A free flap is a three dimensional block of tissue that has an identifiable blood supply that can be relocated to reconstruct form or function. It can be made up of skin, fat, muscle, bone or combinations of all of the above. It is harvested from a donor site and its blood vessels (arteries and veins) are reconnected to suitable blood vessels at the site of reconstruction.
donor sites
There are a myriad of donor sites around the body depending on the type of tissue that is required for the reconstructive goals. Harold Gilles, the father of plastic surgery, decreed that we try to replace lie with like. To that end I try to match the donor site to the defect, whilst minimising the damage caused at the donor site, but this is by definition a compromise. Sometimes the donor site can be closed directly leaving a surgical scar, sometimes it will necessitate a skin graft.
microsugical anastomoses
The purpose of a free flap is to import a well vascularised block of tissue into a reconstruction. To achieve this its blood supply has to be reconnected to new vessels. These vessels are connected under a microscope and take up to 72 hours to resurface the inside of the tubes. During this time the flap is at risk of forming clots in the vessels which can interrupt the blood supply. During the first 3-5 days post surgery you will be closely monitored for any signs of reduced flow which may necessitate an urgent return to theatre to revise the anastomosis. Likewise, if any ooze or bleeding in the wound collects and starts to press on the anastomosis and reduce the blood flow this will need to go back to theatre for a washout and cautery.
Some flaps include muscle, either for bulk, or for function in the cases of facial reanimation, brachial plexus reconstruction, or targeted muscle rein-nervation. In these flaps, where the nerve to the muscle has been connected to a nerve at the reconstruction site, the regeneration of the nerve adds complexity and the dimension of time to the recovery. Nerve regeneration is slow in comparison to blood flow, and the effectiveness of the axonal regrowth can take several years before we understand the functional effectiveness of the muscle in its new location.
post surgical reconstruction
This is very dependent on the location of the reconstruction, and any adjunctive operations in collaboration with other surgical specialities such as orthopaedics, spinal surgery, breast surgery or general surgery. The first 3 days are critical, and in most cases patients stay in hospital for 3-5 days. In some cases the early post operative period may require a stay in the high dependency unit. The wounds are usually healed in the first two weeks, and sutures can be removed in 2-3 weeks. Surgical swelling can last for weeks or months and may require some compression to help it settle. In the lower limb swelling can last longer and this will need a period of adjustment where the limb is gradually allowed to be dependent for increasing periods of time to allow it to acclimatise. Some flaps will require subsequent revisions and adjustments to improve their contours.
Where a graft has been used, either on the flap or the donor site, this will usually adhere in the first week. Thereafter it will gradually mature over the following 3-4 weeks and may require dressings during this time. The grafted skin is only the most superficial layers of skin and does not produce its own natural oils. As such it will always require moisturising and may be more friable than ordinary skin. Where the full thickness of the skin has been removed as part of the flap there will always be a contour defect once the donor has been grafted. Skin grafts can be harvested from a number of places, but usually from the proximal thigh. A split thickness skin graft consists of the epidermis and some of the dermis. This leaves an area akin to a deep graze that heals in 2 weeks. This area can be sore, like sunburn, for the first few days. It heals without a scar, but can leave a patch that is a slightly different colour to the surrounding skin, either lighter or darker depending on your natural skin tone.