Authors: Dr. D. M. Mahajan

Introduction

Acne scars is one of the most common problem nowadays and affects individuals more than acne itself as it stays for longer duration even after acne resolves. Scarring is a particularly distressing phenomenon and is most unwelcome when it occurs on the face. Scars can arise on the face due to a number of causes, the commonest of which is acne vulgaris. Post-acne facial scarring is a psychologically devastating condition and the affected patient invariably suffers from low self-esteem and many other psychological ill-effects because of this condition.¹

Acne scarring occurs subsequent to visible resolution of deep inflammation. Scarring may occur regardless of the severity of acne. Although acne scarring is likely to be associated more often with nodulocystic acne, it may occur in cases with only superficial forms of acne as well, especially when effective treatment is delayed. ^2,3 Atrophic scars can result from any inflammatory skin disease causing sufficient damage to the epidermis and to the dermal collagen. The most common causes of atrophic scars especially on the face are severe nodular or nodulocystic acne, infections like varicella and Herpes simplex, trauma including burns and lastly, surgical procedures. Successful treatment of these scars can be a satisfying experience to the patient and the treating physician.

Facial scars resulting from acne are either hypertrophic or atrophic depending upon whether they are elevated or depressed in relation to the skin surface. The atrophic facial scars are divided into different morphological types depending on the shape and depth of the scars.The four main morphological types of atrophic post acne scars are icepick pitted scars, superficial or deep boxcar scars, rolling scars and linear scars. Treatment of each morphological scar type varies and while one scar type responds the best to some treatment modality, the same treatment option may not be necessarily effective in other type of scars.⁴

Methods of examining patient outcomes require a method of analysis that is simple and meaningful. This was the thinking behind the scale that was developed some years ago to allow easy global analysis of a patient's overall appearance with respect to their scarring ⁵.

Classification of acne scars is essential to assess the severity of cosmetic disfigurement and to choose the therapeutic intervention necessary. ⁶ Broadly acne scars are classified into atrophic and hypertrophic scars. Atrophic scars have been further classified as ice pick, rolling and box car. ⁷ The Europeans acne group (ECCA) has renamed the atrophic acne scars as V-shaped (ice-pick), U-shaped (box car), and W-shaped (rolling).⁸ Goodman and Baron encompassed all the morphological types of post acne scars and used simple clinical examination as the tool to grade the scars on objective lines.⁹

Grading of the atrophic scars as per Goodman and Baron scale is as below:
Grade1 - Macular erythematous hypo or hyperpigmented scars.
Grade 2 - Mild atrophy not obvious at social distances of >50 cm or easily covered by facial make up or beard hair.
Grade 3 - Moderate atrophy obvious at social distance of >50 cm; not easily covered by make up or beard hair; but able to be flattened by manual stretching
Grade 4 - Severe atrophy not flattened by manual stretching of skin. Patients to be taken up for the treatment is to be decided on the basis of various inclusion and exclusion criteria
Inclusion criteria All patients presenting with Goodman and Baron Grade II, III, IV acne scars.

Exclusion criteria

1. Presence of active acne lesions.
2. Patients having keloid scarring or keloidal tendency.
3. History of bleeding disorder and anticoagulant therapy.
4. Oral steroid therapy.
5. Active skin infection like warts, herpes and bacterial infection.
6. Pregnancy and lactation.

Treatment modalities
Chemical Peels

Superficial chemical peels are considered as adjunctive treatments for the management of acne. They are often added to first line therapies such as retinoids and antibiotics, whether topical or systemic. Their addition to the regimen is preferred due to the quick decrease in lesional count as well as the improvement of overall skin texture. A series of chemical peels can give significant improvement over a short period of time, leading to patient satisfaction and maintenance of clinical results. Chemical peels with increased depth of penetration have also been used for the treatment of acne scars, either alone or in combination with other resurfacing procedures. Chemical peels are generally considered safe and effective, forming an important part of a dermatologist's arsenal. However, the use of chemical peels can have adverse effects, such as post-inflammatory hyper pigmentation that is more commonly seen in darker skin types. The most commonly used chemical peels in treating acne and acne scars include salicylic acid (SA), glycolic acid (GA), Jessner's solution (JS), resorcinol, and trichloroacetic acid (TCA). [10) More recently, other peels have emerged that been proven useful in the management of acne such as lactic acid, and a salicylic acid-mandelic acid (SM) combination.

