Fillers in Daegu: the site decides the plane, and the plane decides the product

The author’s conclusion is unambiguous — injected into the dermis it changes the skin’s own thickness; injected below it, it replaces volume. Restoring volume and changing skin quality are done in different planes, even with the same product.

So “which plane are you injecting into” is a more precise consultation question than “which filler do you use”. Once the plane is set the product range narrows, and once the product is set the volume follows. Reverse that order and you end up compensating for a mismatched product with volume.

Product descriptions often use degree of crosslinking to explain firmness. Within one experiment, raising crosslinking from 5% to 20% does raise elastic modulus proportionally. That much is true.

The problem is comparison between products. Here is what measuring 16 commercial hyaluronic acid products under identical conditions showed.

The least crosslinked product was the firmest. On top of that, the same product is reported with different crosslinking values in different sources — Restylane appears as 3% in one and 1.1% in another. Crosslinking figures are only comparable within a single paper.

If a product is recommended to you on the basis of a crosslinking number, it is fair to ask which source that number came from.

Dividing small amounts into the dermis does have placebo-controlled evidence. In a trial splitting the face left and right, product on one side and saline on the other, with both patient and assessor blinded (28 completers) — hydration was +35% on the product side against −10% on saline, the elasticity measure improved −27% on the product side only (p = 0.03), and assessors judged improvement in 82% against 0% (p<0.001).

But this route has its own cost. In booster-type products placed in small dermal aliquots, delayed nodules were reported at 0.8% (131 subjects, appearing at day 122). That is higher than the 0.33% found in a retrospective review of 2,139 conventional filler patients. Superficial is not automatically safer.

Plane and site bear directly on safety. In a review of blindness cases, the 48 new reports between January 2015 and September 2018 were distributed as nose 27 (56.3%), glabella 13, forehead 9, nasolabial 7, cheek 2, upper eyelid 1, with complete blindness in 25 (52%). The midface is not a safe zone either.

The instrument figures usually quoted — vascular occlusion once per 6,410 needle treatments and once per 40,882 cannula treatments — come from a survey in which 370 dermatologists recalled the previous ten years. It is not a comparative trial and carries no patient-level adjustment. Read it as an estimate only.

Fortunately hyaluronic acid is a reversible class. With hyaluronidase, partial or complete recovery after occlusion is reported at 84.2%, and delay beyond five days correlated with permanent damage. A meta-analysis of ultrasound-guided cases (4 studies, 55 patients) found complete recovery of 94.6% — though 55 patients is still a small body of evidence.

Checking authenticity is not difficult. The product licence number is printed on the box, while the long number on clinic material is usually an advertising pre-review number. You may ask to see the box and the syringe before treatment.

Dose is less tidy. Even hyaluronidase has no standard dose for emergencies — international guidance states plainly that no standard concentration or dose is described in the literature. For reference, complete recovery was 88.1% with low dose (≤500 IU) and 69.6% with high dose (>500 IU), and the difference was not statistically significant (p = 0.18).

So “correct dose” is best heard not as a fixed table but as using only as much as the site and plane require.

• Which plane it goes into — ask this before the product name.
• Why that plane for that site — volume or skin quality changes the answer.
• The instrument and the reason — needle or cannula.
• The box and the syringe — licence number distinguished from the advertising review number.
• The emergency route — whether hyaluronidase is kept on site, and when to call.
• What “only as much as needed” means here — whether a total was fixed in advance.

We do not treat filler as simply filling a hollow. We first separate what is to change at that site — volume, or the thickness and hydration of the skin. That distinction sets the plane, the plane narrows the product range, and only then is volume decided.

We also work on the principle of not recommending treatments that are not needed. We do not fix a total first and then find sites to use it on. Hyaluronic acid is a reversible class, but being reversible is not a licence to place more.

Which treatment suits you can differ with skin condition, how much change you want and what you have had before. It is fine to come for consultation and decide later.

• Filler and booster compared · What crosslinked hyaluronic acid is
• What dissolving with hyaluronidase means · Vascular occlusion and blindness
• The ligament approach to filler · Why nodules form
• Nasolabial folds in Daegu: filler or lifting? · Needle or cannula
• How to read approval numbers · All boosters

Dr Lee Chi-Hak, Director, Miso Clinic

4F Bombom Building, 125 Dongdeok-ro, Jung-gu, Daegu (Kyungpook National University Hospital station, exit 1)

+82 53-428-2700 · www.clinicmiso.co.kr

• Any validated depth criteria by site or body type — we could not find one.
• Any standard allowing cross-product crosslinking comparison — the same product is reported with different values.
• Any head-to-head trial of superficial versus deep placement at the same site.
• Nodule rates compared by product or by plane.
• A denominator of treatments by instrument and site — the occlusion frequency figures lack one.
• A standard concentration or dose for hyaluronidase — the guidance itself says none exists.
• Any study validating our sequence of site, plane, product, volume — it is clinical judgement.