Once a person has shoulder subluxation is there a chance of ever reducing the gap?

Hi all, My long-term partner, who had a large left side ischeamic stroke in March 2014, wore a sling pretty much the whole day until about 14 months after the event. He did do plenty of assisted OT exercises (Community rehabilitation and at home), but unfortunately there was not much progress. That continued until the period following on from August 2015 when he had Botox injected in his right arm to immobilise the muscles that turned his arm and hand inwards and upwards towards his chest (due to spasticity of the muscles) and to then have the opportunity to strengthen the opposite muscles. We did intense training exercises at home and weekly OT session for about 5 months and now he can for instance: use his right arm and hand to mow the lawns and change the catcher by himself, play pool and use his right arm in a supporting bilateral role when doing something with his left arm and hand. Since then he has been training his right arm at the gym by using arm machines that strengthen the outward going arm muscles as well as his right shoulder, which has certainly improved his control and ability to lift and move his right arm at will. Thankfully, he has never experienced severe or continues pain in his right shoulder, besides a little discomfort early on in his recovery. I am just wondering though; once a person has shoulder subluxation is there any way of ever reducing the gap? Thank you kindly in advance for your response