"Best operation to have," the doctor says, as he turns on his chair, makes a slow spin, like swivel hips, and I begin thinking of hips – how being hip, swaying hips, hip-hop, bring on the image of youth, and wonder why it is said to be the first body-part to go? Could it be convenience? An easy-sell to prospective patients – buy a titanium metal hip, get screws put in, be rejuvenated so your birthdays are a celebratory "Hip Hip Hooray" and you can dance again with the best of soul-sure hipsters. "Hip" is not always currency: look at…