Monday, September 16, 2013

The Bad Arthritic Triad - BAT - the biconcave glenoid and its management

Current concepts in the surgical management of primary glenohumeral arthritis with a biconcave glenoid

These authors reviewed some of the strategies that have been used for managing what we call the Bad Arthritic Triad (BAT) of the arthritic shoulder: biconcavity, retroversion, and posterior subluxation of the humerus on the glenoid.

In the normal shoulder (shown below) the load from the humeral head is evenly distributed across the glenoid.
In the bad arthritic triad, the glenoid is posteriorly eroded so that humeral head lies posteriorly displaced in a pathologic posterior concavity (see below)
In this situation, humeral hemiathroplasty alone does not manage the glenoid pathology
Anatomic total shoulder arthroplasty has been associated with higher failure rates in shoulders with the BAT because of rocking horse loosening. Posterior bone grafting in association with a total shoulder arthroplasty or total shoulder arthroplasty with posteriorly augmented glenoids have uncertain long term clinical outcomes. Some examples of glenoids with the BAT are shown below.

The authors discuss the use of a reverse total shoulder replacement with posteriorly augmented bone graft and an extra long central peg for the management of shoulders in older patients with retroversion is greater than 27° or posterior humeral head subluxation is greater than 80%.  Success of this procedure requires that the surgery provide sufficient stability of the fixation of the bone graft to allow for healing and that the bone graft incorporates and provides long term stability for the base plate. 

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