Abstract
Summary
Introduction
Atrophic scars cause significant patient morbidity. Whilst there is evidence to guide treatment, there does not appear to be a systematic review to analyse the efficacy of treatment options.
Objectives
To retrieve all evidence relating to atrophic scar treatment and evaluate using the Clinical Evidence GRADE score in order to allow clinicians to make evidence-based treatment choices.
Method
Searches were performed in Medline, EMBASE, CINHL and Cochrane to identify all English studies published evaluating treatment of atrophic scars on adults excluding journal letters. Each study was allocated a GRADE score based on type of study, quality, dose response, consistency of results and significance of results. The end score allowed categorisation of evidence into high, moderate, low or very low quality.
Results
A total of 41 studies were retrieved from searches including randomised controlled trials, observational studies, retrospective analyses and case reports of which 7% were allocated a high-quality score, 10% a moderate score, 7% a low score and 75% a very low score. Treatment modalities included ablative laser therapy, non-ablative laser therapy, autologous fat transfer, dermabrasion, chemical peels, injectables, subcision, tretinoin iontophoresis and combination therapy.
Conclusion
There is a paucity of good-quality clinical evidence evaluating treatment modalities for atrophic scarring. Evidence supports efficacy of laser, surgery and peel therapy. Further biomolecular research is required to identify targeted treatment options and more randomised controlled trials would make the evidence base for atrophic scar treatment more robust.
Introduction
Main causes and risk factors for developing atrophic scars.
There are various atrophic scar treatment modalities in this clinical area of interest. This article aims to describe and evaluate the evidence in published literature including randomised controlled trials (RCTs) for atrophic scarring. The method of evaluation of studies will be via the Clinical Evidence GRADE score, which assigns a score to categorise all interventions according to their likely effectiveness based on type of study, quality, dose response, consistency of results and significance of results.
Methods
We conducted a Medline, EMBASE, Cochrane and CINHL search to retrieve any studies including RCTs evaluating treatment modalities for atrophic scarring. Key words used in each search engine included (with wildcard truncation used as*) atrophic, scar*, therapeutics (mapped to thesaurus to include treatment, intervention), drug treatment, conservative treatment, surgery, laser, treatment outcome and treatment response. We excluded journal letters and interventions on paediatric patients. We included all English publications published in any year analysing the effectiveness of treatment modalities for atrophic scarring. A total of 45 studies were identified which included RCTs, observational studies, retrospective analyses and case reports. No review articles were identified.
All abstracts of studies found were assessed by two independent clinicians against criteria for inclusion to ensure applicability of study within the systematic review. Randomised control trials were included regardless of the length of follow-up period or patient drop-out rate and those that were at least single blinded. A final number of 41 studies were identified.
Clinical evidence GRADE score components (adapted from Clinical Evidence 1 ).
Final score (quality of evidence) High = 4 points overall, Moderate = 3 points, Low = 2 points, Very low = 1 point or less.
RCT: randomised controlled trial.
Results
Forty-one studies reporting treatments for atrophic scars were identified including randomised control trials (8), retrospective cohort study analysis (8), prospective cohort analysis (21) and case studies (4) as demonstrated in Figure 4.
Atrophic scar treatment modality and GRADE scoring.
RCT: randomised controlled trial; TCA: trichloroacetic acid.
Of these studies, three were allocated a high GRADE score (7%), four studies scored as moderate (10%), three scored as low (7%) and the majority of 31 studies scored very low (75%), demonstrated in Figure 5.
Of the eight RCTs evaluated, five were regarded as high- or moderate-quality studies. Studies were deducted points due to low sample size and short-term follow-up although all RCTs showed statistically significant improvement of scars with treatment. Efficacious treatment modalities were CO2 ablative therapy and non-ablative laser therapy. Of the 21 observational studies, identified scores ranged from moderate- to very-low-quality studies. Again score variances identify issues of interstudy heterogeneity with regard to sample sizes, methodology, treatment outcome measures used, and methods of evaluating scar improvement. Lastly, most of the retrospective analysis and case report studies scored as low or very low quality due to the limitations of sample size and generalisability of results.
Discussion
Several key papers that discuss atrophic scarring focus on acne. Community-based studies report acne is prevalent in 90% of adolescent patients and can occur in any regions where there is an abundance of pilosebaceous glands such as the face, shoulders, back and chest. The process of acne is caused by various factors which increase sebum production of pilosebaceous glands such as increased systemic production of androgens and concomitant Propionibacterium acnes proliferation within follicles. The resultant infrainfundibular inflammatory process which ensues can cause follicular rupture or abscess formation. The wound healing process which then occurs can cause atrophic scars. In the adult population, 1% of patients are reported to have persistent acne scarring from adolescence. 43 The risk factors for developing scarring are multifactorial including a genetic predisposition to scarring, and a delay in acne treatment. The extent of scarring in acne can be reduced by early treatment during the inflammatory phase.
