INTRODUCTION

Striae distensae (SD), commonly known as stretch marks, are undesirable dermal lesions that are related to rapid skin stretching, genetic factors, and hormonal changes. Initially, SD occurs as slightly raised or flattened red or pink scars (Lokhande and Mysore, 2019). Eventually, it turns into flat and permanent pale scars. SD normally appears along cleavage lines in the thighs, breasts, hips, and abdomen. The condition develops mainly during pregnancy and puberty growth.

Over the years, there has been development of interventions for patients with striae distensae. They include microdermabrasion, topical agents, light therapies, laser therapies, platelet-rich plasma (PRP) injection, and needling therapy (Hague and Bayat, 2017). While there are many methods used to treat SD, there is no agreement among researchers and practitioners to the gold standard treatment method. This has led to the questions about which method is the most effective. There have also been questions about the safety of each of these interventions.

One of the laser therapies used to treat SD is the non-ablative fractional lasers therapy. This treatment method involves use of a laser to enhance skin appearance. In non-ablative fractional lasers therapy, a laser is moved over the skin, penetrating into the deeper layers of the skin (Farahnik et al., 2017). The laser is moved in a pattern of microscopic dots, resulting in numerous tiny treatment zones. This stimulates the natural healing response of the skin, which in turn, enhances skin appearance. However, like any other intervention, the question of efficacy and safety also lingers for this method. This study is aimed to examine the efficacy and safety of this intervention in relation to striae distensae. This will be done through systematic review.

Rationale

This study is important because non-ablative fractional laser therapy has become increasingly popular. It is thereby important to determine examine whether it is effective and it is safe for patients. Effectiveness and safety are two criteria that any treatment intervention must meet for it to continue being used. While this method may be more effective in treating SD, if it is not safe for patients in that it results in long-term negative health effects, then it should be abandoned. This study aims to provide insight into these factors and recommend whether the method should continue being used or not.

Systematic reviews on the subject have been carried out. However, most have focused on comparing the various interventions of treating SD. This current review is thereby necessary because it will provide better insight into the efficacy and safety of non-ablative fractional laser therapy.

Objectives

• To examine the efficacy of non-ablative fractional lasers therapy

• To determine the safety of non-ablative fractional laser therapy

• To recommend whether the intervention should continue being used or be discarded

METHODS

Eligibility criteria

The eligibility criteria focused on types of studies, the type of intervention, and type of outcome. With regard to the types of studies, randomized clinical trials that examined the use of non-ablative fractional lasers therapy to treat SD were included (Aromataris, and Pearson, 2014). Ideally, only randomized clinical trials that used non-ablative fractional lasers therapy as an intervention method were needed (Chen, 2017). However, there are studies that examine more than one intervention, with one of them being non-ablative fractional lasers therapy. These studies were also included although the analysis was limited to this one intervention.

The type of intervention focused on, as indicated, is the non-ablative fractional lasers therapy. A study had to depict the use of this intervention for it to be considered for inclusion (Rother, 2007). Lastly, efficacy or effectiveness and patient safety were selected as the outcomes of the study. A source had to address these two factors for it to be eligible for inclusion.

Information sources

The information sources considered are reputable databases. They are GoogleScholar, PubMed and Cochrane Library (Jacsó, 2008). While these three databases were the main information sources, a search was carried out widely to get additional sources. The aim was to get as many sources as possible that examine the efficacy and safety of non-ablative fractional lasers therapy in treating SD.

Search strategy

The search for sources was done in the highlighted above. However, there was a general search from other sources in an attempt to get as many sources as possible. The search was carried out using key words that included Striae Distensae, treatments, non-ablative fractional lasers, efficacy, and safety (Munn et al., 2018). The synonyms of some words were also used to get better outcome. For example, effectiveness was also used in place of efficacy to get the sources that used this term. For GoogleScholar, the custom range option was used to select the most recent sources (Aromataris, and Pearson, 2014). The rationale for selecting the most recent sources was these sources were likely to provide better insight into the effectiveness and safety of non-ablative fractional lasers therapy.

