Abstract
Background: Lipoinjection still has several problems to be resolved; low augmentation efficiency, fibrosis and calcification, which are derived from partial necrosis of the injected adipose tissue.
Methods: We have used a disposable screw-type syringe in order to estimate its usefulness for lipoinjection. In 10 cases, lipoinjection for facial rejuvenation and breast augmentation was performed using a screw-type syringe with a threaded plunger and threaded connections for both the connecting tube and needle to allow precise control and high pressure injection through an 18-gauge needle.
Results: No postoperative nodules such as fibrosis and calcification were found clinically and with CT scans, suggesting that the fat was distributed properly at each site. All patients were satisfied with the resulting texture, softness, and absence of foreign materials despite the limited size increase possible with autologous tissue.
Conclusions: The device was originally made for angiography and balloon catheter purposes, but we found it very useful for lipoinjection, especially when a large amount of fat tissue was to be transplanted.

Introduction
Autologous fat transplantation is one of the promising treatments for facial rejuvenation and soft-tissue augmentation due to the lack of incisional scar and complications associated with foreign materials, though there remain some problems to be resolved, such as unpredictability and a low survival rate due to partial necrosis. Lipoinjection can be used for treating aging hollow face, correcting various kinds of depressed deformities such as hemifacial microsomia and pectus excavatum, and is also conducted for breast augmentation in some countries including Japan, although the use of autologous fat for breast augmentation is not accepted in other countries including the United States, which has the highest prevalence of breast cancer.
The low survival rate of transplanted adipose tissue is the biggest problem. Many innovations have been reported in an effort to overcome this problem [1-5] and reviewed previously [5, 6]. It was concluded that we can harvest fat with a 2.5 mm cannula or 18-gauge needle at -250 to -500 mmHg vacuum and reinject it with an 18-gauge needle without significant adipocyte damage [6].
For lipoinjection, the authors used a disposable screw-type syringe, commercially available in many countries but originally made for angiography and balloon catheter procedures, and found it very useful for this purpose, especially when a large amount of adipose tissue was transplanted. With this device, lipoaspirates can be injected smoothly through an 18-gauge needle without pre-cutting the harvested tissue, in precise amounts (e.g. 0.3-1.0 ml each), and easily in a short time.

Surgical Techniques
Adipose tissue was suctioned with a cannula of 2-mm inner diameter and a conventional suction machine under general anesthesia following an infiltration with saline solution with diluted epinephrine (0.001%). Collected liposuction tissues were placed in a funnel-shaped 1-liter vessel with a drain and stopper (liquid separator) (Fig. 1; left, middle), saline solution was added, and the mixture was left for a few minutes until good separation was attained. The stopper was released and the unneeded liquids were drained. This procedure was repeated 6 or 7 times until the tissues were almost free of blood and look bright yellow in color (Fig. 1; right).
The washed lipoaspirates were then put into a screw-type syringe (threaded plunger) with threaded connections for both the connecting tube and needle to allow for precise control and high pressure injection through an 18-gauge needle (Fig. 2; top), and injected into the recipient site of the body (Fig.2; bottom). This device (10 cc LeVeen? inflator, Boston Scientific Corp., MA) is originally designed for angiography and ballon catheter purposes.
For breast augmentation, 200-500 ml lipoaspirates were injected into each breast with the syringe. To reduce the time of procedure, two syringes were used; the second syringe was filled with lipoaspirates prepared for the next injection, while the first one was used for actual injection. A long 18-gauge needle (60 mm long, Nipro Corp., Tokyo, Japan) was used for lipoinjection and inserted subcutaneously at several points around the edge of the breast mound and in the areola (Fig. 2B). When the long needle was inserted at the edge of the breast mound, the operator took great care to insert and place the needle horizontally (parallel to the body line), in order to avoid damaging the plural and subsequent iatrogenic pneumothorax. The needle was inserted in various directions, and was pulled out little by little after each injection of 0.5-1.0 ml of fat, in order to obtain diffuse distribution of transplanted fatty tissues (Fig. 3). The fatty tissues were placed into the fatty layers around and under the mammary glands, and also carefully into the pectoralis muscles. As an assistant rotated the plunger according to the operator's instruction, the operator rigidly held the inserted needle and pulled it back a short distance after each injection of a small amount of adipose tissue, The 18-gauge needle was changed after every 10-20 injections.
For lipoinjection in the face, a short 18-gauge needle was used instead. If an injection of smaller and more accurate volume is required, a regular disposable 1cc-syringe may be used.

Patients
Lipoinjection was performed with this device on a total of 10 patients. In 8 of the cases, adipose tissues were injected into breasts (220-450 ml on each side), while the other 2 cases were injected in the face (65-95 ml) for rejuvenation. Patients' data is summarized in Table 1.

Results
Transplantation of adipose tissue was successfully performed in all cases, and the time of the injection process ranged from 55 to 70 min for breast augmentation, and from 15-25 min for facial rejuvenation. Subcutaneous bleeding was usually seen on some parts of the breasts, and faded away in a week or so.
Transplanted adipose tissues were gradually absorbed during the first 3 months, and the contour showed minimal change thereafter. Representative cases are shown in Figures 4 and 5. In bilateral breast augmentation, the circumference difference (= chest circumference at the nipple - chest circumference under the breasts) increased in all cases, usually by 3 to 5 cm. The increase of the circumference difference seems to correspond to 100-150ml increase in the volume of each breast mound. All cases showed natural softness of the breasts without any palpable nodules, and all patients were satisfied with the resulting texture, softness, and absence of foreign materials despite the limited size increase possible with autologous tissue. Postoperatively, no indurations, such as calcification or fibrosis, were found in any cases, either clinically or with computed tomography.

