AC arthritis may not be secendory to sternoclavicular instability.
Although AC arthritis definitely affect shoulder movements terminally.
Abduction beyond 110 and adduction beyond 40 with rotations are deifnately painful and reduced.
Next Steps
You will be benefitted by arthoroscopic AC debridement and decompression .
Disclaimer : The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding your medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.