I think the fit matters most. And we, the patient, can't know what will fit unless we choose a doc who does custom devices.
That's not exactly true, Jane. If you have a good surgeon, he/she will make sure that the prosthesis fits you, whether it is a custom device, or not.
That's because, once an appropriate size is chosen, your bones can be cut to fit the device exactly. Sometimes this cutting is done using a computer-assisted programme and sometimes the surgeon (with appropriate experience) can do it alone.
Custom made or "off the shelf" it is still the skill of your surgeon that is paramount.
New Zealand