Using a chiropractor for a Nexus

Has anyone had any success using a chiropractor for a Nexus letter? I have been going to the same chiropractor for 20 years for neck pain that occurs when my surgically repaired shoulder flares up. (My shoulder is service connected) He agrees that the neck pain is a result of poor shoulder mechanics. I had an open reconstruction while in service.

I initially submitted for cervical strain secondary to right shoulder surgery with only a medical journal article. It was the first time I had ever submitted a claim and I thought the c and p exam would link them. Oops. If I get a diagnosis of a cervical strain from a Dr and have a history of treatment from my chiropractor with a nexus letter from him … Any input from this group would be appreciated.