Hi,
The previous response was very comprehensive, and covers the usual approach to this type of problem over various age groups.
The significant parts of your specific problem are: Parkinsons' in an elderly anxious person 6 months post shoulder trauma, resulting in lack of movement.
If scans,MRI and ultrasound, have not been undertaken, it would be useful to have them undertaken, but not 100% required.
Diagnosis
I suspect that your patient has anadhesive capsulitis, compounded by a fear reaction of muscle guarding, plus the overlay of a Parkinsons' stiff Tx.
Treatment
If the shoulder structures are stable, which I assume they are, then your best bet would be to have her undertake a glenohumeral hydrodilatation of the adhered capsule. Ensure that this is done by an experienced person. My preference is the non guided technique, provided it is done by a person with good surface anatomy knowledge and experience. My experience with radiologists is mixed, regarding outcome.
Immediately post procedure, the patient should have the arm moved through available range, and continue pendular and self assisted range of movement to avoid readherence of the capsule.
Have the person performing the technique report back to you regarding the feeling of capsule release as felt through the syringe, and at what fluid volume this occurred. eg release at 15 & 25 millilitres of fluid.
Repeat injection can occur at 8-12 weeks, if required.
A small amount of local anaesthetic and cortisone (eg Celestone) is used in conjunction with the saline (up to 40 ml saline).
Check with treating specialists regarding medication interactions before proceeeding.
Hope the above is helpful.
MrPhysio+