What is the difference between breast reconstruction with implants under the muscle or over the muscle?

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What is the difference between breast reconstruction with implants under the muscle or over the muscle?⁠
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In the past, breast reconstruction with implants was always accomplished by placing the implants under the pectoralis muscle. Today, newer techniques allow implants to be placed either under the muscle (UTM) or over the muscle (OTM). ⁠
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Understanding the risks and benefits of these two options is important in deciding which approach is better for you. For some women, placing the implants UTM may be better, while for others implant placement OTM may provide a better outcome. Shared decision-making with your plastic surgeon can help you determine which is best for you.⁠
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The advantage of placing implants UTM is that there is more soft tissue covering the implants, potentially decreasing the risk of implant visibility and rippling. Unfortunately, when implants are UTM there may be unnatural animation of the implants with movement of the pectoralis muscles. This may be unsightly, and uncomfortable.⁠
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The primary advantage of placing implants OTM is that implant animation is avoided. Since natural breast tissue before mastectomy is positioned OTM, placing the implant in this position is also more natural. One potential problem with placement of implants OTM is that there is less soft tissue covering the implants. This can increase the risk of visible implant rippling. Breast reconstruction with implants OTM is best if the thickness and quality of the breast skin after mastectomy allows this approach while avoiding rippling. ⁠
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It is important to understand the risks and benefits of UTM vs. OTM when deciding how to proceed. Many women are not bothered by implant animation and would be more concerned with implant rippling. On the other hand, more active or athletic women may be very unhappy with animation and may prefer implants placed OTM, even at the risk of implant rippling.⁠
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