Calcium hydroxylapatite for décolleté rejuvenation: a prospective study of structural and aesthetic outcomes

Background Chronic ultraviolet exposure makes the décolleté particularly susceptible to thinning, wrinkling, dyspigmentation, and textural deterioration. Prospective data linking calcium hydroxylapatite (CaHA) treatment to serial structural change remain limited. Methods This prospective, single-center, single-arm, uncontrolled décolleté-specific analysis included 22 women treated once with Rennova® Diamond Intense and followed for 120 days. Twenty-megahertz DermaLab skin thickness was measured at baseline and Days 30, 90, and 120; a separate radiologist-performed 22 MHz high-frequency ultrasound (HFUS) dermal-thickness assessment was obtained at baseline and Day 120. Validated Landau photonumeric grades were assessed from standardized photographs at baseline and Day 120, with décolleté-specific S-GAIS and two P-GAIS ratings at Day 120. Results Mean age was 53.3 ± 12.6 years. DermaLab thickness increased from 1.249 ± 0.247 mm at baseline to 1.395 ± 0.232 mm at Day 120; the mean paired increase was 0.146 mm (bootstrap 95% CI, 0.099–0.197), corresponding to a mean within-participant increase of 13.0% (95% CI, 8.5–17.8; Holm-adjusted p < 0.001; rank-biserial r = 1.00). Twenty-one of 22 participants increased. HFUS thickness increased from 1.291 ± 0.218 to 1.573 ± 0.304 mm; the mean paired increase was 0.282 mm (BCa bootstrap 95% CI, 0.214–0.395), with a mean within-participant increase of 22.6% (95% CI, 16.8–35.4; p < 0.001; rank-biserial r = 0.964). Participant-level change scores were weakly correlated (Spearman ρ = 0.232, p = 0.299), supporting group-level directional agreement rather than interchangeability. Clinical severity decreased across all three validated domains; 21/22 participants improved on the validated 0–12 summary score. At Day 120, S-GAIS improvement was 100% (95% CI, 84.6–100), while P-GAIS improvement was 45.5% and 72.7% for the two evaluators. Expected local post-injection reactions were predominantly mild and transient; no décolleté nodularity was recorded. Conclusions In this exploratory, single-arm, uncontrolled study, a single hyperdiluted CaHA treatment was followed by sustained group-level increases in décolleté thickness and improvement in validated clinical grading over 120 days. The two ultrasound approaches provided complementary rather than interchangeable structural information, and the observed thickening cannot be attributed to neocollagenesis or another specific biological mechanism. Controlled studies with longer follow-up and standardized blinded assessments are warranted.