Well, if it works for you, why not, it's better for you than voltarol. But much depends what is meant by 'works' (have to leave that door closed for now).
Back pain can be caused by many things, often complex, but it certainly isn't caused by lack of copper bracelets!
In my work I see a lot of cases of back pain, and whilst many are stubborn, I have never had to resort to copper bracelets to make a difference.
I did see one lady who got much worse after wearing a magnetic vest.
Rationale for treatment is seldom one-to-one. Placing metal against the body, or especially IN the body, creates a galvanic effect, it turns us into a half-cell, two kinds of metal and we become a battery, with very unpredictable consequences.