There is basically no risk of harm from such a thing. If all you are doing is using it verify whether a surgery worked or not, then it's not actually a treatment is it? Surgeons make their own tools, jigs and tests all the time.
And if for some reason you had to, there are different grades of hard with a medical regulating body. For instance, it is super easy to develop medical tools. Harder again to do implants, harder again to do medicines.
So I want to reiterate. Not hard at all.
- source. Worked for a medical device company that did implants, wound care and medical tools. Surgeons would often ask for custom tooling or jigs through us that we would get made up for them.
Some are subjective like pain (VAS or visual analog pain scale, “rate your pain 1-10”), ability to do daily activities, “would you have this procedure again?”, return to pre-injury activity level, etc.
Others are objective like range of motion, strength, bone healing noted on Xray or ct, tendon / ligament healing observed on mri, histiologic healing observed from follow up biopsy, rehospitilzation rates, revision surgery rates, infection rates, or mortality rates (the ultimate objective outcome measure).
There is hardly a shortage of outcome measures out there, and researchers propose new ones all the time, but they need to be validated as relevant and accurate by other studies before they are widely adopted.
Unfortunately questionnaires might be only thing sometimes. My message is that, we should be more sceptical about them