Salicylic acid

Salicylic acid is a beta-hydroxy acid that has a phenolic ring in its chemical structure. ¹¹ It is an excellent keratolytic agent by way of its ability to dissolve intercellular cement thereby reducing corneocyte adhesion. ^12,10 Due to its lipophilicity, it has better penetration into the pilosebaceous unit. This property of salicylic acid accounts for its strong comedolytic effect, and its utility in the treatment of acne. ^{13,14,11,10,15,16} The anti-inflammatory activity of SA makes it useful in rapidly decreasing facial erythema. ¹⁷ Salicylic acid also has very good safety profile with no incidences of salicylism reported till date. It is low in cost, easy to apply and has the ability of self-neutralization. ¹¹ Another benefit of SA is its lightening effect on post-inflammatory pigmentation due to acne. ¹⁵

Glycolic acid

Glycolic acid is widely used as a superficial peeling agent owing to its exfoliative properties. ¹² Exposure of skin to GA leads to reduced corneocyte adhesion, correction of abnormal keratinization in the infundibulum, decreased keratinocyte plugging and ultimately decreased follicular occlusion. ^12,18

Previous studies have reported that alpha hydroxy acids such as GA, do not possess anti-inflammatory properties, making it inferior to SA in the treatment of acne, ¹⁰ despite evidence showing that there was clinically significant improvement of the inflammatory lesions. ¹⁸,¹⁹ A recent study however, has shown that glycolic acid has an anti-inflammatory effect on acne through its inhibitory and bactericidal effect onProprionibacterium acnes. ¹⁸
Jessner's solution

Jessner's solution is a combination of 14% resorcinol, 14% salicylic acid, 14% lactic acid and ethanol. The strength of the peel is determined by how many layers of the solution is applied, and is usually used in combination with other peels to increase the depth of the overall peel. It is a useful peel for patients with acne because of its salicylic acid and resorcinol components. It should however be remembered, that resorcinol may cause post-inflammatory hyper pigmentation in those with Fitzpatrick skin type IV or greater or those who have a tendency to develop dyschromias. There is also a risk of developing contact dermatitis to resorcinol and this peel should therefore be used with caution along with proper patient selection.²⁰

Trichloroacetic acid

TCA is a well-studied and inexpensive peeling agent that can be used either as a superficial, medium depth or deep peel depending on the concentration used. [21],[22] When applied to the skin, TCA causes coagulation of epidermal and dermal proteins, and necrosis of collagen up to the upper reticular dermis. [23] The re-epithelialization begins from the surviving islets of keratinocytes and from the skin appendages.[24] The clinical effects of TCA are due to the resultant increase in dermal volume of collagen, glycosaminoglycans and elastin. [23) TCA is a self-neutralizing peel, therefore it is not absorbed systemically even if high concentrations are used. [21)] It is considered safer compared to phenol peels as there is no systemic absorption nor toxicity and pain is also less severe. ²⁵

Phenol peel

Phenol is a deep chemical peeling agent, with effects lasting for 10-20 years. ²⁶ Phenol causes complete epidermolysis and dermal elastolysis. Fibroblast stimulation then results in neocollagenesis. ²⁷ When absorbed systemically, there may be serious side effects such as cardiotoxicity resulting in fatal arrhythmias, hepatotoxicity, nephrotoxicity and respiratory depression. Cutaneous side effects are hypo-pigmentation, hyper pigmentation, hypertrophic and keloid scarring and prolonged erythema. It has rarely been used in Asians due to hypo-pigmentation, which has been attributed to either melanocyte toxicity or extensive dermal fibrosis following the peel. ²⁷

Most of the peeling agents are evaluated to be safe, efficacious, and easy to administer. Compared to newer machine-based technologies for acne and acne scars, chemical peeling is affordable and with minimal downtime, and can be performed in any dermatologist's office. It is hoped that more randomized clinical trials with larger sample sizes be undertaken in order to strengthen the current body of knowledge on the safety and utility of chemical peeling for patients.

