Managing scars continues to pose a significant challenge in dermatology, particularly when dealing with various causes such as traumatic injuries, acne, or surgical procedures. Traditional approaches to deal with fine-line scars include the use of manual techniques [1], fractional ablative or nonablative lasers, fractional microneedling, the chemical reconstruction of skin scars (CROSS) technique, and chemical peels [2-4]. However, these methods often involve discomfort, recovery time, and potential side effects, leading to a growing demand from patients for effective results with minimal discomfort and downtime, especially in less severe cases.

The current literature surrounding scar resurfacing techniques underscores the significance of advancements in laser technology. While traditional methods have shown efficacy, the Q-switched neodymium-doped yttrium aluminum garnet (Q-Nd:YAG) laser with the multi-depth focusing (MDF) handpiece introduces a new dimension to scar revision by combining fractional treatment with precise MDF, offering precise targeting and controlled energy delivery. This synthesis of technologies presents an opportunity to enhance treatment outcomes and minimize potential side effects, providing clinicians with a versatile tool for scar improvement.

While fractionation of short pulsewidth laser energy in scar revision has demonstrated efficacy [5], the application of this technique to the Q-Nd:YAG laser has been less explored. Previous experiences with acne scars have been described [6], yielding promising results. We describe our experience with seven cases of fine-line traumatic scars, marking the first study to assess this objective. After having had the treatment explained to them in detail, all patients provided written informed consent to participate in the study, including the publication of this case report and the use of their images therein.

Resurfacing of fine-line traumatic scars

We included seven patients who exhibited fine-line scars (Table 1). Most scars originated from blunt trauma (Figs. 1-3); in one patient, it was due to a cat scratch in the left nasolabial and malar region, as depicted in Fig. 4. One patient was male, and the others were female, and had Fitzpatrick skin types ranging between type III and IV.

Table 1 . Patient demographics

Pat. no.	Sex	Age (yr)	FST	Brief description of scar and cause
1	M	55	IV	Scar in the frontal region, resulting from trauma caused by blunt impact. Treatment was initiated two months after the trauma
2	F	49	IV	Scar located above the tail of the right eyebrow, resulting from trauma caused by blunt impact. Treatment was initiated two months after the trauma
3	F	52	IV	Scar following blunt trauma, extending from the frontal region along the right supraciliary area. Treatment was initiated two months after the trauma
4	F	29	III	Scar on right nasal ala following scratch by a cat. Treatment was initiated two months after the trauma
5	F	29	IV	Scar following a puncture wound trauma. Treatment was initiated three months after the trauma
6	F	42	IV	Atrophic linear scar in the cervical region following a thyroidectomy. Treatment was initiated one and a half months after the trauma
7	M	38	V	Scar following blunt trauma. Treatment was initiated four months after the trauma

Figure 1. (A) Traumatic right supraciliary fine-line scar secondary before the procedure. (B) The right supraorbital scar is almost imperceptible after four sessions of Q-switched laser with multi-depth focusing handpiece.

Figure 2. (A) Right supraciliary fine-line scar secondary to trauma before the procedure. (B) Complete resurface of the scar. The previous scar is imperceptible after the procedure.

Figure 3. (A) Left supraorbital fine-line scar of traumatic etiology. (B) Resurfacing of the previous scar following 4 sessions of Q-switched laser with multi-depth focusing handpiece.

Figure 4. (A) Linear fine-line scar associated with a cat scratch compromising from the left malar region to the left upper lip, associated with pinpoint scars from sutures. (B) Complete resurfacing of the scars following 4 sessions of Q-switched laser with multi-depth focusing handpiece.

A new generation Q-Nd:YAG laser was utilized (HOLLYWOOD SPECTRA; Lutronic Corporation). Patients underwent 4 sessions spaced 4 weeks apart with the MDF handpiece at 1,064 nm. The MDF handpiece used fractionates the laser energy into myriad focused microbeams, where the focal waist of the beams is placed in rather than on the target tissue. The focal length of the microbeams is adjustable in three steps: step I, deep; step II, intermediate; and step III, shallow, referring to the placement of the focal waist in the skin. The sessions were conducted by the same physician, and topical lidocaine was applied prior to the procedure. The following parameters were used during the session.

The MDF handpiece was first used at step III, 8 mm spot size, repetition rate 10 Hz, pulse energy of 2 J/cm², delivered with 3 passes each over the surrounding skin, gently targeting more superficial tissue including scar tissue and surrounding normal skin. This was followed immediately by step I, 8 mm spot, 0.8-1 J/cm², 10 Hz, delivered with 3 passes, targeting the lesions only and penetrating into the deeper abnormal fibrotic scar tissue.

Clinical photography was taken at baseline then at 4 months after the final treatment (Figs. 1-4). Patients subjectively scored their satisfaction.

After four sessions, the scar resurfacing was between 80%-100% effective according to the treating physician’s assessment. Table 2 gives a synopsis of the results in each patient. The improvement was clearly visible as demonstrated in representative examples seen in Figs. 1 to 4. Apart from experiencing mild to moderate erythema and purpura, expected for the procedure (Fig. 5), patients encountered no complications. Satisfaction with the treatment was unequivocal in all patients.

