Where should we put the glenoid component in shoulder arthroplasty?

Currently many surgeons find it interesting to use CT-based 3D software to help plan shoulder arthroplasty. The planning software program requires a defined target that specifies the desired values for six degrees of glenoid component freedom: version, inclination, rotation, superior-inferior position, anteroposterior-postion and medial-lateral position. The software then suggests the size and position of the glenoid component, as well as the amount of bone removal and the augments or bone graft that might be used to achieve the target position.

So the question becomes, how should the target for the glenoid be determined?

Premorbid Glenoid Anatomy Reconstruction from Contralateral Shoulders 3D-measurements: A CT scan analysis of 260 shoulders suggests that "Total shoulder arthroplasty (TSA) aims to reconstruct the premorbid anatomy of a pathologic shoulder". In the Introduction, it states that "It seems clear that the objective after anatomic TSA is to restore the preoperative anatomy of the patient". One notes that for most arthritic shoulders, premorbid anatomy and preoperative anatomy are not the same.

The paper goes on to suggest that one way to determine the premorbid anatomic of the glenoid is using a reconstruction of the CT of the contralateral shoulder. To support this concept they compared the 3D anatomy of the right and left shoulders of patients without shoulder pathology or injury. From this study they found that paired right and left scapulae were similar but not statistically symmetrical regarding glenoid version, inclination and width. Yet they concluded that "healthy contralateral shoulders can be a useful template in TSA preoperative planning."  One notes that most patients having shoulder arthroplasty on one side do not have a normal shoulder on the contralateral side for comparison.

Furthermore as explained in Glenoid version: acceptors and correctors, the clinical benefit to the patient of "correcting" glenoid version has get to be rigorously demonstrated. 

In the example below an arthritic shoulder in which the humeral head was nearly centered on the face of a retroverted glenoid was 3D planned to "correct" glenoid retroversion with posterior bone removal and insertion of a posteriorly augmented glenoid component.

Is this approach to reconstruction more effective and robust than the example below of a posteriorly decentered humeral head on a retroverted biconcave glenoid treated with a bone conserving standard glenoid component inserted with "accepting" the glenoid retroversion?

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Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this link).
How to x-ray the shoulder (see this link).
The ream and run procedure (see this link).
The total shoulder arthroplasty (see this link).
The cuff tear arthropathy arthroplasty (see this link).
The reverse total shoulder arthroplasty (see this link).
The smooth and move procedure for irreparable rotator cuff tears (see this link).
Shoulder rehabilitation exercises (see this link).