What exactly is the ACR...
Well, as with all BPI surgeries you have to find out specifically what each surgeon means, as there are different "versions" of even the ACR (which stands for Anterior Capsule Release). The basics are the same, that the anterior joint capsule is released in some fashion, but after that you really need to ask for details from the surgeon.
The form I am familiar with is done by Drs. Pearl/Edgerton (Kaiser, Los Angeles), Waters (Boston Children's) and Kozin (Shriners, Philadelphia). They all do the surgery arthroscopically. The anterior capsular ligaments is usually thickened, and are partially released allowing the ball of the humerus to sit properly in the joint. Some portion of the subscapularis tendon (usually upper working downward) is released near its insertion point inside the joint capsule. The only difference that I am aware of between these surgeons is that Dr. Waters does not do the ACR by itself (as of 2005 at least; I'm not sure if he's changed his mind or not on this), but always in conjunction with tendon transfers. Pearl/Edgerton/Kozin will do just the ACR in younger children, and the combined surgery in older children.
It is possible to do this surgery through an open incision but in order to access the capsule from the outside the pec major tendon and the conjoined tendons of lat and teres major muscles need to be released. The subscapularis tendon cannot be approached in the same way as the arthroscopic form of the surgery, so the subscapularis, if released, must be released either in the muscle body or from its origin on the scapula (there is something known as the "subscapularis slide" where the subscapularis is basically completely lifted off the scapula, shifted towards the shoulder, and tacked back down again. This is a major open procedure). And the glenohumeral ligaments are released differently (from the outside rather than the inside) if at all. Some surgeons call releasing the pec major tendon, which is technically outside the joint capsule, a "capsule release". So you see it can get very confusing!
I've only seen one published paper tracking glenoid improvement after "open reduction and tendon lengthening" ("Changing glenoid version after open reduction of shoulders in children with obstetric brachial plexus palsy"; J Pediatr Orthop. 2003 Jan-Feb;23(1):109-13; Hui JH, Torode IP; they are in Australia and the oldest patient was 7 years old at surgery). Their pre- and post-op pictures of the shoulder joint look very similar to what is seen after the arthroscopic version of the procedure, ie they saw real improvement and normalization of the joint geometry. Unfortunately, they are extremely vague about what exactly was done during the surgery, so it is very difficult to judge if their method was more or less similar to the version done arthroscopically. Neither author has published any other paper on BPI since this paper (2003).
In selecting a doctor to perform any version of this surgery, I would want to see real data results from their specific technique if it differs at all from what is already out there with an established track record. Ask who he/she has trained with and what the results have been with the specific techniques he/she uses. This is no longer a "novel" surgery. There is a lot of experience out there, you just might have to look around some.
Kate