Sunday, July 16, 2017

B2 glenoid, are special implants necessary?

The B2 glenoid is a common form of glenohumeral pathoanatomy characterized by glenoid retroversion, glenoid surface biconcavity and posterior humeral decentering with respect to the glenoid face. 

These pathologies are not seen on the AP view of the right shoulder of this 76 year old patient.

However, the cardinal pathological features are quite evident on the 'truth' view - an axillary view taken with the arm elevated in the plane of the scapula to a functional position. This position is not possible using CT scans or MRI, thus we do not use these imaging modalities in our preoperative or postoperative assessment.

We manage shoulders with this B2 pathology using a standard all-polyethylene glenoid component inserted with conservative, bone preserving reaming and without specific attempt to alter glenoid version (see this post: How important is correcting glenoid version anyway?).

Here are the one year post operative films:

The post operative 'truth' view shows that an anteriorly eccentric humeral head component was used to center the humeral articular surface on the face of the glenoid. It also shows that the placement of the glenoid component in almost 40 degrees of retroversion is not associated with posterior decentering (note that the metal marker in the central glenoid peg points to the center of the humeral head).

Comment: We recognize that many surgeons would have approached this case differently, using perhaps a posterior bone graft, reaming the anterior 'high side', a posteriorly augmented glenoid component or a reverse total shoulder. We are drawn to the approach used here because it provides a stable glenohumeral joint while preserving the maximal amount of bone, leaving the door open for subsequent procedures should they become necessary.

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