Microneedling

Microneedling therapy, also known as collagen induction therapy, is a recent addition to the treatment armamentarium for managing post-acne scars. The treatment is performed as an office procedure after application of a local anesthetic cream, by means of an instrument known as a dermaroller. A dermaroller is a simple, hand-held instrument consisting of a handle with a cylinder studded all around with fine, stainless steel needles 0.5 to 2 mm in length. This needle-studded cylinder is rolled on the skin in multiple directions to achieve a therapeutic benefit and hence the name 'dermaroller'. These needles cause small pinpoint injuries on the treated skin, which apparently heal within two to three days with no post-treatment sequelae. Treatment with dermaroller is performed at four to eight week intervals and multiple sittings are needed to achieve the desired effect on the skin. Microneedling or dermaroller treatment is becoming popular all over the world, not only in the management of post-acne scars but also as an anti-aging therapy. There are certain advantages with dermaroller or microneedling therapy over laser resurfacing; former does not lead to any epidermal injury as is seen with lasers, there is minimal downtime associated with the procedure unlike ablative laser resurfacing and the treatment is far cheaper as compared to lasers. The treatment can be performed in an office setting and does not need any extensive special training or expensive instruments.

Microneedling combination

Atrophic facial scars are always a challenge to treat. Microneedling or Microneedling therapy is a new addition to the treatment armamentarium for such scars. It is a simple, inexpensive office procedure with no downtime. [28] In a study conducted by Imran Majid, 36 out of 37 patients showed good response to microneedling treatment. [29] At the same time, PRP has been used for various surgical and medical ailments. PRP along with microneedling would intensify the natural wound healing cascade because of the high concentration of patients own growth factors. It acts synergistically with growth factors induced by skin needling in order to enhance the wound healing response. PRP contains several growth factors, including platelet-derived growth factor, transforming growth factor B and vascular endothelial growth factors. Vitamin C has been shown to stimulate both type I and type III collagen synthesis and is well known for its antioxidant properties.

Redaelli et al. conducted a study for 3 months with 23 patients and concluded that PRP is a promising, easy to perform technique for face and neck rejuvenation and scar attenuation. ³⁰ Fabbrocini et al. conducted a study and found that PRP combined with microneedling was more effective in acne scars than microneedling alone. ³¹ Farris reported that topically applied vitamin C stimulates the collagen producing activity of the dermis and leads to the clinical improvement in photoaged skin with respect to firmness, smoothness and dryness. ³²

Lasers

The 1540 nm, non ablative, erbium:glass (Er:Glass) laser is a mid-infrared laser said to be useful in the treatment of atrophic acne scars. ^{33,34,35,36,37,38,39} The Er:Glass has the ability to reach a depth exceeding 1000 μm at high pulse energies. ⁴⁰ In a recent analysis carried out by Sardana et al. they revealed that even though the mean depth of penetration achieved by the Er: Glass (679 μm), was less than that of the commonly used fractional ablative lasers (Er:YAG and CO2), on facial skin, the difference in the histological depth of the three above mentioned fractional lasers (Er:Glass, Er:YAG and CO2) would probably be similar for superficial atrophic acne scars. ⁴¹ Furthermore, the 1540 nm wavelength is primarily absorbed by water but also targets the sebaceous glands and surrounding dermal matrix and minimal absorption by melanin makes the laser essentially safe for the treatment of dark skinned individuals. ⁴² Fractional lasers, both ablative and nonablative , are based on the well-established concept of fractional damage to the skin which enable a rapid healing as compared to the conventional ablative lasers as the intervening skin is intact for the reparative process. ^43,44,45 A secondary effect is the dermal remodelling induced in the dermis beyond the narrow zone of coagulation induced by the fractional lasers. ^46,47,48 The carbon dioxide (CO 2 ) laser has a predominant coagulative and necrotic effect (horizontal effect) as compared to the erbium:yttrium-aluminium-garnet (Er:YAG) laser, which has a dose-dependent increase in depth with less necrosis or coagulative effect (vertical effect). Thus, resurfacing procedures may be thought of as having both horizontal (tightening effect) and vertical (depth) treatment vectors on the tissue. Probably, the CO 2 lasers have more of a horizontal effect while the erbium laser has a more vertical effect. For atrophic acne scars, it is important to choose a modality that reaches the appropriate depth to target the deep, boxcar and ice pick scars while concomitantly treating the superficial scars. The conjecture that fractional lasers are effective for acne scars is derived from the fact that the microcolumns (microscopic thermal zone) act akin to the effect of 'needling' which helps to detach the tethering of scars and creates sufficient 'collagen remodelling' to 'lift' up the atrophic scars. Resurfacing procedures are considered by some to be the gold standard for the treatment of postacne scarring, and the mechanism is probably a combination of vertical ablation and horizontal 'tightening' of the tissue. However, it has been proven by experience that no amount of stretching out or ablation of deep dermal and subcutaneous structural loss with resurfacing tools can completely ameliorate the deep scars. The effect of thermal remodelling works in consonance with the depth achieved and thus the histological confirmation of the depth of the microthermal zone (MTZ) is probably more important for scar-specific improvement. Interestingly, while the face is the focus of fractional laser in acne scars, the seminal studies used the forearm for histological assessment. ^{45,46,48,49,50} The paucity of appropriate histologically directed studies in relation to facial acne scars is probably because of a lack of volunteers for histological assessment, which contrasts with the plethora of clinical studies in acne scars where the evidence of improvement is usually based on subjective assessment.

