Scientific Forum. The Comparative Dimensions of Round and Anatomical Saline-filled Breast Implants

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1 The Comparative Dimensions of Round and Anatomical Saline-filled Breast Implants Robert S. Hamas, MD Background: Anatomical saline-filled breast implants have been portrayed as having a more natural shape and greater upright projection than round saline-filled implants. However, there have been no reports in the literature substantiating such claims. Objective: This study was conducted to compare the shapes, proportions, and dimensions of round and anatomical saline-filled breast implants. Methods: A series of 52 Mentor round and 21 McGhan anatomical breast implants were studied with upright true lateral radiographic views of the implants. All were submuscular, without capsular contracture, and at least 6 months postoperative. Upright projection and height were measured from radiographs; recumbent projection and height data were taken from manufacturers catalogs. Statistical analysis was performed on all data to determine the relationship of projection to height and volume. Recumbent implant shape was also studied in a smaller group. Results: Round and anatomical implants have similar teardrop shapes, the same projection for a given height, and practically the same projection for a given volume when patients are upright. In the recumbent position, anatomical implants remain in a teardrop shape and retain relatively more projection for a given height and a given volume, whereas round implants settle back evenly like natural breasts. Conclusions: Round and anatomical implants have similar teardrop shapes and the same proportions in the upright position. Round implants are the more anatomical, with respect to implant shape, in both the upright and the recumbent positions. Anatomical saline-filled breast implants have been portrayed by their manufacturer as having a more natural shape and greater upright protection than round salinefilled implants. 1,2 A previous qualitative study of 14 round (style 1600 and style 2600, Mentor Corporation, Santa Barbara, CA) and 12 anatomic (style 468, McGhan Medical Corporation, Santa Barbara, CA) saline-filled breast implants showed them to have similar teardrop shapes on lateral radiographs with patients upright (Figure 1). With patients recumbent, the anatomical implant was found to remain teardrop-shaped, whereas the round implant settled back evenly. Thus, the round implant was felt to be more anatomical because it behaved more like a natural breast. 3 The present study was done to verify these findings in a larger series of implants and to quantitatively Dr. Hamas is in private plastic surgery practice in Dallas, TX. Presented in part at the 33rd Annual Meeting of the American Society for Aesthetic Plastic Surgery, Orlando, FL, May 14, Accepted for publication June 9, Reprint requests: Robert S. Hamas, MD, 8345 Walnut Hill Lane, Suite 120, Dallas, TX Copyright 2000 by The American Society for Aesthetic Plastic Surgery, Inc /2000/$ /1/ doi: /maj A ESTHETIC S URGERY J OURNAL ~ JULY/AUGUST

2 A B A Figure 1. A and B. Upright radiographs of round and anatomical saline-filled breast implants show a similar teardrop shape. compare round and anatomical implant proportions and projection. Materials Recumbent implant dimensions were taken from manufacturers catalogs. Although they show drawings of upright implants, manufacturers actually measured the dimensions for each size with the implant placed on a flat surface at the minimum fill volume. Tables 1 through 4 list the recumbent dimensions of round implants made by 3 manufacturers and the anatomical implant made by 1 manufacturer. Only round implant sizes that were comparable to the anatomical implant sizes were included. To obtain upright implant dimensions, 35 breast augmentation patients with Mentor style 1600 and style 2600 round saline-filled implants were chosen at random from my practice. Three breast augmentation patients with PIP round saline-filled implants (Poly Implants Prosthesis, Miami, FL) were chosen at random by 3 other surgeons. Fourteen breast augmentation patients with McGhan style 468 anatomical saline-filled implants were chosen at random by 4 other surgeons or referred by patients. All patients were at least 6 months postoperative and without capsular contracture (a unilateral anatomical contracture was excluded). This gave a study group of 52 patients with 103 implants, including the 13 patients with 26 implants discussed in the previously published report. Upright lateral radiographs were taken of all implants, and recumbent lateral radiographs were taken of 10 B Figure 2. A and B. Both round and anatomical implants are teardropshaped in a true lateral view, as indicated by the fill valve at the implant surface. With just 20 degrees of rotation, the view becomes oblique and the implants appear somewhat hemispherical. Mentor round, 2 PIP round, and 9 anatomical implants chosen at random. Since the previous publication, it had been found that implant shape on a radiograph can change with even slight rotation. The anterior fill valve is a good indicator: when at the implant surface, the view is a true lateral; when behind the implant surface, the view is slightly oblique (Figure 2). Only upright radiographs that were true lateral, or as close to that as possible, were included in the present study. This criterion excluded 2 Mentor round implants, 2 anatomical implants, and all 6 PIP implants because these had no fill valve for radiographic orientation. Because most saline-filled implants are now placed submuscularly, 6 round and 2 anatomical implants in the subglandular plane were excluded. Also excluded were 1 anatomical implant that was upside down and 8 round 282 A ESTHETIC S URGERY J OURNAL ~ JULY/AUGUST 2000 Volume 20, Number 4

