Lasers Surg Med. 2009 Feb;41(2):87-95.
Pilot clinical study of a novel minimally invasive bipolar microneedle radiofrequency device.
Hantash BM, Renton B, Berkowitz RL, Stridde BC, Newman J.
Lasers Surg Med. 2009 Jan;41(1):1-9.
Bipolar fractional radiofrequency treatment induces neoelastogenesis and neocollagenesis.
Hantash BM, Ubeid AA, Chang H, Kafi R, Renton B.
Review copyright 2009 https://aestheticdevicereview.wordpress.com
In a pair of articles published a month apart, Hantash and colleagues present the first descriptions of the histological and immunohistochemical effects of the bipolar radiofrequency needle device from Primaeva. Several of the authors are affiliated with Primaeva, and the study was funded by Primaeva. AestheticDeviceReview takes a closer look at these two papers.
Three studies were performed on human abdominoplasty or face-lift patients prior to surgery. In the first study of five patients, a broad range of dosages were applied by varying tissue temperature and duration. Histological results from this group were used to select a narrower range of dosages for examination in a 10-patient second study. Finally, in the third study, a single dosage of 72C for 4 seconds was applied to 22 patients, and both histological and immunohistochemical testing was performed.
Briefly, the radiofrequency device consists of an RF generator attached to a handpiece, which includes a single-patient-use array of 10 needles arranged in 5 pairs. The 250-micron needles are spaced 1.25mm apart, and each needle-pair is independently powered by the generator. Each needle is 6mm long, with the top 3mm insulated and the bottom 3mm exposed to allow electrical current flow. The needles are inserted at a shallow 20 degree angle to the epidermis, such that when properly placed, the tip of the needle is 2mm from the epidermis. Insertion is done by spring-loaded injection. When properly inserted, the exposed portion of the needle is positioned nearly parallel to the skin surface, at 1mm to 2mm below the surface. Each needle pair has a temperature sensor, which is used to control the power so that constant temperature can be maintained. An impedence measurement from each needle-pair also provides feedback on the depth of needle insertion. In this study, a separate skin cooling device is held against the skin after the needles are inserted, maintaining 15C to protect the epidermis from conducted heat from the RF needles. In this prototype configuration, this cooling device requires a 2nd operator, and makes the technique somewhat more difficult to apply.
Because current flows between the two needles in each pair, we expect the RF energy to create five damage zones (one between each pair), and if the heat is applied long enough, temperature conduction should expand the damage zone in all directions, resulting in one contiguous zone of damage. The surface cooling device should prevent the conducted heat from damaging the epidermis. This is exactly what the authors show. In the example shown in the paper, by setting the device at 70C for 1 sec, five zones of about 2mm by 1.25mm x 2.5mm were created. At 70C for 4 seconds, one contiguous zone of damage of about 12mm x 1.5mm x 2.75mm was created. Unfortunately, while many patients were studied, the authors did not present quantitative data on the mean and variation of the size of the damage-zones, so we are left to wonder about intra-patient variation and inter-patient variation.
This description makes it clear that the device does not provide a fractional treatment, which would be characterized by 50 or more micro-thermal-zones of damage per square centimeter. Instead this device creates one to five milli-thermal-zones of damage per square centimeter, so the term “fractional” should not be used. AestheticDeviceReview believes that the relatively large volume of RF-needle-created tissue coagulation may even turn out to offer a clinical benefit compared to fractional treatments, so the fractional label may be unwise as well as unwarranted.
Interestingly, while large amounts of tissue were coagulated, the authors show that important dermal structures such as blood vessels, hair follicles, sebaceous glands, and sweat glands were undamaged by the treatment. Men getting wrinkles treated will not have to worry about bald patches in their beards. Similarly, needles placed into the subcutaneous fat did not cause fat damage, as electrical energy appeared to flow through the interstitial collagen (fibrous septae?). AestheticDeviceReview sees some potential for this technology as a treatment for cellulite.
In the immunohistochemical study, the authors nicely show that the tissue damage is not necrosis, but a zone of thermal coagulation that proceeds through a wound healing response over several weeks, consisting of sequential phases of inflammation, proliferation and ultimately remodelling. Again this should come as no surprise, as this response is similar to that seen with several other radiofrequency devices that have been developed for shrinking collagen-rich soft tissue. For example, temperature-controlled RF needle technology is used to shrink soft palate tissue as a treatment for snoring. See company white paper at: http://www.somnus.com/abstracts/absomnus2.htm
Unlike non-ablative fractional laser treatments, all patients experienced swelling and focal edema which resolved in 48 hours following treatment. Despite the use of skin cooling, erythema appeared on the surface above each thermal damage zone, and this resolved within 8 hours of treatment. Several patients experienced purpura as well, which resolved in less than 7 days. So, overall “downtime” is greater than non-ablative fractional and less than ablative fractional laser treatments.
Is the downtime worth the result? Here, the authors leave us hanging. No data is presented on tissue shrinkage. Why didn’t the authors place tattoos prior to treatment, and measure the effect of treatment on tattoo distance? No data is presented on any change in dermal thickness. Why were so many patients studied, if quantitative histological analysis was not going to be performed? We at AestheticDeviceReview can only wait – perhaps we will see another study next month.