Reviewer response rate was 100 percent. Plastic surgeons averaged 18.8 years of experience in either private (70 percent) or academic (30 percent) practice. Lay individuals averaged 54.7 years of age and represented various nonmedical vocations. The interrater reliability of the study survey was κ = 0.133 for reviewers overall, κ = 0.152 among plastic surgeons, and κ = 0.141 among lay individuals, corresponding each to a slight20 but significant agreement (p < 0.001).
No observable difference in breast aesthetics between anatomical and round implants was reported in 36.4 percent of cases: 43.6 percent by plastic surgeons and 29.2 percent by lay individuals (Table 3).
In the remaining 63.6 percent of cases, reviewers perceived an aesthetic difference between breasts. However, on analysis, neither reviewer group preferred the anatomical side significantly more often than the round side. Surgeons judged the anatomical side superior in 51.1 percent of cases and the round side in 48.9 percent of cases (p = 0.496). Lay individuals judged the anatomical side superior in 46.7 percent of cases and the round side in 53.3 percent of cases (p = 0.140). Moreover, aesthetic preferences were not dependent on manufacturer, among either plastic surgeons (p = 0.860) or lay individuals (p = 0.604) (Table 4).
Both reviewer groups rated the side they judged aesthetically superior to be no more than “moderately” more pleasing than the contralateral side on average, whether an anatomical or round implant was present on the preferred side. Plastic surgeons rated the anatomical side superior on average 1.9 and the round side superior on average 1.9 (p = 0.793). Lay individuals rated the anatomical side superior on average 2.2 and the round side superior on average 2.2 (p = 0.528). This finding of no difference in aesthetic superiority rating between implant shapes was confirmed using linear mixed modeling, among plastic surgeons (p = 0.321) and lay individuals (p = 0.939) (Table 5).
Regarding breast characteristics accounting for perceived aesthetic superiority, plastic surgeons did not choose “better upper pole contour,” “better lower pole contour,” and “better nipple position” more frequently when the preferred side had an anatomical rather than a round device (Table 5). Although “better projection” initially appeared to be selected more frequently by surgeons who preferred the anatomical side (20.8 percent) than by those who preferred the round side (11.6 percent) (p = 0.010), this difference was not statistically significant after the Bonferroni correction was applied.
Lastly, plastic surgeons reported not knowing which implant shape was producing the aesthetic superiority they perceived in 35.0 percent of cases. In the remaining cases, surgeons believed they knew the implant shape, but were able to identify it correctly only 26.5 percent of the time. Furthermore, the identification rate was found not to depend on whether the preferred side contained an anatomical (24.5 percent) or round (28.5 percent) implant (p = 0.143).
The operating surgeon involved in all 75 cases did not perceive an aesthetic superiority of either implant type in any patient. As a result, the patient-approved option of using anatomical implants as the final selection instead of round implants was not applied.
Anatomical implants have been gaining popularity in the United States since U.S. Food and Drug Administration approval in 2012, with a market share estimated at 3 to 26 percent.21 Half of American Society of Plastic Surgeons members report using them at least some of the time.22 However, these devices have not been fully embraced because of notable disadvantages not shared by round implants.
Anatomical implants were conceived to attain a more natural result compared with round implants. Device development began in the 1980s with Surgitek’s Replicon silicone devices,23 and followed with saline anatomical implants. The first highly cohesive gel anatomical implant was not introduced until 1993.24 However, largely because of the U.S. Food and Drug Administration’s silicone implant moratorium from 1992 to 2006, anatomical silicone implants did not become available in the United States until 2012, with device development before that occurring abroad.25 Since then, several U.S. studies have been published showing that breast augmentation with anatomical implants is safe and effective, and produces patient satisfaction rates exceeding 90 percent.13,26–29
There are only a few clinical studies comparing the two different shapes. One evaluated radiographic images of anatomical and round saline implants in vivo and found that both had similar “teardrop” shapes when standing but that round implants appeared more natural supine.15 Three subsequent studies compared postoperative photographs of patients who received either anatomical or round silicone implants and concluded that there was no significant aesthetic difference between them.3,16,17 Reviewers actually scored breast naturalness significantly higher in patients with round implants in one of these studies.17 These findings have led experts to theorize that the breast and wound healing shape the implant rather than the opposite.30
Although these studies indicate that surgeons and lay individuals appraise breast aesthetics using anatomical and round implants similarly, they are observational in design involving patient selection and surgeon biases. Considering that as many as 50 factors influencing results have been identified, a randomized trial offers the best option to control for confounding variables.31 A recent cadaver study compared anatomical and round implants in the same breast, but breast aesthetics were not specifically evaluated.32 This current study is the first randomized trial comparing breast aesthetics between anatomical and round implants within the same patient, therein controlling for important patient selection and surgeon biases.
Reviewers perceived no difference in breast aesthetics between anatomical and round implants in over one-third of cases. When a difference was perceived, neither reviewer group preferred the anatomical side significantly more often than the round side. Moreover, plastic surgeons reported not knowing which implant shape was producing the aesthetic superiority they perceived in 35.0 percent of cases. In the remaining 65.0 percent of cases, surgeons guessed correctly only 26.5 percent of the time, even lower than previous findings of 55.0 to 55.9 percent,3,17 and correct identification was found not to depend on whether the preferred side contained an anatomical or round implant. These results provide compelling evidence that there is no aesthetic superiority of anatomical over round implants in breast augmentation.
