Anatomic total shoulder for the B2 glenoid

In performing an anatomic total shoulder arthroplasty for a B2 glenoid (that is, one with retroversion and a biconcavity)

the use of 3D CT based planning software often suggests the use of a posteriorly augmented glenoid component to correct glenoid retroversion. As suggested by the figure below, this approach may require removal of a substantial amount of dense glenoid bone that could otherwise be of value in supporting the glenoid component

The combination of loss of dense supporting bone and an increased rocking moment

can subject the augmented glenoid component to an increased risk of rocking horse loosening (see Total shoulder arthroplasty complicated by rocking horse glenoid component loosening).

An alternative is a bone conserving reaming approach that minimizes bone removal by accepting glenoid retroversion (see glenoid version: acceptors and correctors). 

The figure below compares the amount of bone removed in each of the two approaches: augmented component on the left and standard glenoid with out correcting glenoid version on the right.

If there is excessive posterior translation of the humeral head on the retroverted glenoid, the joint can usually be stabilized by an anteriorly eccentric humeral head with or without rotator interval plication.

as shown in the case below

noting the amount of glenoid bone preserved, the anterior penetration of the central glenoid peg, and the anteriorly eccentric humeral head component.

The effectiveness of this approach using standard (non-augmented) glenoid components is presented in Anatomic Total Shoulder Arthroplasty with All-Polyethylene Glenoid Component for Primary Osteoarthritis with Glenoid Deficiencies

While the glenoid version was not substantially changed from preop to post op

the humeral centering on the glenoid was vastly improved.

For the B2 glenoids, the average patient age was 68 years, 45% were male, the minimum followup was 2 years. 

Glenoid retroversion averaged 21 degrees preoperatively (range 2 to 36 degrees) and 19 degrees postoperatively (range 8 degrees anteversion to 36 degrees of retroversion).

Posterior decentering averaged 14% preoperatively and only 1% postoperatively

Anteriorly eccentric humeral head components were used in 12%

Preoperative SST averaged 3.0; postoperative SST averaged 9.8 for a 76% maximal possible improvement.

There were no surgical revisions among the 83 type B2 glenoids treated with this method. 

83% had bone ingrowth within the flanges of the central peg.

Here is an example:

A man in his late 60s with a B2 glenoid treated with conservative reaming, acceptance of glenoid retroversion, and an anteriorly eccentric humeral component.

His function at two years after surgery is shown here.

    

As another example, here's a 10 year followup on an active man having an anatomic total shoulder when he was in his mid fifties.

Here are his preoperative x-rays showing type B2 pathoanatomy.

Here are his 10 year postoperative films showing secure fixation of a standard polyethylene genoid component inserted after conservative glenoid reaming without attempting to change glenoid retroversion. Note the central peg penetrating the anterior cortex of the glenoid vault (as also seen in the case above), as well as the impaction grafted smooth standard length humeral stem with no evidence of adaptive changes of the humeral bone. He reports he can perform all 12 of the Simple Shoulder Test functions.

Comment: Glenoid bone conserving reaming, accepting glenoid retroversion and using a standard glenoid component can provide excellent clinical outcomes in patients with a type B2 glenoid component. It would be of interest to compare - in comparable patients - the cost-effectiveness of other methods, such as the use of augmented glenoid components or reverse total shoulder to this approach.

Comments welcome at shoulderarthritis@uw.edu

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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).