Stevens, W. Grant M.D.; Nahabedian, Maurice Y. M.D.; Calobrace, M. Bradley M.D.; Harrington, Jennifer L. M.D.; Capizzi, Peter J. M.D.; Cohen, Robert M.D.; d’Incelli, Rosalyn C. B.A.; Beckstrand, Maggi M.P.H.
Described as “the surgeon’s most immediate concern” by McGrath and Burkhardt in 1984, capsular contracture following breast augmentation remains one of the most studied and prevalent reasons for reoperative breast surgery.1 It has been reported to be the most common reason for reoperation in recently published multisite clinical studies of both smooth and textured breast implants.2,3 Although there are several generally agreed on contributory factors, a specific cause has not been established. Research has suggested that biofilms, infection, hematoma, and irradiation may be possible causes of capsular contracture.4–6
Submuscular placement has also been linked to a lower incidence of capsular contracture.7–10 The surface characteristics of the implants (smooth versus textured) have received attention and are believed to play a role in the development of capsular contracture. Studies have demonstrated that surface texturing has the potential to disrupt capsule formation, leading to a possible reduction in the incidence of capsular contracture.11–13
In the United States, there are currently three different textured surface implants available, each with distinctive methods of texturing, including Biocell “loss-salt” (Allergan, Inc., Irvine, Calif.)14 and Siltex “imprint” stamping (Mentor Corp., Santa Barbara, Calif.).14 The third, Silimed TRUE Texture (Sientra, Inc., Santa Barbara, Calif.), uses a method that avoids the use of sodium chloride, sugar, soak/scrub, or pressure stamping (Fig. 1).
The purpose of this study was to investigate a variety of implant and patient characteristics in addition to surgical techniques and postoperative protocols to identify risk factors that may contribute to the occurrence of capsular contracture following primary breast augmentation. Sientra has enrolled the largest definitive single-study population to date, which provides the opportunity to perform the first capsular contracture analysis specific to round, smooth, and textured implants.
PATIENTS AND METHODS
Analysis was based on 5-year results from Sientra’s U.S. Food and Drug Administration–approved, large, prospective, open-label, U.S.-based clinical study of silicone breast implants to assess safety and effectiveness. Patients were enrolled based on defined inclusion and exclusion criteria,15 and informed consent was obtained for all patients by the various surgeons under the institutional review board–approved protocol. The data used for this analysis include 5109 implants in 2560 primary augmentation patients implanted by 34 plastic surgeons (median, 138.5 implants). To provide a focused analysis, patients that received shaped implants or who had transaxillary or mastopexy incisions were not included.
All patients were monitored by their surgeons at 1-year intervals or more often, as needed. The occurrence of capsular contracture was documented on study case report forms using the Baker Classification Scale. An explanation of the Baker Classification Scale was included in the study protocol to ensure consistent data collection across surgeons. Those patients that developed Baker grade III and IV capsular contractures were included. Resolutions to reported complications were collected on follow-up case report forms.
Potential patient- and device-related risk factors were collected on the study case report forms (Table 1). These risk factors included patient age at implantation, body mass index, type of implant surface (textured or smooth), and device size (in cubic centimeters). The potential surgery-related risk factors included method of anesthesia (general or local), incision site (periareolar or inframammary), surgical facility (surgeon’s office or hospital/surgical center), and implant pocket placement (submuscular or subglandular). Submuscular placement included the various dual-plane techniques and subglandular included subfascial placements.16 The various irrigation practices that included antibiotic, povidone-iodine, or steroid solutions used alone or in combination were also evaluated as potential risk factors. Postoperative factors included for analysis were hematoma or seroma formation before capsular contracture onset and the recommendation of a surgical bra and/or massage protocols.
