How often should I get therapeutic ultrasound treatments for thick scar tissue resulting from pseudo bursa? (Photo)

Unfortunately you have had the complications associated with seromas that even in the best PSs hands can have less than favorable outcomes. Your PS is obviously trying to help you achieve the best result after the complication and should be lauded. While ultrasound for scar tissue have been shown to be effective it does take multiple treatments possibly over a year. Deep tissue massage that you can do can also help reform scar tissue and soften the contour irregularities which would be much less expensive. Overall things usually will continue to improve over the next 2 years. Best of Luck

The ultrasound is almost certainly harmless, but almost as certainly ineffective for this indication. If there is a persistent pseudobursa, excision is the reliable way to be rid of it, but it is not without its own problems since its removal can leave a contour defect. My suggestion would be to get another opinion from another plastic surgeon. All the best. 

Pseudo-bursa formation can be a side effect of seromas especially if they do not resolve quickly.  Scar tissue begins to form around the fluid.  The fluid can disappear, but the scar tissue doesn't.  Sclerosing agents and abrading the smooth surfaces of the capsule to get it to stick together have resulted in uneven success as seen by the "shelving" you have.  Ultrasound will not help.  The scar tissue is not going to go away or smooth out unless it is excised.  I know you don't want another surgery, but it may be the best answer and one your surgeon may have suggested already.  If you want another opinion see another board certified plastic surgeon who has the training and knowledge to advise you on this.