Once the shoulder is significantly subluxed is there any way in which this can be rectified?

Hi all, My long term partner had a large ischaemic stroke (left parietal-temporal infarct) in March 2014. He wore a sling till March 2015. Unfortunately, whilst the occupational therapists did work on his right arm, hand and shoulder there was not much improvement in functionality. Until, August 2015 when he had Botox injections and we did intensive exercises to train the opposite muscles for about 5 months. Since then he can for instance: use his right arm and hand to mow the lawns and change the catcher by himself, play pool and can often use his right arm in a supporting bilateral role when doing something with his left arm and hand. For the last 12 months he has also been training his right arm and shoulder muscles at the gym with outwards going exercises and his arm has got a lot more strength. He has significant shoulder subluxation, but fortunately enough he has never experienced any more than a little niggle soon after his stroke and never severe and/or ongoing pain. I am wondering, since there is wide gap of over 2cm, if there are any methods to be able to close this to as it was before his stroke? Thank you kindly in advance for your response, Indygo