Evaluating the Pros and Cons of Fractional CO2 Laser Versus Microneedling in Atrophic Acne Scars in the Skin of Color: A Split Face Study

Abstract

Background:

Post-acne scarring causes severe physical and psychological distress. Multiple treatment modalities are available with no single gold standard treatment.

Aim and Objectives:

To assess and compare the efficacy and safety of fractional CO2 laser and microneedling in atrophic acne scars and corelate with variables like scar type, duration, and Fitzpatrick skin types.

Materials and Methods:

Thirty patients (aged 20–40 years) with facial post-acne atrophic scars with the same Goodman and Baron (GB) grade on both sides of the face were included in the study after written informed consent. After priming skin, four monthly sessions of fractional CO2 laser on the right and microneedling on the left side were performed with 2 months follow-up.

Results:

GB (3.53 to 2.37) grade and patient’s subjective score (8.63 to 4.37) showed 32.9% and 49.4% improvement over the fractional CO2 laser side and 9.3% (3.53 to 3.20) and 19.7% (8.63 to 6.93) improvement over the microneedling side, respectively, and the difference between the two modalities being statistically significant. Rolling (42.90% vs. 16.18%) and boxcars (36.18% vs. 3.74%) also showed more improvement with fractional CO2 laser. Ice-pick scars responded the least with both modalities. Scars of less than 10 years duration responded better to both modalities with sustained improvement during the study. However, postinflammatory hyperpigmentation (30% vs. 6.67%) was greater with fractional CO2 laser (more in higher Fitzpatrick skin types).

Limitations:

Small sample size, short follow-up period, and subjective assessment methods.

Conclusion:

Both microneedling and fractional CO2 laser improve the overall appearance of atrophic post-acne scars. The latter was more effective than the former but with a slightly longer healing time and greater post-procedure hyperpigmentation.

Introduction

Acne is one of the most common causes of disfiguring facial scars.[1,2] Recent epidemiological studies have shown that nearly 80% of patients with acne have some scarring and 50% have clinically relevant scarring.[3] Psychological stress like lowered self-esteem, anxiety, low academic performance, and unemployment can occur in these patients.

Acne scar treatment must include considerations like the severity of scars, psychological impact and expectations of the patient, cost, efficacy, and side effect profile of the treatment.

Microneedling is a method that involves using thin needles to create hundreds of very thin holes on the skin which allow the skin to begin to regenerate by producing collagen and elastin. Fractional ablative lasers induce thermal ablation in microscopic columns of epidermal and dermal tissue while sparing the remaining skin. This approach leads to a significantly faster recovery time and better results when compared to traditional ablative resurfacing and nonablative lasers, respectively.[4]

However, there are limited data comparing the efficacy and safety of these two modalities, particularly in correlation with variables like scar type, duration, and Fitzpatrick skin types.

Material and Methods

This was an interventional prospective split-face study conducted over a period of 2 years (December 2018 to January 2021) in patients aged 20–40 years with atrophic post-acne scars of grades 2, 3, and 4 (Goodman and Baron grade). Patients with a similar grade of acne scars on both sides of the face were included to ensure matching and avoid bias. Pregnant and lactating women and patients with medical conditions, active acne or infections, keloidal tendency, and history of procedures for acne scars within the last 3 months were excluded.

After approval by the Institutional Ethics Committee and written informed consent, 32 patients were enrolled, of which 30 patients successfully completed the study, while two patients were lost to follow-up. The right and left halves of the face of each patient were treated with fractional CO2 laser and microneedling, respectively, subjected to four sessions at 4-week intervals, followed by monthly assessment for the next 2 months [Flowchart 1].

Flowchart 1.

