Microneedling versus microcoring: A review of percutaneous collagen induction for the face and neck

Microneedling (MN) and microcoring (MCT) are both methods used for percutaneous collagen induction. This minimally invasive technique involves creating controlled damage in cutaneous tissue to induce neocollagenesis and neoelastogenesis. MN utilizes solid microneedles and is commonly combined with radiofrequency (RF) to add thermal energy, while MCT involves hollow microneedles capable of removing excess tissue without inducing scar formation.


| INTRODUC TI ON
Minimally invasive skin rejuvenation has shown promise in treating aging skin.Microneedling (MN), and more recently microcoring (MCT), are methods of percutaneous collagen induction (PCI), promoting collagen remodeling and neocollagenesis to improve skin texture and appearance.The number of patients seeking these therapies continues to rise.As such, it is necessary for clinicians to understand existing therapies and remain up-to-date with progressing technologies.
MN is characterized by repetitive skin penetration with solid microneedles, generating micro-conduits extending into dermal tissues. 1 As the dermis undergoes microscopic injury, local inflammation prompts growth factor production leading to neocollagenesis and neoelastogenesis. 1,2Addition of radiofrequency (RF) enhances focal inflammation and subsequent cutaneous remodeling. 1,3T is a more-recent method of PCI, using hollow needles to remove microscopic tissue cores while preventing scarring. 4MCT combines collagen stimulation with excess tissue removal to improve skin laxity.MCT does not use thermal energy, protecting tissues from coagulation injury. 5MCT also allows clinicians to specify the tissue surface area extracted. 5rrent literature on MCT is limited compared to MN.Although currently used clinically, additional studies are needed to guide MCT and evaluate its effectiveness compared to MN.This review summarizes recent literature on MN and MCT, to highlight key features, differences, and areas for future investigation.Exclusion criteria included duplicates, reviews, retrospective studies, case reports, studies not addressing key words contained in the search algorithm, studies evaluating other treatment modalities, and studies not pertaining to the face and neck.

| Depth
Depth ranged from 0.5 to 2.5 mm, and varied with anatomy.Both    TA B L E 1 (Continued) skin. 8,9Zhang also treated 0.5 mm for forehead skin. 8Depths of 2.0 and 2.5 mm were used for buccal, mandibular, and nasolabial fold skin. 10-12

| Pulse duration
Pulse duration was reported for RF MN, and ranged from 50 ms for periorbital and forehead skin 8 to 320 ms for lower face and submental skin. 13Additional frequencies included 100, 15 110-140, 14 and 200 ms. 16

| Power level
Power applied through RF MN ranged from 5 to 20 W, depending on clinician and anatomy. 9-12,14-16Nilforoushzadeh et al applied 5-10 W to the eyelids and nasolabial folds, 10 while Gold et al applied up to 20 W to the cheeks and neck. 14Tanaka et al. applied 14 W to the cheek, 12 W to the neck, and 10 W to the forehead, nose, periorbital region, perioral region, and mandibular region. 12

| Number of passes
Number of passes ranged from one to four. 12,1414,16 Zhang et al performed a first pass with unipolar RF, and second pass with bipolar RF. 9

| Needle characteristics
Needle characteristics varied based on the device.Others assessed four sessions over 3 months, 18 four sessions at 1 month intervals, 8 three sessions at 1 month intervals, 11,14,15 or three sessions over 6 months. 16

| Locations
MCT was applied to the mid to lower face and preauricular region.

