Review of Soft Tissue Filling Substances
BULLETIN FOR MEDICAL PRACTITIONERS
Ms Elizabeth Tian
Senior Pharmacist
National Skin Centre
Over the years, many soft tissue filling substances and devices have been developed to cosmetically improve soft tissue defects and deficiencies. There is, presently, a veritable abundance of agents that are available (Table 1).
Autologous materials are harvested from the patient and therefore have no risk of immunologic rejection or nosocomial infection, but require a harvesting procedure and may have a restricted reservoir. Allograft materials, harvested from human cadaveric tissue, typically have slightly greater longevity and minimal risk of allergic reaction but may carry risk of infection and bring up ethical issues of using cadaver tissue for cosmetic purposes. Fully synthetic materials generally provide much longer-lasting soft tissue correction and have a potentially unlimited supply. However, these materials may be rejected and often do not give the most natural augmentation. Semisynthetic xenograft materials carry risks of infection and rejection and are generally reabsorbed more quickly.
This review will focus on bovine collagen and hyaluronic acid derivatives. The former is the most commonly used injectable material for soft tissue augmentation, while the latter is a new material with promising potential.
Collagen
Injectable collagen is a highly purified form of collagen made from calf skin. Selective removal of the nonhelical amino and carboxy terminal telopeptides significantly reduces the antigenicity of bovine collagen molecules. There are presently 3 forms of bovine collagen available: Zyderm I, Zyderm II, and Zyplast. Zyderm I has a collagen concentration of 35mg/mL, comprised of 95% type I collagen and 1% to 5% type III collagen. Zyderm II
contains 65mg/mL of collagen. Zyderm Collagen is dispersed in phosphate-buffered physiological saline containing 0.3% lidocaine. Zyplast, cross-linked with glutaraldehyde, is able to resist digestion by collagenase more than the Zyderm products and lasts a bit longer in tissue. Zyplast is also colonized by host fibroblasts and may stimulate new collagen deposition.
Mode of Action
After injection, the collagen implant undergoes syneresis and, as the saline is lost, the suspended collagen condenses into a soft cohesive network of fibres. This network is responsible for restoring skin contour. Once established, the implant takes on the texture and appearance of normal host tissue and is subject to the same stresses and aging processes.
Indications and Usage
Skin testing to exclude allergy to bovine collagen is required prior to augmentation.
The following conditions are amenable to treatment with bovine collagen implants:
- Depressed scars (postsurgical, trauma induced, or resulting from acne or other disease)
- Wrinkles, creases and lines caused by facial expression or aging
- Dermal atrophy from disease or from corticosteroid injections
- Angular cheilitis
- Facial contour enhancement e.g. thicker lips
Bovine collagen implants are supplied in a syringe and injected through a 30-gauge needle. The needle should pierce the skin, usually at a 45-degree angle for Zyderm and 20-degrees for Zyplast, and then be advanced once within the dermis to the proper level of implantation.
Non-crossed-linked collagen implant is injected into the papillary dermis and is used for very superficial rhytides. Crossed-linked collagen implant is injected into the reticular dermis and is used for deeper lines, furrows and scars.
To decrease the total number of treatment visits required, it is recommended that the contour deficiency be overcorrected to compensate for the loss of saline in the suspension. Over-correction to 1.5-2.0 times the initial depth of the lesion is recommended for non-crossed-linked collagen implant with concentration of 35mg/mL. A lesser degree of over-correction is required to achieve a given level of correction with the implant of concentration of 65mg/mL. The defect should not be overcorrected when cross-linked collagen is implanted.
After implantation, the collagen undergoes degradation by the body’s own mechanism. Touch-up implantations at 6 - 18 month intervals will be required to maintain maximum correction. The interval at which touch-up implantations are needed depends on the nature of the lesion, the amount of implant introduced, the plane of placement and the stresses that may exist at corrected sites.
Use of Zyderm I in an individual patient should be limited to 30ml over a one-year period while use of Zyderm II should be limited to 15 ml. The combination of these products or of Zyderm in conjunction with Zyplast in an individual patient should be limited to 30 ml over a one-year period.
