Diluted and Hyperdiluted Calcium Hydroxylapatite/Carboxymethylcellulose as a Technique Platform: A Narrative Review with Practical Taxonomy, Injection Mapping, and Safety.

backgroundCalcium hydroxylapatite in a carboxymethylcellulose carrier (CaHA/CMC; Radiesse®) has evolved from a primarily volumizing implant to a biostimulatory platform increasingly used in diluted and hyperdiluted forms for skin tightening and quality improvement across facial and extra-facial sites.

methodsThis narrative review provides an author-curated synthesis of clinically relevant experimental studies, clinical investigations, and consensus statements addressing diluted and hyperdiluted CaHA/CMC. Targeted searches of PubMed/MEDLINE and Google Scholar (January 2016-December 2025; English language) were performed, supplemented by reference-list and citation-trail screening. Evidence was synthesized qualitatively because substantial heterogeneity existed among treatment applications, preparation protocols, injection techniques, and outcome measures.

resultsThe review organizes heterogeneous protocols into a descriptive preparation taxonomy linked to handling characteristics and clinical intent (Table 1), an anatomy-based injection map specifying plane, device, dispersion geometry, and reported dilution tiers (Table 2), and a summary of combination-treatment paradigms highlighting sequencing and preparation variables (Table 3). Safety considerations are summarized using a technique-focused prevention and a triage-oriented management framework.

conclusionsDiluted and hyperdiluted CaHA/CMC represent a tunable approach for balancing structural support and wide-field biostimulation. The proposed taxonomy and injection mapping provide a descriptive framework for organizing current evidence and clinical practices. However, because available evidence remains heterogeneous and predominantly consists of prospective pilots, retrospective cohorts, case series, and consensus recommendations, these frameworks should be interpreted as descriptive tools rather than validated treatment algorithms. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .