Tissue expander or implant-based techniques enable breast reconstruction in patients who are unable to undergo autologous breast reconstruction because of anatomical or functional limitations. A primary challenge with this approach is the soft-tissue dynamic around the prosthesis,1 which involves optimal submuscular coverage of the expander/implant, control of lower pole location, and integrity of the inframammary fold.
Acellular dermal matrix is frequently used in implant-based breast reconstruction to cover and support the inferior aspect of the breast pocket.2 – 5 Its interposition reduces musculofascial dissection with less need to elevate the fascia, serratus anterior muscle, or rectus abdominis muscle.
The performance profile of acellular dermal matrix remains equivocal. Professed benefits of its use include improved control of inframammary fold position1 and lower pole projection,6 reduced superior migration of the pectoralis muscle with expansion,4 reduced duration of or need for tissue expansion,2,3,5 greater initial fill volumes,7 and reduced number of subsequent fills to completion.7 More recently, reported complications include infection8,9 and postoperative seroma.8
Aesthetic outcomes and the final outcome of the inframammary fold are not well described, although reports indicate a superior result with acellular dermal matrix reconstruction by maintaining muscle coverage of the upper and middle breast with support of the lower pole.4,5 This study was undertaken to directly compare acellular dermal matrix to non–acellular dermal matrix immediate breast reconstruction and to assess the final aesthetic outcome, with particular attention to the inframammary fold.
PATIENTS AND METHODS
We performed a retrospective review of all patients who underwent implant-based immediate breast reconstruction at our institution from January 1, 2000, through December 31, 2008. Data were collected in accordance with requirements of our institutional review board.
Two groups of patients with implant-based immediate breast reconstruction were evaluated: acellular dermal matrix and non–acellular dermal matrix cohorts. Nonmatrix reconstruction was used from January of 2000 through June of 2004, and acellular dermal matrix reconstruction was used from July of 2004 through 2008. The same surgeons operated on both cohorts, minimizing surgeon-related variables. Patients who underwent delayed reconstruction were excluded from the study. Patients who underwent autologous flap reconstruction in combination with an expander/implant were also excluded to achieve a homogenous study population.
The surgical techniques for both types of breast reconstruction are well described.2 Acellular dermal matrix reconstruction involves elevating the pectoralis major muscle from its inferior and lateral origin, reestablishing the inferolateral aspect by inserting acellular dermal matrix between the pectoralis major muscle and the inframammary fold, and placing the prosthetic device (expander or implant) within this pocket. This technique allows muscle coverage of the upper and middle breast with support of the lower pole. The acellular dermal matrix used in our series was AlloDerm (LifeCell Corp., Branchburg, N.J.). Nonmatrix reconstruction involves total muscular coverage or partial muscle coverage with creation of a breast pocket deep to the pectoralis major and serratus anterior muscles with use of external bolsters to cover the inferolateral aspect of the breast and placement of the prosthetic within this pocket.
One or two closed-suction drains were used for each breast reconstruction. When two drains were used, typically for larger breast reconstructions, the first was placed along the inframammary fold and the second was placed toward the axilla. Drains were removed when output over a 24-hour period was less than 30 ml, which usually occurred on postoperative days 10 to 14. The drain and expansion protocol was the same for both cohorts.
Direct comparisons were made between acellular dermal matrix and nonmatrix groups to evaluate functional and cosmetic outcomes. Patient-related variables, such as body mass index, medical comorbidities, smoking status, and the indication for reconstruction, were identified. Surgical complications such as wound infection, seroma/hematoma, dehiscence, and skin problems were evaluated. Hematoma was defined as greater than expected bruising and firmness of the breast postoperatively or if surgical exploration showed significant blood around the implant. Infection was defined as abnormal erythema, tenderness, fever, and swelling. Skin thinning included visible attenuation of the skin envelope.