Contra-indications
Individuals with personal histories of autoimmune diseases (immunologic disorders), such as lupus erythematosus, polyarteritis, polymyositis, rheumatoid and psoriatic arthritis should not be treated with injectable collagen.
Side Effects
The usual side effects are erythema, edema, whealing and bruising. One percent to 3% of persons having a negative single skin test reaction will have a hypersensitivity treatment site reaction after their first treatment with non-cross- linked implant. The reaction is identical to those of a test site hypersensitivity reaction. Fewer reactions can be expected with cross-linked collagen.
Hyaluronic Acid Derivatives
Hyaluronic acid is a glycosaminoglycan biopolymer composed of alternating residues of the monosaccharides D-glucuronic acid and N-acetyl-D-glucosamine linked in repeating units. Its ability to bond water assists in hydration and provides skin turgor. Hyaluronic acid is naturally occuring, in the same identical form, in the intercellular matrix of dermal layers of the skin of all species, and has a high biological compatibility. The amount of hyaluronic acid in the skin decreases with age, and loss of this substance results in reduced dermal hydration and increased folding.
The most commonly used sources of hyaluronic acid are rooster combs, the umbilical cord, the vitreous humour, tendons, skin and bacterial cultures. Restylane, produced by bacterial fermentation, is available in Singapore.
Mode of Action
Hyaluronic acid works by volume augmentation. Small amounts of the product are injected directly into the dermis. No active tissue reactions or spontaneous improvements will occur after the injection.
Indications and Usage
There are three products, Restylane Fine Lines, Restylane and Perlane, which are designed for different purposes and effects. Restylane is recommended for wrinkle correction and lip enhancements; Restylane Fine Lines for correcting thin, superficial lines, for example worry lines, periorbital lines and perioral lines; Perlane for shaping facial contours, such as cheeks and chin, correcting deep folds, and for volume augmentation of the lips.
A major benefit of hyaluronic acid is that due to its high biocompatibility, the preliminary skin test is not needed. Being produced by biotechnology, it carries very little risk of transmissible infectious bacterial or viral diseases.
Hyaluronic acid is injected through 27 or 30 gauge needles, and requires a full correction of the defect. After the injection, the material should be lightly massaged to conform to the contour of the surrounding tissues. For each treatment site a maximum dosage of about 1.4ml is recommended. After the first treatment, an additional implantation may be necessary to achieve the desired level of correction.
For the majority of the patients after a wrinkle treatment about 50-80% of the effect remains after 6 months and most people choose to have a touchup treatment done within a year of the original treatment. For lip augmentation, a new treatment is needed after about 6 months.
Side Effects
After the treatment some common treatment site reactions may occur, such as swelling, redness, pain, itching, discolouration and tenderness at the implant site. These typically resolve spontaneously within one to two days after injection into the skin and within a week after injection into the lips. Other types of reactions are very rare, but about 1 in 2000 treated patients have experienced localized reactions thought to be a hypersensitivity nature. These have usually consisted of swelling at the implant site, sometimes affecting the surrounding tissues.
References
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Rohrer T. Soft tissue filler substances. Curr Probl Dermatol, Jan/Feb 2001
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Klein A, Elson M. The history of substances for soft tissue augmentation. Dermatol Surg 2000;26:1096-1105
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Drake L, Dinchart SM, Farmer ER, et al. Guidelines of care for soft tissue augmentation: collagen implants. J Am Acad Dermatol 1996;34:695-7
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Duranti F, Salti G, et al. Injectable hyaluronic acid gel for soft tissue augmentation. Dermatol Surg 1998;24:1317-25
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Zyderm/Zyplast physician package insert. Collagen Biomedical, Palo Alto, California, 1992
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Restylane physician package insert. Q-med, Sweden
DEDICATED TO EXCELLENCE IN DERMATOLOGY
By National Skin Centre (Singapore)
Copyright (C) 1995 - National Skin Centre (Singapore)
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