Consort Statement Flow Chart

Priming with sunscreen and pigment lightening cream (kojic acid, arbutin) was done 15 days preceding the treatment; the latter was used for patients with a higher (IV and V) Fitzpatrick skin type. Topical EMLA (eutectic mixture of local anesthetic) was applied for 45 minutes on both sides of the face. After precooling on the right side, Alma Pixel fractional CO2 laser (scanner mode using square option, single pass, focal length 100 mm) was performed with an initial energy of 30 mJ/cm2 and increased by 10 mJ/cm2 every 4 weeks up to a maximum of 60 mJ/cm2 in the fourth sitting. For microneedling over the left side, the area to be treated was stretched with one hand, and with the other hand, a microneedling device (Dermaroller 1.5 mm, 540 needles; greater number of needles were chosen with the intention to achieve more density of pricks per cm² and thereby more collagen induction) was rolled over the skin in all four (horizontally, vertically, diagonally left and right) directions to cover an area of 2 * 2 inches till uniform pinpoint bleeding, ensuring an even pricking pattern (approximately 300 pricks/cm²). The patient was sent home on topical antibacterial with strict photoprotection.

Assessment parameters used were patients’ subjective score (PSS), where patients were asked to score the severity of acne scars from 0 to 10, and Goodman and Baron qualitative acne scar grading (GB grade) system. Acne scar improvement was correlated with the duration and type of acne scars. The downtime and side effect profile of each modality and their relation to Fitzpatrick skin type were also documented.

Statistical analysis was performed using IBM SPSS 28:0 software. Wilcoxon signed rank test was used to compare pre- and post-treatment GB grade and PSS on right and left sides. Mann–Whitney test was used to compare the percentage change in scores between right and left sides after treatment. Acne scar duration and GB grades and PSS were correlated using paired and unpaired t-tests. A P value of less than 0.05 was considered as statistically significant.

Results

The 30 patients comprised 17 (56.7%) males and 13 (43.3%) females with a mean age of 26.94 years and 25.31 years, respectively. Fourteen (46.7%) patients had Fitzpatrick skin type III, followed by ten (33.3%) with type IV and six (20%) with type V. Twenty (66.67%) patients had GB grade 4, while six (20%) cases had grade 3, and four (13.33%) cases had grade 2. Seventeen (56.7%) had a duration of scars less than 10 years, while the remaining (43.3%) were older than 10 years. The baseline median GB grade was 3.53 for both cheeks. With every sitting, the GB grades reduced on both sides, with the second follow-up resulting in 22 (73.3%) patients of GB grade 2, 5 (16.67%) and 3 (10%) patients of GB grade 3 and 4, respectively, on the fractional CO2 (right) side, and 6 (20%) patients of GB grade 2 and 12 (40%) patients each of GB grade 3 and 4 on the microneedling (left) side. There was 32.9% (3.53 to 2.37) improvement in GB grade on the right side, while improvement on the left side was 9.3% (3.53 to 3.20), [Table 1] with a significant statistical difference (P < 0.001) between the sides. The patients’ subjective score improved by 49.4% (8.63 to 4.37) on the right side and 19.7% (8.63 to 6.93) on the left side [Table 2], again the difference being statistically significant (P < 0.001).

Table 1.

Change in mean Goodman and Baron grade with each sitting

GB Grade	Right		Left
	Mean	SD	Mean	SD
Pretreatment	3.53	0.73	3.53	0.73
1st sitting	3.53	0.73	3.53	0.73
2nd sitting	3.07	0.87	3.37	0.81
3rd sitting	2.70	0.88	3.23	0.77
4th sitting	2.53	0.82	3.23	0.77
1st follow-up	2.43	0.68	3.20	0.76
2nd follow-up	2.37	0.67	3.20	0.76

Table 2.

