can also become permeable to bacteria if wound exudate soaks through the entire thickness of the dressing. Furthermore movement of the donor site dressing produces shearing forces that may cause pain, dislodge the dressing and impair the migration of epithelial cells. At the time of removal, the dressing is adherent and liable to damage the fragile regrown epithelium.^1,6

Studies have shown that a moist environment promotes healing in a partial thickness skin loss. The use of polyurethane film, a semi permeable dressing maintains a moist environment allowing diffusion of oxygen and water vapour while providing a barrier to the passage of wound exudates. It has claimed to reduce the healing time and donor site pain. However it has proved difficult to use as wound exudate collects beneath the film and is liable to leak out.^1,6 Other experiments have used silicon gel sheets, also a semi permeable dressing with similar results.

During the last decade newer dressing materials have been developed which interact with the wound exudate to form a moist non adherent gel. Commonly used dressings are calcium alginate and bilaminate hydrocolloid membranes. They both have been reported to accelerate healing at the donor site. However the main drawback of both dressings is the time required to apply the dressing. The hydrocolloid dressing has the added disadvantage of leakage of wound exudate which requires redressing.⁶

Recent experiments have shown that biological dressings create the most physiological interface between the wound surface and the environment and permit the body’s reparative and immune system to function most efficiently. These dressings are natural, non immunogenic, non pyrogenic and hypo allergenic. Experiments have been carried out using porcine xenografts, amniotic membranes and collagen sheets. However both have shown poor results. Porcine xenografts showed a large percentage of abnormal healing due to sub epithelial incorporation and rejection and the amniotic membrane dressings showed a delayed healing.^3,4

We have used collagen sheets as a donor site dressing which comes close to being called an ideal donor site dressing. We hereby present our experience with the same.

A group of 30 patients were included in this study with 21 males and 9 females ranging from age 18 to 72 years. All patients required split thickness skin grafts of approximately 100-250 cm2 in area to provide cover for various indications. All grafts were taken from the anterior and medial aspect of the thigh. The donor site of patients was prepared for five minutes with povidone iodine scrub and draped with sterile sheets. The skin and knife blade were lubricated with sterile liquid paraffin. Split thickness skin grafts were harvested with a Humby’s knife, following which pressure was applied to the donor site with saline soaked gauze pieces to achieve haemostasis. A collagen sheet of the required dimension was selected and washed in normal saline to remove the preserving medium. It was then applied to the donor site while ensuring that all the entrapped air was removed. Oozing of blood immediately after application was seen, but the blood was easily removed by cautious pressure over the sheet. A light dressing was given over a non-adherent padding.

In the immediate post-operative period the patient was asked to assess the pain or discomfort caused by touch or pressure on the donor site. Pain being a subjective assessment was graded as none, mild, moderate or severe. In the later post operative period pain felt on walking was similarly assessed and the requirement of analgesics for donor site pain was evaluated in both cases.

The donor site dressing was inspected daily for soakage of blood and exudate. If the dressing was soaked, painful or foul smelling, it was opened to look for infection, haematomas or an allergic reaction to the collagen. In these patients a redressing was done using a framycetin impregnated paraffin gauze. In the remaining patients, the dressing was opened directly on the fourteenth day and donor site re-epithelialisation scored as 100% healed, 90-100% healed and < 90% healed. At the same time the ease of removal of dressing and associated pain at the time of removal was noted. The patients on follow up were inspected for hypertrophic scarring of the donor site area. The dressing was thus assessed based on the following criteria - healing at 14 days, infection, and donor site pain.

Fig. 1 : Sterile collagen dressing.

