Impact of post-operative infection on revision procedures in breast reconstruction: A marketscan database analysis.

BACKGROUND: Esthetic complications, such as capsular contracture and soft-tissue contour defects, hinder the desired outcomes of breast reconstruction. As subclinical infection is a prevailing theory behind capsular contracture, we investigated the effects of post-operative infections on these issues and revision procedures. METHODS: We conducted a retrospective database study (2007-2021) on breast reconstruction patients from the MarketScan® Databases. Esthetic complications were defined by their associated revision procedures and queried via CPT codes. Severe capsular contracture (Grade 3-4) was defined as requiring capsulotomy or capsulectomy with implant removal or replacement. Moderate and severe soft-tissue defects were determined by the need for fat grafting or breast revision, respectively. Generalized linear models were used, adjusting for comorbidities and surgical factors (p < 0.05). RESULTS: We analyzed the data on 62,510 eligible patients. Post-operative infections increased the odds of capsulotomy (OR 1.59, p < 0.001) and capsulectomy (OR 2.30, p < 0.001). They also raised the odds of breast revision for severe soft-tissue defects (OR 1.21, p < 0.001). There was no significant association between infections and fat grafting for moderate defects. Patients who had post-operative infections were also more likely to experience another infection after fat grafting (OR 3.39, p = 0.0018). In two-stage reconstruction, infection after tissue expander placement was associated with greater odds of infection after implant placement. CONCLUSION: Post-operative infections increase the likelihood of developing severe soft-tissue defects and capsular contracture requiring surgical revision. Our data reinforce the role of infections in the pathophysiology of capsular contracture. Additionally, infections elevate the risk of subsequent infections after fat grafting for moderate defects, further increasing patient morbidity.

Polyurethane Implants in Revisional Breast Augmentation: A Prospective 5-Year Study.

BACKGROUND: Revisional surgery for aesthetic breast augmentation remains a challenging procedure. Polyurethane (PU) implants have been found to avoid capsular contracture recurrence as well as to prevent implant displacement by bio-integrating with the pocket. OBJECTIVES: Our study aimed to assess the use of PU implants in breast revisional surgery and to provide an algorithm. METHODS: Over a 5-year period, a prospective study was conducted involving consecutive patients undergoing implant revision. Patient demographics, previous breast procedures, and specific surgical details were documented. Postoperative outcomes were followed up. RESULTS: Out of 92 patients (184 breasts), 78 (156 breasts) were included in the analysis. The average age was 47.5, with a BMI of 22.3 and a mean follow-up of 5 years. A majority (63%) represented secondary revisional cases, while 37% were tertiary cases. Implant size averaged 296 cc, with 53% placed in retropectoral position and 47% prepectoral. Significantly more implants in secondary cases were changed from prepectoral to retropectoral (P = .005), and in tertiary changed from retropectoral to prepectoral (P = .002). Complete capsulectomy was performed in 61.5% and partial in 25.6%. Additional lipofilling was performed in 32%, and concurrent mastopexy in 40%. Revisional surgery in our series had a 1.9% acute complication rate, 4.5% longer-term reoperation rate for corrections, 0.6% implant exchange rate, and no recurrent capsular contracture. CONCLUSIONS: This is the first study to provide data on outcomes of revisional breast augmentation surgery with PU implants. It shows that polyurethane implants offer consistent stability and have low rates of recurrent capsular contracture in revisional surgery.

Systematic Review of Capsular Contracture Management following Breast Augmentation: An Update.

