Predicting vertical length of ADM required in direct-to-implant breast reconstruction with fenestrated ADM sling

Hyung Chul Lee, Jin Sup Eom
Department of Plastic Surgery, Asan University, Seoul, Republic of Korea

In breast reconstruction using implants, acellular dermal matrix (ADM) is increasingly used for several advantages. There are reports that fenestrated ADM has better cosmetic results, can reduce capsular contracture and can reduce rate of seroma formation. When the added length and area of elevated pectoralis muscle and fenestrated ADM are almost equal to the breast skin flap after mastectomy, the lower pole expansion can be sufficient and the cosmetic outcome can be better. After implant insertion, fenestrated ADM was sutured and the vertical length was measured at several points, and the relationship between the longest vertical length and the profile of the implant was examined. We derived an equation that predicts the length of the ADM required when the implant was selected.

From May 2016 to April 2017, 50 patients had direct-to-implant breast reconstruction by single surgeon. Mastectomy weight, horizontal and vertical length of ADM, vertical length after fenestration, profile of the implant was recorded. After elevation of the pectoralis major muscle, implant was inserted and fenestrated ADM was sutured with pectoralis major muscle’s lower margin, inframammary fold and lateral border. The vertical length of fenestrated ADM was measured at 5 points; 2cm from most medial side, between medial side and nipple, nipple, between lateral side and nipple, 2cm from most lateral side. Among them, longest length was compared with the profile of implant to find the factors with high correlation. The linear regression analysis was used to derive the coefficients.

The mean vertical length of the ADM before fenestration was 6.36 (±1.03) cm, and the mean vertical length after fenestration was 11.22 (±1.98) cm, which was an average 76.3% increase. Average mastectomy weight was 345g and average implant size was 290cc. The mean length of the longest vertical length of fenestrated ADM was 9.41 (±1.54) cm. Pearson correlation coefficient of the longest vertical length with implant height was 0.846 (p<0.001) and with implant projection was 0.833 (p<0.001). When the linear regression analysis was carried out, the R squared value was 0.764 and the F value was 72.926, which was significant (p<0.001). The regression equation was derived as (the longest vertical length = implant height * 0.494 + projection * 0.876 + 0.259). The simplified formula would be (the longest vertical length = height * 0.5 + projection). And this value multiplied by 0.567 would be the vertical length of the ADM needed before fenestration.

If extent of the increase in length after fenestration can be expected and the longest vertical length can be predicted when implant is selected, adequate ADM can be determined. It can prevent the constricted shape after suturing relatively small ADM to inframammary fold, and it can also minimize cutting off expensive ADM.