Introduction

Adipose tissue has been considered an organ of energy storage, the largest endocrine organ, a soft tissue filler (augmentation by micro-fat grafting), and a cosmetically unnecessary tissue discarded by liposuction. Adipose tissue physiologically turns over very slowly. Adipocytes have a life span of 10 years;¹ several thousands of adipocytes die and are replaced with new adipocytes every second in our body. Adipose tissue has many cells other than adipocytes, though adipocytes constitute more than 90% of adipose tissue volume. Through collagenase digestion, cellular components other than adipocytes are extracted as a cell pellet, which is called stromal vascular fraction (SVF). SVF contains adipose stromal cells (ASC), vascular endothelial cells (VEC), pericytes, adipose-resident macrophages, etc. (Fig. 48.1). It was found that the adipose stromal cell population contains not only monopotent progenitor cells responsible for the tissue turnover, but also multipotent mesenchymal stem cells,² which are now called adipose (-derived) stem cells. These are regarded as a potent tool for cell-based therapies, comparable to bone marrow-derived mesenchymal stem cells, because they can be obtained in a large amount through a less invasive approach. For adipose tissue engineering/regeneration, it is a critical point to understand the physiological roles and functions of ASC; this population, working together with VEC and stem/progenitor cells recruited from bone marrow, is a main player for adipose tissue engineering, which means adipogenesis and angiogenesis.

FIG. 48.1 From liposuction to isolation of adipose stem/progenitor cells.

Stromal vascular fraction (SVF) can be obtained through collagenase digestion of the lipoaspirates. SVF contains many blood-derived cells (CD45⁺) and adipose-derived cells (CD45⁻); the latter is further divided into CD31⁺/CD34⁺ endothelial cells (ECs), CD31⁻/CD34⁺ adipose progenitor cells (ASCs) and CD31⁻/CD34⁻ other cells.

Autologous fat transplantation is one of the promising cosmetic treatments for facial rejuvenation and soft-tissue augmentation due to minimal incisional scars and lack of complications associated with foreign materials. However, certain problems remain, such as unpredictability and a low rate of graft survival due to partial necrosis. Implantation of prostheses has been a golden standard for breast augmentation, but complications such as capsular contracture remain to be resolved. Recently, autologous fat injection has been re-evaluated as a potential alternative to artificial implants for breast augmentation.³ This re-evaluation may reflect recent advances in autologous fat transfer and the radiological detection of breast cancer.

In this chapter, biological principles and surgical techniques of fat injection for breast augmentation are discussed as well as our novel approach of autologous fat grafting called cell-assisted lipotransfer (CAL),^4,⁵ which is concurrent transplantation of aspirated fat tissue and adipose progenitor cells (Fig. 48.2).

FIG. 48.2 Scheme of cell-assisted lipotransfer (CAL).

Relatively adipose-derived stromal/stem cells (ASC)-poor aspirated fat tissue is converted to ASC-enriched tissue by supplementation with ASCs isolated from a part of the lipoaspirates. The ASCs are attached to the aspirated fat tissue, which is used as a scaffold in this strategy. SVF, stromal vascular fraction.

Preoperative Preparation

There seem to be several patient factors that may affect the clinical result of lipoinjection; skin redundancy of the breasts, age, BMI, personal quality or character of fat tissue, adhesive scars, breast implant and its capsule, systemic disease such as autoimmune disease, oral corticosteroid, etc.^4,⁶ Good candidates are those who have sufficient fat at donor sites and the redundant breast skin with healthy vascularity and without scars. Lipoinjection can be performed in any patients from teens to 70s, but patients with low BMI (less than 18) are not good candidates due to difficulty in harvesting a sufficient volume of fat tissue without severe morbidity. Patients who want a large-volume (250–400 ml) augmentation, are not good candidates because augmentation volume achieved by a single session of lipoinjection is limited (100–200 ml).

