Wednesday, April 11, 2018

Is there evidence that stemless shoulder arthroplasty is better or safer?

Sidus Stem-Free Shoulder System for primary osteoarthritis: short-term results of a multicenter study

These authors reviewed their experience with 105 shoulders treated with the Sidus Stem-Free Shoulder System at 9 centers in Europe at 2 or more years after surgery.

The main indication was primary osteoarthritis (80.1%). Total shoulder arthroplasty was performed in 73 cases and hemiarthroplasty in 32. Clinical scores were improved.  Radiologically, neither migration nor loosening was found. However, radiolucent lines of 2 mm or greater could be detected around the glenoid in 2 cases, but none of them have had clinical relevance yet. The overall complication rate was 6.7%, and the revision rate was 0%.

The authors concluded that patients receiving the Sidus Stem-Free Shoulder System achieve good clinical and radiologic short term results that are comparable with the results of other stem-free shoulder implants.

Comment: The motivation for pursuing 'stemless' humeral components apparently comes from concern about "stem-related complications", including intraoperative humeral fracture, postoperative periprosthetic humeral fracture, proximal humeral bone loss  due to stress shielding, humeral stem loosening, osteolysis, and difficulty in explanting a well-fixed stem in the case of revision.

The complication rate with this stemless implant was 6.7% including one humeral fracture.  There was a 9.5% rate of radiolucent lines around the glenoid components. In their review of the literature on stemless implants, these authors point out revision rates for stemless shoulder arthroplasties ranging from 2 to 11% and relatively high rates of glenoid radiolucent lines.

An important perspective can be gained by comparing theses complication and revision rates to those from a recent review of complications for shoulder arthroplasty (see this link) which found that humeral complications in shoulder arthroplasty were relatively uncommon: " Humeral component failure occurred in 47 shoulders, for a prevalence of 0.2%. Stem loosening appeared to be dependent on the glenoid implant status in TSA, rather than the mode of humeral stem fixation."
"Periprosthetic humeral and glenoid fractures demonstrated a prevalence of 1.0%"

The data in this paper do not provide evidence that a stemless humeral implant is superior to an impaction grafted thin stem (see this link), which avoids each of the "stem-related complications" listed above using a conventional implant that is applicable to most shoulders without limitations related to bone quality:

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