Saturday, March 19, 2016

Glenoid retroversion in total shoulder arthroplasty - changing version with a metal wedge

Total shoulder arthroplasty using trabecular metal augments to address glenoid retroversion: the preliminary result of 10 patients with minimum 2-year follow-up.

These authors report on 10 ten patients (4 women and 6 men; aged 60 to 79 years) with Walch grade B2 or C glenoids that had a trabecular metal glenoid augment inserted between the glenoid bone and the glenoid polyethylene component (augment shown in green below).

Preoperative imaging for these patients indicated a retroversion >15 degrees. Either a 15° or 30° wedge to correct this glenoid retroversion before the glenoid component was cemented. 

At followup, all patients were satisfied, and all scores were improved. There were no complications and no hardware failures or displacement. All glenoid components were implanted to within 10° of neutral glenoid version. Radiographs at 24 months show good incorporation of the TM augment and the glenoid component.

The authors state that these wedge augments have the advantage of immediate secure fixation, no tendency to collapse, and the ability to correct retroversion of 25° or more.

Comment: As pointed out in a prior post, there is confusion when the term 'subluxation' is used to refer to the position of the humeral head in relation to the plane of the scapula rather that with respect to the glenoid. The example below shows that while the humeral head is posterior to the plane of the scapula, there is no glenohumeral subluxation (i.e. the humeral head is centered on the glenoid concavity).

These authors kindly included the preoperative images for the cases. It is interesting to note that few, if any, of these shoulders show preoperative posterior glenohumeral subluxation. Postoperatively in some cases there is substantial anterior displacement of the humeral prosthesis in relation to the scapula.

In our practice of ream and run and total shoulder arthroplasty, we emphasize centering of the prosthetic humeral head on the glenoid, but not 'correction' of glenoid retroversion or posterior positioning of the humeral head with respect to the plane of the scapula; our approach is shown in this post.


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