BACKGROUND: Capsular contracture is one of the most frequent indications for revision following breast augmentation. Management goals focus on restoring breast aesthetics and minimizing subsequent recurrence of capsular contracture. As new data emerge, close review of the data are merited to build evidence-based clinical guidelines to inform surgical practice and management of capsular contracture. METHODS: A systematic review of the MEDLINE, Embase, and Cochrane Database of Systematic Reviews databases was conducted to characterize the surgical management of capsular contracture in revision breast augmentations. The primary endpoint was capsular contracture recurrence rate. RESULTS: The review was conducted in November of 2021. Primary search revealed 14,163 results. Initial screening by title left 1223 articles. Abstract review left 90 articles for full-text review, of which 34 were ultimately included and were all observational in nature. CONCLUSIONS: Capsular contracture management remains an important topic, with limited high-level evidence for establishing clear evidence-based treatment guidelines. Although more evidence is required to assess the effects of capsulectomy, implant exchange, and plane change, these appear to be useful mechanisms for reducing recurrent capsular contracture. There is more evidence regarding the use of acellular dermal matrix, although this still requires long-term follow-up studies. New developments regarding textured implants limit the revision breast augmentation surgeon to smooth devices.

Contextualizing the Impact of Pop Culture on Breast Implant Illness and its Medical Relevance.

INTRODUCTION: Despite a lack of data demonstrating causation, there is growing concern over breast implants and systemic illness. This study examines the impact of rising public interest in breast implant illness (BII) and its implications on breast implant removals (BIR). METHODS: A Google Trends (GT) analysis of each year between 2010 and 2022 was performed globally, and then separately for the United States alone (US), using the search terms "capsular contracture," "breast implant illness," and "breast implant(s) removal". Linear regression was performed to determine significant correlations. Data on BII-related Facebook advocacy groups, relevant pop culture events, numbers of BIR surgeries, and number of BII-related publications were collected and analyzed alongside GT data to determine relevance. RESULTS: For global GT, there was a significant relationship between "breast implant illness" and "breast implant(s) removal" in 2016 (R2=0.62, ß =0.33, p<0.01), 2020 (R2=0.53, ß =0.23, p=0.01), and 2022 (R2=0.60, ß =0.44, p=0.01). In the US, 2016 (R2=0.53, ß =1.75, p=0.01) 2018 (R2=0.61, ß =1.93, p<0.01) and 2020 (R2=0.72, ß=0.91, p<0.01) were significant. In 2020, "capsular contracture" and "breast implant(s) removal" was significant in the US (R2=0.58, ß=0.4, p=0.01). In 2016, Facebook was the platform for the largest BII advocacy group and in 2020 YouTube was the platform for the first BII documentary and TEDx talk. From 2010 to 2020, PubMed publications containing "ASIA" and "BII" increased 24-fold and ASPS reports on BIR rose 70%. CONCLUSION: This study suggests that BII is a topic of global concern and has implications on both academic medicine and clinical practice. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Efficacy of Acellular Dermal Matrix Type in Treatment of Capsular Contracture in Breast Augmentation: A Systematic Review and Meta-Analysis.

BACKGROUND: Capsular contracture is a known complication of breast augmentation and is among the top reasons for revisional breast augmentation procedures. The use of acellular dermal matrix (ADM) has been shown to reduce the rate of capsular contracture in breast reconstruction and augmentation, theorizing that it acts as a protective barrier between the implant capsule and inflammatory process responsible for capsular contracture. The role of ADM in treatment of capsular contracture has been investigated in numerous studies, with a variety of ADMs. OBJECTIVES: The aim of this study was to perform a systematic review of existing literature on the use of ADM for treatment of capsular contracture in aesthetic breast augmentation patients to investigate differences in efficacy of ADM types. METHODS: The PubMed, Embase, and CINAHL databases were systematically reviewed for articles pertaining to capsular contracture, acellular dermal matrices, and breast augmentation. Number of patients, type of ADM, Baker grade, follow-up time, complication rate, and capsular contracture rate were recorded from identified articles. Data was pooled from studies to calculate a capsular contracture rate for each ADM type, with a chi-squared test performed for analysis. Identified studies with a comparative group were included in a meta-analysis utilizing risk ratio (RR) to assess the efficacy of ADM. RESULTS: Nine articles including ADM for treatment of capsular contracture in breast augmentation met criteria for inclusion, with a total of 481 breasts. Strattice was the most commonly utilized ADM (n = 391), followed by AlloDerm (n = 57). There was a statistically significant difference in efficacy of ADM among the studied ADM types (P < .001). AlloDerm, FlexHD, and DermaMatrix had the lowest capsular contracture rates (0%). NeoForm and SurgiMend had the highest capsular contracture rates (each 25%, but with n = 4 and n = 8, respectively). Strattice had a capsular contracture rate of 1.53% in the pooled data, and meta-analysis showed that Strattice reduced the risk of capsular contracture (RR 0.14 [95% CI 0.06, 0.31]) compared with conventional treatment. CONCLUSIONS: Acellular dermal matrices appear to be effective at treating capsular contracture after breast augmentation while maintaining a low complication rate. Overall capsular contracture rates are low with the use of ADM. There is a statistically significant difference in efficacy among ADM types. Meta-analysis shows that Strattice is effective at reducing the risk of capsular contracture in breast augmentation patients when compared to conventional treatment. Future research, especially in the form of randomized controlled trials, is needed to further investigate the efficacy of various ADMs in the treatment of capsular contracture.

