Hi there, do you really mean "contractures" or have you, by accident used the word to translate "contrazione" as in spasms, muscle contractions, hypertone muscles and so on? (contractures are not the same as contractions)
Does he always grind his teeth at night independant of sleeping position? (when on his back or side or prone)
Does he always sleep prone with the head to one side? This alone over many hours can account for problems in neck, shoulders and upper back.
Has he had a proper physio assessment of neck, shoulders and upper back, what was found? treatment if any so far? postural advice given for during waking and sleeping?
Grinding teeth can be due to stress. Neck symptoms can also have stress as factor.
I'd expect headaches and or triggerpoints in relevant muscles from grinding. Upper back seems a bit far away, but one has to assess the whole situation. I think you'll have to find out more and get a better picture of your friends problem.
regards JM