Table 2 . Synopsis of results

Pat. no.	Result	Efficacy (%)
1	Most of the scar has undergone resurfacing. Smoother and more uniform skin texture. Subtle residual erythematous coloration in the treated area	80
2	Resurfacing of the scar, imperceptible compared to the surrounding skin. Subtle residual erythematous coloration	95
3	Resurfacing of the scar. Its color has likely faded to better blend with the surrounding skin. Even texture of the skin	90
4	Scar became much less distinct with improvement in overall size and skin texture	90
5	Resurfacing of the scar, improvements of skin texture, subtle erythematous coloration in treated area	90
6	Scar has become nearly indistinguishable from the surrounding skin. Improvement of texture of the skin	90
7	Enhancement in overall appearance, with a smaller size and resurfacing. Slight erythematous coloration	90

Figure 5. Moderate erythema immediately after the session with the Q-Nd:YAG laser and MDF handpiece on the (A) left and (B) right sides of the face in a patient with acne scars. Q-Nd:YAG, Q-switched neodymium-doped yttrium aluminum garnet; MDF, multi-depth focusing.

This is the first study describing the experience of a Q-Nd:YAG laser using a novel fractional MDF handpiece in seven patients with scars of traumatic origin.

Under specific circumstances comprising ultrashort pulses and very high irradiances, lasers targeting the skin can induce thermally-initiated laser-induced optical breakdowns (Ti-LIOBs), which involve athermal ionization, meaning that the temperature increase is less than 1°C [6]. Upon exceeding a threshold value of 10¹³/cm² W in water, this leads to the formation of a plasma vacuole that nonlinearly absorbs the laser energy, a phenomenon termed photodisruption [7]. This vacuole, which can be either epidermal or dermal, subsequently sends an osmotic shock wave to the surrounding tissue, causing a localized response in that area [7]. Eventually, the plasma is rapidly reabsorbed, leaving a dermal cavity where the creation of the Ti-LIOB induces the formation of collagen, elastin, and other components of the extracellular matrix during the regeneration stage of wound healing [8,9]. At the point of Ti-LIOB formation, acoustic waves are formed, whose action also impacts on vasodilation, cellular metabolism, and celullar proliferation, therefore resulting in facial rejuvenation and scar revision.

The Q-Nd:YAG laser employed in the present case reports, using the fractional MDF handpiece, emits a 5 ns pulsewidth at 1,064 nm, delivered via a flat-top beam of homogenized radial microbeams [6]. One of its innovative features includes delivering the highest power available in the first one-third of the 5 ns pulse, allowing uniform delivery of output power throughout the pulse duration, the combination of which induces photomechanical undulation in the target tissue with enhanced benefits in tissue regeneration. Furthermore, it features the MDF handpiece based on microlens array (MLA) optics. This fractionates the laser beam into multiple microbeams of 100-150 μm on the skin surface, targeting multiple skin layers according to the selected step and fluence, and it can be used with either 1,064 or 532 nm. Moreover, the combined beam diameter can be fine-tuned from 4 to 8 mm, while the focal depth of the microbeams can be tailored across deep (step I), intermediate (step II), and shallow settings (step III), allowing precise control over the location of the microbeam waists within the tissue at which the Ti-LIOBs are generated by the very high irradiances created at the beam waists [6,8].

It has been shown that the MDF handpiece used with the 1,064 nm Q-Nd:YAG in the present study produces Ti-LIOBs similar to picosecond lasers, with the advantage of being able to deliver sequential shots in multiple skin layers. Pattern analysis studies of immediate tissue reactions induced by picosecond-domain lasers at 532 and 1,064 nm wavelengths have been conducted on ex vivo pigmented micropig skin. Different wavelengths and fluences were measured, and histopathological effects on the tissues were evaluated. Picosecond-domain laser treatment, particularly with MLA-type handpieces at 532 and 1,064 nm generated fractionated zones of laser-induced micro-vacuolization in the epidermis and dermis, enhancing tissue regeneration and collagen formation [8].

A previous pilot study evaluated a Q-switched laser using novel fractional MDF handpiece used in 10 patients with acne scars. After approximately 3 months, there was an average percentage improvement for pores and acne scars of 57.8% ± 15.2% (p = 0.001) and 34.2% ± 24.3% (p = 0.0004), respectively, as measured by ANTERA software (Antera 3D Image Analysis System; Miravex Ltd.) [6].

Similar to acne scars, our study demonstrated excellent outcomes in linear traumatic scars, following four sessions spaced one month apart. Besides expected erythema, purpura, and edema from the therapy (Fig. 5), there were no significant adverse effects, and the patient satisfaction rate reached 100%. As limitations, this study had a small sample size, and evaluations were conducted solely by the attending physician; nonetheless, as is shown in Figs. 1 and 2, the results were promising.

In conclusion, the Q-Nd:YAG laser using a novel fractional MDF handpiece stood out for its capacity to modify the composite diameter of the entire treatment beam, and the variable focal depth of the microbeams provided meticulous control over treatment across various skin layers, thereby enhancing skin resurfacing. As previous research has demonstrated with acne scars, our study suggests that the Q-Nd:YAG laser with the MDF handpiece exhibited promising results in improving scars caused by trauma, with minimal adverse effects and high patient satisfaction. This underscores its potential as a treatment option for enhancing the appearance of skin impacted by traumatic injuries.

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Conceptualization: IPH. Data curation: IPH, DS. Formal analysis: IPH, DS. Methodology: IPH, DS. Project administration: IPH. Validation: IPH. Writing–original draft: IPH, DS. Writing–review & editing: all authors.

No potential conflict of interest relevant to this article was reported.

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