Radiesse for Neck Wrinkles: 120-Day Skin Thickness Study Explained

Key Points: A 2023 clinical study published in Clinical, Cosmetic and Investigational Dermatology found that diluted Radiesse (CaHA) injected into the neck increased dermal thickness by an average of 14.9% at 120 days. Unlike traditional filler, the diluted technique targets collagen stimulation rather than volume filling — making it a distinct approach for the delicate, thin skin of the neck.

Why Is the Neck Harder to Treat Than the Face?

The neck is one of the most visible signs of skin aging, yet it is frequently overlooked in aesthetic care — largely because it requires a fundamentally different approach than the face. The skin on the neck is thinner, more mobile, and far more prone to showing injection marks if treated incorrectly.

Filling neck wrinkles the same way you would fill facial lines risks creating visible ridges or unnatural contours. The constant movement of the neck throughout the day means that injected material must be distributed differently, and the technique must account for how the skin folds and stretches during everyday motion.

This is why the most effective strategies for neck rejuvenation focus not on volumizing, but on rebuilding the skin itself from within — using agents that stimulate the skin's own collagen production rather than physically pushing wrinkles outward.

Understanding this distinction is key before considering any neck treatment. Patients who have already experienced significant skin laxity may fall outside the scope of what collagen-stimulating approaches can realistically address, which is an important point the clinical evidence also reflects.

What Does the 2023 Clinical Study on Radiesse (CaHA) for the Neck Actually Show?

The study referenced here was published in the peer-reviewed journal Clinical, Cosmetic and Investigational Dermatology in 2023. It enrolled 22 adult women and followed them for 120 days after receiving diluted Radiesse (CaHA) injections in the neck — providing both photographic assessments and objective ultrasound measurements of dermal thickness.

A key methodological strength was that photographic grading was conducted by separate physicians who were blinded to whether images were taken before or after treatment. Critically, skin thickness was not estimated visually — it was measured directly using ultrasound imaging, which removes potential bias from lighting or camera angle differences.

Given the sample size of 22 participants, the results should be interpreted as a directional trend rather than a definitive conclusion. However, the use of objective measurement tools adds meaningful weight to the findings compared to purely subjective photo ratings.

The study tracked outcomes at multiple time points, with the primary endpoint measured at day 120. Participants received two treatment sessions spaced 45 days apart, meaning results reflect the cumulative effect of a staged protocol rather than a single session.

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How Does Diluted Radiesse (CaHA) Work Differently From Standard Filler?

Radiesse (CaHA) contains calcium hydroxyapatite microspheres — particles finer than a strand of hair — suspended in a gel carrier. When injected, the gel provides an immediate, temporary volume effect, while the microspheres remain in the tissue and act as a scaffold to stimulate new collagen production over the following weeks and months.

In this study, the researchers diluted 1.5 mL of Radiesse with lidocaine and saline to reach a total volume of 7.5 mL — a fivefold dilution. At this concentration, the gel component is too sparse to meaningfully fill volume. The goal shifts entirely to distributing the CaHA microspheres broadly across the treatment area to maximize collagen-stimulating coverage.

The researchers explicitly note in the paper that at this dilution, the volumizing effect is largely absent, leaving predominantly the biostimulatory mechanism. This is a meaningful distinction: the treatment is not filling wrinkles — it is rebuilding the dermal tissue that creates them.

Injection placement was also standardized. The neck was divided into five vertical zones, and small amounts were deposited in the superficial dermis of each zone. This systematic approach ensures even distribution of the CaHA particles rather than concentrating them in a single area.

What Were the Measurable Changes in Skin Thickness Over 120 Days?

Across all three measurement zones, dermal thickness increased by an average of 14.9% at 120 days compared to baseline. This increase reflects genuine structural change within the dermis — not the temporary swelling that follows an injection, and not an optical illusion created by photographic conditions.

The response varied meaningfully by location. The central neck showed a 9.6% increase, the mid-lateral zone showed 11.1%, and the lateral neck showed the largest gain at 23.0%. This regional difference suggests that the sides of the neck may be particularly responsive to this approach — a factor worth considering when planning treatment distribution.