| Histologic change
El-Domyati et al reported increased collagen, tropoelastin, and epidermal thickness following 6 MN treatments. 17Additionally, clinical and histologic improvement were correlated. 17Wamsley et al noted increased epidermal density, elasticity, attenuation, and blood flow following 4 MN sessions. 8The study observed increased expression of collagen and elastin on histology. 8Another study noted welldemarcated coagulation zones directly adjacent to the RF microneedle tip, with no thermal coagulation zones along the needle track. 13

| Biometric change
Nilforoushzadeh et al reported significant reduction in pore size, spot number, and transepidermal water loss, as well as increased epidermal thickness and elasticity. 10Nasolabial fold depth was noted to be 90% decreased 3 months after RF MN. 10 No changes in color, melanin, or sebaceous content were induced. 10These measures were assessed by Calorimeter, Tewameter, Cutometer, Mexameter, Sebumeter, high-resolution photography, and ultrasound.Wamsley et al reported improved cutaneous density, elasticity, attenuation, and blood flow, as well as increased collagen and elastin gene expression and dermal muscle formation resulting from MN. 8 These changes were assessed through high-resolution ultrasound and optical coherence tomography. 8RF MN was associated with significant changes in the gnathion angle of 28.9 degrees and cervicomental angle of 16.6 degrees (p < 0.001). 13Tanaka et al reported a median reduction in skin volume of 12.1 mL at 6 months following non-insulated RF MN. 12

| Aesthetic change
Alqam et al reported significant reduction of rhytides with the Lemperle Wrinkle Assessment Scale (LWSS) following MN. 18Lee et al also reported improvement in periorbital wrinkles by 5-point Wrinkle Assessment Scale (WAS) (−1.075 ± 0.52, p < 0.001). 15The same study reported dermatoscopic improvement in wrinkle appearance following RF MN. 15 Clinicians and patients reported significant improvement by the Global Aesthetic Improvement Scale (GAIS). 1593% of patients noticed high levels of rhytide improvement. 18Lyons et al reported an aesthetic improvement rate of 67% with RF MN, while 70% endorsed improved rhytides and skin laxity, and 80% of subjects were satisfied with the treatment. 19lforoushzadeh et al reported 90% of patients experienced moderate or good satisfaction 3 months post-treatment. 10Gold et al found that RF MN lead to decrease in Fitzpatrick Wrinkle and Elastosis Scale measurements from 5.04 to 3.5 (p < 0.001). 14100% of subjects improved by GAIS in this study. 14Lu et al reported reduction in periorbital rhytides, nasolabial fold depth, and skin laxity at 3 months following RF MN. 11 Greatest MN treatment effect occurred at 3 months, although improvement from baseline was still significant at 1 year. 11Clementoni and Munavalli reported 100% of subjects improved by the clinician GAIS (CGAIS), with 81.8% of patients ranked as moderate or greater improvement. 13u et al noted that skin treated with RF MN demonstrated a mean change in GAIS of 3.34, compared to 0.89 in untreated locations (p < 0.001). 16Zhang et al noted reduction in Global Photoaging Scale (GPS), from 2.54 at baseline to 1.98 6 months after therapy with fractional RF MN (p < 0.01). 989% of patients experienced rhytide improvement, 100% experienced skin laxity improvement, and 52% experienced overall skin complexion improvement at 6 months. 9Overall, 93% of patients were either satisfied or very satisfied with the results. 9Tanaka et al found that 90% of patients were either satisfied or very satisfied with treatment outcomes of non-insulated, fractional RF MN, with correlation between volumetric reduction and patient satisfaction. 12

| Histologic change
No in-vivo, human studies assessed the histological effects of MCT.

| Biometric change
Pozner et al reported an increased facial thickness from 1856 um to 2097 um following MCT (p < 0.05). 7Pozner et al also noted reduced facial skin surface area by 9.4% at 30 days (p < 0.01). 7

| Aesthetic change
In assessing MCT at 3.0-5.0mm with 22-gauge needle, Gfrerer et al reported an average change in LWSS of 1.3 grades following treatment. 6The same treatment led to GAIS improvement in 89.7% of study subjects, and an 85.6% patient satisfaction rate. 6bjects experienced visible rhytide reduction and were very much aesthetically improved by subject and investigator GAIS at 90 days post-treatment, with scores of 2.9 and 2.8, respectively. 6,7