Complications were identified independently by the attending surgeon at follow-up visits and included problems of the inframammary fold, bottoming-out, rippling, shifting of the implant, and capsular contracture. Capsular contracture was evaluated using standard definitions from the Baker classification system modified for prosthetic breast reconstruction, with grade 1 defined as free of contracture, grade 2 as minimal contracture with mild firmness of the reconstructed breast, grade 3 as a moderately firm reconstructed breast with a readily detectable implant, and grade 4 as severe contracture with symptoms. Rippling was the presence of wrinkling of the skin and abnormal contour irregularity. Mechanical shift was implant displacement away from initial placement resulting in lateral projection. Bottoming-out was downward displacement of the implant causing asymmetry with increased nipple-to–inframammary fold distance. The integrity of the inframammary fold was defined as the overall quality of the length, curvature, and contour of the fold, with the ideal fold at or above the sixth rib10 and appropriate height, centering the axis of the implant at the level of the nipple-areola complex. The term “problems of the inframammary fold” was defined as a separate category to represent inframammary fold issues not specified by other complications such as bottoming-out or shifting but related to the integrity of the fold. This included characteristics of symmetry, contour, and curvature.
Two cosmetic outcomes were evaluated: aesthetics of the overall reconstruction and the final outcome of the inframammary fold. Professional patient photographs with frontal and oblique views were used to quantify cosmetic outcomes. The photographs were obtained at the completion of second-stage/final reconstruction. Aesthetic outcomes of the overall reconstruction were graded on a four-point scale and based on an established scoring system.11 An excellent result was scored as 4, a good result as 3, a fair result as 2, and a poor result as 1. Aesthetic outcome of the inframammary fold was also rated on these established categories.12 – 14 The fold was rated excellent if it was well-defined and symmetrical (score of 4), good if it was well-defined and asymmetrical (score of 3), and fair or poor if it was ill-defined (score of 2 or 1). A panel of four blinded individuals including a male surgeon, a female secretary, and two female medical students reviewed the photographs and assigned a composite score for the overall aesthetic appearance of the reconstruction and the outcome of the inframammary fold. Representative photographs are shown in Figure 1. Follow-up after reconstruction was 100 percent in our patient population, extending through second-stage reconstruction.
Statistical comparisons were performed using unadjusted and multivariate logistic regression. Pearson chi-square and Fisher's exact tests were used for all unadjusted pairwise categorical data comparisons. The t test and analysis of variance were used for continuous pairwise and multigroup comparisons. Continuous variables were described as mean ± SD. Multivariate logistic regression adjusted for clinical characteristics (i.e., body mass index, smoking, indication for reconstruction) and postoperative complications (i.e., infection, seroma, inframammary fold problems, capsular contracture, mechanical shift, bottoming-out, rippling, and wound problems) using a backward-stepwise regression. The Hosmer-Lemeshow goodness-of-fit statistic was 88 percent in our model. A value of p < 0.05 was considered statistically significant for all unadjusted comparisons. Adjusted odds ratios and 95 percent confidence intervals were reported for the multivariate results. Statistic analyses were performed using SPSS (SPSS, Inc., Chicago, Ill.).
During the study period, a total of 203 patients underwent 337 immediate expander-based breast reconstructions [acellular dermal matrix group, n = 208 (61.7 percent); nonmatrix group, n = 129 (38.3 percent)]. The majority of non–acellular dermal matrix reconstructions used partial muscle coverage (n = 119). There were no differences between partial and total muscle coverage subgroups.
Patient characteristics are listed in Table 1 and were similar between groups, and included age, body mass index, and smoking status. The primary indication for reconstruction was mastectomy for cancer [n = 182 (90 percent)]. Other indications for reconstruction were mastectomy for BRCA gene mutation–positive status, silicone mastitis, and congenital breast asymmetry.
