Comparative Analysis of Laser Therapies for Striae Distensae: Fractional CO vs Combined Q-Switch Nd:YAG

Introduction

The origin of striae distansae (SD) is multifactorial and the exact etiopathogenesis of SD still remains controversial. Striae generally develop in various physiological states such as pregnancy, growth spurt during puberty, or rapid change in proportion of specific body regions such as in weight lifters, obesity, or weight loss [1]. Other factors like genetic predisposition, mechanical stress, and hormones, especially corticosteroids (both topical and systemic), also play an important role in SD formation. Hypercortisolism like Cushing’s syndrome, and genetic disorders such as Marfan syndrome, drugs such as local or systemic corticosteroid therapy can also cause SD. Striae distensae occur in pregnancy (43% to 88%), puberty (6% to 86%), and obesity (43%) [1]. A positive family history is a risk factor for SD. During pregnancy, SD are more common in younger women than in older women [1].

Striae distensae may initially appear as edematous striations that evolve to the red-to-purple, flat, or atrophic plaques known as striae rubrae (SR) that eventually progress to striae albae (SA), which are hypopigmented, scar-like depressions with fine wrinkling. This progression often occurs over the course of 6 to 10 months. Striae albae persist indefinitely and may become more prominent with age as the skin thins and loses additional elasticity [1,2].

In the early stage of SR, several treatments are available to improve their appearance, including topical tretinoin, microdermabrasion, mesotherapy, micro-needling, radiofrequency, photothermolysis, carboxytherapy, intense pulsed light, ablative and non-ablative lasers, and fractional lasers; however, no consistently effective treatment modality has been established [2,3]. Lasers have recently emerged as an alternative treatment, but studies have reported conflicting results and adverse effects, such as post-inflammatory hyperpigmentation (PIH) and persistent erythema [4]. Heat-based devices and lasers combined with adjuvant mesotherapy protocols are currently among the most popular treatment practices [4]. Due to the variety of available laser devices and the differing parameters reported in the literature, the optimal laser for treating striae SD remains unclear.

Fractional carbon dioxide (FrCO2) laser (10 600 nm) has been shown to stimulate dermal collagen production and has been successfully used in the treatment of wrinkles, atrophic scars, and striae gravidarum, as well as for skin rejuvenation [4–6]. Q-Switch neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (1064 nm) has been used for pigmentation disorders, tattoo removal, and persistent erythema [7,8]. It is also effective for skin rejuvenation, collagen stimulation, skin tightening, and toning [9]. Reports on the success of picosecond lasers and long-pulsed (LP) Nd:YAG lasers for SD treatment suggest that the Q-Switch Nd:YAG laser can also reduce the brightness and erythema of SR [10–12]. Given that SA share clinical and histological similarities with atrophic scars, and SR resembles pigmented, vascular erythematous tissue, the combination of Q-Switch Nd:YAG and FrCO2 lasers could be effective for both. Therefore, this study aimed to compare the efficacy of the FrCO2 laser alone and in combination with the Q-Switch Nd:YAG for the treatment of SR and SA.

Material and Methods

PATIENT SELECTION AND RANDOMIZATION OF SD:

Approval for the study was obtained from the Ethics Committee of Recep Tayyip Erdogan University Training and Research Hospital (number: 2025/35). Informed consent was obtained from all participants after receiving approval of the experimental protocol from the ethics committee. This study included 392 SD lesions from 49 volunteer patients aged 20 to 45 years, with Fitzpatrick skin phototype II-IV and SD on the abdomen, inner arms, breasts, hips, calves, lumbar region, and buttocks. Sex, age, history of SD during pregnancy, familial history of SD, SD localization and duration, body mass index (BMI), and Fitzpatrick skin phototype were recorded.