No particular preparation is generally needed preoperatively. However, for breast reconstruction patients with adhesive scars, an external negative pressure device (Brava®, Brava LLC, Miami FL, USA) possibly improve clinical outcomes. For young patients with small breasts and tight skin, injection volume is limited due to the tight skin envelope. In these cases, a secondary lipoinjection (replacement with fat tissue after temporary breast implant) would be recommended. This allows for her breast skin to be stretched by the implants.

For preoperative examination, physical measurements (maximum and bottom breast circumferences, etc.), mammogram, MRI, echogram, photograph, and videograph are performed. We also adopted a 3-dimensional measurement system that enables a volumetric evaluation of the breast mound in a standing position (Fig. 48.3). An echogram is easy to perform at every patient’s visit and sensitive enough to detect small cyst formation. Long follow up with an annual mammogram up to 5 years is recommended to detect abnormal signs such as calcifications.

FIG. 48.3 Three-dimensional system for measuring breast volume.

Two cameras take photos with striped light shed on the breast. A software program calculates the volume over the standard plane. Using this system, breast volume can be measured while the patient is in a standing position.

Surgical Technique

Breast Augmentation

Donor sites are usually the thighs alone or the thighs and the abdomen or flanks, decided according to the patient’s preference and BMI. After the liposuction site is infiltrated with saline solution with epinephrine (0.001%) under general anesthesia, adipose tissue is suctioned using a cannula with 2–3 mm inner diameter and a conventional liposuction machine. We use screw-type syringes (with a threaded plunger) to allow for precise control and avoid a flushing injection (Fig. 48.4). To reduce the time of the procedure, two syringes are used; while one syringe is being used for an injection, the other is filled with the graft material in preparation for the next injection. A 16- or 18-gauge needle (150 mm long) is used for lipoinjection and inserted subcutaneously from the inframammary fold or areolar margin (Fig. 48.5A). The operator takes care to insert and place the needle horizontally (parallel to the body), in order to avoid causing a pneumothorax. The needle is inserted in several layers and directions, and is continuously and gradually retracted as the plunger is advanced (Fig. 48.5B). This technique is used to obtain a diffuse distribution of the graft material. The grafts are placed into the fatty layers on, around, and under the mammary glands (but not into the mammary glands), and also into the pectoralis muscles. After training, it is not hard for an operator to recognize the mammary gland or pectoralis fascia as a harder tissue than the fat or muscle tissue. Injection is discontinued when the skin tension becomes tense; injection volume is usually 200–300 ml for each breast in Asian patients.

FIG. 48.4 Injection devices.

A high-pressure injection can be performed with a disposable syringe with a threaded plunger. A 150-mm long 16- or 18-gauge needle is connected to the syringe with a connecting tube threaded at both ends. The injection needle is rigidly manipulated by an operator, while an assistant rotates the plunger according to the operator’s instruction. (A) a 10 cm³ LeVeen™ inflator (Boston Scientific Corp., MA); (B) a 20 cm³ screw injector original syringe (Medical U&A, Japan).

FIG. 48.5 Schematic instruction of the injection method for breast augmentation.

(A) The needle is inserted from either one of two points on the areola margin or one of two points at the inframammary fold in various directions and planes to achieve a diffuse distribution. (B) A small amount of fat tissue is injected as thin strings (1 ml fat corresponds to a 10 cm long string) with a long needle while the needle is continuously withdrawn.

Breast Implant Replacement

For patients with implants, lipoinjection can be performed simultaneously with implant removal.⁷ Breast implants are removed through a periareolar incision, which is placed at a caudal third of the areolar margin. The lipoinjection is begun at the deepest layer (under the implant capsule when the implant was subglandular) and completed with the injection into the most superficial subcutaneous layer. During the injection, the operator can insert fingers into the implant capsule and recognize the location of the injection needle (Fig. 48.6). Injection into the mammary glands or into the capsular cavity is not performed. Finally, the capsular cavity is irrigated with saline to remove any fat tissue injected and the periareolar incision is closed.