Selection process

The first stage of the selection process was the examination of the title of the sources. The reviewer examined that the title of each source to determine if it met the criteria. The reviewer was keen to identify the keywords used to search in the title (Isenberg et al., 2013). For example, the reviewer examined the title of the source to determine if it talked about the efficacy and safety of non-ablative fractional lasers therapy. Those studies whose title indicated that the focus was to examine the effectiveness and safety of non-ablative fractional lasers therapy were selected.

However, there were those studies whose titles did not explicitly indicate that they examining the efficacy and safety of this intervention. The reviewer thereby examined the abstract of these studies to determine if the efficacy and safety of non-ablative fractional lasers therapy has been addressed (Aromataris, and Pearson, 2014). This was particularly the case for studies that examined more than one intervention. A significant number of studies examine the various treatment methods for SD and compare them to determine the one that is more effective and safer.

Data collection

Only one reviewer was involved in this study. The reviewer screened and categorized all the selected articles. The articles were screened using their titles and abstracts. The full text of the articles was then screened and relevant data extracted. The screening and extraction of data was done manually.

Data items

The outcome domains for which data was sought are effectiveness and safety. The data sought was one which highlighted the efficacy and safety of non-ablative fractional laser therapy when used to treat SD. All the results were compatible with each of these domains (Munn et al., 2018). This was given considering that these two domains were among the criteria that had to be met by a source before inclusion. The variables for which data was sought are safety and effectiveness. The focus was to collect data on safety and efficacy of non-ablative fractional laser therapy (Chen, 2017). Variables such as participant characteristics and intervention were not considered because they were uniform among all studies. For example, all participants in the studies reviewed had to be SD patients while the intervention used had to be non-ablative fractional laser therapy.

However, during the search, one change was made in relation to the eligibility of the sources selected. It was noted that restricting search to striae distensae yielded very few eligible sources. A decision was made to expand the scope to include other types of striae. The other types of striae considered included striae alba and striae rubra. The assumption made was if a treatment method is effective for the other types of striae then it is likely to be effective for striae distensae (Rother, 2007). However, there was one downside to this approach which is the severity of the diferent types of striae. For example, striae alba is old and more developed than striae distensae. This means that there was the risk of the intervention examined failing to be effective for this type of striae (Munn et al., 2018). As such, using the results from the other types of striae was likely to result in wrong conclusions in relation to the effectiveness of non-ablative fractional laser therapy in treating striae distensae. Adjustment in the search was also made to focus on stretch marks in general, that is, whether non-ablative fractional is effective and safe in treating stretch marks.

Risk of bias assessment

Risk of bias in this study was assessed using Cochrane risk of bias tool. The Cochrane risk of bias tool comprises of six domains which are selection bias, performance bias, detection bias, attrition bias, reporting bias, and other sources of bias (Ma et al., 2020). Each of the domains has criteria that are used to determine the risk of bias level.

Results

The search carried out yielded a total of 755 articles across the three databases. Out of the the 755, 708 were from GoogleScholar, 46 from PubMed while Cochrane Library had only one article. The articles were reviewed based on the tittles, abstract, and the eligibility criteria. After consideration of all factors and even including the expanded scope of striae, 6 articles were identified as the most relevant. These articles examined efficacy and safety of non-ablative factional laser therapy on patients with stretch marks in general. The following figure shows the selection process of the articles.

Risk of bias

The risk of bias in all the sources selected is low for all domains especially in relation to the objectives of this study. One of the reasons why this is the case is there are no comparable groups involved. All studies selected do not involve control groups which could have increased the level of selection bias (Lundh and Gøtzsche, 2008). All the studies are randomized controlled trials. The studies are controlled in the sense that all participants had to be patients of striae. On the other hand, they are randomized because even in situations where more than one intervention was used, participants were allocated randomly (Ma et al., 2020). In addition, with the focus of the study being solely focused on the efficacy and safety of non-ablative fractional lasers therapy alone, the results obtained were not affected by any selection bias as a result of allocation concealment.