Capsular Contracture Rate in Augmentation Mammoplasty With Motiva Breast Implant Insertion: A Single-Center Experience in Korea.

BACKGROUND: Capsular contracture is the most common complication following breast implant surgery, and the implant shell characteristics are important in preventing this complication. OBJECTIVES: The aim of this study was to evaluate the capsular contracture rate for SmoothSilk Motiva implants (Establishment Labs Holdings Inc., New York, NY) in females who underwent primary and revisional breast augmentation over a 3-year period. METHODS: A total of 1324 cases that took place from 2017 to 2020 were retrospectively analyzed, with 1027 being primary surgeries and 297 being revisional surgeries. RESULTS: In the 1324 cases of augmentation mammoplasty with SmoothSilk Motiva implants, the overall capsular contracture rate was 1.8% (n = 24). The capsular contracture rate in the 1027 primary surgery cases was 1.07% (n = 11), and the capsular contracture rate in the 297 revisional surgery cases was significantly different at 4.39% (n = 13, P = .0001). More specifically, the capsular contracture rate in 182 revisional surgery for cases without capsular contracture was 1.12% (n = 2), and it showed no statistically significant difference from the rate in primary surgery cases (P = .965). However, the rate in 115 revisional surgery for cases with capsular contracture was 9.57% (n = 11), and it showed a statistically significant difference from the rate in primary surgery cases (P = .000) and the rate in revisional surgery for cases without capsular contracture (P = .001). CONCLUSIONS: Augmentation mammoplasty with SmoothSilk Motiva implants demonstrated a lower rate of capsular contracture than traditional smooth or textured implants. Revisional surgery for cases without capsular contracture showed a similar rate of capsular contracture to primary surgery cases, but the rates were higher in revisional surgery for cases with capsular contracture.

Baker Grade IV Capsular Contracture Is Correlated with an Increased Amount of Silicone Material: An Intrapatient Study.

BACKGROUND: Breast implant surgery is one of the most frequently performed procedures by plastic surgeons worldwide. However, the relationship between silicone leakage and the most common complication, capsular contracture, is far from understood. This study aimed to compare Baker grade I with Baker grade IV capsules regarding their silicone content in an intradonor setting, using two previously validated imaging techniques. METHODS: Twenty-two donor-matched capsules from 11 patients experiencing unilateral complaints were included after bilateral explantation surgery. All capsules were examined using both stimulated Raman scattering (SRS) imaging and staining with modified oil red O (MORO). Evaluation was done visually for qualitative and semiquantitative assessment and automated for quantitative analysis. RESULTS: Using both SRS and MORO techniques, silicone was found in more Baker grade IV capsules (eight of 11 and 11 of 11, respectively) than in Baker grade I capsules (three of 11 and five of 11, respectively). Baker grade IV capsules also showed significantly more silicone content compared with the Baker grade I capsules. This was true for semiquantitative assessment for both SRS and MORO techniques ( P = 0.019 and P = 0.006, respectively), whereas quantitative analysis proved to be significant for MORO alone ( P = 0.026 versus P = 0.248 for SRS, respectively). CONCLUSIONS: In this study, a significant correlation between capsule silicone content and capsular contracture is shown. An extensive and continued foreign body response to silicone particles is likely to be responsible. Considering the widespread use of silicone breast implants, these results affect many women worldwide and warrant a more focused research effort. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Ideal Implant Structured Breast Implants: Core Study Results through 10 Years.

