The Treatment of Contour Scars: Filling Agents
Gary D. Monheit, M.D.
Associate Professor
Department of Dermatology
University of Alabama at Birmingham
Birmingham, Alabama

Over the past thirty years, the methods available for the removal or improvement of acne and contour scars on the face increased exponentially with the advent of new skin filler substances, improved techniques for elevating existing scars and technology for abrading and resurfacing facial contours. It seems that every month, a new and improved filling agent or laser is available that will be the best of all available methods. In the midst of these technological breakthroughs, the basic mechanisms still remain the same. There are three categories of techniques presently available to improve acne scars: 1) scar removal and revision; 2) filling depressed scars; 3) contouring the surface of scars.

Thirty years ago, one would either excise a scar or dermabrade the surface. Combinations of these two methods were beginning along with punch grafts and the use of autodermal grafts. The basic work-up and evaluation of these scars essentially remains the same because these same choices are available for types of scars the clinician will evaluate for improvement. This review will discuss skin filling agents available for scar correction.

Distensible cutaneous scars are best elevated with filling material. A distensible scar is defined as one which will rise to the surface when tension is placed on either side. This simple test will tell the clinician if scars respond to filling material. Those fibrotic ice pick and bound down scars cannot be elevated because the scar tissue extends through to the subcutaneous tissue plane. Placing filling material in the dermis will only elevate the surrounding skin, producing a donut effect and making the scar appear worse.

The ideal skin filling agent is safe, physiologic, simple and permanent. At this point, there is no known substance that meets all these criteria. Each of the available substances have side effects that detract from these properties but all of them strived to perfect their qualities to fulfill these requirements. The list of injectable filling materials increases each month with both synthetic and natural substances. Other implant materials are surgically placed. The excisional procedures place the synthetic implant materials within or below the scar for elevation. A current list of implant material available for acne scars is listed in Table I.

Injectable Filling Material
1)Zyderm and Zyplast Collagen
The first injectable filling material to be approved by the FDA is Zyderm collagen. This porcine collagen implant has been used for approximately ten years and the injection technique has been standardized. Each is delivered in 1 cc. syringes packaged with lidocaine and a 30 gauge needle. There are three variations available for this collagen implant. Zyderm I collagen is a 25% suspension of purified porcine dermis in saline with a 0.3% lidocaine. The saline carrier is absorbed and the remaining implant persists for six to ten months. Zyderm I is used most successfully to treat shallow distensible scars and fine scars. Zyderm II has double the concentration and is a more viscid substance. The longevity of scar correction is increased and it can be used for larger filling defects. Zyplast is a cross-linked derivative of porcine collagen which is a heavier filling material and has greater longevity. Zyplast can be used for larger scars that require a greater and deeper filling of volume and will last longer. It is placed deeper in the dermis and gives 100% correction at the time of implantation rather than 150% used for Zyderm I. Zyderm I has a longevity of six weeks to three months; Zyderm II, four to five months, while Zyplast may last nine months to one year, especially in a relatively immobile scar.

These two filling agents are the most commonly used in implants in the United States today with a low abuse potential. They are user friendly, relatively easy to inject, and can be integrated into a simple office visit for the patient requesting dermal augmentation. Frequent maintenance, though, is necessary and the question always arises whether it is cost-effective. The filling agent is technique dependent for longer lasting results, proportional to the clinician’s ability to place the collagen correctly. Adverse reactions have been noted including allergic reactions, hypersensitivity reactions with Zyderm I and II and vascular necrosis occurring with Zyplast, particularly in the glabella and on the nose. Though these complications are rare, they have been reported and proper allergy testing must be done for each patient.

2) Fibrel
Fibrel has been an effective method of elevating scars utilizing three agents – gelatin, amino caproic acid and plasma that are injected within or under a scar to stimulate collagenosis. This has subsequently been refined and simplified so that the plasma is not a necessary component in the mixture. This “new Fibrel” is composed of a gelatin powder, amino caproic acid mixed with saline and 1% lidocaine. The mixture is placed within distensible scars and gives correction for over one year. In selective cases, scar elevation has persisted for up to five years. Side effects have included a prolonged inflammatory reaction in selective cases, probably related to an idiosyncratic sensitivity response to the products. It has been used extensively in Zyderm allergic patients and has been a reliable filling agent for acne scars. Recent problems with production and availability presently make this product hard to find for clinical use.

3) Artecoll
Artecoll is a synthetic mixture of polymethyl methacrolate microspheres (PMMA) suspended in collagen, saline and 0.3% lidocaine. The mixture is injected deeply in the dermis and subcutaneous tissue and following injection, the collagen is gradually degraded with the permanent deposition of the PMMA spheres. Artecoll should be injected subdermally and overcorrection avoided with no blanching of the dermis. Broad experience in Europe has found this product reliable and long-lasting and its use in acne scars is well documented. It presently is not available in the United States but soon to be approved by the FDA for widespread usage.