Meta-analysis

The meta-analysis aspect of this study is supposed to examine heterogeneity, sensitivity, and inconsistency level. However, as indicated, all the studies selected did not include control groups (Field and Gillett, 2010). This means that it was not possible to calculate effect measures like risk ratio and mean difference among the studies (Field and Gillett, 2010). With there no mean difference, risk ratio, or any other effect estimate in the studies, especially in relation to the efficacy and safety of non-ablative fractional lasers therapy when examined in isolation, it was not possible to determine the degree of diversity among the studies.

Summary of results

Study Number of participants Country

Intervention Outcome

Yang and Lee (2011) 24 South Korea Non-ablative fractional laser therapy Improved appearance and no long-term side effects

Guertler et al (2019) 16 Germany Non-ablative fractional lasers therapy Improved skin appearance and no lasting negative side effects

De Angelis et al (2011) 51 Italy Non-ablative fractional lasers therapy Overall mean improvement mean score of between 51% and 75% and minimal side effects

Malekzad et al (2014) 10 Iran Non-ablative fractional lasers therapy Clinically appreciable improvement in striae and no significant adverse effect

Viviano et al (2022) 25 Italy Non-ablative fractional lasers therapy Excellent improvement in 88% of patients and outstanding improvement in the remaining 12% of the patients. No long-term side effects observed

Tretti Clementoni and Lavagno, (2015) 12 Italy Non-ablative fractional lasers therapy Good clinical improvement among patients and no long-lasting or severe adverse effects observed

Tang et al (2021) 15 China Non-ablative fractional lasers therapy Improvement appearance and no long-lasting or severe adverse effects

Guida et al (2018) 10 Italy Non-ablative fractional lasers therapy Overall improvement in 80% of patients and two adverse effects which are erythema and oedema were observed although they last between 1 and 5 days and were self-limiting

Naspolini et al (2019) 20 Brazil Non-ablative fractional lasers therapy Improvement in striae. Adverse effects experienced are erythema, crusting, hyperpigmentation, and post-procedure pain and lasted for an average of 4 days. No long-term side effects

Wang et al (2016) 9 USA Non-ablative fractionated laser All patients demonstrated clinical improvement and no significant long-lasting adverse effects

Gokalp (2017) 16 Turkey Non-ablative fractional laser Mean striae width reduced from 6.94 mm to 3.25 mm at the first follow-up visit and further to 3.13 mm in the second follow-up visit. The striae length, on the other hand, reduced from 6.06 cm to 2.75 cm at the second follow-up visit. No long-lasting side effects

Tang et al (2021) 15 China Non-ablative fractional laser therapy Effective improvement and no-long lasting side effects

DISCUSSION

Main findings

In this systematic review and meta-analysis study, evidence was gathered from 12 studies that examine the efficacy and safety of non-ablative fractional lasers therapy. While initially the focus was to examine how effective and safe this intervention is in relation to treating striae distensae, the search gave few studies and as such, studies that examined the treatment of other types of striae using non-ablative fractional lasers therapy were also considered to be eligible. In total, the studies involved a total of 223 participants across 9 nations. On the question of efficacy, systematic review shows that non-ablative fractional lasers therapy is effective in treating not only striae distensae but all types of striae. All studies show that in general, there was improvement among all patients that were treated using this therapy. The improvement was both clinical and aesthetic. Aesthetically, all patients showed improved skin appearance. The clinical improvement, on the other hand, involved reduction of striae.

On the question of safety, the systematic review revealed that in general, non-ablative fractional lasers therapy is a safe treatment method for striae in general. This is reflected in the absence of long-term side effects. In all the studies, patients experienced short-term side effects which included pain, erythema, and crusting. However, these lasted utmost 2 months, with majority of the side effects lasting only a few days. On the question of pain, all studies indicate while all patients felt pain during treatment, in most cases the pain was tolerable. In other words, patients could withstand the pain as a result of the treatment procedure.

