UW Shoulder and Elbow Academy: Shoulder joint replacement arthroplasty

The Kaiser Permanente Shoulder Arthroplasty Registry

Results from 6,336 primary shoulder arthroplasties

These authors analyzed 6336 shoulder arthroplasties entered into the Kaiser Permanente registry between January 2005 and June 2013. Median follow-up time for all primaries was 3.3 years; 461 cases were lost to follow-up by ending of health plan membership. Primary cases were predominantly female (56%) and white (81%), with an average age of 70 years. The most common reason for surgery was osteoarthritis in 60% of cases, followed by acute fracture (17%) and rotator cuff tear arthropathy (15%). In elective shoulder arthroplasty procedures, 200 all-cause revisions (4%) were reported, with glenoid wear being the most common reason.

Revisions were defined as any procedure after the registered index arthroplasty involving the addition, removal or replacement of at least 1 implanted component, so that soft tissue procedures would not be included.

Much of the story can be told by the numbers:

Comment: This is a most impressive overview of a large case series with a very low rate of cases lost to followup.

In interpreting these data it is important to understand that this is NOT a pure comparison of procedures, rather it is a comparison of surgeons electing to perform certain procedures on certain patients with certain diagnoses. We must wonder why surgeons chose to do 818 hemiarthroplasties and 130 resurfacings on patients with osteoarthritis - was it because they were not comfortable with their ability to do a total shoulder in these cases, because the patient did not want a glenoid, or because the surgeon thought the patient had involvement of the humeral side of the joint only (a rarity in glenohumeral arthritis). In any event, we must conclude that there was something different about these cases from those receiving total shoulder arthroplasty. This may explain why there was such a high revision rate for "glenoid wear" following hemiarthroplasty or resurfacing (27% of all revisions). Among elective hemiarthroplasties, the revision rate was 6% with glenoid wear as the reason for revision in 52% of cases, while the revision rate following TSA in particular was only 2%. It is of note that resurfacing arthroplasties had by far the highest revision rate.

So...these investigators have a wonderful opportunity to explore the "4P" factors associated with the need for revision: (1) the problem (diagnosis, the preoperative pathoanatomy of the shoulder), (2) the physician (surgeon identity, training, age), (3) the patient (age, gender of the patient, co-morbidities), and (4) the prosthesis used. In addition, as the authors were careful to point out that implant survival alone fails to capture patients with under performing shoulder arthroplasties who simply decline revision surgery. Thus it is possible that older individuals would be less likely to elect revision even if the outcome of their surgery was unsatisfactory.

Be sure to click on this link to the Shoulder Arthritis Book.