As demonstrated in Prearthroplasty glenohumeral pathoanatomy and its relationship to patient’s sex, age, diagnosis, and self-assessed shoulder comfort and function, the defining feature of B1 and B2 glenoids is posterior decentering of the humeral head on the face of the glenoid.

In the B1 glenoid there is posterior decentering with minimal posterior bone loss and without a biconcavity.

Whereas in the B2 glenoid there is posterior decentering with posterior bone loss and a biconcave glenoid surface.

Male patients typically have a higher frequency of B2 glenoids and a lower frequency of A2 glenoids.

Interestingly, shoulders with glenoid types B1 and B2 did not have worse preoperative self-assessed shoulder comfort and function than those with types A1 and A2 glenoids.

While posteriorly augmented glenoid components have been designed help manage the type B glenoids

it is unclear whether these more complex components are associated with superior results in comparison to those obtained with a standard glenoid component.

One way of approaching this question is to compare the clinical results of total shoulders using a standard non-augmented glenoid component for shoulders with type B glenoids to the clinical results of total shoulders using a standard non-augmented glenoid component for shoulders with type A glenoids.

If the results for a standard component with type B glenoids are not inferior to those for a standard component with type A glenoids, it may be worthwhile re-examining the indications for an augmented glenoid component.

Here are a few publications that bear on this question:

One and two-year clinical outcomes for a polyethylene glenoid with a fluted peg: one thousand two hundred seventy individual patients from eleven centers the authors found that the clinical outcomes with a standard, non-augmented glenoid component in shoulders with B glenoids were not inferior to those with type A glenoids,

In Anatomic Total Shoulder Arthroplasty with All-Polyethylene Glenoid Component for Primary Osteoarthritis with Glenoid Deficiencies the clinical and radiographic outcomes for type B glenoids were not inferior to those for type A glenoids.

The rate of bone integration into the central peg for type-B2 glenoids (83%) was not inferior to the rates of bone integration into the central peg for other glenoid types.

In Does Postoperative Glenoid Retroversion Affect the 2-Year Clinical and Radiographic Outcomes for Total Shoulder Arthroplasty? the clinical outcomes for 39 type B glenoids using a standard glenoid component were not inferior to those for the 32 type A glenoids treated with the same component.

Short-term clinical and radiographic outcomes of a hybrid all-polyethylene glenoid based on preoperative glenoid morphology; in this study in which a non-augmented glenoid was used, the clinical and radiographic outcomes for the B1 and B2 glenoids were not inferior to those for type A1 and A2 glenoids.

Comment: It is possible that long term clinical and radiographic studies may indicate which types of shoulders may benefit from the more complex augmented glenoid component in comparison to a standard glenoid component. However, at present, appropriate use criteria for this type of implant are lacking.

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