Agreements and disagreements among studies

There is a general agreement among reviewed studies on the question of efficacy and safety of non-ablative fractional lasers therapy in treating striae distensae. As indicated, all studies show improved in striae following the improvement. On the other hand, the studies show that there are generally no lasting side effects. However, one area of disagreement is with regard to the level of effectiveness. Some studies show that the level of effectiveness is moderate while there are others that show there is excellent improvement of striae in patients. For example, De Angelis et al (2011) found that there is mean score improvement of between 51% and 75%. It implies that after treatment using non-ablative fractional lasers therapy, stretch marks reduced by between 51% and 75%. On the other hand, Viviano et al (2022) found that there was excellent improvement among 80% of patients. It means that following the treatment, 80% of the patients were completely healed of stretch marks, with possibly excellent improvement in skin appearance.

On the question of safety, the point of disagreement among the studies is in relation to the adverse effects experienced among different patients. For example, Guida et al (2018) established that only two side effects were experienced among patients and these are erythema and oedema and they lasted for only a short time. On the other hand, Naspolini et al (2019) established that some of the side effects include post-procedure pain, erythema, crusting, and hyperpigmentation.

There are a number of possible reasons why there are differences in terms of the level of effectiveness and the side effects. One of them is the type of striae involved. As indicated, this systematic review study was not limited to the striae distensae. There are other types of striae that were examined. The severity of each of striae is different. As such, the level of effectiveness of non-ablative fractional lasers therapy can be different. This argument can be examined by looking at the results of the different studies. The studies by De Angelis et al (2011) and Viviano et al (2022) both examine striae distansae yet they have varying level of effectiveness. In the case of these two studies, there is likely to be a different factor for the difference other than the type of striae in question. One of them is age. Viviano et al (2022) examined the effectiveness and safety of non-ablative fractional lasers among adolescents. The study by De Angelis et al (2011) does not indicate the ages of participants. However, it is possible that they are older. As one grows older, the ability of the body to self-heal reduces. As stated, the non-ablative fractional lasers therapy is focused on stimulating the skin to self-heal. In this case, adolescents are likely to experience faster healing when compared to older individuals and this may explain the difference between in the level of effectiveness. The age of the stretch marks could also be a contributing factor. Older stretch marks are generally difficult to heal when compared to newer ones. De Angelis et al (2011) indicate in their study that the stretch marks they were examining were aged between 3 and 20 years. On the other hand, with Viviano et al (2022) examining stretch marks among adolescents, it implies that these stretch marks were newer, most probably have experienced as a consequence of puberty growth.

Other factors that could be contributing the differences in the level of effectiveness and safety of non-ablative fractional lasers therapy are skin type, number of sessions, laser parameters and patient compliance. Skin type may influence how effective the intervention is and the kind of side effects that will be experienced. For instance, darker skin is at a higher risk of hyperpigmentation and scarring after treatment. Laser therapy does not also result in optimal outcomes in terms of skin appearance. This may explain why there are different levels of effectiveness as well as different types of side effects among different studies, even those that examine the same type of striae.

The number of sessions one undergoes also determines the outcomes. The number of sessions needed to achieve desired results may vary among different people depending on severity of the condition and one’s response to treatment. For example, if the condition is severe in that stretch marks are significantly developed, one may need more sessions. Similarly, if one responds slowly to treatment as a result of factors such as age and skin type, they may be needed to be subjected to more sessions. The number of sessions could also explain the differences in the outcomes in these studies, especially with respect to the effectiveness of non-ablative fractional lasers therapy. For example, in their study Guertler et al (2019), patients received three treatments at the interval of 4 weeks. On his part, Gokalp (2017) had patients undergo treatment five times at the intervals of 4 weeks. Examining the results, it shows for Guertler et al (2019), the depth of atrophic lesions reduced by 31.7%. On the other hand, for Gokalp (2017), the strial width fell from 6.94 mm to 3.24 mm which was more than 50% reduction. While the parameters considered in these two cases are different, the fact that there are differences in reduction of stretch marks with a different of number of sessions, with the study that involves more sessions showed better results is an indication that the number of sessions could be a determining factor with regard to the effectiveness of non-ablative fractional lasers therapy.

