Ortho Charm. The Ortho Charm mattress has a build featuring a dual response open coil spring unit, providing double the comfort and support from the 650 back-care springs. The mattress also contains layers of rich white fibre giving a supportive surface which is ideal particularly for back pain sufferers. A heavy gauge wire edge is built in for extra support as are the cotton felt tufts. The Ortho Charm comes in a wide range of sizes to suit your bed frame. So buy this Ortho Charm Now £309.00.