Histological Analyses of Capsular Contracture and Associated Risk Factors: A Systematic Review

BACKGROUND

Capsular contracture is a severe complication to breast surgery with implants. Previous studies suggest multiple risk factors are associated with capsular contracture, but the etiology is still unknown. We performed a literature review to investigate existing studies on histological analyses of breast implant capsules and how clinical risk factors impact the capsule morphology.

METHODS

The literature search was conducted in PubMed. Studies that performed histological analyses of breast implant capsules were included. Animal studies or studies with a study population of less than five patients were excluded.

RESULTS

Fifty-two studies were included. The histological analyses showed that the breast implant capsules were organized in multiple layers with an inner layer of synovial-like metaplasia which was reported to diminish in capsules with capsular contracture. The remaining layers of the capsule mostly consisted of collagen. The alignment of the collagen fibers differed between contracted and non-contracted capsules, and capsules with higher Baker grade were generally thickest and contained more tissue inflammation. Studies investigating capsules affected by radiotherapy found a more pronounced inflammatory response and the capsules were generally thicker and fibrotic compared with nonirradiated capsules.

CONCLUSIONS

The included studies offer valuable insights into the histological changes caused by capsular contracture and their relation to clinical risk factors. Further studies with larger sample sizes and more strict inclusion criteria are needed to further investigate implant capsules and the role of the synovial-like metaplasia for the development of capsular contracture.

LEVEL OF EVIDENCE III

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Bilirubin binding in the plasma of newborns: critical evaluation of a fluorescence quenching method and comparison to the peroxidase method

Bilirubin binding affinities and capacities and apparent unbound ("free") bilirubin levels were determined in serum samples from 47 high-risk newborns, in 22 samples of cord serum, and in serum samples from 15 Greek children with marked hyperbilirubinemia, by both fluorescence quenching and peroxidase methods. The free fatty acid:albumin molar ratio was also determined for serum samples from high-risk newborns. In vitro and in vivo measurements suggest that free fatty acids are rarely present at levels that produce significant displacement of bilirubin, which is in agreement with previous studies. The two bilirubin binding assays showed only fair correlation with sizable discrepancies for many specimens. Technical difficulties inherent in the fluorescence quenching method and possible sources of error are discussed. Our observations suggest that routine application of these two assays as the primary criterion for therapeutic intervention (e.g., exchange transfusion) is premature.

The pathochemistry of kernicterus

The stoichiometry of bilirubin--albumin interaction has been analyzed and quantitated in several recent studies, confirming that albumin binding of bilirubin obeys the law of mass action [4, 5, 14, 16, 26, 36, 43, 46, 61, 65, 73, 92, 111]. These studies provide a basis for interpreting bilirubin transport, cell uptake and toxicity from physicochemical and pharmacologic perspectives [35, 42, 58, 59]. In this report, we propose a model of the pathogenesis of kernicterus which views serum albumin and tissue as competing with each other for binding the miscible bilirubin pool. Evidence is presented to show that bilirubin normally binds reversibly to cellular membranes and certain soluble enzymes just as it does to albumin; the unbound bilirubin concentration is the driving force for both albumin and tissue binding. We propose that albumin binding is determined by the concentration of free bilirubin anion (which is essentially unaffected by physiologic pH changes), and that tissue binding is mainly determined by the concentration of free bilirubin acid (which is greatly influenced by pH). When bilirubin--tissue complexes are formed, essential cell functions may be inhibited, producing cellular acidosis, irreversible intracellular aggregation of bilirubin, and cell death. In developing this argument, we will sequentially discuss relevant features of bilirubin chemistry, the binding of bilirubin to albumin, the formation of bilirubin--tissue complexes, bilirubin toxicity, alternative viewpoints of bilirubin transport, and, finally, the implications of this model to the clinical management of jaundiced infants. It should be emphasized that this paper is an attempt to analyze bilirubin transport and toxicity using basic chemical principles; it is an extension of previously published proposals [17, 77], and will undoubtedly require further modification as additional experimental data becomes available.

Mechanized determination of the apparent unbound unconjugated bilirubin concentration in serum

The peroxidase method for determining the apparent unbound bilirubin concentration in serum has been automated by use of a programmable, computer-directed spectrophotometer. This mechanized assay determines the total bilirubin concentration and apparent unbound bilirubin concentration in serum samples and titrates the serum with bilirubin to estimate the effect of increasing total bilirubin concentrations on the apparent unbound bilirubin concentration. The entire analysis requires 0.1 mL of serum and 4 min operation time, as compared with about 30 min for the manual method. The coefficients of variation for determination of the apparent unbound bilirubin concentration in bilirubin-enriched commercial control serum were 2.8% within-day and 5.6% between-day. Bilirubin--albumin binding in serum samples from infants with severe hyperbilirubinemia was analyzed by the manual peroxidase method, the automated peroxidase method, and Sephadex gel filtration. Good correlation was found among all three methods.

Mechanized determination of the apparent unbound unconjugated bilirubin concentration in serum

The peroxidase method for determining the apparent unbound bilirubin concentration in serum has been automated by use of a programmable, computer-directed spectrophotometer. This mechanized assay determines the total bilirubin concentration and apparent unbound bilirubin concentration in serum samples and titrates the serum with bilirubin to estimate the effect of increasing total bilirubin concentrations on the apparent unbound bilirubin concentration. The entire analysis requires 0.1 mL of serum and 4 min operation time, as compared with about 30 min for the manual method. The coefficients of variation for determination of the apparent unbound bilirubin concentration in bilirubin-enriched commercial control serum were 2.8% within-day and 5.6% between-day. Bilirubin--albumin binding in serum samples from infants with severe hyperbilirubinemia was analyzed by the manual peroxidase method, the automated peroxidase method, and Sephadex gel filtration. Good correlation was found among all three methods.

Kinetics of bilirubin oxidation with peroxidase, as applied to studies of bilirubin-albumin binding

In the determination of unbound bilirubin by rate of oxidation with peroxidase, errors may be caused by (1) phenol, propylparaben, and phenothiazines (free radical acceleration), (2) haemoglobin (peroxidase effect), and (3) ascorbate (inhibition). Such errors may be diminished by dilution 1:40, or with an anti-oxidant, tert-butyl-p-hydroxyanisole, and ascorbate oxidase.

Displacement of bilirubin from albumin by indomethacin

The primary albumin binding site of indomethacin is remote from the bilirubin binding site. Indomethacin is, at most, a weak displacer of bilirubin at low serum drug concentrations. When administered at dosages less than 1 mg/kg, indomethacin would appear to be safe with respect to serum binding of bilirubin in premature infants.

The effect of paraben preservatives on albumin binding of bilirubin

The interaction of methylparaben and propylparaben with bilirubin-albumin complexes was studied using difference spectra, Sephadex gel filtration, red blood cell uptake of bilirubin, and the peroxidase assay. Methylparaben was found to be a weak competitor with bilirubin for binding to primary albumin-binding sites but a strong binding competitor (similar to sulfisoxazole) at secondary sites. The displacing effects of methylparaben and sulfisoxazole were additive. Propylparaben bound to albumin but did not displace bilirubin. Drugs and injectable saline and water preparations which contain methylparaben should be avoided in jaundiced newborn infants when the high-affinity albumin-binding sites approach saturation.

Effects of gentamicin on albumin binding of bilirubin

The effects of gentamicin on albumin binding of bilirubin and bilirubin transport were studied using Sephadex gel filtration, spectrophotometric analysis, peroxidase assay, and red blood cell uptake. No significant interaction between gentamicin and bilirubin binding or transport was observed.