The majority of patients had no significant comorbidities [n = 141 (70 percent)]. The incidences of hypertension [n = 20 (10 percent)], diabetes [n = 2 (1 percent)], cardiovascular problems such as arrhythmia or valvular disease [n = 4 (2 percent)], and coagulopathy such as history of pulmonary embolism/deep venous thrombosis or von Willebrand disease [n = 4 (2 percent)] were similar between groups (p > 0.05). Initial fill volumes were similar between both groups (acellular dermal matrix, 150 ± 76 ml; nonmatrix, 100 ± 69 ml; p > 0.05). The median time to second-stage reconstruction was also similar between groups [acellular dermal matrix, 171 days (range, 34 to 855 days); nonmatrix, 164 days (range, 45 to 513 days); p > 0.05]. The mean follow-up after implant exchange was 29 months.
Complications are listed in Table 2. Overall, complications occurred in one-third of patients (33.5 percent) and were less with acellular dermal matrix reconstruction (odds ratio, 0.61; 95 percent confidence interval, 0.38 to 0.97). Capsular contracture, problems with the inframammary fold, bottoming-out, rippling, and mechanical shift of the implant were all less with acellular dermal matrix compared with nonmatrix reconstruction. The overall revision rate was 30.9 percent and was similar between groups (p = 0.168). The incidences of seroma/hematoma (p = 0.59), infection (p = 0.31), overall wound problems (p = 0.26), wound dehiscence (p = 0.26), and skin thinning (p = 0.149) were also similar between groups.
Noteworthy results from multivariate logistic regression are listed in Table 3. After adjusting for clinical characteristics and postoperative complications, acellular dermal matrix use was associated with less capsular contracture (odds ratio, 0.18; 95 percent confidence interval, 0.08 to 0.43) and mechanical shift (odds ratio, 0.23; 95 percent confidence interval, 0.06 to 0.78). In addition, there was an overall trend for less problems of the inframammary fold (odds ratio, 0.49; 95 percent confidence interval, 0.23 to 1.01). The confidence interval of this category extended across 1.0 with a value of p = 0.055. Other demographic and clinical variables were not significant.
Table 4 shows ratings of final aesthetic outcomes for acellular dermal matrix and nonmatrix reconstructions. Overall aesthetic outcome of immediate expander-based breast reconstruction was higher in the acellular dermal matrix group (3.26 ± 0.71; nonmatrix, 2.87 ± 0.63; p < 0.05). Aesthetic outcome of the inframammary fold was also higher in acellular dermal matrix breast reconstruction (3.35 ± 0.69; nonmatrix, 2.94 ± 0.65; p < 0.05).
Many alternative techniques exist for immediate breast reconstruction, and the choice depends on patient and physician variables. In available case series of immediate breast reconstruction with acellular dermal matrix (Table 5), the reported frequency of complications ranges from 4 to 46 percent1,3 – 7 – 9,15 – 19 and appears similar to the incidence of complications with other types of immediate breast reconstruction.20
In this study, 33.5 percent of all patients had a postoperative complication, with fewer complications in acellular dermal matrix breast reconstruction compared with nonmatrix reconstruction (29.3 percent versus 40.3 percent, p < 0.05). Univariate analyses showed less capsular contracture, problems with the inframammary fold, bottoming-out, rippling, or mechanical shift of the implant in the acellular dermal matrix group. Regression analysis showed that use of acellular dermal matrix was associated with less capsular contracture and mechanical shift. Although not significant, there was a trend toward fewer problems with the inframammary fold (p = 0.055). Infectious and wound complications and seroma/hematoma did not differ between groups. The final overall aesthetic outcome of the reconstructed breast and the inframammary fold were higher with acellular dermal matrix–based reconstruction.
Although this study provides the largest experience of immediate breast reconstruction with acellular dermal matrix in direct comparison to nonmatrix reconstruction, there are limitations to our study. The study is retrospective. Four primary surgeons performed reconstructions, and surgeon-related variables may have contributed to the incidence of postoperative complications. Aesthetic outcome was scored on an established rating system by a mixed panel but is subjective. The expectations of trained surgeons may focus heavily on the final outcome of the inframammary fold position and contour and may differ from patient satisfaction. Patient satisfaction ratings were not used in our aesthetic data, and these ratings may provide a more accurate aesthetic assessment of the final reconstructed breast.21 Our study population was homogenous, with relatively low body mass index and nonsmokers, and the impact of both of these variables may be underestimated.
