Enriched Autologous Fat Grafting for Treating Pain at Amputation Sites

Traumatic amputations are prevalent and pose many challenges for our wounded warriors. A recent publication reported that during the current conflicts, over 950 military personnel have sustained combat-related amputations, with 15% of them occurring more than 12 weeks after initial injury (1). Updated statistics place this number of amputees at over 1050 (personal communication, COL Paul Pasquina, Chief of the Integrated Department of Orthopaedics and Rehabilitation, Walter Reed National Military Medical Center-WRNMMC). The ability of a wounded warrior to gain optimal function after an amputation most often depends on his or her ability to successfully fit and adapt to a prosthesis. Once out of the acute phase, many patients with amputations suffer from pain when wearing a prosthesis, either from thin soft tissue cover over bony structures or peripheral nerves not well padded with soft tissue. Extrinsic residual limb pain is usually mechanical in origin related to the prosthetic socket or other prosthetic components. It is often the result of a mismatch between residual limb tissue tolerance and the prosthetic loads on the soft tissues. This sensitivity is often accentuated by superficial nerve trunks or neuromas at severed nerves that are exposed to excessive external mechanical loading (2). Poor socket interface, secondary skin breakdown, and/or pain may severely limit function.

This presents a very difficult clinical problem and historically, when possible, the clinical procedure would be to involve the surgical revision of the amputation site with associated shortening of the bone, lengthy scars, and prolonged healing. If a below the knee amputation has to be converted to an above knee level, then there are serious functional implications. For local tissues at the amputation site that are of poor quality (e.g. scarred or covered with a skin graft), a distant muscle flap may be required (3,4). These flaps may require transfer to the amputation site using microvascular anastomosis of the blood vessels. The procedure is highly invasive and can add the morbidity of decreased function, deformity, and risk of wound healing problems at the muscle donor site. Failure rates in lower limb flaps can be as high as 18.5% (5, 6). Flap ulceration rates tend to be higher in these weight-bearing flaps, both skin and muscle free flaps frequently need secondary debulking procedures to improve function, and painful neuromas are not uncommon (6,7).

A clinical solution that allows for the minimally invasive generation of new soft tissue padding at an amputation site without the need for further limb shortening, lengthy scars, a prolonged recovery, and significant donor site morbidity would have the potential to significantly help our wounded warriors and change clinical practice.

Autologous fat grafting as a potential solution. Grafting of autologous fat tissue is a minimally invasive surgical technique that starts with the harvest of fat tissue from the abdomen or thighs using liposuction through incisions less than 5mm in length. The lipoaspirate is then processed to concentrate the adipose fraction and reinjected into the donor site. This surgical procedure involves the immediate transplantation of a patient's own tissue in a single operative procedure. It has the advantages of:

• Minimal access incisions
• Ability to transfer significant amounts of tissue (hundreds of grams of tissue)
• Can be used in setting of previous surgical procedures and presence of hardware
• Usually performed as outpatient procedure
• Minimal donor site morbidity at graft harvest site
• Low risk compared with more invasive surgical procedures
• Can be repeated multiple times, if necessary, even using the same donor sites