Wear and Damage in Retrieved Humeral Inlays of Reverse Total Shoulder
Arthroplasty – Where, How Much and Why?
These authors sought to quantify the linear and volumetric wear in reverse total shoulder arthroplasties (RTSA), and to qualitatively assess the PE damage modes to describe the material degradation in 39 retrieved humeral PE inlays from failed of RTSAs.
Damage on the rim of the humeral PE inlays was more frequent and severe than on the articulation surface. Irrespective of the damage mode, the inferior rim zone sustained the greatest amount of wear damage followed by the posterior zone.
Burnishing, scratching, pitting and embedded particles are most likely to occur in the articular surface area, whereas surface deformation, abrasion, delamination and gross material degradation are predominantly present in the inferior and posterior rim zones.
The retrieved inlays exhibited a mean volumetric wear rate of 296.9 cubic mm/year.
Components from shoulders with scapular notching showed a five-fold increase in polyethylene wear rate in comparison to those from non-notched shoulders.
Comment: Much attention has been directed at measuring the amount of scapular bone lost from notching.
When the poly cup is worn, polyethylene debris can cause immune cell activation, which results in inflammation in the periprosthetic tissues. In turn, this inflammation may initiate joint pain, stiffness and periprothetic osteolysis that can lead to loosening of the implant (see this link).
The best "treatment" for notching is "prevention" by assuring that there is plenty of clearance between the medial aspected of the humeral poly and the lateral aspect of the scapular neck.
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