All 30 patients were followed upto complete healing of the donor site. In the group all patients tolerated the collagen dressing well and there was no allergic reaction. In the early postoperative period on assessment of donor site pain to touch and pressure, 2 patients in the group had no pain, 23 rated the pain as minimal while 7 patients assessed the pain as moderate and tolerable. There was no complaint of severe pain and none of the patients required additional analgesics for donor site pain. Once the patients were mobilized by the third postoperative day they were assessed again for pain while walking. In the patient group 21 patients assessed the pain as minimal, 7 assessed the pain as moderate and 2 as severe. The 2 patients who had severe pain on walking also had severe pain on touch and pressure and required additional analgesics to relieve them of the donor site pain. All other patients had no analgesic requirement for the donor site.
All donor site dressings in the study group were inspected daily. In 2 patients soakage of wound exudate was seen on the fifth and eighth post operative day respectively. These were the two patients in whom there was significant donor site pain. In both patients the donor site dressing was foul smelling and the wound was covered with purulent discharge with degradation of the collagen sheet. The infection was limited to the donor site with no evidence of cellulitis of the surrounding skin or fever. The infected sites were redressed with framycetin impregnated paraffin gauze. In both patients the wounds were redressed after forty-eight hours by which time pain had subsided.

Fig. 2 : Donor site of a patient covered with a collagen dressing.	Fig. 3 : Healed donor site.

On the fourteenth post operative day the donor site dressings were soaked in saline and easily removed with no pain in 5 patients, while 18 and 7 patients had minimal and moderate pain respectively. None of them complained of severe pain. In the group 24 patients showed 100% reepithelialisation, 4 showed between 90-100%, while the two with infected donor sites had < 90% reepithelialisation. In the group 1 patient had a haematoma beneath the collagen dressing but there was complete re-epithelialisation beneath the haematoma. On late follow up of 26 patients, 2 showed hypertrophic scarring of the donor site.

Collagen dressings used are composed of type 1 and type 3 bovine collagen which is similar to human collagen and thus prevents rejection. It is commercially available in a sterile pack and is thus easy to use.

Collagen as a donor site dressing has shown that the time to complete reepithelialisation is comparable with other dressing materials. However it is not possible to assess the true wound healing as the wound cannot be kept under continuous observation and the mean time to the first dressing may be longer. Thus many of the donor sites may have healed long before they are first inspected.

Patients with collagen dressings are found to have only minimal to moderate pain in the entire post operative period and during the first dressing. In these patients analgesic requirement is reduced and early mobilisation can be done. Thus the major advantage of using collagen as a donor site dressing is decreased pain.
The collagen sheet once adherent to the wound has low friction between the wound surface and dressing and this has made it suitable for awkwardly sited donor sites. Also once applied it does not require a bulky dressing which would hamper mobilisation, or require a change of dressing as there is no soakage of the dressing due to wound exudate.

The collagen provides a scaffolding for epithelial regrowth and prevents exudation from the raw area.7,8 After 48 hours the film is transformed into a stiff sheet which is stable enough to withstand pressure and shearing of clothes. Thus it protects the donor site from mechanical trauma and infection. When reepithelialisation is completed the overlying film and coagulated blood separates spontaneously. Thus removal of the dressing is easy and pain free.

Disadvantages seen with the use of a collagen dressing is the formation of an haematoma in cases where meticulous haemostasis has not been achieved. Also infection at the donor site causes a complete degradation of the film and is associated with significant donor site pain. Thus donor site pain in patients where collagen dressing is used is highly suggestive of wound infection.4,9 The wound infection is usually limited to the donor area with no associated systemic infection, and it does not convert the donor site to a full thickness loss and once the wound is redressed it does not affect the time of reepithelialisation.⁴

Thus collagen dressings appear to have a great advantage over other dressing materials for donor sites especially in terms of a pain free donor site and thus early mobilisation of the patient and a decreased morbidity. With its ease of application, with no need for redressing, a pain free donor site reepithelialisation in the accepted time it attempts to fulfil the criteria of an ideal donor site dressing.

However this is only a preliminary study and further evaluation of pain using various pain scales and comparative studies with other dressings will be required before its advantage can be confirmed.