Thicker dermis has practical implications for appearance. Skin that has regained structural density is less likely to crease sharply when the head is turned, and fine horizontal lines may appear shallower as the tissue beneath them becomes more substantial. This is a different mechanism from filling a wrinkle — it is improving the underlying tissue quality.

Visual assessments aligned with the ultrasound data. At 120 days, 86.4% of the 22 participants showed at least a one-grade improvement in horizontal neck wrinkle severity based on blinded photographic scoring. While individual outcomes varied, the direction of change was consistent across the majority of participants.

Who Is a Realistic Candidate, and What Should You Expect From the Timeline?

The 22 participants in this study were women aged 35 to 55 with mild to moderate neck aging. Those with significantly advanced skin laxity were excluded from enrollment. This is an important boundary — collagen biostimulation can meaningfully rebuild skin thickness, but it is not a substitute for addressing substantial tissue sagging, which may require different modalities.

The timeline also requires realistic expectations. Participants received two sessions spaced 45 days apart, and the documented thickness increase was measured at day 120. This is not a treatment where results appear the next day. Collagen synthesis and structural remodeling take time — the benefit accumulates gradually rather than appearing immediately after the procedure.

Reported side effects in the study were mild and transient: bruising, temporary palpable nodules, and a warm or flushed sensation. These resolved without intervention. However, because the follow-up period ended at 120 days, how long the improvements are maintained beyond that point cannot be determined from this study alone.

Individual variation matters. The figures presented — including the 14.9% average thickness increase — represent group averages across a small cohort. How any individual responds depends on their starting skin condition, age, lifestyle factors, and how their tissue processes the biostimulatory signal. A staged, measured approach over time tends to yield more predictable outcomes than attempting to achieve everything in a single session.

For those exploring neck rejuvenation, understanding what collagen-stimulating treatments can and cannot do is an essential starting point. The evidence here points to a meaningful structural change in skin that falls within the right candidate profile — but a personalized assessment remains the necessary first step.

Frequently Asked Questions

How is diluted Radiesse (CaHA) different from regular dermal filler for the neck?

Standard dermal filler works primarily by adding volume to push out wrinkles. Diluted Radiesse (CaHA) uses a much thinner concentration where the gel carrier is too sparse to fill volume meaningfully. Instead, the calcium hydroxyapatite microspheres spread broadly through the tissue and stimulate the skin's own collagen production. The goal is to rebuild dermal thickness over time, not to physically fill in lines.

How long does it take to see results from this neck treatment?

Based on the 2023 clinical study, measurable increases in dermal thickness were documented at 120 days, following two treatment sessions spaced 45 days apart. This is a gradual, collagen-dependent process — results are not visible immediately after treatment. Expecting meaningful change within the first few weeks is unrealistic with this approach; the benefit builds as new collagen forms and matures within the tissue.

Is this neck treatment suitable for everyone with neck wrinkles?

Not necessarily. The study enrolled women aged 35–55 with mild to moderate neck aging. Participants with significantly advanced skin laxity were not included. This reflects a realistic scope: collagen biostimulation can improve skin thickness and texture within a certain range of skin aging, but it is not designed to address severe sagging. Individual suitability depends on current skin condition and overall neck aging severity.

What side effects were reported in the study?

The side effects observed were mild and temporary. Participants reported bruising, transient palpable nodules at injection sites, and a warm or flushed sensation. All of these resolved on their own without requiring additional treatment. The study followed participants for 120 days, so effects beyond that period are not captured in this particular research.

Why did the lateral (side) neck show a larger response than the central neck?

The study found that dermal thickness increased more in the lateral neck zones (23.0%) than in the central zone (9.6%) at 120 days. The exact reason for this regional difference is not fully explained in the paper, but it may relate to differences in baseline skin thickness, tissue vascularity, or how the CaHA particles distribute in different anatomical zones. This finding suggests that treatment planning should account for zone-specific differences rather than applying a uniform approach across the entire neck.