hi stanjupiter, I hope you and the family are well.
spinal cord stimulators are different to TENS in that they are surgically implanted devices similar to a pacemaker which stimulate the spinal cord via electrodes placed in or near the epidural space. There are other devices which function like permanent epidurals and deliver opiates or other drugs such as baclofen into the spinal fluid or the epidural space.
I imagine they don’t work well for RA as there are usually too many joints involved, often in both the arms (especially the hands) and legs. To cover the arms you would need to put the stimulator in the neck which would involve more risk than the lower back.
One key issue with many of these devices (and indeed with MSC’s) is that chronic pain results in psychological and neurological changes that reinforce pain behaviours. Thus any physical intervention should best be used in association with psychology/exercise etc to improve outcomes. I suspect that is why MSB has target patients with imaging proven disk degeneration (which makes up a reasonable proportion of patients), hopefully tightening the inclusion criteria to this specific subset of patients with chronic back pain will avoid diluting positive results with those who would not respond to any physical treatment at all.
and you are absolutely right about the lack of options for back pain - hence the foothold opioids managed to get in that market
(20min delay)