BACKGROUND: The Ideal Implant structured breast implant uses different technology than unstructured saline or silicone gel implants, making it a third type of implant. U.S. Food and Drug Administration (FDA) and Health Canada granted approval in November of 2014. This saline-filled implant has an internal structure consisting of a series of nested shells that support the upper pole when upright and control movement of the saline to provide a natural feel. Because women can look in the mirror to know their implants are intact, they have peace of mind. In contrast, most women are concerned about silicone gel implant ruptures, which are silent and require FDA-recommended magnetic resonance imaging or ultrasound scans for detection. METHODS: This U.S. trial enrolled 502 women: 399 for primary and 103 for revision augmentation. Investigators were 45 American Board of Plastic Surgery-certified plastic surgeons at 35 sites. Of the 502 women enrolled, 426 (84.9%) completed 10-year follow-up visits, a higher percentage than all other FDA breast implant trials. RESULTS: Through 10 years of follow-up, surgeon satisfaction was 94.8% for primary and 87.4% for revision augmentation; and patient satisfaction was 92.7% for primary and 82.3% for revision augmentation. Cumulative Kaplan-Meier risk rates for two major adverse events were lower than in the silicone gel implant trials: Baker class III and IV capsular contracture was 6.6% for primary and 11.5% for revision augmentation; and rupture/deflation was 3.7% for primary and 4.7% for revision augmentation. CONCLUSION: Ten-year results from 426 women show the Ideal Implant has high patient and surgeon satisfaction, a low rate of capsular contracture, and a low rate of rupture/deflation. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Risk Factors for Capsular Contracture in Alloplastic Reconstructive and Augmentation Mammaplasty: Analysis of the National Surgical Quality Improvement Program (NSQIP) Database.

BACKGROUND: Capsular contracture is the most common complication of breast augmentation and reconstruction. It occurs in up to 45% of patients and is theorized to occur secondary to an immune reaction. It can lead to pain, dissatisfaction with aesthetic outcomes, and reoperation. The gold standard for management is capsulectomy. Prior similar studies are limited by narrow inclusion criteria, single-surgeon analysis, small sample size, or univariate analysis. The goal of the following study is to prospectively identify possible risk factors for capsular contracture using a national database. METHODS: A retrospective review was conducted utilizing the National Surgical Quality Improvement Program (NSQIP) Database of prospectively collected data of patients undergoing periprosthetic and/or total capsulectomy for capsular contracture from 2013 to 2016. Odds ratios (OR) with 95% confidence intervals (CI) were calculated for variables using a multivariable binary logistic regression model. RESULTS: A total of 6547 patients underwent reconstructive or augmentation mammaplasty with a prosthetic implant, out of which 2543 (39%) underwent capsulectomy. Capsular contracture was more likely in older (OR: 1.10, 95% CI: 1.09-1.10, p<.001), overweight (OR: 1.12, 95% CI: 1.10-1.13, p<.001), and cancer patients (OR: 7.71, 95% CI: 2.22-28.8, p=0.001). Wound infection was associated with capsulectomy (OR: 6.69, 95% CI: 1.74-25.8, p<.001). CONCLUSION: These identified risk factors should be comprehensively addressed with patients during the informed consent process before breast augmentation or reconstruction with implants. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The Double Capsule Phenomenon in a Case Series and its Relationship with the Macro-Textured Breast Implant.