4) Hylaform Gel
Hylaform Gel is a hylauronic acid derivative of a mammalian polysaccharide. It is a cross-linked derivative of natural hylauronan polymer with little immunologic activity and no species specificity. It is an intradermal injection used to augment scars. No skin test is required but the procedure requires a series of injections rather than a single treatment session. After two or three injections, the initial clinical trials have resulted in 80% of patients satisfied with their correction at twelve weeks. Longevity, though, is nine months to one year and reinjection then is necessary. Adverse reactions have been minimal including erythema, ecchymosis and acneiform dermatitis with no reported allergic reactions. This product is available in Europe and under investigation in the United States.

5) Resoplast
Resoplast is a monomolecular bovine collage product suspended in solution at 3.5 and 6.5% concentration. It is very similar to Zyderm I and II and its indications and techniques of implantation are the same. A skin test is necessary with similar risks of allergenicity. If one is allergic to Zyderm collagen, it also applies to Resoplast as the products have similar antigenicity.

6) Autologen
Autologen is an injectable dermal implant harvested from autologous collagen. It provides two theoretical advantages on an implant material:
1) It is autologous: allergic and tissue reactions should not occur;
2) It contains intact dermal collagen fibers which may exhibit greater resistance to enzymatic degradation.
The skin material is provided from skin specimens obtained from plastic and reconstructive surgery procedures in which skin is removed and discarded. The removed skin is processed into collagen dispension concentrations from 25 mg/ml to 100 mg/ml and injected through a 27 gauge to 30 gauge syringe.

Results from controlled evaluations in thirty patients show that three layered Autologen treatments provided greater than 75% correction for more than one year.

7) Isolagen
Isolagen is also a method of harvesting autologous collagen, purifying the material and packaging it in a suspension for intradermal injection. Results are promising but objective data is presently not available.

Methods include harvesting the skin from patients prior to the procedure which they are sent to home laboratory for processing. From this model, autologous collagen is produced, repackaged and sent back to the clinician. Because the product is autologous, there is little risk of allergic response and the collagen functions as an autoimplant. Once harvested and processed, a long term supply of collagen is then available for the patient as secondary procedures are required to maintain scar correction. These are currently under investigation and may soon be available for selected patients.

8) Fat
Fat injections have been available and performed over one-hundred years as live, free fat grafts. Liposuction has made the harvesting of fat a simpler procedure and for grafting, this is done with a syringe in an atraumatic manner. The best donor sites include the thighs, buttocks, knees and abdomen and the resultant fat is then gently centrifuged to separate the intact fat cells from supernatant serum free lipid. Fat cells are then injected into a subcutaneous plane under larger scars with a 16 to 18 gauge needle. Fat is used as a subcutaneous filling substance and is not indicated in dermal augmentation. Thus, it is reserved for those large, atrophic defects that include skin and fat. Larger acne scars and lipodystrophies are best for fat correction. Recent techniques have resulted in fat survival for over one year and 50% or greater of patients treated. These results are technique sensitive requiring many different methods to purify, wash, separate, centrifuge or prepare the fat. Each investigator seems to have a different method to justify results. Unified techniques are needed to standardize the technique.

Surgical Methods
Other procedures include surgical methods of replacing or implanting material into dermis for scar elevation. 1) Dermal grafting is not a new technique but recently has been perfected by Swinehart. Dermis is surgically harvested and de-epithelialized. According to Swinehart’s method, the area for surgical excision is first dermabraded to remove the epidermis. An excision of collagen is then performed and the defect closed. A prime location is the retroauricular sulcus and neck. The dermis is defatted, placed in saline, and then divided into sections to fit the size defect needed. A simple stab incision is made to create a pocket within and under the scar in which the dermal implants are placed. Because this represents a graft rather than just substance, there is little absorption and the results appear to be long term. It is truly a skin transplant of both cellular fibroblasts and collagen that maintain long-term correction. It is, though, a surgical procedure more complex than a simple injection and is quite technique sensitive.

2) Similarly, synthetic grafts such as Gore-Tex and SoftForm can be used to fill scars also. These are synthetic products that are placed surgically within and under the dermis for augmentation. Gore-Tex is a polytetrafluorethylene product that has been used extensively in cardiovascular, urologic and reconstructive surgery. Its placement for skin augmentation must be done in the superficial subcutaneous tissue below the skin and anchored in a subdermal pocket. It is a technique sensitive operation with adverse reactions that include infection, foreign body extrusion, and movement of the implant from the site of placement. The product is best for atrophic scars and full thickness skin defects and subcutaneous defects and requires significant augmentation. The implant, though, is permanent and movement or extrusion needs replacement and will require surgical revision.

The use of either injectable or surgically placed implants for the correction of acne scars is dependent upon the surgeon and the patient’s desires. Many patients are satisfied with the simple but repeatable procedure of Zyderm collagen while others insist upon a single procedure. Both of these choices are available with the advent of new injectable and implantable skin filling substances.