3 Table 1. Mentor round style 1600 and style 2600 recumbent dimensions Vol (cc) Proj (cm) Hgt (cm) Proj/Hgt ratio Data from Mentor Corporation. Vol, Volume; Proj, projection; Hgt, height. Table 2. McGhan round style 168 recumbent dimensions Vol (cc) Proj (cm) Hgt (cm) Proj/Hgt ratio Data from McGhan Medical Corporation. Table 3. Hutchison round high-profile recumbent dimensions Vol (cc) Proj (cm) Hgt (cm) Proj/Hgt ratio Data from Hutchison International, Baton Rouge, LA. Table 4. McGhan anatomical style 468 recumbent dimensions Vol (cc) Proj (cm) Hgt (cm) Proj/Hgt ratio Data from McGhan Medical Corporation. implants that had underexposed radiographs, which precluded measurement of their dimensions. Only fully filled implants were included; 2 round implants not filled to at least the manufacturer s recommended maximum volume and 1 anatomical implant not filled to at least the manufacturer s recommended minimum volume were thus excluded. This left 2 fairly well-matched groups: (1) 52 Mentor style 1600 and style 2600 round submuscular implants; average volume, 385 cc; total fill to 102% of the manufacturer s recommended maximum volume; and (2) 21 McGhan style 468 anatomical, submuscular implants; average volume, 332 cc; total fill to 99% of the manufacturer s recommended maximum volume. Methods As in the previous study, all radiographs were taken on a mammography unit by the same technician through use of a chest wall view technique with an aluminum/molybdenum filter and manual exposure. Nothing touched the The Comparative Dimensions of Round and A ESTHETIC S URGERY J OURNAL ~ JULY/AUGUST Downloaded from Anatomical Saline-filled Breast Implants

4 Figure 3. Upright radiographs were taken with the arm relaxed, extended, and internally rotated, so there was no tension on the pectoralis muscle. Nothing touched the breast being radiographed here, the left breast. Figure 4. Positioning the arm up, as in Figure 3, or hanging the arm down at the side did not affect round implant shape on radiographs. Table 5. Mentor round style 2600 upright dimensions from radiographs Vol (cc) Proj Hgt Proj/Hgt Range Actual (cm) (cm) ratio * * * * Table 5. Continued Vol (cc) Proj Hgt Proj/Hgt Range Actual (cm) (cm) ratio * * * * *Style Data from McGhan Medical Corporation. 284 A ESTHETIC S URGERY J OURNAL ~ JULY/AUGUST 2000 Volume 20, Number 4

