@vdm, one of our long time members was successful in getting his neck curve back by doing exercises. He posted extensively about that in several posts on our forum. Here are two links to get you started, but if you search “military neck”, many posts come up that discuss it.
A helpful quote as well:
[quote=“vdm, post:18, topic:10052, full:true”]
My alleged line of thought is that styloid anomalies might have developed to prevent the head from bending down (“nodding”) too much at the occipital/C1 level, in case there is something wrong with the occipital muscles (Suboccipital triangle - Wikipedia ) and/or any other ligaments/muscles that are supposed to act as “stoppers”.
Straight neck (aka military neck, loss or neck lordosis, neck kyphosis, flat neck Military Neck: Causes, Symptoms, Treatment) might be result of many factors, including reversible ones (poor posture, weak muscles and so on).
What I’ve been also suspecting, that some physios/doctors don’t take into account that the straight neck perhaps indicates imbalance problems with muscles in the neck (some are too long, some are too short, some are too strong, some are too weak), and when they give exercises like “chin-tucks”, they ignore that the strongest muscles will likely take majority of the action in that movement, and just get stronger, while the weak muscles/stuck vertebrae will remain weak/stuck.
In my humble opinion, a good neck/spine physio/kinesitherapist might help to gently and slowly restore the neck curve over the time, which might move the styloids away from the C1. I wish I had a flexible skeleton model to show what I mean, but I guess you can imagine.