Does Size Matter? Tissue Expander Inflation Rate, Native Breast Dimensions and the Odds of Developing Capsular Contracture
Yunchan Chen BS1, Marcos Lu Wang BA1, Paul A. Asadourian MEng12, Nancy Qin BA1, Grant G. Black BA1, Jaime L. Bernstein MD1, Malini Chinta MD1, David M. Otterburn MD1
1Division of Plastic Surgery, Weill Cornell Medicine, New York, NY2Division of Plastic Surgery, Columbia University Irving Medical Center, New York, NY
Background: Capsular contracture is a common complication after two-stage breast reconstruction. Previous studies have examined whether implant surface characteristics (smooth vs. textured), sub-glandular vs. sub-muscular placement, the presence of post-operative hematoma and a history of radiation can lead to an increased risk of capsular contracture. However, the relationships between native breast size, the rate of tissue expander expansion and capsule formation have not been elucidated. This study aims to evaluate how these factors contribute to capsular contracture formation and establish cut-off values for increased odds.
Methods: A dataset consisting of 209 patients (406 samples) who had undergone two-stage breast reconstruction between 07/20/12 - 09/17/2021 with one plastic surgeon at a tertiary-care facility was used in the study. The starting volume (v_0) is defined as the intra-operative filling volume of the tissue expander at the time of initial placement. The final volume is defined as the final expanded volume (v_f) at the time of the implant surgery. The time elapsed (t) is defined as the period between the final tissue expansion date and initial tissue expander placement surgery in days. The rate of expansion is estimated as (v_f-v_0)x7/t in mL/weeks. The native breast size was estimated using the weight of specimen (grams) and various pre-operative breast measurements. Further stratified analysis evaluated patients separately based on post-operative radiation status, as adjuvant treatment may delay expansion.
Results: Out of the geometric measurement that were examined, greater nipple-inframammary fold (NF) distance (OR 0.90, p-value 0.03) and faster tissue expander enlargement rate (OR 0.998, p-value 0.02) conferred decreased odds of developing capsular contracture. On stratified analysis, faster tissue expansion rate was not a statistically significant negative predictor of contracture formation in the non-radiated cohort (350/406 breasts, 86.2%), but remained a significant negative predictor for those who received post-operative radiation (OR 0.996, p-value 0.03). Cut point analysis showed an expansion rate of <49.6 mL/month (ROC AUC 0.58), a NF value of <10.5cm (ROC 0.56) as conferring greater odds of capsular contracture.
Conclusion: Smaller native breast dimensions and a slower rate of tissue expander enlargement correlate with an increased odds of developing capsular contracture. When evaluating patients at the initial visit and making treatment decisions, breast geometry should be taken into account for risk stratification of the various surgical procedures (implant vs. flap reconstruction). Additionally, longer delays between implant exchange and initial tissue expansion should be avoided if clinically feasible.
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