Change in mean patient subjective score with each sitting

Patient subjective score	Number of patients	Right		Left
		Mean	SD	Mean	SD
Pretreatment	30	8.63	1.27	8.63	1.27
1st sitting	30	8.63	1.27	8.63	1.27
2nd sitting	30	6.60	1.28	8.20	1.30
3rd sitting	30	5.60	1.87	7.73	1.20
4th sitting	30	5.00	2.10	7.33	1.24
1st follow-up	30	4.50	2.16	7.07	1.31
2nd follow-up	30	4.37	2.21	6.93	1.26

The line diagram [Graph 1] depicts the baseline GB grade on both sides as 3.53, which reduced consistently to achieve a mean of 2.53 on the right side and 3.23 on the left side at the completion of treatment (4 sessions) and reduced further to 2.37 and 3.20, respectively, at the end of the follow-up period. Similarly, the baseline patient subjective score on both sides was 8.63, which reduced consistently with every session (conducted at 4-week intervals) to achieve a mean score of 5.00 on the right side and 7.33 on the left side at the end of 4 months (4 sessions) and 4.37 and 6.93, respectively, at the end of the follow-up period.

Graph 1.

Line diagram showing improvement in Goodman and Baron grade with every session (every month) and during follow-up period

Ice-pick scars [Figure 1] showed minimal change from 7.10 [SD: 2.12] to 6.87 [SD 2.05] over the right side and from 7.10 [SD: 2.12] to 7.07 [SD 2.12] over the left side; the P value was statistically significant on the right side (P = 0.008) but not on the left (P = 0.317). The difference between both the sides was insignificant. The mean score of rolling scars [Figure 2] changed from 6.00 [SD 2.84] to 3.03 [SD 1.94] on the right side [fractional CO2 laser] and from 6.00 [SD 2.84] to 5.03 [SD 2.58] on the left side [microneedling]. The difference in reduction of mean scores on both sides was statistically significant [P < 0.001]. The mean score of boxcars [Figure 3] on the right side reduced from 4.53 [SD 2.84] to 2.70 [SD 1.94], which was statistically significant [P = 0.001, Z = 4.586], and on the left side, it reduced from 4.53 [SD 3.31] to 4.30 [SD 3.18], again statistically significant (P = 0.008). The difference in reduction between both sides was not statistically significant though (P = 0.051). On comparing mean percentage change in grades, we found rolling scars showed the greatest response with 42.90% improvement, followed by boxcars, which improved by 36.18% on the right side. On the left side, the final outcome was less than that on the right side [16.18% improvement in rolling type scars and 3.74% improvement in boxcars] [Figure 4]. The difference between right and left sides in percentage improvement of rolling and boxcars was statistically significant (P < 0.001). On the right side, the mean percentage change in score of ice-pick scars was 3.13% [SD 6.26], while on the left side, it was 0.42% [SD 2.28] after treatment. As per the Mann–Whitney test [Z = 0.018], there was a statistically significant difference between right and left sides (P = 0.026). Patients with scars of a duration less than 10 years showed statistically significant (P < 0.001) improvement in GB grade on both sides, while patients with scars older than 10 years were comparatively less responsive. Hence, there was statistically significant association between response and scar duration (P 0.002) on both sides.

Figure 1.

Patient with predominant ice-pick scars, pretreatment and post-treatment photographs of left (microneedling- GB grade 3 pre and post) and right sides (fractional CO2- GB grade 3 reduced to 2)

Figure 2.

Patient with predominant rolling scars, pretreatment and post-treatment photographs of left (microneedling- GB grade 3 reduced to 2) and right sides (fractional CO2- GB grade 3 reduced to 2)

Figure 3.

Patient with predominant boxcars, pretreatment and post-treatment photographs (erythema) of left (microneedling- GB grade 4 reduced to 2) and right sides (fractional CO2- GB grade 4 reduced to 2)

Figure 4.

Comparison of mean percentage change in ice pick, rolling, and boxcars between right and left sides

Transient early side effects (erythema, edema, stinging) were noted in all the patients equally on both sides, which resolved within a mean period of 3–4 days. Late side effects like atrophy, scarring, persistence of hematoma/nodule formation, and recurrence were not encountered in any subject. Nine (30%) and two (6.67%) patients developed postinflammatory hyperpigmentation (PIH) after fractional CO2 laser (right side) and microneedling, respectively, whereas one patient developed hypopigmentation on the right side. On the CO2 laser side, 3 out of 14 patients (21.43%) with Fitzpatrick Skin type III, 3 out of 10 patients (30%) belonging to Type IV, and 3 out of 6 patients (50%) belonging to Type V developed postinflammatory hyperpigmentation (PIH), whereas on the microneedling side, 1 out of 10 (10%) patients of Fitzpatrick skin Type IV and 1 out of 6 (16.6%) patients of Fitzpatrick skin type V developed postinflammatory hyperpigmentation.

