Well it turns out we are both right. Or wrong. Or something.
Once used on a patient, these nuts, bolts, plates and screws etc are indeed discarded.
The obvious question is - if these are supplied for single-use, why are they not supplied sterile, in appropriate packaging....?
The answer is that they are (at least in the UK), unpacked and added to the rest of the surgical orthopaedic equipment tray. The equipment tray is subjected to continuous decontamination and sterilisation cycles for the reasons I described above.
The nuts and bolts are used as required, if not all used immediately, they go round the cycle again and again until they are.
The problems are that:
a) traceability of the nuts and bolts is usually immediately lost when they are "thrown into the mix".
b) there is a risk of cross-contamination. Thus whilst the nuts and bolts might arrive non-sterile, they may actually get
more dirty, and biohazardous to boot.
(Yes, of course everything should be wonderfully clean and sterile, but the reality is sometimes different.)