Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_998_Библиотеки_им_академика_М_И_Перельмана

the long-term integration of biological tissue and silicone implants; (2) an introduction to the prob­lems of interfacing biological tissue and silicone implants; (3) a description of methods currently available to modify implants; and (4) a descrip­tion of novel ideas drawn from tissue engineer­ing, regenerative medicine, and biomedical engineering that may be applicable and useful to the implementation of interfacing biological tis­sue and silicone implants. These methods should be applicable to implants that are intended to be in place for an extended period of time, and, in most cases, indenitely. There is a need to improve surgical silicone implants integration with surrounding tissues.

Nowadays, an incredible variety of devices using disparate materials (from plastics to met­als) have been developed by researchers, con­structed by the medical device industry, and implanted by surgeons. However, it is important to evaluate whether current medical implants and technology require substantial improve­ments, and, if so, how by understanding the shortcomings of these current devices. Existing literature about the failure rates and economic impact of all currently available medical implants is difcult to nd. Nonetheless, it is possible to nd specialized reviews by implant type, and the economic costs of implant failure have been evaluated for certain types of implants [1]. Moreover, some patients require multiple device replacements, and it is expected that the number

Medical devices and surgical implants have seen a drastic technological improvement in the past few decades, widely extending their applicability and usability. In the eld of cosmetic and recon­structive surgery, silicone implants are widely used [3, 4]. As such, there has been an increased interest recently to nd solutions that better pro­vide long-term integration with surrounding tis­sues and organs. A possible way to better biointegrate silicone implants and biological tis­sue may be to implement methods drawn from the eld of tissue engineering and regenerative medicine to the areas in contact with medical implants, in addition to the normal approach of functionalizing or modifying surgical implants. Although silicone implants are approved for clin­ical use, local complications, such as capsular contracture, implant rupture, and gel bleeding, have not yet been fully resolved [5, 6]. One of the most serious complications is capsular contrac­ture, which has been reported to occur in up to 30% of patients after the insertion of silicone implants [7, 8]. When a silicone implant resides in the body for a prolonged period, excessive brous connective tissue, which is mainly com­posed of collagen and broblasts, accumulates around it, isolating the implant from the local tis­sue environment [9, 10]. Subsequently, a contrac- tile force originating from the collagen and myobroblasts, which are differentiated from broblasts, causes capsular contracture around the silicone implant. In serious cases, this can require secondary surgery, posing a great deal of inconvenience to patients [7, 11].

This pathological phenomenon usually occurs due to prolonged inammation, resulting in chronic inammation from acute inammation [12]. In such a scenario, the period of acute inammatory response can also be prolonged from days to weeks [13]. Once the silicone implant is inserted, acute inammation initiates with inltration of polymorphonuclear leuko­cytes (PMNs) from the blood vessels to the implant site [13]. Then, these PMNs secrete cys­teinyl leukotrienes (CysLTs), which are potent inammatory lipid mediators [14] and also involved in the recruitment and survival of PMNs via autocrine and paracrine signaling [15, 16]. The persistent presence of the silicone implant leads to chronic inammation, in which CysLTs stimulate the migration and proliferation of broblasts [17, 18]. During this stage, broblasts differentiate into myobroblasts and synthesize collagen, which is mediated by transforming the growth factor (TGF)-b secreted by the bro­blasts themselves [19–21], leading to the forma­tion of capsules by brosis. Eventually, both the smooth muscle actin (i.e., a-SMA), which is expressed on the myobroblasts, and tension, which is caused by collagen brils, cause capsu­lar contracture, i.e., a contractile force around the silicone implant [9, 22, 23]. Therefore, inhib- iting CysLT production may prevent the forma­tion of capsular contractures. Furthermore, decreasing the number of CysLTs would reduce the recruitment and proliferation of broblasts, thereby decreasing the amount of myobroblasts and collagen during the chronic inammation stage. Montelukast is a potential therapeutic agent for the inhibition of CysLT production [24,

Smooth implants, such as silicone, illicit a mild inammatory reaction at the time of implantation and gradually develop a brous capsule around them, causing some authors to be concerned for possible infection and rejection in the near future. The rate of infection with silicone implants hov­ers around 3.9% with an extrusion rate of 2.9% [44]. Serna etal. [41] hypothesized that infection from silicone implants may be secondary to lim­ited delivery of immunocompetent cells to the implant pocket due to the thick capsule. These implants also experience frequent shifts in posi­tion, given the smooth surface and lack of soft­tissue ingrowth, as well as higher rates of bone resorption compared with their softer, porous counterparts. If the implant pocket is too large, the mobile implant can induce persistent seroma or cause chronic peri-implantitis, both of which increase the tendency for extrusion [41, 45]. However, these implants are easily removed (because of the brous capsule), have lower costs, and are easy to use [41].

dystopia. It is important to note that their review included the use of solid implants for orbital oor repair following blowout fractures [ Ridwan-Pramana etal. [48] looked at the out­comes from 69 MedPor facial implants and found an overall complication rate of 31.8%. This was signicantly higher than the rates doc­umented in other studies (which ranged from

Complications of midface implantation include inadequate correction or overcorrection, malpo­sition, implant migration, infection, extrusion, nerve hypesthesia/anesthesia, and facial nerve injury [40]. For malar implants, the average infection rate is 2.4% and displacement rate is

2.3%. [44] In terms of orbital and periorbital

niques have been noted in the literature attempting to inltrate selected antibiotics into porous alloplastic implants during head and neck reconstruction, including just dipping the implant into the antibiotic, completely immers­ing the implant in the antibiotic, and, nally, applying negative pressure to create suction and inltrate the implant with the antibiotic. In 2009, Keefe and Keefe [ study looking at the efcacy of the above tech­niques in preventing Staphylococcus growth on GoreTex and MedPor implants. They found that the negative pressure technique was most effective, with a statistically significant advantage over the other two techniques. This information is beneficial, but there is still a paucity of objective evidence in the literature suggesting that these intraoperative tech­niques are effective for preventing postopera­tive infection invivo. In a prospective study by Niechajev [ following MedPor implantation, all implants were impregnated with cloxacillin using a suction infiltration technique before implan­tation. The author also reports the use of densely placed sutures to create a watertight seal, preventing contamination of the implant pocket with microorganisms, as well as a 7-day postoperative course of flucloxacillin. Their overall infection rate was 2.8%; all cases were nasal reconstructions. Several other authors are proponents of preoperative antibiotic soak or impregnation, especially during rhinoplasty [61, 65–71]. Although the rates of infection are relatively low in these studies, none of them are formally controlled trials, and there is little objective evidence that the above techniques are effective. Furthermore, in 2003, Godin etal. [72] inves­tigated the complications following GoreTex chin implantation and found no difference in the infection rate between preoperative antibi­otic soaking (gentamicin or bacitracin) and no preoperative antibiotic soaking. They did not discuss the use of perioperative systemic anti­biotics or postoperative oral antibiotic prophylaxis.