BACKGROUND: Silicone breast augmentation remains one of the most common aesthetic surgery procedures, and 2022 marks the 60th anniversary of the first case. Recent studies suggest a link between double capsule (DC) formation and macro-textured devices. METHODS: Between 2010 and 2015, 268 aesthetic patients underwent bilateral mammary prosthesis exchange for indications including PIP exchange, adverse capsular contracture and ultrasonographic evidence of rupture. All surgery, in the form of implant exchange and capsulectomy, was undertaken by the senior author using standard techniques. A retrospective review was undertaken, and data analysed with descriptive statistics and Fisher's exact and Mann-Whitney U tests. RESULTS: Of 268 patients identified, 40 (14.9%) showed some degree of capsular duplication and bilateral involvement was marginally more common (52.5%). Two macroscopic patterns of duplication were observed: complete and subtotal. Complete DCs correlated with a clinical triad of extreme firmness, mobility and minimal-to-no pain. Whilst a wide range of manufacturers was represented, macro-textured devices were associated with the highest DC prevalence (58.3% vs. 5.6%) (Fisher's exact test p < 0.00001). Patients with DC had been implanted for less than half the time, median 52 versus. 120 months (p = 0.0003) of those without. DISCUSSION: An elevated prevalence of duplicate capsules in macro-textured prostheses is reconfirmed in addition to a novel symptom constellation that may assist with clinical diagnosis. Our study reinforces the aetiopathogenic influence of the elastomer in DC formation and reports DC for the first time in non-macrotextured implants. Single-surgeon cohort of 268 consecutive patients with 532 implants Statistically significant association of macro-textured devices with DC Statistically significant reduced duration of implantation of macro-textured devices First report of DC in non-macro-textured devices LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Correlation between Capsular Contracture Rates and Access Incision Location in Vertical Augmentation Mastopexy.

BACKGROUND: Plastic surgeons commonly use one of three access incisions to place breast implants during vertical augmentation mastopexy, including inframammary, vertical, and periareolar. It is not known whether there is a correlation between capsular contracture and access incision location. The purpose of this study was to investigate in a single-surgeon series the incidence of capsular contracture associated with access incision locations in silicone vertical augmentation mastopexy. METHODS: Patients undergoing a vertical augmentation mastopexy between 2013 and 2017 were studied retrospectively. All patients underwent a standardized, dual-plane breast augmentation with smooth surface silicone gel implants. Patients were evaluated 1 year postoperatively by the Baker scale. RESULTS: A total of 322 patients met study criteria. Eighty-four had periareolar access, 86 had vertical access, and 152 had inframammary access. There were no differences in patient age or mean implant size between the groups. The capsular contracture rate of the periareolar group was 5.36 percent; in the vertical access group, 3.48 percent; and in the inframammary access group, 1.64 percent. Capsular contracture rates correlated inversely to the distance to the nipple-areola complex, with the periareolar access rates the highest, the vertical access rates intermediate, and the inframammary access rates the lowest. Inframammary incisions were associated with lower capsular contracture rates than periareolar incisions when performed in conjunction with vertical augmentation mastopexy ( p = 0.043). Vertical access capsular contracture rates were intermediate between periareolar and inframammary groups. CONCLUSION: Surgeons should take into consideration the capsular contracture rates associated with access incision location when planning or performing vertical augmentation mastopexy. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Complete Implant Wrapping with Porcine-Derived Acellular Dermal Matrix for the Treatment of Capsular Contracture in Breast Reconstruction: A Case-Control Study.

BACKGROUND: Capsular contracture (CC) represents one of the most common complications in breast reconstruction surgery, impairing final result and patients' well-being. The role of acellular dermal matrixes (ADM) has been widely described for the treatment and prevention of contracture. The aim of the study was to evaluate the efficacy and safety of complete implant coverage with porcine-derived ADM in preventing CC limiting complications. In addition, patients' reported outcomes were evaluated in order to define the role of ADM in improving sexual, physical and psychosocial well-being and satisfaction. METHODS: 42 patients who underwent surgical treatment of 46 contracted reconstructed breasts from May 2018th to May 2019th were collected in the two groups (ADM group vs. Control group). RESULTS: The ADM group showed lower rate of CC recurrence and a higher rate of implant losses and minor complications. A significant difference was observed in red breast syndrome (27.3% in the ADM group vs. absent in control the group) and skin ulceration rates (18.2% in the ADM group vs. 4.18% in the control group). As for patients' perceived outcomes, the ADM group showed a statistically significant higher postoperative Satisfaction of Breast Scale score compared to the control group. In addition, a significant difference was observed in the improvement of Physical Well-Being of the Chest Scale and the Satisfaction of Breast Scale after surgery, in favor to the ADM group. CONCLUSION: Complete implant coverage with ADM may reduce the risk of CC recurrence in breast reconstruction. An accurate patient selection allows minimizing complications improving patient well-being and satisfaction. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The Value of Capsule Thickness on Breast Ultrasound as an Indicator of the Severity of Capsular Contracture and Its Correlation with the Baker Classification.

