Articles
Polyurethane Covered Breast Implants
Silicone containing breast implants have been used since 1964. The first polyurethane covered breast implants (PCBI) have been used since 1968 to reduce one of the commonest problems associated with breast implants namely capsular contracture. Silimed have been manufacturing PCBI in Brazil since 1983. This history lesson is to give an idea of the reliability associated with PCBI.
Capsule formation is the bodies response to a foreign material. It is a normal process and problems only arise when the tissue shortens. Scar tissue develops around the implants or other medical device, over time this may contract. Fibrous scar tissue aligns longitudinally and is therefore able to overlap and shorten. There may be certain cells that aid this contraction.
With implants the first sign is a firmness or hardness followed by an obvious visual change and distortion. Finally the implants may become uncomfortable and even painful. The longer the implants have been in the body the more likely this is to occur. Studies of the incidence of capsule contracture vary from about 8% at 3 years to 16% at 8 years. This is the most common reason that implants need to be exchanged. The incidence of contraction for PCBI is quoted as 1% at 15 years.
Polyurethane foam has a 3 dimensional lattice and mesh structure over a moderately textured breast implant. This structure does not allow and breaks up the longitudinal scar tissue orientation therefore preventing contraction. The layer of polyurethane foam is bonded to the implant by a process of vulcanization. This limits delamination and separation.
Implant rotation may occur and this is especially problematic with tear-drop shaped implants. Implant moving sideways has been described. The PCBI have a softer foam surface which has a “Velcro” type effect on the interface with tissue. PCBI limits this rotation of implants. This effect also allows a more rapid recovery with less need for strapping or supportive bras. Once the implants are sited, they remain in that position. Downward displacement or “bottoming –out” and lateral displacement are also unlikely to occur.
Issues initially quoted as being associated with PCBI have been extensively studied and not been shown to be valid. The incidence of infection, implant removal difficulty, seroma or fluid collection, rupture and late contracture formation have not been shown to be any different to currently used silicone filled, cohesive gel implants. As mentioned the commonest problem of capsule contracture is significantly less.
A temporary, localized, itchy rash that occurs in less than 3% of cases is reported. This is most common in the second week and lasts about a week. Resolution of the rash occurs with no long term issues.
These implants were initially recommended for problematic cases such as repeat or early capsule formation, implant rotation and downward or lateral displacement. A growing number of surgeons recognize the distinct advantage of these implants and are using them first up as their implant of choice. Why wait for a problem to occur and then treat it when it may be possible to reduce the incidence of problem from the start?
The advantages include a capsule contracture rate 10 times less than conventional implants, the higher co-efficient of friction or “Velcro” effect limits rotation and downward or lateral displacement. The cohesive gel is also slightly softer giving a more natural feel. There is a long safety record over many decades.