An antibiotic-releasing hip stem would count as a combination device since it has the characteristics of a drug and a device. However, since its primary mode of action will be as a hip implant that will the user in regaining their lost function, it would count as a Class 3 device. The antibiotic within the implant is simply supplementary as it only helps the user accept the foreign implant. The hip stem as a drug-delivery device would not make sense and would be extraneous and so, it makes sense that the hip stem only restores lost hip function while the drug is simply for a better compatibility of the device with the user. Although it may not be necessary, I think that an IDE would do more benefit than harm because it will, overall, include the efficacy of the product. Since this device will be inside the body, in-vitro and in-vivo studies must also be done.