An observational study of normal scarring shows that histologically the scar maturation process occurs over a year with fibroblastic changes in dermal layers of skin; however, clinically the appearance remains unchanged except from diminishing erythema as angiogenesis ceases. 44 In addition, atrophic scarring is reported to worsen with age due to the natural lipoatrophy which further accentuates the scars. 45
Atrophic scars are defined histologically as scars showing a loss of collagen. They have been subclassified into the icepick scars which are the most prevalent subcategory at 60–70%, boxcar scars at 20–30% and rolling scars at 15–25%.
46
Icepick scars are described as a ‘V shaped’ extension scar into dermis whereas boxcar and rolling scars are more superficial with a wider base (Figure 1).
Subcategories of atrophic scars (adapted from Jacob et al.
46
).
However, boxcar and rolling scars can be deep and all three subcategories can co-exist making clinical identification of type difficult. Histologically, atrophic scars exhibit thinning of the skin with a loss of collagen, elastin and deep dermal fat which cause a downward traction pull of the epidermis (Figure 2). Atrophic scar formation over time can be demonstrated in Figure 3.
Immunostaining of anti-β-catenin in (a) atrophic scar and (b) keloid. Sparse staining in (a) correlates with reduced growth factor activity compared to (b). Haemotoxylin and eosin staining.
47
Histopathology of atrophic scar (a) and keloid (b). Scale bar: 100 μm Acne inflammatory lesions progressing to scars over time; (a) 0 weeks, (b) numbers of weeks from zero.
48
Bar chart showing percentages of various atrophic scar study types. Bar chart showing number of studies in each GRADE category.



The histological changes noted and described arise due to the inflammatory and reparative process of wound healing. The reparative phase is subdivided into (a) inflammation, (b) granulation and (c) matrix remodelling phases.
The main causes for patient distress from acne are facial disfigurement from inflammation, pigmentation and scarring. The psychosocial consequences resulting from acne were first recognised by Sulzberger and Zaidens. 49 A study examining the quality of life acne patients reported showed they experienced psychological and emotional morbidity comparable to chronic, disabling conditions such as epilepsy, diabetes and arthritic pain. 50 In addition, severe acne has been correlated with depression and suicidal ideation. 51 Patients can experience body dysmorphia due to the visible acne; however, the degree of psychological distress may not always correlate with the severity of acne and can be present in clinically mild acne causing low self-esteem and a reduced confidence to socialise. 52 Due to these recognised psychological comorbidities acne patients may have, it is important to offer holistic management and recognise psychological symptoms early.
Given the significant patient morbidity, our study highlights a lack of robust, good-quality evidence evaluating treatments. Overall, there is a lack of evidence evaluating treatment of this particular scar subcategory in comparison to keloid or hypertrophic scarring. In addition, there appears to be a lack of concrete pathophysiological knowledge of how atrophic scars occur and develop which could explain the paucity of treatment evidence as further biomolecular and pathological research examining the nature of atrophic scars needs to be conducted to further identify targets for treatment.
We chose the Clinical Evidence GRADE Score system to evaluate the quality of studies in our review over other scoring systems as we aimed to focus on outcome evidence of scar severity improvement, which clinicians could use to make judgements about efficacy of treatment for individual patients. Hence, the end scores assigned to each study do not take into account detailed analysis of methodology such as single or double blinding as well as wider practical issues such as treatment cost effectiveness. Two independent clinicians assigned each final score and crosschecked for congruence and in cases of discrepancy the paper was re-examined and the end score was achieved together. Despite this, the main disadvantage of the GRADE scoring system is that it is prone to being more subjective than other scores as it relies on the assessor’s own judgement about certain criteria and where studies have very different methodologies comparison for scoring purposes can be difficult.
As is evident, there is a scarcity of RCTs and all are single blinded due to the nature of treatments subjected to trial; however, they provide a basis for further large-scale studies particularly with regard to the injectable therapies and the CROSS method of trichloroacetic acid (TCA) chemical peel therapy. Clearly, further RCTs with standardised methodology would need to be conducted before a meta-analysis of results can be compiled.
Hierarchy of therapy for atrophic scars based on GRADE scores.
Other treatments (scores less than +2): autologous fat transfer, dermabrasion, injectables, tretinoin iontophoresis, subcision and artefiller and triple therapy.
RCT: randomised controlled trial.
Pros and cons of each treatment modality.
The main limitation of our study is the lack of total number of articles retrieved from which to draw a sound conclusion. However, we did not search for articles in other languages or non-published data rendering the results subject to publication bias. In addition, the scoring system used evaluates efficacy of treatment but not patient tolerance of treatment, which may affect options offered. For example, most patients did not tolerate CO2 ablative therapy well due to pain during and immediately after therapy as well as multiple side effects.
Conclusion
In summary, our review identifies an overall lack of published data regarding treatment of atrophic scarring and poor study methodology. Further research at a molecular level may be able to better define atrophic scarring and allow targeting of therapy. Our review allows the possible identification of areas where further RCTs may be conducted. Whilst our review reveals various treatment options which may be utilised to treat atrophic scarring, the ultimate choice of a particular treatment modality will depend on an individual patient’s circumstances, preference and aims of treatment outcome.