| Adverse event profile
Patients experienced mild to moderate pain after MN, with an average VAS measurement of 4.0/10. 13,14Bipolar RF microneedling was significantly more painful than unipolar. 9MN resulted in mild to moderate erythema and edema for 12 h post-treatment. 14Associated crusting, erythema, edema, and petechiae persisted longer with deeper treatments (3.8 days vs. 2.3 days, p < 0.01). 11Several patients had pinpoint purpura resolving within 7 days and hyperpigmentation resolving in up to four weeks. 9,15Patients experienced downtime of 2 to 4 days. 13MCT resulted in pain from 0 to 2.8/10. 6,7With MCT, bleeding, ecchymosis, crusting, and erythema occurred, requiring 3 days downtime. 6,77 | Subjective measurement scales

| Patient demographics
Most patients were female.Several study populations were entirely female. 10,11,16Age ranged from 31 to 80 years, with mean of approximately 50 years.Multiple studies assessed Asian patients exclusively. 9,12,15,16All Fitzpatrick skin types were included, with no differences in outcomes between types.Of 12 studies evaluating MN, nine assessed RF MN.Non-RF MN resulted in mean improvements in the clinician and subject GAIS of 3.06 and 3.16, respectively, compared to 3.34 after RF MN. 16,18 Non-RF MN improved cutaneous thickness, rete ridge development, and tropoelastin and collagen content at 3 months, and dermal muscle formation after 4 months. 8,1712][13]16 RF MN resulted in thermal coagulation injury at the needle penetration depth, not seen without RF. 11,13All patients were pretreated with topical anesthesia.Numerical pain values were not reported by studies assessing non-RF MN.For RF MN, average reported pain ranged from 3.19 to 5.63 out of 10. 14 Bipolar RF was significantly more painful than unipolar. 9Two of three studies assessing non-RF MN did not report adverse events.One study reported erythema and edema resolving in 24 h post treatment, with patients having 2 days of downtime.For RF MN, erythema, edema, crusting, sloughing, burning, and hyperpigmentation were reported, with downtime from 2 to 4 days. 13,15T resulted in a mean GAIS improvement of 2.9. 7MCT led to an increase in cutaneous thickness and a significant reduction in skin surface area, although no studies assessed histologic effects.

| DISCUSS ION
Pain ranged from 0 to 2.8 out of 10, with some patients receiving pretreatment intradermal anesthesia. 6,7Bleeding, ecchymosis, erythema, and hyperpigmentation were reported, with an average downtime of 3 days. 7llow-up ranged from one to 12 months for MN, and 1-5 months for MCT.The maximum subjective improvement, as well as increase in skin thickness, tropoelastin, and collagen occurred at 3 months after MN. 17 The most significant volumetric changes occurred at 6 months after MN. 12 For MCT, skin thickness and surface area changes were only assessed at 1 month, while subjective improvement was only assessed at 3 months. 7Given the relatively short follow-up durations for all studies in this review, and variation among studies, assessing the long-term effects and precise duration of effects of PCI was challenging.
Despite limited in-vivo histologic data in humans, Fernandes et al characterized histologic effects of MCT in swine.The study reported fibroblast induction and rete-ridge formation, with a 196% increase in papillary dermal and epidermal thicknesses and an 89% increase in collagen content. 4Ramot et al tested robotic MCT in swine, demonstrating time-related elimination of necrotic tissue and fibroblastic replacement. 20These results suggest the histologic effects of MCT similar to those expected in humans.
When biopsy and direct histologic analysis may not be possible due to concern for cosmesis, three-dimensional and biometric analysis can be used. 8,10,12,13These noninvasive technologies analyze rhytide depth, skin texture and thickness, blood flow, and other measures of skin laxity, as shown by several studies in this review.While subjective and objective improvement scales are commonly used, nonuniformity between studies makes direct comparison difficult.As biometric analysis tools are more widely used, this will allow for improved objective comparison of MN and MCT.
Other studies reported similar adverse effects of MN to those reported by this review, including discomfort with increasing treatment depth, erythema, edema, pigmentary changes, and granuloma formation. 21The addition of electrical current has been reported lessen the perception of pain through induced vibration. 22For patients unable to tolerate treatment discomfort, oral pain medication, or nerve blocks may be considered. 23rrent literature suggests that adjunctive platelet rich plasma (PRP) or growth factors may act synergistically with MN to improve aesthetic outcomes, given increased penetration and absorption of PRP with MN. 24 Given the similarities and differences between MN and MCT, future studies will likely demonstrate efficacy of PRP with MCT.
In conclusion, existing literature on PCI lends support to the use of MN and MCT for improving skin laxity of the face and neck, although additional investigation is needed.As a more recent development, there is a relative scarcity of literature assessing the clinical and histologic efficacies of MCT.Additionally, no existing studies have conducted head-to-head comparison of MN and MCT.This limits the conclusions that can be made regarding the superiority of one PCI modality over the other.Should standardized pretreatment anesthetic regimens, assessment scales and modalities, reporting of adverse events, and follow-up duration be implemented in future studies comparing MN and MCT, differences in efficacy and treatment tolerability may be better understood.

