Acne Scarring. Comparative analysis of effectiveness of CO2 laser and microneedling radiofrequency in treating atrophic acne scarring

Introduction.

Acne scarring affects thirty percent of world population. Ninety five percent develop acne scarring, which has a profound psychological impact, especially in younger adults. ^(1-4)

Acne scarring occurs due to inflammatory destruction of collagen in the affected areas.

P. acnes factors and peptidoglycan dose‑dependently augmented production of proMMP‑2 in sebocytes and dermal fibroblasts, indicating bacterial‑driven induction of MMPs that can degrade ECM and promote scarring (5)

The types of common atrophic acne scarring are; box scarring, rolling scars and ice pick scars. The scars are graded using Goodman and Baron global qualitative acne scar grading scale from I to IV.  ⁽⁶⁾

For Fitzpatrick skin types I to III, acne scarring can commonly be associated with erythematous scarring, especially in the early stages. In Fitzpatrick skin types VI to VI, it can commonly be associated with post inflammatory hyperpigmentation (PIH).

Ablative fractional CO2 laser (FCO) and microneedle radiofrequency (MNRF) constitute two energy-based therapeutic approaches that have demonstrated effectiveness in the treatment of acne scars, particularly with regard to the rolling scar and box scar variants.

This literature review compares treatment outcomes for 2 commonly used modalities across Fitzpatrick skin types; fractional co2 laser (FCO) and fractional radiofrequency microneedling (MNRF). FCO has been the most common modality in aesthetic dermatology for some years. MNRF is the newer modality. ^(7-13)

Both modalities rely on the mechanism of creating controlled microtrauma, stimulating production of collagen.

Both modalities use inflammatory cascade for the process of neocollagenesis.

FCO laser uses photothermal energy to ablate the skin, creating a thermal injury and coagulation of the tissue working from “outside in” ⁽¹⁴⁾

MNRF uses mechanical stimulation of microneedling, and thermal stimulation of RF energy delivered exactly to the precise depth, therefore stimulating collagen at the dermis level. It stimulates the collagen from “inside-out” ⁽¹⁴⁾

In addition to the treatment outcome data, it is important to cover the real-world decision making factors of patients and clinics.

These factors consider; downtime after the treatment, ability to go to work, ability to wear make-up, cost of the treatment, acne eruptions, risk of PIH and the amount of time required to restore the skin’s barrier function.

Treatment selection is multidimensional, it is not as simple as looking at the best efficacy percentages.

Three articles were selected for this literature review. The articles explore; effectiveness of FCO compared to MNRF for skin types III-V (Fitzpatrick), effectiveness of FCO to MNRF in skin types II and III and effectiveness laser approach to RF approach in skin types III and IV. These articles were selected to gain understanding of effectiveness, safety and tolerability of the modalities of FCO and MNRF across Fitzpatrick skin types.

Study 1. Rajput, C. D., Gore, S. B., Ansari, M. K., & Shah, S. M. (2021). A Prospective, Nonrandomized, Open-label Study, Comparing the Efficacy, Safety, and Tolerability of Fractional CO2 Laser versus Fractional Microneedling Radio Frequency in Acne Scars. Journal of Cutaneous and Aesthetic Surgery, 14(2), 177–183. https://doi.org/10.4103/JCAS.JCAS_65_19

This paper was chosen for the literature review because of the Fitzpatrick skin types it covers (III - V), and the methodology used.

Objective.

Assess and compare clinical efficacy, safety and tolerability of Fractional Carbon Dioxide Laser (FCO) versus microneedling radiofrequency (MNRF)

It is the first comparison study involving the darker Fitzpatrick skin types.

Methodology.

Prospective, observational, non-randomised, open-label study of 50 patients. The patients were selected according to Goodman and Baron global qualitative acne scar grading scale.

The study involved 50 patients were divided into 2 groups of 25 (non-randomly). They were divided into two groups and 25 patients were given 4 sessions of MNRF with a 2 month interval and the other 25 patients were given 4 sessions of FCO with a 2 month interval. Objective and subjective assessments were carried out 2 months after the last sessions. The study had a total duration of 10 months.

Detailed protocols were described for MNRF and for FCO.

Results were assessed by the treating doctor and by an independent doctor. Statistical methods were used involving percentages, means plus/minus standard deviation, chi-square test.

Main findings.

FCO group, mean score decreased from a base line of  29.24 to 10.7. A reduction of 63.41%.

MNRF Group mean score decreased from a base line of  33.24 to 13.04. A reduction of 60.72%.

Both of the above were calculated by Goodman and Baron global qualitative acne scar grading.