The Fitzpatrick scale includes 6 skin phototypes. Patients with type 1 always sunburn, never tan (palest, freckles), and have very light or white “Celtic” type skin. Type 2 means they usually sunburn, tan minimally (light colored but darker than pale), and have light or light-skinned European-type skin. Type 3 means they sometimes mildly sun burn, tan uniformly (golden honey or olive), and have light-intermediate or dark-skinned European-type skin. Type 4 means they burn minimally, always tan well (moderate brown), and have dark-intermediate or “olive skin”. Type 5 patients burn very rarely, tan very easily (dark brown), and have dark or “brown” skin. Type 6 means they never burn (deeply pigmented dark brown to darkest brown) and have very dark or “black” skin [13].

Patients with a history of keloids or hypertrophic scars, malignancy, or systemic diseases and pregnant women were excluded from the study. Slightly raised, erythematous to bluish, pink or violaceous linear marks were accepted as SR, which fade over months to years. Besides flattened, hypopigmented, whitish colored, wrinkled SD with atrophic surface that follows the lines of cleavage were confirmed as SA [2] (Figures 1, 2).

If a patient had symmetrical abdominal SD lesions on the abdomen, these were included; otherwise, symmetrical extra-abdominal SD lesions were selected. Eight SD lesions consisting of either SR or SA were identified on each patient. Four SD on the right side of the body were randomly assigned to Group 1 and 4 symmetrical SD were randomly accepted to Group 2, in each patient by the same dermatologist (Figure 3). All lesions were photographed with the same 3D camera before treatment.

In Group 1 (n: 49), an FrCO₂ laser was applied alone to 4 SD localized on the right half of the body in each patient. In Group 2 (n: 49), the Q-Switch Nd:YAG laser was applied in combination with the FrCO₂ laser to the other 4 SD on the opposite left side of the body in each patient. The treatment areas were cleaned with an alcohol swap, and topical anesthesia was applied for 30 minutes under occlusion. Before the procedure, SD areas were wiped with wet gauze to remove the anesthetic cream. Informed consent was obtained from all patients prior to treatment.

LASER APPLICATION PROCEDURE:

For Group 1, the FrCO₂ laser (Fraxis Duo Illoda^®) was applied with round pulses, using a spot size of 4.5 mjoules, i-stack 3, and pulse distance of 0.7 mm, with a single pass, by adjusting the spot size according to the SD diameter. For Group 2, first the Q-Switch Nd:YAG laser (Fotona Starwalker MaQX^® superpico laser, 1064 nm) was applied in full-beam mode with 1.8–2 joules/cm² fluence, 8 mm spot size, and 10 hertz, using an R28-D handpiece for 3 passes. This was followed by the superpico laser in fractional mode at 86 Joule/cm² fluence, 9X9 spot size, 0.5 hertz with an FS20A handpiece for 2 passes. Cooling was also provided. The FrCO₂ laser (Fraxis Duo Illoda^®) was then applied sequentially in the same session at the same doses as in Group 1, after wiping the application area with physiological saline-soaked gauze. The patients in both groups were treated every 4 weeks for a total of 3 sessions. All patients participating in the study were given necessary warnings about sun protection. Laser parameters were constant for all of the participants with different Fitzpatrick skin types and were accepted as safe. None of the patients had skin type more than type 4.

MORPHOLOGICAL EVALUATION:

The presence and number of SR lesions were also noted for both groups (0–4) in each patient. The mean difference in the pre-and post-treatment SR counts was compared. Pre-treatment and post-treatment (first-month) clinical and dermoscopic evaluations included scores for stria color-brightness (0–3), vascularity (0–3), and atrophy (0–4). The largest measurable width and length (mm) were calculated. Mean differences in vascularity, color, atrophy, SD width, and SD length were analyzed. Photographs were taken using a Leofarma^® digital dermoscopy camera (×20) before and after treatment for an objective assessment. Adverse effects such as PIH, prolonged or persistent erythema, scarring, telangiectasia, irritation, pain, and infection were documented. One SD lesion in the photograph was automatically marked using a straight line along the SD using the Image Meter software, and the width and length of the SD were measured on the computer.