5 Table 6. McGhan anatomical style 468 upright dimensions from radiographs Vol (cc) Proj Hgt Proj/Hgt Range Actual (cm) (cm) ratio Figure 5. Height was measured at the implant s longest point. Projection perpendicular to the ribs was measured at the implant s thickest point. breast. All upright radiographs were taken with the arm extended. The arm was completely relaxed, without tension on the pectoralis muscle, and internally rotated as shown in Figure 3. In addition, upright radiographs of 14 round implants were taken with the arm hanging at the patient s side. There was no difference in implant shape as a result of arm position (Figure 4). Similarly, recumbent radiographs were taken with the arm extended and relaxed, without tension on the pectoralis muscle. Implant height was measured from top to bottom at the implant s longest point (Figure 5). The measurement of the implants was not used, because it would vary with the slope of the implant on each patient s chest wall. Projection perpendicular to the ribs at the implant s thickest point was measured from the front of the implant to the front of the ribs. The ribs rather than the back of the implant were used because the implants were submuscular and the ribs provided a clearer landmark. Projection measurements included the insignificant thickness of the posterior capsule. Measurement data from the 2 implant groups are shown in Tables 5 and 6. All of the data in Tables 1 through 6 were statistically analyzed and plotted (Table 7 and Figures 6-11). The trend lines in Figures 6 and 7 show the statistically significant relationships between projection and volume; they were found by performing a linear least squares regression analysis of projection versus volume without forcing the intercept through zero. The trend lines in Figures 8 and 9 show the statistically significant relationships between projection and height; they were found by performing a linear least squares regression analysis of projection versus height with the intercept forced through zero. Results The 52 round and 21 anatomical implants had similar teardrop shapes with patients upright. With patients recumbent, the 10 round implants settled back evenly whereas the 9 anatomical implants remained in a teardrop shape. Analysis of the data showed an extremely high degree of statistical significance, as indicated by the small P values The Comparative Dimensions of Round and A ESTHETIC S URGERY J OURNAL ~ JULY/AUGUST Downloaded from Anatomical Saline-filled Breast Implants

6 Table 7. Statistically significant relationships Relationship Trend line formula P value Proj vs Vol Recumbent Mentor Proj = Vol 1.29E-08 Recumbent McGhan Proj = Vol 1.18E-09 Recumbent Hutchison Proj = Vol 4.91E-09 Recumbent anatomical Proj = Vol 2.99E-09 Upright Mentor Proj = Vol 2.19E-20 Upright anatomical Proj = Vol 3.77E-06 Proj vs Hgt Recumbent Mentor Proj/Hgt = E-15 Recumbent McGhan Proj/Hgt = E-22 Recumbent Hutchison Proj/Hgt = E-20 Recumbent anatomical Proj/Hgt = E-17 Upright Mentor Proj/Hgt = E-58 Upright anatomical Proj/Hgt = E-25 E-, Number of places that decimal point is moved to left. listed in Table 7 (the smaller the P value, the more significant or meaningful the result). For example, the projection/height ratio of the upright Mentor round implant is , the P value being 7.99E-58 (in this notation, the E-58 indicates that the decimal point is to be moved 58 places to the left). Thus, this ratio provides a measure that is highly predictive of upright projection for a given height. The plot of recumbent projection versus volume from data in the manufacturers catalogs (Figure 6) shows that the recumbent projection of the anatomical implant is from 6 to 12 mm greater than that of the Mentor round implant, depending on the volume. The plot of upright projection versus volume from radiographic measurement data (Figure 7) shows trend lines that are very similar for the round and anatomical implants. The data provide statistically significant formulas (Table 7) by which to predict upright projection of the anatomical ( volume) and the Mentor round ( volume) implants, depending on the volume. According to these formulas, the upright projection of the anatomical implants on radiographs varies from no greater than that of the round implants for a 200-cc volume to only 2 mm greater than that of the round implants for a 400-cc volume. The plot of recumbent projection versus height from data in the manufacturers catalogs (Figure 8) shows that each implant s proportions, as indicated by its projection/ height ratio, are relatively constant. For any given height, the recumbent projection of the anatomical implant is greater than that of the Mentor round implant. The plot of upright projection versus height from radiographic measurement data (Figure 9) shows trend lines that are practically the same for both the round and anatomical implants. The data provide statistically significant projection/height ratios (Table 7) by which to predict upright projection relative to height. On the basis of the virtually identical projection/height ratios, upright round and anatomical implants have the same projection for any given height and therefore the same proportions. The plot of recumbent projection/height ratio versus volume from data in the manufacturers catalogs (Figure 10) shows each implant s proportions (its projection/height ratio) to be relatively constant and unrelated to volume. The plot of upright projection/height ratio versus volume from radiographic measurement data (Figure 11) shows that projection/height ratios fall in a cluster for both round and anatomical implants. Upright implant proportions showed no relationship to volume. Discussion If recumbent implants were measured by the manufacturers at the recommended maximum rather than at the minimum volumes, it is likely that the recumbent projections and projection/height ratios would be greater. This increase would be more marked for round implants because they have a larger range between the manufacturer s recommended minimum and maximum fill vol- 286 A ESTHETIC S URGERY J OURNAL ~ JULY/AUGUST 2000 Volume 20, Number 4

