Figure 23. Back patch of Heyer-Schulte Style 1600 implant. Same Heyer-Schulte implant as shown in Figure 22, showing the posteriorly placed back patch and annulus inside the implant shell, with an "M" on the overlap portion of the shell and the back patch (arrow). The back patch on saline-filled implants such as this are necessary to close the shell hole remaining after the shell is formed on a mandrel. These patches can sometimes be seen at mammography, and also on MR images (Fig 24).