Hi.
Do you experience any other symptoms that would point to the shoulder injury as the cause for your current symptoms? Although your previous injury could present with the twitching symptoms, the duration between the injury and the symptoms make the relationship less likely, although nothing can be certain at this point. Twitching can also occur in other conditions such as diabetes, stress, anxiety, and some endocrine disorders.
If you are concerned about this, you should consult a physician to evaluate your condition.
Have you looked at symptoms of Early Onset Parkinsons?