Subjective assessment: patient satisfaction

FCO      30% (6 out of 25)

MNRF  70% (15 out of 25)

Crusting and scaling

FCO      100%

MNRF  0

Post Inflammatory Hyperpigmentation/ Post Inflammatory Hypopigmentation

FCO      24% after 6 weeks, 16% after 2 months, all resolved at the end.

MNRF  4% after 6 weeks, all resolved at the end.

Immediate edema

FCO      6%

MNRF  48%

No pain was reported for either modality.

No use of topical anaesthetic was mentioned.

Conclusion.

FCO and MNRF are both highly effective treatment modalities for atrophic acne scars. Clinical outcomes are comparable, however, the satisfaction and PIH complication rate is lower with MNRF for darker skin types.

Limitations.

Use of imaging. Only the photographic equipment was used, no 3D imaging was utilised for more accurate measurements.

The final outcomes were assessed at 10 months point after the first treatment. Longer follow up time. Collagen maturation process of collagen type 3 evolving into collagen type 1 takes 12 months on average. ⁽¹⁵⁾

Specific equipment being used. MNRF equipment brand was detailed in the paper, FCO was not, however technical characteristic for both equipment types were presented, as well as detailed protocols.

Patients could have been allocated to each group randomly instead of being assigned intentionally. This practice mitigates bias and enhances the robustness and reliability of the results.

Split face study. Each patient could have been administered one treatment on one side of the face while receiving a different treatment on the contralateral side. This approach facilitates direct intra-individual comparison and minimizes variability among subjects.

Larger sample size. Including a cohort exceeding 50 patients would enhance the reliability of the findings and facilitate their extrapolation to a broader population.

Study 2. Hendel, K., Karmisholt, K. E., Hedelund, L., & Haedersdal, M. (2023). Fractional CO2‐laser versus microneedle radiofrequency for acne scars: A randomized, single treatment, split‐face trial. Lasers in Surgery and Medicine, 55(4), 335–343. https://doi.org/10.1002/lsm.23655

This paper was chosen for the literature review because of the Fitzpatrick skin types it covers (I to III), and the methodology used. As the aim of this literature review is to have a comprehensive overview for comparing effectiveness of modalities of FCO and MNRF across the Fitzpatrick spectrum, using various methodologies.

Objective.

Fractional CO2 laser (FCO) has been the most common modality for treatment of acne scarring by dermatologists world-wide. MNRF is a relatively new modality. The aim of this study is to compare the effectiveness of these modalities in terms of outcomes, but also to explore local skin reactions such as erythema, hyper and hypo pigmentation, pain and loss of skin integrity with associated transepidermal waterloss.

Methodology.

Direct, controlled, side by side comparison of the FCO and MNRF modalities using a split face trial with blinded response evaluation, objective measures and patient reported outcomes.

There were 15 patients in the trial, all over the age of 18 with Fitzpatrick skin types I to III. They had moderate to severe acne scarring on Goodman and Barron scale.

It was a direct controlled trial where FCO was tested against MNRF side by side, a randomised split face trial. Therefore, there were 30 treatment areas.

The participants received 1 treatment. Half of the face was treated with FCO and half of the face was treated with MNRF.

Standardised multilayer protocols were used for FCO and MNRF.

Topical anaesthetic tetracaine lidocaine was used to control the pain.

The outcome metrics used were as follows.

A blinded assessment of the clinical enhancement of scar texture (0–10 scale) at 1- and 3-months post-treatment. 

The study has also measured the following local skin reactions: pain, skin integrity by transepidermal water loss and patient satisfaction.

Clinical assessments conducted at baseline and during follow-up at 1 and 3 months were executed in a blinded manner concerning treatment allocation by a qualified medical practitioner.

Local skin reactions (LSRs) were assessed without blinding due to the inherent distinguishability of the administered treatments.

Skin texture was evaluated using a descriptive and visually assisted

scale at baseline and at 1- and 3-month follow-ups.

Clinical photography as well as 3d imaging was used (VISIA).

Redness, hypo and hyper pigmentation were graded.

Main Findings

Fifteen participants successfully completed the study.

Texture.

Both modalities showed a comparable median advancement of 1‐point in texture after a follow‐up period of 3 months.

Optimal responders recorded enhancements of up to 3 points.

Erythema.

FCO application was associated with greater degree of erythema than MNRF.

Pain.

Patients indicated that MNRF (VAS 7.0) was significantly more painful than FCO (5.5)

Patient satisfaction. 

Patient satisfaction was rated as 6 (out of 10) for both modalities.

Patient satisfaction did not correlate with improvements in skin texture nor with the pain experienced during treatment.

Local Skin Reactions.

