Methods Used for Evaluation of Volume Retention Rate in Autologous Fat Grafting for Breast Augmentation: A Systematic Review

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Methods Used for Evaluation of Volume Retention Rate in Autologous Fat Grafting for Breast Augmentation: A Systematic Review

Autologous fat grafting (AFG) has become a prominent technique for breast augmentation due to its natural aesthetic outcomes and reduced risk of complications compared to synthetic implants. Despite its growing popularity, the procedure’s long-term efficacy is often debated due to inconsistent reports of volume retention rates, which range from 10% to 82% across studies. This variability has been attributed to differences in surgical techniques, such as fat harvesting, processing, and injection methods. However, the tools and protocols used to evaluate post-operative volume retention remain underexplored as potential contributors to these discrepancies. This systematic review aims to assess whether the method of breast volume measurement influences reported retention rates, providing insights into the reliability of current evaluation practices.

Background

Breast augmentation remains the most performed aesthetic surgical procedure globally. The shift toward AFG gained momentum after Coleman standardized the technique in the 1990s, emphasizing its safety and adaptability. Unlike implants, AFG uses the patient’s adipose tissue, reducing risks of rejection and enabling nuanced contouring. However, its adoption is hindered by unpredictable graft survival. Volume retention rate, defined as the percentage of injected fat remaining viable after resorption, serves as the primary efficacy metric. Yet, studies report wildly divergent retention rates, with factors like fat processing (centrifugation, sedimentation, stromal vascular fraction [SVF] enrichment), injection planes, and pre-operative expansion (e.g., Brava device) often cited as reasons. Less examined is the role of volumetric assessment tools—MRI, 3D imaging, and water displacement—in these inconsistencies.

Methodology

Search Strategy and Study Selection

A comprehensive search of PubMed, Embase, Cochrane Library, and Web of Science identified 618 articles published up to February 2019. After removing duplicates, 145 studies were screened. Twelve studies (1,337 patients) met inclusion criteria: (1) primary AFG for cosmetic augmentation, (2) clear description of volume measurement methods, and (3) reported retention rates. Excluded studies focused on reconstructive cases, combined procedures (e.g., implant removal), or lacked quantitative outcomes.

Data Extraction and Quality Assessment

Two reviewers independently extracted data, including patient demographics, fat harvesting/processing methods, injection volume, follow-up duration, and measurement tools. The Methodological Index for Non-Randomized Studies (MINORS) assessed study quality, with non-comparative studies scoring an average of 12.5/16 and comparative studies 21.0/24, indicating moderate reliability.

Comparative Analysis

Retention rates were compared across studies using identical fat grafting techniques but differing measurement tools. For instance, studies utilizing centrifugation followed by 3D imaging were evaluated against those using MRI. Similarly, the impact of SVF-enriched fat grafts was analyzed across varying measurement protocols.

Key Findings

Study Characteristics

The 12 studies included diverse techniques:

  • Fat Harvesting: Suction-assisted (SAL), ultrasound-assisted (UAL), and water-jet assisted (WAL) liposuction.
  • Processing: Centrifugation, sedimentation, SVF enrichment (cell-assisted lipotransfer [CAL]), and platelet-rich plasma (PRP) addition.
  • Injection Sites: Subcutaneous, retromammary, and intramuscular planes.
  • Volume Measurement: MRI (7 studies), 3D imaging (4 studies), and water displacement (2 studies).

Retention Rate Variability

Same Technique, Same Measurement Tool

Even with identical grafting and measurement methods, retention rates varied:

  • Centrifugation + 3D Imaging: Rates ranged from 37.6% (Spear et al.) to 65.0% (Lin et al.), highlighting variability potentially due to differing patient anatomy or follow-up durations.
  • CAL + MRI: Rates spanned 46.8% (Jung et al.) to 67.6% (Peltoniemi et al.), suggesting SVF enrichment alone does not guarantee consistency.
  • Sedimentation + MRI: Guo et al. reported 56.6%, whereas Peltoniemi et al. noted 81.6%, possibly due to differences in injection volume (207 mL vs. 204.5 mL).

Same Technique, Different Measurement Tools

Discrepancies were pronounced when tools differed:

  • CAL Grafts: MRI-measured retention averaged 54.2% across three studies, while Chiu et al. reported 68.7% using 3D imaging, suggesting tool-specific biases.
  • Centrifugation + Pre-Expansion (Brava): MRI-based studies by Khouri et al. (82%) and Del Vecchio et al. (64%) showed a 18% difference, possibly due to MRI coil limitations affecting larger breasts.
  • Direct Comparison: Spear et al. found 3D imaging overestimated retention (37.6%) compared to MRI (30.0%), emphasizing tool accuracy disparities.

Measurement Tool Limitations

  • MRI: Limited by fixed coil sizes, leading to compression artifacts in larger breasts. High cost and accessibility issues restrict frequent use.
  • 3D Imaging: Inability to capture deep breast boundaries (e.g., pectoralis muscle) results in incomplete volumetric data. Respiration and posture affect reproducibility.
  • Water Displacement: Though considered the gold standard, practical challenges (patient compliance, measurement errors) limit clinical utility.

Discussion

Sources of Variability

The review identified two critical factors influencing retention rate discrepancies:

  1. Protocol Inconsistencies: Even with the same tool, variations in patient positioning, respiratory state, and breast boundary definitions skewed results. For example, Liu et al. demonstrated respiration changes could alter 3D scans by 2–5%.
  2. Tool-Specific Biases: MRI’s inability to standardize breast boundaries across time points and 3D imaging’s superficial scanning led to systematic errors.

Clinical Implications

  • Standardization Needs: A unified protocol defining breast boundaries (e.g., osseous markers), respiratory states, and menstrual cycle timing (hormonal volume fluctuations) is critical.
  • Tool Selection: 3D imaging suits frequent follow-ups due to non-invasiveness, while MRI remains optimal for accuracy despite cost.

Study Limitations

The review’s findings are constrained by:

  • Predominantly observational studies with small cohorts.
  • Heterogeneous grafting techniques complicating direct comparisons.
  • Limited data on long-term (>2 years) retention rates.

Conclusions

This systematic review underscores the significant impact of measurement tools on reported AFG retention rates. Current methods—MRI, 3D imaging, and water displacement—each have limitations affecting reliability. To reconcile inconsistent outcomes, standardized protocols for breast boundary definitions, patient positioning, and tool calibration must be adopted. Future research should prioritize randomized controlled trials comparing measurement tools under identical grafting conditions, enabling evidence-based guidelines for volumetric assessment.

doi.org/10.1097/CM9.0000000000000415

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