Sunday, December 14, 2014

Total shoulder outcomes and value for arthritis with concentrically and eccentrically eroded glenoids

The effects of glenoid wear patterns on patients with osteoarthritis in total shoulder arthroplasty: an assessment of outcomes and value

These authors conducted a comparative cohort study of 309 patients with a total of 344 TSA procedures for primary glenohumeral osteoarthritis. 196 had concentric wear by CT scan and 148 had eccentric wear.

Notably in performing the arthroplasty, these authors did not try to make a major change in glenoid version, rather they only reamed until a concentric surface was obtained. In concentric cases, increased native retroversion of the glenoid was left uncorrected. In reaming the eccentric glenoids, a compromise in version was made between the pathological and the normal version. Anterior highside reaming was minimized in an attempt to preserve as much subchondral bone as possible. Bone graft was not used in cases of eccentric biconcavity.

At an average of over 4 years of followup, there was no significant difference in American Shoulder and Elbow Surgeons (ASES) score in the concentric group (80.8 ± 20.8) compared with the eccentric group (77.6 ± 21.2). Range of motion and final visual analog scale for pain score were similar between the 2 groups. 

However, radiographic evidence of gross glenoid loosening was significantly lower in the concentric group [11 of 195 (5.6%)] compared with the eccentric group [18 of 147 (12.2%)] 

The average total hospital costs for a primary total shoulder (with either a concentric or eccentric glenoid) was $15,900.

A value assessment also showed no significant difference between the concentric and eccentric groups [concentric 26.1 vs. eccentric 25.5 (ΔASES score/$10,000 hospital cost) . The cost included preoperative, intraoperative, and postoperative hospital costs associated with the admission, but apparently not the surgeon's fee.

Revision rates were similar between the concentric group [4 of 195 (2.0%)] and the eccentric group [3 of 147 (2.0%)]. The average total hospital costs for a revision were $37,449.

Comment: This is an interesting study that points to the difficulties in managing the posteriorly eroded glenoid.

While the discussion includes the statement that for eccentric glenoids, "... greater economic value could be gained by investing in advanced surgical instrumentation (i.e., patient specific) and new implant options (i.e., augmented glenoids, reverse shoulder arthroplasty)." - it remains to be seen if any of these options yield superior outcomes for the eccentrically eroded glenoid.

Finally, the terms 'concentric' and 'eccentric' do not fully describe the pathoanatomy. For example,  the authors state that "concentric glenoid wear demonstrates a symmetric distribution of bone sclerosis, cyst formation, and bone erosion. It is considered uniconcave only and is independent of glenoid version and glenohumeral subluxation measurements, as shoulders with increased native retroversion or subluxation are still considered concentric as long as there are no signs of asymmetric wear." Thus it would appear that the highly abnormal glenoid shown on the image below would reconsidered 'concentric'.



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