CLINICAL EFFICACY AND SIDE EFFECTS ANALYSIS:

At week 16, the Global Aesthetic Improvement Scale (GAIS) (physician version) score, clinical response rate, patient’s subjective satisfaction score (SSS-p), Visual Analog Scale (VAS) score for pain, and tolerability score (TS) were measured in both groups. GAIS scores were also compared for patients with SR in both groups. Using GAIS, a 5-point scale (0–4), the researcher rated global esthetic improvement in appearance based on pre- and post-treatment photographs as “worse,” “no change,” “slight improvement,” “significant improvement,” or “very significant improvement” [14]. Clinical response rate was measured on a three-point scale: 1=poor (<33% visual improvement), 2=moderate (33–66% visual improvement), and 3=good (≥66% visual improvement). SSS-p was evaluated using a five-point Likert scale (0–4): 4=very satisfied, 3=satisfied, 2=neutral, 1=dissatisfied, and 0=very dissatisfied. Treatment tolerability was rated on a scale of 1 to 4: 4=very well tolerated, 3=tolerable, 2=difficult to tolerate, and 1=not at all tolerable.

STATISTICAL ANALYSIS:

Statistical analyses were performed using SPSS version 26.0 for Windows. Descriptive measures were presented as mean and standard deviation values and percentage distributions. The conformity of the data to the normal distribution was checked using the Shapiro-Wilk test. The Wilcoxon test was used to compare continuous variables, and the McNemar chi-square analysis was used to compare distributions. The significance level was taken as p<0.05.

Results

DEMOGRAPHIC DATA:

Of the 49 patients participating in the study, 18 (36.7%) were male, and 31 (63.3%) were female, with a mean age of 29.8±8.7 years. Eleven of the 13 patients (84.6%) with a history of pregnancy had experienced SD during pregnancy. Accompanying SR was detected in 31 patients (63.3%). A total of 392 SD lesions were evaluated. Regarding the distribution of SD lesions, 29 patients (59.2%) had lesions on the abdomen, 19 (38.8%) on the inner arms, 12 (24.5%) on the breasts, 32 (65.3%) on the hips, 24 (49%) on the calves, 32 (65.3%) on the lumbar region, and 36 (73.5%) on the buttocks. Among the patients, 17 had Fitzpatrick skin type 2, 22 had skin type 3, and 10 had skin type 4. Based on BMI, 3 (6.1%) patients were underweight, 15 (30.6%) had a normal weight, 14 (28.6%) were overweight, 12 (24.5%) were obese, and 5 (10.2%) were severely obese. The duration of SD was less than one month in 2 patients (4.1%), 1–6 months in 9 patients (18.4%), 6 months-1 year in 10 patients (20.4%), 1–5 years in 14 patients (28.6%), and more than 5 years in 14 patients (28.6%).

MORPHOLOGICAL FEATURES:

In both groups, post-treatment scores for color, vascularity, and atrophy were statistically significantly lower compared to pre-treatment scores (p<0.001). The difference in pre- and post-treatment vascularity scores was statistically significantly higher in Group 2 than in Group 1. However, no significant difference was noted between the 2 groups in terms of color score changes (p=0.092). Regarding atrophy, Group 2 showed a statistically significantly greater improvement than Group 1 (p<0.001). Overall, the combination of the Q-Switch Nd:YAG laser with the FrCO2 laser was more effective than the FrCO2 laser alone in improving vascularity and atrophy, although both groups exhibited similar results in terms of color (Table 1).

WIDTH AND LENGTH ANALYSIS OF SD:

In Group 1, the mean SD width decreased from 3.39±1.08 mm at week 0 to 2.35±1.17 mm at week 16 (p<0.001). In Group 2, the mean SD width decreased from 3.61±1.09 mm at week 0 to 1.57±1.10 mm at week 16 (p<0.001). In both groups, the pre-treatment SD width was statistically significantly greater than the mean post-treatment SD width (p<0.001). The reduction in SD width in Group 2 was statistically significantly greater than in Group 1 (p<0.001) (Table 2).