Both modalities yielded comparable LSR profiles. However, it was observed that FCO induced a significantly greater degree of erythema and transepidermal waterloss after a duration of 2 to 4 days in comparison to MNRF.

Hyper and hypo pigmentation.

Hyperpigmentation was observed subsequent to treatment in a singular case (female, Fitzpatrick skin type II) who exhibited discernible hyperpigmented regions necessitating corrective intervention in the FCO treatment zone after a duration of three months.

Apart from the above case, no further redness, hypo or hyper pigmentation was observed.

Conclusion.

FCO and MNRF are both highly effective treatment modalities for atrophic acne scars. Clinical outcomes are comparable, however, the satisfaction and PIH complication rate is lower with MNRF for lighter skin types.

Limitations.

Sample size. The study has been thorough with the methods being used, well described protocols and evaluation methods. However, the sample size of greater than 15 patients would enhance the reliability of the findings.

Number of treatments. Only 1 treatment was performed. In real clinical environment, more than 1 treatment would be performed to treat acne scarring that is on higher scale of Goodman and Baron.

Timeframe. Assessments were made at 1- and 3-months period after the treatment. A greater timeframe would give more accurate understanding of full collagen development after treatment. Collagen maturation process of collagen type 3 evolving into collagen type 1 takes 12 months on average. (ref 14)

Study 3. Yan, C., Phinyo, P., Yogya, Y., Chuamanochan, M., & Wanitphakdeedecha, R. (2025). Comparative Effectiveness and Safety of Fractional Laser and Fractional Radiofrequency for Atrophic Acne Scars: A Retrospective Propensity Score Analysis. Reproductive and Developmental Biology, 15(9), 1379. https://doi.org/10.3390/life15091379

This study was chosen as the most recent paper on the subject, with one of the largest amounts of patients in the study (397 patients) spanning a timeline of 2012 to 2023. The patients belong to skin types III-IV Fitzpatrick. Where paper 1 gives us understanding of how darker Asian skin reacts, paper 2 gave us understanding on how white skin reacts, this paper explores how light Asian skin reacts. Altogether, the 3 papers should give a thorough insight into comparison of the modalities across ethnicities and skin types.

Given that UK is a multicultural country, having an insight into clinical outcomes and possible complications in the skin of different ethnicities is the right approach to take.

Objective.

This is a statistical clinical study based on patient records to ascertain effectiveness of outcomes between modalities of Fractional Laser (FL) and Fractional Radiofrequency (FRF) for patients aged 18-60, of Thai ethnicity, between the years of 2012 and 2023 as a primary objective. The patients would have received at least 2 treatments of either FL or FRF to treat acne scarring and achieved at least 25% improvement in the texture of acne scarring within 6 months. Secondary objective was to review adverse events.

Methodology.

This is a retrospective, statistical study of the real-world clinical outcomes based on the medical records of patients with atrophic acne scars at Siriraj Skin and Laser Centre (SISL), Siriraj Hospital, Mahidol University, between 2012 and 2023.

The records were classified into 2 categories, depending on the type of treatment chosen: FL or FRF. FL was defined as laser-based treatments, including Fractional CO2, Factional Erbium YAG laser and Fractional Picosecond Lasers. FRF were defined as MNFR and grid-based RF (superficial RF via electrode arrays)

Out of 397 patients, 254 were treated with FL and 143 with FRF. The primary endpoint was achieving 25% or more improvement at scarring at 6 months. An equivalence margin of 20% was specified as the maximum clinically acceptable difference.

Patients were of Thai origin, skin types III to VI, 18-60 years of age, suffering from acne scarring with box scars, rolling scars and ice pick scars. Only those with baseline photographs were included in the study. Those who received less than 2 sessions were excluded.

Two independent dermatologists had graded and compared the proportion of patients who achieved 25% or more clinical improvement in acne scarring in the above declared modalities using photographic assessment. Secondary objective was to grade and compare adverse events in these modalities by 2 independent dermatologists.

Descriptive statistical methods were used to summarise baseline patient characteristics. Various statistical methods were used.

Main findings.

Clinical improvement outcomes.

Out of 254 FL patients and 143 FRF patients, at 1,3 and 6 months follow up the proportion of patients achieving 25% or more clinical improvement was higher for FRF.

Months	% Improvement FRF	% Improvement FL
1	73%	60%
3	82%	69%
6	82%	72%

Percentage wise FRF outcomes are higher, however, the study states that FRF higher outcomes are not statistically significant.

Pain.

FRF        5.65

FL            4.14

Patients found FRF more painful.

Hyper and hypo pigmentation.

FRF        4.71%

FL            5.45%

PIH was low in both modalities.

