Poly-L-lactic acid

Published on 16/03/2015 by admin

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7 Poly-L-lactic acid

Stephen H. Mandy, Rebecca Fitzgerald

Summary and Key Features

• Gradual, subtle, and natural results with a long duration (>2 years) are achievable with poly-l-lactic acid

• As experience has been gained with this product and technical issues have evolved, it has been found to be a safe and effective product with predictable and reproducible results

• Attention to the simple yet critical techniques in the preparation and injection of this biostimulatory agent will minimize adverse events

• Methodology is an important factor in biocompatibility. Remember that the amount of product used at one session is determined solely and completely by the amount of surface area to be treated at that session. The final volumetric correction is determined by the number of treatment sessions

• Experience with facial augmentation has taught us that very empty faces or those with a very elastotic outer skin envelope may be challenging to volumize, requiring a substantial amount of product – any product – to achieve a desirable result. This should be expected in this patient population and discussed prior to any filler treatment to prevent unnecessary frustration for both the patient and the physician

• Thoughtful facial analysis of changes in all structural tissues will enhance site-specific augmentation of volume loss and enhance outcomes

• Patients are starting cosmetic treatments earlier than they have traditionally done. The 2010 American Society of Aesthetic Plastic Surgeons statistics revealed that 44% of cosmetic patients are now ‘genXers’ (age 35–50) and 28% are ‘baby boomers’ (51–65). This younger group often needs less product and fewer treatment sessions than the older group and is very gratifying to treat

Introduction

Poly-l-lactic acid (PLLA) is a synthetic polymer derived from lactic acid that is both biocompatible and biodegradable.

The purpose of this chapter is to discuss current techniques used with PLLA to effectively and safely address changes observed with facial aging. Proper patient selection and assessment, as well as attention to technique in the preparation and injection of the material, will minimize adverse events and optimize results.

Product and mechanism of action

The currently commercially available form of PLLA consists of microparticles of PLLA measuring 40–63 µm in diameter. This particle size ensures that the particles are large enough to avoid phagocytosis by dermal macrophages or passage through capillary walls, but small enough to be easily injected by needles as fine as 26 gauge.

The mechanism of action of PLLA begins with a subclinical inflammatory tissue response following implantation, followed by encapsulation and subsequent fibroplasia. This fibroplasia volumizes the tissue and produces the desired cosmetic result.

Poly-L-lactic acid: technical considerations

Methodology is an important determinant of biocompatibility with stimulatory agents. This is outlined below and summarized in Box 7.1.

Box 7.1

image Even distribution and proper placement of the implanted PLLA is key to a desirable outcome

image Proper dilution, reconstitution, and deep placement are critical

image Product must be evenly suspended immediately prior to every injection

image Immediate post-injection massage

image Superficial placement leads to visible neocollagenesis

image Placement in active muscles leads to localized overcorrection

image Diffuse papules/nodules likely an issue with reconstitution, i.e. shaking vial immediately after adding water (crystals on sidewalls of vial won’t hydrate), inadequate hydration time, poor suspension immediately prior to injection

image Focal papules/nodules are likely an issue of placement, i.e. redeposition at the apex of the ‘fan’ when using the fanning technique

Product reconstitution

No less than 5 mL of sterile water, with a hydration time of no less than 2 hours, but preferably overnight (bacteriostatic saline for injection has been substituted for sterile water by some injectors but is ‘off-label’). Add fluid gently and leave to hydrate. Do not shake the vial until it is adequately hydrated to avoid deposition of dry clumps of material on the wall of the vial. Currently, a final dilution of 8–9 mL is the most commonly used. This final dilution can be achieved by adding additional water and/or lidocaine 1–2% with or without epinephrine at the time of hydration or immediately prior to injection.

Pearl 1

Product must be evenly suspended immediately prior to every injection.

Product amount

The amount of product used at any single treatment session should be determined solely and completely by the amount of surface area to be treated at that session. The final volumetric correction is addressed by the number of treatment sessions. (The novice injector should be aware that it is initially difficult to resist the temptation to treat to full correction at any one session.)

Product placement

This can be done with a 1 mL or 3 mL syringe and a 25-gauge (long or short) or 26-gauge (short) needle. The depth of placement varies with the location. The product may be placed in the subcutaneous layer in the cheeks, nasolabial folds, and lower face using the cross-hatch or fanning technique (using 0.1–0.2 mL/cm) and may be placed as depot injections supraperiosteally (using 0.2–0.3 mL per injection) along the zygoma, maxilla, and mandible. Deep injections should be avoided around the parotid gland and the masseter. A reflux maneuver should be carried out prior to each injection to avoid inadvertent intravascular injection. This can also be minimized by the use of a 25-guage blunt-tip cannula for injection. Temple injections are placed deeply, under the temporalis muscle. The manufacturer’s instructions are to place 0.05 mL depots in the temple; however, it is common practice among experienced users to place 0.3–0.5 mL depot in this area, followed by vigorous massage.

Pearl 2

Proper dilution, reconstitution, and deep placement are critical. Superficial placement leads to visible papules.

Product placement precaution

Avoid placement in or through areas of dynamic muscle movement in close proximity to the lips and eyes, which leads to clumping of particles manifesting clinically as lumps and bumps. It may be prudent to inject slowly in a cross-hatch pattern while becoming familiar with the product as PLLA is mixed in water, making for a very low-viscosity solution. Most experienced users prefer the fanning technique (which is more efficient and has the advantage of fewer needle sticks); however, the novice injector must be vigilant to avoid multiple deposits at the apex of the fan.

Pearl 3

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