In Group 1, the mean SD length decreased from 45.5±13.7 mm at week 0 to 37.1±11.9 mm at week 16 (p<0.001), while in Group 2, the mean SD length decreased from 48.0±14.4 mm to 33.9±11.3 mm during the same period (p<0.001). As with SD width, the reduction in SD length was statistically significantly greater in Group 2 than in Group 1 (p<0.001) (Table 2). Thus, the combined laser treatment was more effective than the FrCO2 laser alone in reducing SD width and length.

CLINICAL EFFICACY RESULTS:

In both groups, the number of SR lesions significantly decreased after treatment compared to before treatment (p<0.001). The reduction in the number of SR lesions was significantly higher in Group 2 than in Group 1 (Table 3).

The mean GAIS scores, clinical response rate, and SSS-p scores were all statistically significantly higher in Group 2 compared to Group 1 (p<0.001) (Table 4; Figure 4). Among patients with SR, the mean GAIS was statistically significantly higher in Group 2 than in Group 1 (p<0.001). In terms of GAIS, 13 patients in Group 1 and 2 in Group 2 showed a worse response; 15 patients in Group 1 and 21 in Group 2 showed no change; 18 patients in Group 1 and 12 in Group 2 showed slight improvement; and 3 patients in Group 1 and 10 in Group 2 showed significant improvement. A very significant improvement was seen in only 4 patients in Group 2. Clinical response in Group 1 was poor in 26 patients (53.1%), moderate in 18 (36.7%), and good in 5 (10.2%). In Group 2, the clinical response was poor in 15 patients (30.6%), moderate in 16 (32.7%), and good in 18 (36.7%).

ADVERSE EFFECTS:

Adverse effects were observed in 8 patients. PIH was detected in 8 patients (16.3%), prolonged/persistent erythema in 5 (10.2%), irritation in 5 (10.2%), and pain in 3 (6.1%). No significant difference was noted between the 2 groups in terms of adverse effects. The mean VAS score was 2.9±1.3 in Group 1 and 5.3±1.7 in Group 2, with statistically significantly higher pain levels reported in Group 2 (p<0.001). Lastly, the mean TS was statistically significantly higher in Group 1 than in Group 2 (p<0.001) (Table 4).

Discussion

STUDY LIMITATIONS:

We believe that the lack of the evaluation of variable laser parameters including different doses and pulse durations and the lack of the clinical results in terms of different Fitzpatrick skin types were limitations of our study. The SD localized on sun exposed areas may have also acted on the clinical results. Although we found a significant better response with the combination laser treatment on SR, the further evaluation of the specific morphological features such as vascularity and color on SA and SR separately would be scientifically more valuable.

Conclusions

For effective SD treatment, a comprehensive patient evaluation is crucial, including a thorough history, SD type, and skin type assessment. Future studies should include well-designed clinical trials with larger sample sizes, longer follow-up periods, and comparisons of different laser parameters, skin types, and SD locations to better address the issue of the optimum laser management of SD.

It is recommended to combine the FrCO2 laser with the Q-Switch Nd:YAG or another non-ablative laser to achieve better outcomes in the treatment of SD lesions. This combined treatment strategy may further enhance collagen remodeling and elastic fiber production, particularly in patients with SA. This study showed that the combination of the Q-Switch Nd:YAG laser with the FrCO2 laser yielded superior results in reducing SD vascularity and atrophy compared to the FrCO2 laser alone. In the very early stages of SR, specifically in immature lesions, the Q-Switch Nd:YAG laser may also be an effective first-line treatment to diminish redness and vascularity. Overall, the combination treatment appears to be a better choice for both SR and SA, particularly in addressing vascularity, atrophy, SD width, and SD length, ultimately leading to higher patient satisfaction.

Declaration of Figures’ Authenticity

All figures submitted have been created by the author who confirms that the images are original with no duplication and have not been previously published in whole or in part.