Discussion

Online literature search led us to a few studies comparing the same modalities; however, different assessment parameters and end points made the comparison with our study difficult.

Fractional CO2 laser (32.9% improvement in GB grade) was found to be significantly more effective than microneedling (9.3%) in our study. In a study by Pooja et al. in 2020[5] on 60 patients, 20 each were treated with fractional CO2 laser, microneedling, and PRP using GB qualitative and quantitative scales. Mean improvement was 68.7% and 60.3% post fractional CO2 laser and post microneedling, respectively, after four sittings. In contrast to the aforementioned study, we observed a statistically significant difference in efficacy between the two modalities. Abel et al.[6] in 2020 on comparing the same modalities as our study in 182 patients noted a reduction of 37.63% for microneedling and 41.22% for fractional CO2 laser according to the global acne scarring classification system, the difference in percentage reduction between the two being statistically significant for severe scars as in our study, but a different grading system was used. Monisha et al.[7] in 2021 compared the two modalities in 140 patients and found significant reduction via both the modalities with a significant difference between the two. Obaid et al.[8] in 2021 also compared these two modalities in 40 patients and found satisfactory response in 41.6% and 73.9% in microneedling and fractional CO2 laser groups, respectively. Saoji et al.[9] in 2017 did the same comparison in 50 patients and found 12% and 20% showed reduction of scars by two grades in microneedling and fractional CO2 groups, respectively [Table 3].

Table 3.

Comparison of different studies found in online literature with our study

Study	No. of patients	Microneedling	Fractional CO2 laser	Statistically Significant difference	PIH
Pooja et al.[5]	60	60.3% improvement	68.7%	No	4 -CO2 laser 1-microneedling
Abel et al.[6]	182	37.63% mean reduction	41.22% mean reduction	significant	6 -microneedling 9 - CO2 laser
Monisha et al.[7]	140	Significant reduction	Significant reduction	significant	-
Obaid et al.[8]	40	41.6% satisfactory response	73.9% satisfactory response	-	17.4% - CO2 group
Saoji et al.[9]	50	Change by grades 88% - 1 grade 12% -2 grades	Change by grades 80% -1 20%- 2	-	20% - CO2 0 - microneedling
Our study	30	9.3% GB grade improvement	32.9%	significant	30% - CO2 6.67%- microneedling

PIH - Postinflammatory hyperpigmentation; GB - Goodman and Baron grade

We noted that improvement in mean patient’s subjective score (PSS) on the fractional CO2 laser side (49.4%) was significantly more than that on the microneedling side (19.7%). The observations could also represent bias as a form of “Hawthorne effect”.[10] However, the improvement observed in PSS after treatment was consistent with that seen with GB grade.

