Predicting Changes in Breast Dimensions and Volume Post Primary Breast Augmentation

Goals/Purpose:

This study aimed to evaluate the changes that occur to breast dimensions pre and post aesthetic primary augmentation using silicone implants and to determine whether post augmentation dimensions could be predicted based on the implant used. It also aimed to establish whether the change in breast volume during augmentation as calculated by the anthropometric formula could be correlated to the volume of the implant used.

Methods/Technique:

Consecutive patients undergoing primary breast augmentation using textured round silicone implants (Inspira™, Allergan) were prospectively enrolled into the study. For each patient, 10 anthropometric measurements were taken in the supine position at three time points: preoperatively, immediately after surgery and 7 days post augmentation. The 10 measurements included:

• RIGHT sternal notch to nipple
• LEFT sternal notch to nipple
• Inter nipple distance
• RIGHT nipple to inframammary fold (RIGHT IR)
• LEFT nipple to inframammary fold (LEFT IR)
• RIGHT medial mammary radius (RIGHT MR)
• LEFT medial mammary radius (LEFT MR)
• RIGHT lateral mammary radius (RIGHT LR)
• LEFT lateral mammary radius (LEFT LR)
• Mammary projection (MP)

The implant size and dimensions were recorded.

The corresponding anthropometric measurements were compared statistically using a paired t-test at the three time points. In addition, the implant dimensions were used to estimate the expected post augmentation anthropometric measurements; these were then correlated to the observed post augmentation measurements using regression analysis.

Finally the breast dimensions were used to calculate the breast volume pre and post augmentation using a validated previously published anthropometric technique where the breast volume = ∏/3 + MP² x (MR + LR + IR - MP). The resulting calculated difference between the pre and post volumes was correlated to the volume of the implant placed.

Results/Complications:

Complete data was available on all 50 patients.

No statistical difference was identified between any of the anthropometric measurements taken post operatively and at day 7.

Seven of the 10 anthropometric measurements changed significantly (p<0.05) between pre & post implant insertion:

• both medial mammary radii
• both lateral mammary radii
• both nipple to IMF distances
• mammary projection.

Correlating the post implant measurements with the expected measurements showed the following consistent findings:

• the observed medial mammary radius was 1.6x the calculated expected medial mammary radius (r² = 0.55)
• the observed lateral mammary radius was 2.1x the calculated expected radius (r² = 0.55)
• the observed nipple-IMF radius was 1.6x the calculated expected nipple-IMF radius (r² = 0.63)
• the observed mammary projection was 0.8x the calculated expected projection (r² = 0.97)

Finally the calculated difference in breast volume between pre and post implant insertion overestimated the implant volume by 1.5x consistently (r² = 0.97).

Conclusion:

This study helps to highlight the key anthropometric measurements that change significantly during primary augmentation. It also suggests that no statistically significant changes occur to the breast dimensions in the time period immediately after surgery up to 7 days post augmentation. In addition this study also shows that post augmentation breast dimensions can be estimated based on the implant selected thus aiding in the initial patient consultation process. This may be particularly beneficial when modern three dimensional imaging systems are unavailable. Finally, a consistent relationship was found between the implant size used and the breast volume change calculated using the anthropometric formula, supporting its use in this scenario.