Plastic surgeon reviewers were queried on the characteristics accounting for perceived aesthetic superiority. Possible responses were based on four key features previously reported to define aesthetically pleasing shape: upper pole–to–lower pole ratio of 45:55; upward nipple angulation of approximately 20 degrees; linear or slightly concave upper pole contour; and a tight, convex lower pole.33,34 Taking into account that surgeons and patients can prefer different breast shapes,35 response choices also integrated feedback provided by the content validation survey completed during instrument pretesting. However, none of the breast characteristics linked to aesthetic superiority was chosen more frequently for either implant type (Table 5). This further supports the thesis that implant shape per se has little effect on breast aesthetics.36,37
Proponents claim that anatomical implant shape creates a more natural result, and that round implants are contraindicated in patients desiring a natural appearance.2,10–14 They have also asserted that anatomical implants are the best choice for patients with a very thin body habitus or who have less than the 1.5- to 3-cm thickness of upper pole breast parenchyma needed to hide the edge of a round implant.2,17,38 Other purported advantages of anatomical implants include greater correction of breast ptosis and more flexibility in selecting the ideal implant by considering three dimensions (height, width, and projection) instead of only two (diameter and projection) with round implants.38 However, considering the evidence to date including this study, such claims are based on expert opinion alone.
Anatomical implants have disadvantages not shared by round implants (Table 6). They feel more firm to the touch because of the highly cohesive filler consistency designed to resist deformational changes in vivo.23,39,40 In addition, the asymmetric implant design creates a potential for rotation within its pocket, referred to as “malrotation” when breast shape is clinically altered. This is estimated to occur in 1.1 to 2.6 percent of patients,13,27,41,42 although ultrasound screening of asymmetric patients suggests a rate as high as 25 percent.43 Predisposing factors include pocket overdissection, unstable implant orientation before capsule maturation, excessive intracapsular fluid, and double-capsule formation.14,44,45 Treatment for malrotation requires external manipulation and taping of the breasts for weeks at the least, but more commonly necessitates corrective surgery.14,46 Besides needing another procedure, the patient now has to embrace using round implants, an option originally passed over.
Anatomical implants have a more aggressively textured surface compared with textured round implants. Whereas the intent in the latter example is to reduce the risk of capsular contracture, the primary purpose of aggressive texturization in anatomical implants is to securely hold them in the proper orientation by means of a hook-and-loop fastener–like bond.14,47 Currently, there is a growing body of evidence linking implant texturization to late seromas, double capsules, and ALCL.5–7 Although presumed rare, 7.1 percent of 1067 American Society of Plastic Surgeons members recently surveyed reported having witnessed a case in their practice.4 Considering that many studies have not supported a lower rate of capsular contracture with textured implants, especially when placed in the subpectoral plane,10 it appears prudent to avoid using textured implants of all types until the precise mechanism of ALCL pathogenesis is elucidated.
There are other disadvantages too. Incision choice is largely restricted to the inframammary approach because greater length is often needed to accommodate the stiffer gel and surface texturization of anatomical implants. Moreover, this approach also facilitates precise pocket sizing, another anatomical implant requirement. Shorter incisions are possible, but then a funnel is needed to ease insertion and prevent gel fracture. Anatomical implants are significantly more expensive than round implants with all three manufacturers, ranging to as high as twice the cost.21 In addition, anatomical implants have limited applicability in secondary cases because either a capsulectomy or a neopocket is mandatory to minimize the potential for malrotation.2
Some assert that anatomical implants have a more demonstrable shape advantage in the subglandular plane because subpectoral placement compresses the implant, thereby neutralizing shape differences.48 However, this point may be moot given that subpectoral placement favors improved breast imaging.49,50 Furthermore, the subpectoral plane has a clear advantage in terms of minimizing the development of capsular contracture.50–53 Subpectoral placement is therefore generally preferred, outweighing the small risk of significant animation deformity.
Regarding study limitations, it could be argued that resolution of surgical edema is necessary to demonstrate the aesthetic advantage of anatomical implants. However, significant edema did not develop within the first hour of the procedure during which time the experimental component of this study was performed. Although anatomical implants are thought to not “drop” as much over time as round implants, this and other issues related to long-term implant settling are beyond the scope of this study.27
Although silicone sizers were used instead of actual anatomical implants for two of the manufacturers, the sizers are identical to the implants except for lacking surface texturization (Fig. 2). Moreover, the actual implants used in the Sientra subgroup yielded findings no different than those with the sizers. Among all devices used, however, the maximum size was 385 cc. Subsequently, the conclusions of this study may not apply to larger implant sizes.
It might be argued that the optimal anatomical model was not selected for each patient. However, torso length and width were taken into consideration as important factors to include in the selection process. Variation in chest dimensions can influence preferred anatomical implant height and base shape (round or oval). Although five of the 10 U.S. Food and Drug Administration–approved styles were used, one style from each manufacturer predominated. These three styles were quite different from one another, yet there was no superiority of any manufacturer demonstrated. It could be extrapolated from this that differences in models within a manufacturer’s styles would not have a significant impact in breast aesthetics either.
Lastly, although the reviewer survey was created using rigorous instrument design principles, it remains subject to measurement error. However, this was minimized by pretesting to optimize content validity, face validity, utility, and adequately powering the study. As a result, interrater reliability was higher in this study than for those designed for similar purposes in the literature.54
In this randomized controlled trial of anatomical versus round implants, reviewers commonly reported perceiving no difference in breast aesthetics between implant shapes. When a difference was noted, neither the anatomical nor the round side was preferred more often. Moreover, plastic surgeons identified implant shape correctly in only a minority of cases and often reported not knowing which implant shape was responsible for perceived superior aesthetics.
Considered together, the results of this study provide Level I evidence showing no aesthetic superiority of anatomical over round implants. Given the significant disadvantages enumerated, these findings argue against the continued routine use of anatomical implants in breast augmentation.
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