The type of laser employed and its parameters like the wavelength, energy level, and pulse duration may influence the effectiveness as well as the safety outcomes for striae patients. This is better reflected in thein the study Wang et al (2016). In their study, Wang et al (2016) examined the efficacy and safety of a 150-nm and 140-nm non-ablative fractional laser. They found that 33% of those treated using the 150-nm laser depicted good or excellent while 28% of those treated using the 140-nm laser showed similar results. Assuming that the patients had similar characteristics in terms of the skin type, age, and severity of striae, it can be concluded that the 150-nm type of non-ablative fractional laser is more effective.

Lastly, patient compliance can be a key factor in determining the ultimate outcome. For example, one of the requirements following the non-ablative fractional lasers therapy is one has to avoid exposure to sun to facilitate healing. Those patients that comply with this requirement are likely to have better results when compared to those that fail to comply.

In general, the results show that as a whole, non-ablative fractional lasers therapy is an effective and safe intervention in the treatment of striae distensae and all types of stretch marks. However, the level of effectiveness differs, with some patients showing better outcomes than others. With respect to safety, all studies show while the side effects experienced differ for different patients, they are all short-term and heal on their own. There are no long-term side effects.

Limitations

This study provides insight into the effectiveness and safety of non-ablative fractional lasers therapy, information that can be used to inform the use of intervention in treating stretch marks. However, it has a number of limitations that reduce the reliability of the results. One of them is most of the treatments in the reviewed studies were carried out in one study only. With only one study carried out, it is not possible to accurately conclude that the results are highly reliable. This is despite there being evidence of positive outcomes of the treatments. Any shortcomings in these studies are thereby reflected in the results obtained in this study.

Another limitation is publication bias. A publication bias is occurs when studies that highlight desired results are published while those that do not reveal the desired results are not published. The publication bias is likely to have occurred in this case because all studies show effectiveness and safety of non-ablative lasers therapy. While the positive results could be because in reality this intervention method is effective and safe, the fact there is 100% agreement among all studies raises questions about publication bias.

There is a limitation in relation to the studies reviewed which have led to discrepancies with respect to the efficacy and safety level among different studies, despite all of them showing that non-ablative fractional lasers therapy is an effective and safe intervention. The objective of this study was to examine how effective and safe non-ablative fractional lasers therapy when used to treat striae distensae. Ideally, the studies that should have been reviewed are only those that examine the use of non-ablative fractional lasers therapy on striae distensae. However, due to the limited number of studies that specifically examine the use of this intervention to treat this specific type of stretch marks, studies that examine use of non-ablative fractional lasers to treat other types of striae like striae alba were included. This raises questions about the reliability of the results obtained, especially if they are to be used to draw conclusions about the efficacy and safety of non-ablative fractional lasers therapy in patients with striae distensae.

Other limitations of this study include heterogeneity, quality of studies reviewed, and confounding factors. Heterogeneity was not statistically determined in this systematic review because of lack of more than group in any study with regard to use of non-ablative functional lasers therapy. However, this does not mean that there were no actual differences in reviewed studies which are likely to have affected the results obtained. For example, the participants in each of the studies reviewed had unique characteristics in terms of age, ethnicity, and severity of striae they were suffering from. The patients in each study were also subjected to different number of sessions. As such, each study had unique results which make it hard to consolidate all of them to draw an accurate conclusion.