The potential risk factors (Table 1) were analyzed for a possible association with capsular contracture. Most factors were collected as binomial variables (present/not present). Continuous factors (i.e., device size, patient age, and body mass index) were categorized into two groups for analysis based on their medians. All factors (e.g., smooth device, surgical bra) were used by at least five surgeons. The data were described using frequency and multivariate models. Multivariate generalized estimating equations were used, with the device as the unit of analysis, and included a covariate for implantation time; the potential correlation arising from bilaterally implanted patients was adjusted for in the analysis using PROC GENMOD in SAS (SAS Institute, Inc., Cary, N.C.). Initially, each factor was modeled individually to evaluate its association with capsular contracture without adjusting for effects of other variables. Because individual models (exclusion of significant factors) can yield inaccurate estimates and models with too many factors can yield imprecise estimates and possibly require complex interpretation, a backwards elimination process for factor selection was used. This process involved including all factors with a value of p < 0.20 from the individual models and then eliminating factors one by one based on their p values. The elimination process continued until only variables with a value of p < 0.05 were present for the final multivariate model. Model fit was assessed using quasi-likelihood under the independence model criterion,17 where a lower quasi-likelihood under the independence model criterion score indicated better model fit.
Kaplan-Meier survival analysis was used to describe the risk associated with the two strongest factors determined from the multivariate analysis. The risk of capsular contracture was calculated within each subgroup of devices and presented with 95 percent confidence intervals.
The median patient age at the time of enrollment was 36 years (range, 18 to 66 years), with the majority of patients being Caucasian, married, and having an annual household income that exceeded $60,000. The median body mass index was 20.8 kg/m2 (range, 14.4 to 40.2 kg/m2). The majority of study patients had completed some college education, with 48 percent holding at least a bachelor’s degree and 10 percent having completed postgraduate level education.
All implants included in this analysis (Table 2) were round, with a median size of 355 cc (range, 135 to 700 cc). A slight majority of the implants had a smooth shell (62 percent; median, 360 cc) versus textured (38 percent; median, 355 cc). The incision site was inframammary in 71 percent and periareolar in 29 percent. Device location was submuscular in 56 percent and subglandular in 44 percent.
A total of 265 capsular contracture events in 179 patients were reported (86 bilateral and 93 unilateral) through 5 years. Baker grade III capsular contractures were more common than Baker grade IV contractures (86 percent and 14 percent, respectively). Almost half of the capsular contractures (47 percent) occurred within the first 2 years of implantation, and 83 percent occurred within the first 4 years. Among those with resolution follow-up, 72 percent were resolved with treatment, 21 percent resolved without treatment, and 7 percent refused treatment. Nearly all (92 percent) of the treatment resolutions involved a reoperation, with the type of procedure recorded as an open capsulotomy, capsulectomy, implant exchange, and/or implant removal without replacement. Other treatments included closed capsulotomy, massage, and leukotriene modifiers.
Unadjusted Risk Factor Results
To identify the individual risk factors for capsular contracture, unadjusted risk factor results are reported (Table 3). Seven factors were found to be associated with increased odds for capsular contracture development, without adjusting for the effects of the other factors. For example, smooth implants were 2.3 times more likely to be associated with capsular contracture when compared with textured implants. Implants placed with periareolar incisions had a 6.9 percent incidence of capsular contracture compared with 4.5 percent for those placed with inframammary incisions. Implants placed in the subglandular position had an 8.2 percent incidence of capsular contracture as opposed to 2.8 percent for those placed in the submuscular position. Pocket irrigation (antibiotic and steroid), postsurgical bra, and massage recommendations were also found to be associated with increased odds for capsular contracture development. These unadjusted odds ratios were statistically significant at the α = 0.05 level. The remaining factors, such as patient age and body mass index, were not significant predictors of capsular contracture (p = 0.53 and p = 0.65, respectively).
Multivariate Analysis Results
Of the nine individual factors that met inclusion criteria for the multivariate model (p < 0.20), only six were found to have enough statistical influence to be included in the final model. Assessment of fit showed that quasi-likelihood under the independence model criterion decreased, indicating improved model fit from the full model with all factors to the final model.
Results of the multivariate analysis showed that device placement (submuscular/subglandular), device surface (smooth/textured), incision site (inframammary/periareolar), hematoma/seroma development, device size, and surgical bra were risk factors for capsular contracture (Table 4). After adjusting for the other variables in the model, the odds of developing capsular contracture was 4.7 greater in smooth implants (p < 0.0001) and 4.6 times greater in implants placed in the subglandular position (p < 0.0001). Statistically significant findings were also reported for device size, incision site, hematoma/seroma, and surgical bra. All multivariate findings were statistically significant at the α = 0.05 level.