BACKGROUND: We conducted this study to explore the value of the capsule thickness as an indicator of the severity of capsular contracture (CC) alternatively to the Baker classification system in patients who were treated with an implant-based augmentation mammaplasty. METHODS: A total of 117 eligible patients (202 breasts) were included in the current study. We measured the capsule thickness using ultrasound and histologic examination in association with the Baker grades I, II, III and IV. Then, we analysed agreement of the capsule thickness between the two methods using an intra-correlation coefficient (ICC 2,1) with 95% confidence intervals (CIs). The CC of Baker grades II, III and IV (105 breasts), for which the capsule thickness could be measured using US, served as Model 1. Moreover, Model 1 including the CC of Baker grades I (97 breasts) served as Model 2. RESULTS: The capsule thickness was measured as 0.58 ± 0.11 (0.4-0.8) mm, 1.07 ± 0.16 (0.8-1.31) mm and 1.89 ± 0.55 (1-4.1) mm on ultrasound in association with Baker grades II, III and IV, respectively. In addition, it was also measured as 0.28 ± 0.07 (0.09-0.41) mm, 0.58 ± 0.08 (0.42-0.75) mm, 1.06 ± 0.14 (0.79-1.34) mm and 2.13 ± 1.14 (1.38-6.98) mm on histologic examination in association with Baker grades I, II, III and IV, respectively. In Model 1 and 2, the ICC was calculated as 0.942 (95%CI 0.914-0.961) and 0.955 (95%CI 0.940-0.966), respectively. The cut-off values between the Baker grades I-II, II-III and III-IV were calculated as 0. mm, 0.8 mm and 1.2 mm, respectively. CONCLUSIONS: In conclusion, the capsule thickness might be used as an indicator of the severity of CC alternatively to the Baker classification system. But further studies are warranted to establish our results. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Biomechanical Principles of Breast Implants and Current State of Research in Soft Tissue Engineering for Cosmetic Breast Augmentation.

Currently there are limited implant-based options for cosmetic breast augmentation, and problems associated with those have been increasingly appreciated, most commonly capsular contracture, which occurs due to a chronic foreign body reaction against non-degradable implant materials such as silicone and polyurethane leading to scar tissue formation, pain, and deformity. The underlying biomechanical concepts with implants create a reciprocal stress-strain relationship with local tissue, whilst acting as a deforming force. This means that with time, as the implant continues to have an effect on surrounding tissue the implant and host's biomechanical properties diverge, making malposition, asymmetry, and other complications more likely. Research directed towards development of alternative therapies based on tissue engineering and regenerative medicine seeks to optimize new tissue formation through modulation of tissue progenitors and facilitating tissue regeneration. Scaffolds can guide the process of new tissue formation by providing both an implant surface and a three-dimensional space that promotes the development of a microenvironment that guides attachment, migration, proliferation, and differentiation of connective tissue progenitors. Important to scaffold design are the architecture, surface chemistry, mechanical properties, and biomaterial used. Scaffolds provide a void in which vascularization, new tissue formation, and remodelling can sequentially occur. They provide a conduit for delivery of the different cell types required for tissue regeneration into a graft site, facilitating their retention and distribution. Whilst recent research from a small number of groups is promising, there are still ongoing challenges to achieving clinical translation. This article summarizes the biomechanical principles of breast implants, how these impact outcomes, and progress in scaffold-guided tissue engineering approaches to cosmetic breast augmentation. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .