The graft of adipose tissue goes through an initial period of ischemia and obtains nutrition through plasmatic imbibition [46]. Circulation is restored to the grafted fat cells in a manner similar to the revascularisation of a skin graft. In the first 4 days, host cells, such as polymorphonuclear leukocytes (PMNs), plasma cells, lymphocytes and eosinophils, infiltrate the graft. On or about the fourth day, neovascularisation is evident. Histiocytes act only to remove fat from disrupted cells.

More recently, the role of adipose-derived stem cells and pre-adipocytes in transplanted fat has been investigated. These cells appear to be more resistant to trauma than mature adipocytes due to lower oxygen consumption requirements. Some researchers have proposed that survival of adipose-derived stem cells in the stromal cell fraction of transplanted fat is a major factor and may account for the variability in survival of fat grafts between individuals [43].

63.11Histological Evaluation of Transplanted Fat

Multiple animal models have been proposed to study the technique of autologous fat transfer. Recent histologic evaluation of transplanted fat grafts to the lips of rabbits has demonstrated an early inflammatory response to the injected fat followed by sequestration of nonviable tissue. The transplanted fat remained viable at 1 year, with good overall survivability and minimal fibrosis [47]. However, there are few studies to evaluate the histologic fate of reinjected fat in humans. Niechajev et al. obtained biopsies of transplanted fat to the cheeks of 9 patients with subcutaneous fat atrophy, 7–36 months after transplantation. Histologic analysis showed an organised lobular structure of transplanted fat at 7 months with more pronounced fibrosis between lobules in the specimens obtained at 36 months [48].

Carpaneda studied collagen alterations in adipose tissue transplanted to abdominal subcutaneous fat prior to abdominoplasty [49]. He found a type 1 collagen capsule around the grafted fat and several alterations to type 1 and type 3 collagen synthesis, degradation and remodelling. A shift in the inflammatory process from the peripheral viable region to the central unviable region was also demonstrated, where pseudocysts were present. Chajchir et al. [50] performed biopsies on

the sites of grafted fat at intervals. Three months after transfer, zones of cystosteatonecrosis, lipophagic granulomas, lymphocytes, adipocytes, giant multinucleated cells and new vessels were found. At 6–8 months, the specimens were infiltrated heavily by PMNs in a fibrotic matrix, and, at 1 year, a large amount of connective tissue and fibrotic reaction was present. Some fat was still present, but the authors felt that the inflammatory reaction may contribute more to the long-term result. There is some disagreement about the role of fibrosis. Some authors believe that fibroblasts cause contraction, while others believe that they can provide augmentation. A fibrous host reaction may be all that occurs in some patients although it may be argued that it ultimately fulfilled the role of soft-tissue augmentation.

63.12 Technique

63.12.1Assessment of Patients with HIV-Associated Lipodystrophy

Autologous fat transfer for the treatment of HIVassociated lipodystrophy may be performed under local or general anaesthesia depending on patient preference and anaesthetic risk. Assessment of anaesthetic risk in HIV-infected patients requires knowledge of the potential effects of HIV infection on each organ system combined with a full history, examination and appropriate investigations.

To ensure optimal safety for both the patient and the operating team, it is recommended that the HIV-1 RNA viral load should be maximally suppressed at the time of surgery (HIV-1 RNA < 50 copies/ml) [51]. Recommendations on preoperative CD4 count are lacking, although a CD4 count less than 200 cells/Pl is considered suboptimal for elective procedures by some surgeons.

Surgical assessment of patients with HIV facial lipoatrophy involves quantification of the severity of facial wasting, and generalised clinical examination to identify other morphological features of HIV lipodystrophy and potential donor sites for fat harvest.

A classification of facial lipoatrophy has been proposed by James et al. to assist in treatment decisions [29]. Grade 1 is mild and localised, and the appearance is almost normal. Grade 2 has longer and deeper central cheek atrophy, with the facial muscles