CO N FLI C T O F I NTE R E S T S TATE M E NT
The authors declare no conflicts of interest.
Wamsley et al and Zhang et al targeted 0.5 mm for periorbital F I G U R E 1 PRISMA diagram detailing screening and selection of articles included in the review.TA B L E 1 Fourteen studies pertaining to search algorithm results for microneedling (MN) and microcoring (MCT) in human facial and neck skin.Studies published from 2013 to 2023 meeting inclusion and exclusion criteria were reviewed.Twelve studies evaluated MN, while two evaluated MCT.

10 TA
tropoelastin, acanthosis with rete ridge development Increased mean thickness from 58 um to 63 um (p = 0.03) at 1 m, 72.9 (p = 0.007) at 3 m Increased tropoelastin from 15.1% to 21.9% (p = 0.02) at 3 m Increased collagen content from 14.1% to 21.8% (p = 0.01) at 3 months Maximum wrinkle improvement, satisfaction at 3 Quantitative collagen, elastin Increased density, elasticity, attenuation, blood flow, collagen and elastin gene expression, follow-up Pore size, color change, transepidermal water loss, elasticity, melanin and hemoglobin concentration, sebaceous content, epidermal thickness and density Patient satisfaction No changes in color, melanin, or sebaceous content Significant reduction in pore size and spot number Significant Increase in epidermal density and thickness Significant decrease in transepidermal water loss -Significant increase skin elasticity -Reduced nasolabial fold depth −90% of patients had moderate or good satisfaction at 3 months Gold et al. 14 Multicenter clinical trial Evaluate the effect on non-insulated fractional RF MN system (Endymed Pro Intensif) on wrinkle reduction 49 subjects aged 35-65, 46 female (Cheek)110-140 ms, 10-Significant decrease in FWES (5.04 ± 1.22 to 3.5 ± 1.66, p < 0.001) −100% patients improved by GAIS -Mild to moderate erythema, edema for up to 12 h after treatment -No hyperpigmentation, epidermal burns, scar formation -Average pain 4/ MN and MCT were both well-tolerated in improving laxity of the face and neck in human subjects.The technologies differed with respect to pretreatment anesthesia, treatment depth, skin surface area reduction, treatment discomfort, and assessment and reporting of patient outcomes.Variation in assessment scales and modalities, as well as blinded reviewer assessments between studies limited the comparison of MN, RF MN, and MCT.Nonuniformity of pretreatment anesthetic regimens, reporting of adverse effects, and follow-up duration also limited accurate comparison in these areas.No studies directly compared MN and MCT, or MN and RF MN.No studies assessed histologic effects of MCT.
Tanaka et al. applied a single session, 12 while El-Domyati et al applied up to six sessions at 2 week intervals.