Acneiform eruptions

FRF        3.53%

FL           6.67%

Post treatment scarring

FRF        0.83%

FL           3.03%

Important points raised in the study state that picolaser was include within the FL group. Picolaser do not use thermal ablation, therefore picolaser results are more modest.

The study’s meta-analysis reported that ablative lasers give greater improvement than non-ablative lasers or RF modalities, however with longer downtime.

Yan et al. 2025 state that their findings are in line with Rajput et al. and Hendel et al.reported equivalent clinical efficacy for both modalities, though FRF was better tolerated, with lower instances of PIH and complications. Both methods are safe, efficient and tolerable.

Patients have found FRF more painful, which can be attributed to deeper dermal stimulation, compared to FL.

Conclusion.

FCO and MNRF are both highly effective treatment modalities for atrophic acne scars. Clinical outcomes are comparable, however, the satisfaction and PIH complication rate is lower with MNRF for skin types II - VI

Limitations.

This study has a limitation due to its retrospective design. Although statistical methods were used to reduce baseline confounding, residual bias may still occur.

Treatment allocation was not random but based on clinical judgement of treating staff at the time.

There were multitude of equipment and protocols used for both FL and FRF.

Although it reflects the real-world clinical practice, pooling of these results may have introduced unexpected variability.

Results were assessed using photographic images. No 3D imaging was used.

There was unequal distribution of between the groups, FL 254 and 143 FRF.

All 3 reviewed studies have concluded that the application of MNRF treatment in treating acne scarring in skin types I-V produces similar or better results with lower downtime and lower complication rates.

Literature review conclusion.

In a real-world setting, downtime is an important consideration for the patients. MNRF is a preferred treatment modality in this aspect. With MNRF mechanism targeting the dermal tissue, the risk of unresolved PIH is lower, which is evident in these 3 studies.

The first 2 studies, Rajput at el. and Hendel at el. show patient satisfaction being higher with MNRF.

Overall, MNRF is emerging as a safe option with high satisfaction rate and low complication rate.

Studies such as these are important for running of the clinical practice to bring the best, most clinically proven technology for the benefit of patients.

Aesthetic medicine is not just about looks but about how our patients’ satisfaction with their look affects their mental well-being and success in the society.  In the explored cases with acne scarring, for example, clinical practice sees many cases of acne scarring following hormonal acneic eruptions that commonly happen in teenage years.

These would be adults in their twenties, in the prime of their childbearing life, where they would naturally be looking for life partners. Being dissatisfied with your looks is likely to affect these young people in how they see themselves and in their search of a life partner. Which then can have a bearing on the rest of their life. Having a safe, proven solution to their problem could be life changing.

The above research has demonstrated that MNRF has much lower downtime and comparable effectiveness to FCO. This can result in the patient being more likely to have several treatments and not give up, due to the first treatment causing crusting, oozing, hypo and hyperpigmentation, effects that would later resolve themselves. However, for a young person in their late teens and 20s, having up to 6 months of PIH would be a cause for anxiety.

Having a course of collagen stimulating treatment would then mean that their acne scarring is reduced, and their self -confidence increased. And, as we know, this could be life changing for the better.

In broader terms, aesthetic medicine is a fast-developing field, with new treatments and modalities entering the market all the time. Unlike traditional medicine, it is commonplace that new treatments get adopted with little evidence and without robust scientific research. For example, in the UK market, there is a big topic of exosomes. It is the new trending modality for treating acne scarring, PIH and rhytids. It looks like it can treat multiple concerns in one. However, investigative journalists have identified that some clinics are using human derived exosomes. This is legal in South Korea, for example, but it is not legal in the UK.  The use of human exosomes can cause diseases to be transferred, an outcome for which there is evidence.

Rigorous study design, detailed, transparent reporting and critical appraisal is important to separate the claims from fact. Scientific research in aesthetic medicine, therefore, not only improves clinical outcomes and techniques but it is tied to safeguarding the patients’ psychological well-being.

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14.  Hendel, K., Karmisholt, K. E., Hedelund, L., & Haedersdal, M. (2023). Fractional CO2‐laser versus microneedle radiofrequency for acne scars: A randomized, single treatment, split‐face trial. Lasers in Surgery and Medicine, 55(4), 335–343. https://doi.org/10.1002/lsm.23655

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16.  Yan, C., Phinyo, P., Yogya, Y., Chuamanochan, M., & Wanitphakdeedecha, R. (2025). Comparative Effectiveness and Safety of Fractional Laser and Fractional Radiofrequency for Atrophic Acne Scars: A Retrospective Propensity Score Analysis. Reproductive and Developmental Biology, 15(9), 1379. https://doi.org/10.3390/life15091379