Although device size (p = 0.117) and development of hematoma or seroma (p = 0.053) were not significant risk factors for capsular contracture in the unadjusted analysis (Table 3), they were found to be significant after controlling for the other factors in the multivariate model (Table 4). In contrast, massage and antibiotic (although significant in the unadjusted analysis p < 0.0001) were no longer significant after controlling for the other factors in the multivariate model. Of note, massage was recommended more often with smooth devices than with textured devices (67 percent of smooth versus only 34 percent of textured devices with a massage recommendation).
Based on the multivariate analysis, the two strongest contributing factors in determining the development of capsular contracture were smooth surface and subglandular placement. Overall, the Kaplan-Meier rate for capsular contracture was 7.6 percent (95 percent confidence interval, 6.76 to 8.63 percent). Within the overall 7.6 percent, four Kaplan-Meier subset analyses were created. The subset analyses of smooth surface and subglandular placement are described in Table 5. Of the 7.6 percent overall rate of occurrence, implants with a textured surface had the lowest rates of capsular contracture, regardless of submuscular or subglandular placement (2.1 percent and 4.9 percent, respectively).
Analysis of the distribution of factors by surgeon revealed that many used individualized “common practices.” For example, 21 surgeons used smooth implants in over 95 percent of their implantations. Thirteen of the 21 commonly used smooth with submuscular placement in over 85 percent of their implantations. Eight surgeons used textured implants in over 95 percent of their implantations. Only three surgeons used all four combinations of implant surface (smooth/texture) and placement (subglandular/submuscular). The use of a surgical bra was very consistent within each surgeon’s data. For example, 23 surgeons recommended use of a surgical bra in over 85 percent of their implantations, with 17 of those recommending the surgical bra to all of their study patients.
The authors further analyzed the surgeon-specific incidence of capsular contracture as it related to surgical and postoperative practices, within higher volume sites (>100 devices implanted). This analysis revealed that there were clear differences in device/surgical practices between surgeons with a high versus a low incidence of capsular contracture. Three surgeons accounted for 51.3 percent of the reported capsular contractures but enrolled only 16.5 percent of the devices (Fig. 2). These surgeons all used only smooth implants (100 percent), and surgical or sports bra after implantation was recommended for 96 percent of their implants. When the three surgeons with higher contracture incidences were excluded from the multivariate model, the analysis continued to show smooth, subglandular, and hematoma/seroma as significant predictors of capsular contracture. Surgical bra also continued to be significant but at a lower level (OR, 3.7 versus 2.8).
As a related analysis, eight surgeons with low capsular contracture rates (<2 percent each) were evaluated for their surgical and postoperative practices. This group recommended the surgical bra and used smooth implants less often (Fig. 2). Similarly, all other protective factors from the multivariate analysis were more common among the surgeons with low capsular contracture rates, except for device size.
Device Size Analysis
In an effort to gain further understanding of the point at which the device size appears to impact the development of capsular contracture, a subanalysis was run to further break out the device size ranges into smaller groups. As shown in Table 6, as the device size increases, the odds of developing capsular contracture decrease. The incidence of capsular contracture among the smaller devices was 6.8 percent compared with 3.9 percent in the devices larger than 420 cc.
Although the cause of capsular contracture continues to be examined, the results from this analysis of a large prospective clinical study indicate that implant placement (submuscular/subglandular), implant surface (smooth/textured), incision site, hematoma/seroma development, device size, and surgical bra appear to play an important role. Much of the literature regarding the associations between these characteristics and capsular contracture has been based on univariate analyses; therefore, the multivariate regression analysis presented in this research provides a sophisticated and statistically powerful addition to the literature.
In this study, textured implants were found to be associated with a significantly lower incidence of capsular contracture. Previous reports using a meta-analysis methodology have also demonstrated a protective effect of textured implants in gel and saline implants18,19 and smaller gel-only sample sizes.20–22 One meta-analysis with only primary subglandular breast augmentation patients found that textured surface devices resulted in a significant reduction in capsular contracture.19 These findings are consistent with results from this study, clearly indicating a reduction in the incidence of capsular contracture using textured implants regardless of the placement, albeit with a lesser benefit when placed in the submuscular position.
