First read your code descriptions. 996.49 is for a mechanical complication, 996.78 is other complication, pain, infection, etc. Then read the note and determine what is happening, did the hardware break, is it painful, has it caused an infection? That will help you to determine the correct code. If there are no problems and the hardware is just being remove (i.e. a percutnaeous pin) then your cocde would be V54.01
Not to pick on you or call you out, but I see your type of question as a problem. As professionals we are asking providers to trust us and we keep telling them we know what we're doing, but your question proves otherwise to them. I realize that we all have questions and nobody knows everything that's why we have these forums, but your question is a basic read the note, determine the problem check the code book, compare the codes and determine which one is correct type of thing. You should be able to get the information you need form the documentation or by asking the doctor if it's not clear. The ICD and CPT books as well as insurance carriers specific guidance should be our first source for any questions we have. As coders we need to know how to research and apply that knowledge to our work, this is part of our job and each of needs to develop these abilities.