7 Figure 6. Plot of recumbent projection versus volume from data in manufacturers catalogs. Trend lines were determined by statistical analysis. Figure 7. Plot of upright projection versus volume from radiographic measurement data. Trend lines were determined by statistical analysis. The Comparative Dimensions of Round and A ESTHETIC S URGERY J OURNAL ~ JULY/AUGUST Downloaded from Anatomical Saline-filled Breast Implants

8 Figure 8. Plot of recumbent projection versus height from data in manufacturers catalogs. Trend lines were determined by statistical analysis. Figure 9. Plot of upright projection versus height from radiographic measurement data. Trend lines were determined by statistical analysis. 288 A ESTHETIC S URGERY J OURNAL ~ JULY/AUGUST 2000 Volume 20, Number 4

9 Figure 10. Plot of recumbent projection/height (P/H) ratio versus volume from data in manufacturers catalogs. P/H is unrelated to volume. Figure 11. Plot of upright projection/height (P/H) ratio versus volume from radiographic measurement data. P/H is unrelated to volume. The Comparative Dimensions of Round and A ESTHETIC S URGERY J OURNAL ~ JULY/AUGUST Downloaded from Anatomical Saline-filled Breast Implants

10 umes. In addition, it is likely that the recumbent dimensions would be slightly different if the manufacturers measured implants on a convex surface, such as the chest wall, rather than on a flat surface. There is a small degree of magnification on all radiographs that is related to the distance of the object from the film plate. For this study, radiographic magnification was assumed to be similar for both implant groups and for both projection and height. Thus, although the plots of upright projection versus volume give meaningful trends for comparison of round and anatomical implants, they do not give the actual projection of a given implant in a given patient. Because ratios of projection to height are not affected by radiographic magnification, they give a reliable indication of implant proportions on radiographs, on drawings, and in patients. The finding of similar shapes and the same proportions (projection/height ratios) for upright round and anatomical saline-filled implants negates any claims that anatomical implants give breasts a more natural shape, more projection for a given height, or noticeably more projection for a given volume. On the basis of the results of this radiographic study, it is not surprising that there are no published reports of an objective difference in postoperative appearance between breasts with anatomic implants and breasts with round implants. Conclusion Upright round and anatomical saline-filled breast implants have similar teardrop shapes and the same proportions. They project the same amount for a given height and almost the same amount for a given volume. Recumbent anatomical implants remain teardrop-shaped and retain more projection for a given height and for a given volume than round implants. Recumbent round implants settle back evenly like natural breasts. When both the upright as well as the recumbent implant shape is considered, the round implant is the more anatomical. Statistical analysis was performed by N. Shirlene Pearson, PhD, Director, Center for Statistical Consulting and Research, Southern Methodist University, Dallas, TX. I thank Barbara A. Marshall, RT(M), for her technical advice and assistance in obtaining the radiographs. References 1. Choosing breast augmentation. Santa Barbara, CA: McGhan Medical Corporation; 1998: McGhan Medical Corporation. Perfectly natural anatomical breast implants. D 2000;27: Hamas RS. The postoperative shape of round and teardrop saline-filled breast implants. Aesthetic Surg J 1999;19: A ESTHETIC S URGERY J OURNAL ~ JULY/AUGUST 2000 Volume 20, Number 4