Similar to the findings of this study, other reports have described the protective effect of submuscular placement with regard to the development of capsular contracture8–10,23 and infra mammary incision sites.9,24,25 Regarding device size, Henriksen et al. found that implants with volumes greater than 350 cc significantly increased the risks of complications requiring secondary surgical procedures. However, when the relationship between size and grade III to IV capsular contracture was specifically analyzed, the relationship was no longer statistically significant. This study found a protective effect with larger implants. The reasons for this are speculative, and one possible cause is that increased weight and volume of the device result in increased motion within the periprosthetic space and thereby result in a less aggressive capsule. Another hypothesis regarding the protective effect of larger implants is that these implants may typically be placed in patients with a higher body mass index and a better vascularized skin envelope. These patients with larger implants may have a healthier pocket and more soft-tissue coverage and thus a reduced capsular contracture rate.
Although the results of this study provide evidence that certain surgical practices may lead to less capsular contracture, it is recognized that the occurrence of capsular contracture is multifactorial and that the decreased risk associated with a particular risk factor must be balanced with other potential risk factors. For example, subglandular placement may result in a higher incidence of capsular contracture but less postoperative pain and discomfort26 and less unwanted implant movement with pectoralis contraction.27 Submuscular placement may reduce the risk of capsular contracture but may increase the risk of developing a hematoma.9,16 Inframammary incisions have been demonstrated to result in less capsular contracture but may not be advised when preoperative breast volume is less than 200 g, when the breast shape is tubular or ptotic (grades I to II), or when the inframammary crease is nonexistent or high.26
Interestingly, the results of this study have demonstrated that there is an increased risk of capsular contracture associated with the use of a postoperative surgical bra; however, the reasons for this are not clear. Because study data indicated that surgical bra use is generally a practice-wide decision (not specific to device type/size or body shape), it is plausible that the use of a surgical bra is correlated with another postoperative recommendation/treatment, surgical technique, or other unknown surgeon-specific variable.
Interpretation of results should be considered with care because of some study design and analysis restrictions. The prospective cohort study design was nonrandomized and some previously hypothesized factors were not included in the analysis; examples include genetic disposition, nipple shields, and blood loss.6,8,28,29 These factors were not included because they were unmeasured. In addition, to provide an overall risk profile, the analysis did not include separate models for early and late contractures. Constructing a late-contracture risk profile would depend on devices remaining contracture-free during the early period, thereby requiring a complicated interpretation of the results and complex implications for clinical practice recommendations.
It should be noted that the two postoperative recommendation factors (surgical bra and massage) are limited and that avoidance of these measures at this time is premature. These findings were based on surgeon recommendation and not on patient compliance. Furthermore, definitions for surgical bra and massage are subjective and may include sports bras and various massage techniques. Another study demonstrated findings contrary to the present study and found that daily “compression” for 3 months after implantation reduced the incidence of capsular contracture.30 The use of a postsurgical support or massage requires further investigation before any final recommendations can be made.
This large-scale study analysis through 5 years has identified several important factors that affect the development of capsular contracture following primary breast augmentation. These include the nature of the implant surface (smooth or textured), implant placement (subglandular or submuscular), incision site, hematoma and seroma development, device size, and use of a surgical bra. Although individual patient factors and surgeon preference will influence the decision between smooth or textured implants and submuscular or subglandular placement, these results should be taken into consideration during the preoperative planning process.
Many of the multivariate risk factors in this analysis confirm what has been previously demonstrated regarding the cause of capsular contracture. Further research on the effects of contributing factors that were not included in this analysis is warranted. These include the use of surgical sleeves, acellular dermal matrix, smoking, and patient compliance with postoperative instructions.
In addition, further research may be warranted regarding surface texture. The protective-textured finding from this study cannot necessarily be extrapolated to other manufacturers’ implants because comparable data are not available and surface texturing methods differ. The authors look forward to analyses from other manufacturers to determine whether there is a corresponding reduction of capsular contracture in their data. Such a collection of results can add to our current understanding of this phenomenon and further establish evidence-based outcomes.
The analysis of this large clinical study conducted in accordance with the approved U.S. Food and Drug Administration protocol has identified a variety of factors that impact capsular contracture and provides compelling evidence that textured surface implants and submuscular placement play significant roles in reducing the incidence of capsular contracture. These findings provide additional guidance to surgeons in the continued effort to reduce reoperations and improve patient outcomes.
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