Background
One of the most significant signs of aging is the appearance of deep lines that run from each side of the nose to the corners of the mouth \[i.e., nasolabial folds (NLFs)\]. These folds are defined by facial structures that support the buccal fat pad and separate the cheeks from the upper lip. The NLFs form due to volume shifts in the face, caused by a combination of fat descent and bone absorption, which results in sagging skin and hollowing.
Soft tissue augmentation can effectively restore the youthful, harmonious contours of the face. The most popular non-invasive treatment options for volume loss in the face include the use of hyaluronic acid (HA) fillers. Injections of HA for skin rejuvenation are one of the most common aesthetic treatments performed worldwide. Due to their effectiveness, safety, low immunogenicity (HA is a normal component of human skin) and reversibility with hyaluronidase, HA fillers are understandably a popular option for facial volume restoration.
Through recent advances in manufacturing technology, various types of HA fillers have been approved for the correction of facial wrinkles and folds, such as NLFs. Two such fillers, i) Restylane + Lidocaine and ii) Restylane Lyft, are well tolerated and provide significant improvement in this indication. These products contain the same amount of HA (i.e., 20mg/mL) and are manufactured using the same technology \[i.e., non-animal stabilized hyaluronic acid (NASHATM)\], but differ primarily in their particle size.
Small particle size HA (Restylane + Lidocaine): was the first non-animal stabilized HA-containing filler approved for use in the United States. Because of its particle size (i.e., 330-430 μM), Restylane + Lidocaine is referred to as small gel-particle HA (SGP-HA). NASHA small gel contains approximately 100,000 gel particles per mL.
Large particle size HA (Restylane Lyft): was approved in the United States in 2010 and is considered a large gel particle hyaluronic acid (LGP-HA). Restylane Lyft also contains the anesthetic lidocaine. NASHA large gel contains approximately 10,000 gel particles per mL.
The difference in gel size between the two products results in different viscosity and lifting capabilities, which is anticipated to affect treatment outcomes. While the comparative research is limited, a small number of clinical trials have compared the two products. For example, two randomized studies performed using US populations have shown equivalent safety and similar efficacy of Restylane + Lidocaine and Restylane Lyft, in subjects of all Fitzpatrick skin types; and one recent study found that both products exhibit similar safety and efficacy in a Chinese population. These three comparative studies found no significant differences in safety of LGP- and SGP-HA however, efficacy changes can occur due to the injection techniques and depth of injection used by the investigators.
This study is designed to assess and compare the efficacy of these two HA fillers on moderate, severe and extreme NLF, when using a modified technique. This modified technique will use a single puncture technique in each NLF, in comparison to others who have used a multi puncture, fanning or linear threading injection technique. For each NLF, a single bolus of product will be placed within the nasal pyriform aperture, on the periosteum. The location of the puncture will also vary from previous trials, in which injections were performed directly within the NLFs (to replace soft tissue volume). It is hypothesized that when these two products are used for replacing bone loss due to age-related resorption in the pyriform aperture, differences in efficacy will be observed that are not evident when they are used in soft tissue for volume augmentation. It is expected that while aesthetic outcomes and longevity of effect may be similar between the two products, the volumes required to achieve these same results will differ significantly, due to their different particle sizes.
Study Rationale
Larger HA gel particles result in better lifting capacities. Therefore, Restylane Lyft should display better efficacy in comparison to Restylane + Lidocaine when a "firm" product with a high lift capacity is required, such as when trying to replace or reshape bone. This is in contrast to replacing soft tissue volume, which was evaluated in earlier studies. However, as previous authors have reported, when these two products are used to replace soft tissue volume they both provide adequate lifting capabilities and thus result in similar efficacy levels.
