Prisoner is a legal term for a person who is imprisoned. In section 1 of the Prison Security Act 1992, the word prisoner means any person for the time being in a prison as a result of any requirement imposed by a court or otherwise that he be detained in legal custody.
To qualify for insurance coverage under the medically necessary definition, one would have to practically be skeletally deformed...in essence, one would need a whole lot more than just braces for correction. Please read the link below to read what conditions qualify for medically necessary.
Regardless what rigid brace you need, your brace will be custom fit by an orthotist (a specialist who designs and fits braces). Ensuring that your brace fits you perfectly is so important. Also important is that you follow your doctor's specific instructions for the wear and care of your spinal brace.