Mean percentage improvement in the rolling type of scars with fractional CO2 (42.90%) laser was greater than that in microneedling (16.18%). Rolling scars have sloped and shallow borders with a normal skin texture at the base and are about 4 to 5 mm wide. Treatment is aimed at correcting the abnormal fibrous anchoring and responds to both microneedling and laser resurfacing.[11] In a study by Patil and Patil, correlating the response to microneedling with the morphological type of scarring using GB grade in 30 patients, a good to excellent response in rolling and boxcar scars was noted, while pitted scars showed only moderate improvement.[12] In a study by Majid and Imran on 60 patients with moderate to severe atrophic facial acne scars treated with 3–4 sessions of fractional CO₂ laser resurfacing at 6-week intervals, rolling scars responded the best to fractional laser resurfacing monotherapy, while ice-pick scars responded the least, leading to the same conclusion as ours.[13] The mean score of boxcars on both sides of the face showed a significant reduction; however, the improvement with CO2 laser (36.2%) was greater than that with microneedling (3.74%). Boxcars are round to oval, or rectangular, depressions with sharply defined vertical edges that can be shallow (0.1–0.5 mm) or deep (>0.5 mm). The mean score of ice-pick scars showed a statistically significant reduction on the right side [fractional CO2 laser] but not on the left side (microneedling). Ice-pick scars are narrow (<2 mm) and extend vertically into the deep dermis or subcutaneous tissue; therefore, conventional skin resurfacing options like microneedling will not adequately treat these types of scars; however, laser resurfacing has slightly better efficacy than microneedling.[11] Previous studies have also documented similar suboptimal response in ice-pick scars with laser resurfacing.[12,13]

We found better outcome in patients with recent scars (<10-year duration) as compared to those with older scars (more than or equal to 10 years). Since the number of patients in the two subgroups was unequal, it is difficult to compare their results. Similarly, platelet-rich plasma or subcision was not found to improve the outcome significantly in older post-acne scars in another split-face study by Deshmukh and Belgaumkar.[14] This difference could probably be explained by the concomitant effect of aging, which through the loss of active elastin tissue makes the depression in the scar more accentuated.[15]

The early transient side effects like stinging, erythema, and edema were seen with both modalities. A small proportion of patients developed hematoma and dryness over the microneedling site. Similar, early postprocedure adverse effects have been documented by other authors.[5,6,8,9] The CO2 laser-treated side required a significantly longer healing time (mean 7.60 days) than the microneedling side (mean 3.73 days), a finding that was consistent with previous studies. This period included healing of postprocedure edema, erythema, and crusting on both the sides and the characteristic transient dotted pigmentation over the fractional CO2 laser side. Abel et al. reported the similar results attributable to the transient dotted pigmentation of the laser in a majority of the patients.[6] Fractional CO2 laser resurfacing patients may experience crusting after the procedure, which renders it difficult for them to resume their routine work for a few days after each laser session. PIH was greater in patients with darker skin types and with fractional CO2 laser (30%) in our study. A single patient developed hypopigmentation after fractional CO2 laser. In patients with Fitzpatrick skin types IV–VI, the risk of pigmentary change is higher with the deeper wounding that may be achieved with acne scar revision procedures like fractional lasers.[16] PIH was reported by other authors too.[5,6,8,9] Fractional lasers are certainly capable of damaging the skin enough to cause disruption of melanogenesis, which may result in hypopigmentation. Less postprocedure hyperpigmentation with microneedling can be attributed to the expression of matrix metalloproteinases speculated to attenuate hyperpigmentation.[17]

Strength

We compared the efficacy and safety of two modalities in a split-face study and attempted to correlate the outcome measures with variables like skin type, duration, and type of acne scars using P values.

Limitations

We had a small sample size, a short follow-up period, and subjective assessment methods. Ice-pick scars are known to respond suboptimally to both the modalities; however, we could not exclude it as almost all our patients had a combination of the three types of scars. Subcision was not done in any of our patients as we wanted to compare the two modalities without confounding the response by using subcision.

Conclusion

Microneedling and fractional CO2 laser are both effective in treatment of post-acne scars. However, CO2 laser showed greater improvement in our study with a longer downtime. Maximum response for both the modalities was seen for rolling scars, followed by boxcars. Ice-pick scars were almost equally resistant to both. Patients with recent onset scars responded better. The effect of both the modalities was sustained during and at the end of the follow-up period. The most frequently encountered late side effect was postprocedure hyperpigmentation, which was greater for fractional CO2 laser and a higher Fitzpatrick’s skin type. Authors recommend prudent patient selection, customized parameters in CO2 laser, priming, and postprocedure skin care as the key factors in achieving optimum outcome in the skin of color.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.