Microneedling Radiofrequency

A microneedling fractional radiofrequency (RF) device is available for commercial use (Lutronic corporation USA) with a maximum energy output of 50 W and capable of delivering energy in increments of 2.5 W in 20 equally graded energy level settings (Level 1-2.5 W to level 20-50 W).

The duration of each energy pulse can be set from 10 ms to 1,000 ms. A good control over the tissue damage can be achieved by changing the exposure time rather than altering the power level. Although the maximum power is higher than many other devices, the large range of exposure time enables the user to apply safe and consistent levels of coagulation in the dermis to achieve the desired effect. The energy delivery system consists of a disposable tip with 49 gold-plated needles. The entire length of the needle is insulated and it delivers bursts of RF energy through the tip. The depth of the needles can be adjusted from a minimum of 0.5 mm to a maximum of 3.5 mm. 51

The ability to set multiple needle depths per pass is an advantage, allowing discrete electrothermal coagulation at different layers of the dermis. The insulated needles prevent electrothermal damage from occurring anywhere in the dermis but at the very tip of the needle and never in the epidermis.

The mechanisms involved are neo-collagenogenesis by needle penetration stimulating the release of growth factors and relative sparing of epidermis and adnexal structures which contribute to rapid healing. 51

Ramesh et al. treated facial acne scars of 30 subjects with a matrix tunable radiofrequency device pretreated with oral antibiotics, topical tretinoin and subcision. The visual analog scale of improvement in scars ranged from 10-50% at end of 2 months to 20-70% at the end of 6 months. 52

Despite these differences both studies show that fractional radiofrequency is both safe and effective for treatment of acne scars in skin types 3, 4 and 5. Cho et al. evaluated efficacy of fractional radiofrequency in treatment of 30 patients with mild to moderate acne scars and large facial pores. The grade of acne scars and investigator global assessment of large pores improved in more than 70% of the patients. ⁵³

The encouraging results prompted us to conduct retrospective analysis of efficacy and safety of MFR to treat atrophic acne scars in patients of Indian ethnicity, skin type 4 and 5. Estimation of improvement with Goodman and Baron's Global qualitative Acne Scarring System showed that in 14 patients with Grade 4 scars, 85.71% showed improvement by 2 grades, 14.28% showed improvement by 1 grade. In 17 patients with Grade 3 scars, 76.47% improved by 2 grades and 23.52% showed improvement by 1 grade. Of the 31 patients with Grade 3 and Grade 4 acne scars, 80.64% showed improvement by 2 grades and 19.35% showed improvement by 1 grade. Rolling and box scars showed better response than ice-pick scars. Estimation of improvement with Goodman and Baron's Global quantitative Acne Scarring System showed that 58% of the patients had moderate improvement, 29% had minimal improvement, 9% had good improvement and 3% showed very good improvement Hence, all 31 patients (100%) showed improvement in their scars with no failure rate. The treatment was well tolerated with transient side effects such as mild erythema, post-inflammatory hyperpigmentation and track marks of the device.

Conclusion

This paper enforces on the multiple modalities of treatment needed for curing acne scars. Since such wide spectra of management is required for this condition it clearly indicates that it is a difficult modality to manage and hence a single approach is not enough and a combination approach is the right choice.

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