The quality of the studies reviewed is not known. In carrying out the studies, the researchers may have been biased, only choosing to publish only the results that are in line with their beliefs. If the quality of the studies is poor, then the reliability of the results obtained in this study is questionable. Lastly, there are confounding factors that are not were not captured in the studies but which may have affected the outcomes. These include the baseline characteristics of participants involved and co-interventions.

In general, reliance on already published studies raises questions about the reliability of the results in this study because of many factors that include the quality of the studies, the publication bias, the confounding factors, and heterogeneity.

Implications

There are both theoretical and practical implications of the results. One of the practical implications of the studies is there is need to use non-ablative fractional lasers therapy more in treating striae distensae and any other type ofstriae. This is because the results indicate that this intervention method is both effective and safe. The results also imply that there is need for policies that that will result in mainstreaming of this treatment option as a clinical practice. Nona-ablative fractional lasers therapy is a fairly new treatment option for striae and most probably there have been concerns about its effectiveness and safety. With these results showing that it is generally effective and safe, it can now be used widely.

As highlighted, although the results show that in general non-ablative fractional lasers therapy is effective and safe, its effectiveness varies. This implies that there is need to personalize the kind of non-ablative fractional lasers therapy to use. For example, there are patients that would need to be subjected to a higher number of sessions to ensure desired results are achieved. The parameters of the lasers may also need to be adjusted for different patients depending on the severity of the striae, age, and other factors.

Lastly, while the systematic review shows that non-ablative fractional lasers therapy is safe, there are short-term negative effects, some of which last a considerable amount of time. There are also cases where the pain experienced during treatment was almost intolerable for some patients. This intervention method thereby needs to continue being developed so that these side effects can be mitigated so that the treatment method can be safer.

Theoretically, the results imply that there is need for more research on the subject to gain better insight. One aspect of research that should be examined in future is the moderating factors that affect the effectiveness of non-ablative fractional lasers therapy. As highlighted, some of the possible factors that may affect the efficacy of this intervention method include age, severity of striae and even the type of striae. Examining these moderating factors will help come up with strategies on how to improve the method and make it more effective. An examination of the moderating factors may also be key to customizing the intervention so that it can treat all form of striae.

Another area of research in future is comparison with other intervention methods. There are a number of studies that examine the difference in the effectiveness and safety of non-ablative fractional laser therapy and other interventions. However, more research is need in this area to provide better insight into this intervention. This will inform whether it should continue being used or whether another method should be opted for.

Conclusion

Essentially, striae distensae is a common condition that affects many people. However, it is more common among pregnant women. While in some cases stretch marks heal on their own, especially in case of pregnancy, in other cases it persists. While this condition does not have any negative effect, it has a negative effect on skin appearance and as such, those who suffer from it are comfortable with it. Thre are a number of interventions for patients with striae distensae and they include microdermabrasion, topical agents, light therapies, laser therapies, platelet-rich plasma (PRP) injection, and needling therapy. Among the laser therapies is the non-ablative fractional lasers therapy. In this systematic review and meta-analysis study, the effectiveness and safety of this method is examined. A systematic review yielded 12 articles that examine efficacy and safety of this intervention method. While initially the focus wa to review intervention method in relation to striae distensae alone, the search was expanded to include other types of striae. The databases used for search are GoogleScholar, Cochrane Library, and PubMed. All the studies considered were randomized controlled trials. A review of the results showed that in general, non-ablative fractional lasers therapy is effective and safe as a treatment option for striae distensae and any other type of stretch marks. This is reflected in the improvement of skin appearance and lack of long-term side effects following the use of this intervention. However, there are differences in the level of effectiveness, with some studies showing that the intervention has a very high level of effectiveness and others showing that the effectiveness of this method is moderate. In relation to safety, the studies show that there are multiple short-term side effects and they include post-procedure pain, erythema, crusting, and oedema. However, these side effects are self-limiting in the sense that they heal without any additional interventions. The practical implications are that this intervention method should be adopted although more research should be carried out on it to determine how to make it effective for all patients and for all kinds of striae.

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