Discussion
A number of modifications of lipoinjection techniques have been tried in order to improve the survival rate of injected fat. Among those, it is well accepted that adipose tissue should be transplanted as small particles, preferably within 3 mm in diameter [1]. To perform diffuse distribution of suctioned fat more efficiently, we have used a disposable syringe with a threaded plunge and connections.
Though more than half of the grafted fat seemed to be absorbed, we did not see any indurations such as calcification or fibrosis, which have been the only factor against the use of lipoinjection for breast augmentation. No abnormal signs were detected with postoperative CT scans in our small number of cases. The results of CT scans showed that transplanted fat tissues survived and formed a significant thickness of the fatty layer not only subcutaneously around the mammary glands but also between the mammary glands and the pectoralis muscles, indicating successful augmentation of the breast mounds. Breast volume was nearly settled 6 months after transplatation. Maximum breast augmentation with this technique appeared to be 100-150 ml. However, it is a definite advantage that we do not have to worry about postoperative complications induced by artificial materials, which include capsular contracture, hardness, immune response, and breast deformity in the future.
It has been revealed that adipose tissue contains not only adipogenic progenitor cells but multipotent stem cells which can differentiate into fat, bone, cartilage, and others [7-10]. Suctioned fat appears to lose a significant amount of these precursors during mechanical liposuction process compared to non-suctioned adipose tissue (in preparation), so this relative deficiency of precursors may contribute to the low survival rate of transplanted lipoaspirates. It is expected that a variety of new innovations including stem cell technology will be further developed and contribute an improved transplanted fat survival rate fat in the future. Further improvements of the technique could make fat transfer the first choice for breast augmentation in the future.

Correspondence to: Kotaro Yoshimura, M. D.
Department of Plastic, Reconstructive, and Aesthetic Surgery, University of Tokyo,
7-3-1, Hongo, Bunkyo-Ku, Tokyo 113-8655, Japan.
Phone: +81-3-5800-8949
Fax: +81-3-5800-6929
E-mail: yoshimura@cosmetic-medicine.jp


References
1. Carpaneda, C.A., and Ribeiro, M.T. Percentage of graft viability versus injected volume in adipose autotransplants. Aesthetic Plast. Surg. 18:17, 1994.
2. Lewis, C.M. Correction of deep gluteal depression by autologous fat grafting. Aesthetic Plast. Surg. 16: 247, 1992.
3. Ullmann, Y., Hyams, M., Ramon, Y., Peled, I.J., and Leiderbaum, E.S. Enhancing the survival of aspirated human fat injected into nude mice. Plast. Reconstr. Surg. 101: 1940, 1998.
4. Har-Shai, Y., Lindenbaum, E.S., Gamliel-Lazarovich, A., Beach D., and Hirshowitz, B. An integrated approach for increasing the survival of autologous fat grafts in the treatment of contour defects. Plast. Reconstr. Surg. 104: 945, 1999.
5. Ersek, R.A., Chang, P., and Salisbury, M.A. Lipo layering of autologous fat: an improved technique with promising results. Plast. Reconstr. Surg. 101: 820, 1998.
6. Shiffman, M.A., and Mirrafati, S. Fat transfer techniques: the effect of harvest and transfer methods on adipocyte viability and review of the literature. Dermatol. Surg. 27: 819, 2001.
7. Zuk, P.A., Zhu, M., Mizuno, H., et al. Multilineage cells from human adipose tissue: implications for cell-based therapies. Tissue Eng. 7: 211, 2001.
8. Zuk, P.A., Zhu, M., Ashjian, P., et al. Human adipose tissue is a source of multipotent stem cells. Mol. Biol. Cell 13: 4279, 2002.
9. Dragoo, J.L., Samimi, B., Zhu, M., et al. Tissue-engineered cartilage and bone using stem cells from human infrapatellar fat pads. J. Bone Joint Surg. Br. 85: 740, 2003.
10. Stashower, M., Smith, K., Williams, J., and Skelton, H. Stromal progenitor cells present within liposuction and reduction abdominoplasty fat for autologous transfer to aged skin. Dermatol. Surg. 25: 945, 1999.

Legends

Fig. 1. (left) A funnel-shaped liquid separator with a drain and stopper. The size of the vessel is about 1-liter. (middle) Suctioned tissues were poured into the vessel and kept it in an upright position for a few minutes. A clear separation between suctioned fat and a liquid portion were obtained. Note that the liquid portion contained a significant volume of blood and could be discarded by opening the clamp. (right) After repeated rinsing with saline solution, floating fat tissue was cleansed and looked bright yellow.

Fig. 2. (above) A disposable screw-type syringe with a threaded plunger (10 cc LeVeen? inflator, Boston Scientific Corp., MA). A 60 mm-long 18-gauge needle is connected with a connection tube, which has threaded connections on both sides. (below) The device was used for autologous fat transplantation. The injection needle is rigidly held by an operator, and a high-pressure injection can be performed by rotating the plunge by an assistant.

Fig. 3. An injection needle is inserted in variable directions and planes to complete a diffuse distribution of fatty tissues. A small amount of fat tissue (0.3-1.0 ml) is injected to each site as the needle was repeatedly pulled by a centimeter.

Fig. 4. Case #2 (See Table 1.) (top) A preoperative view. (middle) A view 6 weeks after surgery; 450 ml of fat tissue was transplanted into each breast mound. (bottom) A view at 6 months. Augmented breast mounds were maintained without leaving any injection scars or subcutaneous indurations. No more reduction in size was seen thereafter.

Fig. 5. Case #4 (See Table 1).

Table 1. Summarized data of cases.