Hi, thanks for writing to HCM.
Generally, bones in elderly persons are osteoporotic and the implants may fail in certain situations when they lack good hold in the native bone.
If you are not an elderly person, the above statement will not hold true. And there could be some other reason for loosening of the screws. Bone densitometry
is routinely not advisable before surgery as simple Xrays will generally show up the "Cortical" density of the bone through which the screws go inside.
If the implants are loose and not holding the bone, there is no good reason to retain them inside.