The risks associated with acellular dermal matrix are equivocal. Its use has been associated with increased postoperative infection8,9 and seroma formation.8,15 This was not shown in our current study, which analyzed a homogenous patient population with immediate breast reconstruction at a single institution excluding flaps and patients who underwent serratus anterior or rectus abdominis musculofascial dissection. Other series have found no increase in infection or seroma with acellular dermal matrix–based reconstruction.3,6,18,19
Hypotheses for increased infection include greater native breast skin flap necrosis with acellular dermal matrix–based reconstruction,8 greater seroma formation with acellular dermal matrix leading to secondary infection,8 and use of an additional foreign material (porous scaffold) in conjunction with a prosthetic device. Increased seroma formation may be attributable to institution-specific drain protocols or increased dead space with acellular dermal matrix–based reconstruction. At our institution, drains (typically n = 2) are placed between the mastectomy skin flaps and the AlloDerm/muscle interface. One surgeon also places a drain submuscularly adjacent to the tissue expander. There are no differences in outcomes in our patient population based on drain protocol, and the same drain protocol was used for both cohorts. Drains were left in place until output was less than 30 ml over 24 hours, which typically occurred at 2 weeks after reconstruction.
Higher body mass index and larger mastectomy breast size (>600 g) have also been independently reported to increase seroma formation and infection after acellular dermal matrix–based reconstruction.8,9 Higher body mass index is an established risk factor for complications after breast reconstruction.22 Body mass index, age, and axillary dissection have been reported as independent risk factors of complications associated with acellular dermal matrix–based reconstruction15; however, these variables were not significant after logistic regression analysis in our study. Our patient population had a more homogenous body mass index, and subgroup analysis for higher body mass index was not possible because of small sample size. The interplay of body mass index with dead space, breast size, and drain protocol may have contributed to the infections associated with acellular dermal matrix–based reconstruction; however, prospective studies would be needed to answer these questions.
On multivariate analysis, capsular contracture and mechanical shift of the implant were less likely with acellular dermal matrix–based reconstruction. Aesthetic scoring revealed significant improvement in the inframammary fold in acellular dermal matrix reconstruction compared with nonmatrix reconstruction. Less capsular contracture3,6 has been reported by earlier case series but not with other direct comparison studies of acellular dermal matrix to nonmatrix reconstruction. The mechanism by which acellular dermal matrix use improves the outcome of the inframammary fold is not known but may be related to the distribution of tension across the muscle interface to allow improved control of inframammary fold positioning.1
Our study is the first to quantify the aesthetic outcome of immediate breast reconstruction directly comparing acellular dermal matrix and nonmatrix cohorts. The overall aesthetic outcome of the reconstruction and final outcome of the inframammary fold are likely secondary to reduction in problems affecting the fold, such as mechanical shift and capsular contracture. Reduction in these complications may enable improved second-stage implant exchange with reduced capsulotomy/capsulectomy and subsequent adjustments of the inframammary fold that may impact the final appearance of the reconstructed breast.
This is the largest direct comparison of acellular dermal matrix in implant-based immediate breast reconstruction without the use of autologous flaps. Optimizing the inframammary fold with acellular dermal matrix creates a superior aesthetic result. Its use appears safe and is associated with less capsular contracture and mechanical shift, and an improved appearance of the inframammary fold without increase in postoperative complications. We continue to endorse the usefulness of acellular dermal matrix in immediate implant-based breast reconstruction.
Presented at the 79th Annual Meeting of the American Society of Plastic Surgeons, in Toronto, Ontario, Canada, October 1 through 5, 2010.
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