Glenohumeral arthritis comes in a wide variety of forms. While these are often described in terms of glenoid version, inclination, biconcavity, and bone loss, these terms only partially capture the complexity of each arthritic shoulder as exemplified by this 3D reconstruction
To further complicate things, changes in glenoid pathoanatomy may be associated with other important features of the shoulder. For example, superior inclination can be associated with rotator cuff dysfunction (see for example link, link, link) which may have a profound effect on anatomic glenoid component durability and post arthroplasty shoulder function.
The authors of Mid-term Radiographic Outcomes of Anatomic Total Shoulder Arthroplasty in Biplanar Glenoid Deformities sought to separate the effects of combined retroversion ≥ 20 degrees + inclination ≥ 10 degrees in 28 shoulders from a matched set of 28 shoulders with retroversion ≥ 20 degrees alone. All shoulders were managed with "hi side reaming" and a standard glenoid component.
The goal at surgery was to achieve 80% glenoid component seating and final retroversion within 10-15 degrees of neutral with no specific attempts to correct glenoid inclination.
Using preoperative CT-based 3D planning software, they found that the biplanar shoulders had greater inclination (14.5 ̊ versus 5.3̊) and greater retroversion (30.0 ̊ versus 25.6 ̊)
Using postoperative plain radiographs, they found that biplanar shoulders had greater implant superior inclination (5.9 ̊ vs. 3.0 ̊).
In that 2 different imaging methods were used it is difficult to know if 14.5̊ vs 5.9 ̊ represents the actual amount of change in inclination.
The initial postoperative posterior decentering was 3.5% vs 1.8%.
On final follow-up plain radiographs, biplanar shoulders had higher Lazarus radiolucent scores (2.4 vs. 1.6) and higher proportion with glenoid radiolucency (68% vs. 39%).
Preoperative biplanar deformity was the only significant predictor of glenoiod radiolucency (odds ratio 3.3).
Posterior decentering increased for both groups to 7.6% vs 4.0%.
Comment: This is an interesting paper calling attention to the variability in preoperative glenohumeral arthritic pathoanatomy.
In considering the possible contributing factors to the increased rate of glenoid lucencies in the biplanar shoulders one could consider (a) concomitant cuff dysfunction in the shoulders with increased inclination (see above), (b) the increased rate of posterior decentering, (c) the greater postoperative inclination risking rocking horse loosening from superiorly directed loading of the glenoid component, and (d) the increased amount of bone removal necessary to achieve 80% seating in the superiorly inclined shoulders.
Additional larger studies will help sort out the relative importance of these variables. It would be desirable if these future studies used the same method of measuring glenoid inclination, glenoid version, and humeral head centering preoperatively and postoperatively so that one could determine the amount of change in these two important variables.
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).
