These authors sought to better understand the prevalent problem of rotator cuff failure after anatomic total shoulder arthroplasty. They evaluated contact pressures between the rotator cuff tendons and the humeral head prosthesis after anatomic total shoulder arthroplasty and compared the results with the tendon-contact pressures in the native shoulder in a cadaver model. Contact pressures were measured using pressure-sensitive film.
They found that both joint angle and shoulder joint replacement surgery had significant effects on the maximum contact pressure measured between the humeral head and all rotator cuff tendons except the teres minor.
The supraspinatus demonstrated a significantly larger peak tendon contact pressure after total shoulder arthroplasty at 45° of abduction relative to that in the native shoulder, while the subscapularis had a significantly larger maximum contact pressure at 10° of abduction.
Comment: In the discussion section of this paper the authors point out that metal-backed glenoid implants (such as that used in this study) have lower survival rates than cemented all-polyethylene components. Furthermore, this component materializes the humerus by over 10 mm relative to the native position. In the illustration below, the horizontal arrow indicates the lateralization of the tuberosity in comparison to the lateral acromial line (vertical arrow).
This increased offset can be even greater if the arthritic humerus is medialized before surgery (see below).
Stresses on the cuff tendons can be further increased if the humeral component is not fully seated (as is a risk in prosthesis with a tight fit in the canal, causing it to sit about the tuberosity - see arrow below).
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Stresses on the cuff tendons can be further increased if the humeral component is not fully seated (as is a risk in prosthesis with a tight fit in the canal, causing it to sit about the tuberosity - see arrow below).
There are a number of other factors that may contribute to cuff failure after a total shoulder:
(1) injury to the cuff insertion during the exposure or during the resection of the humeral head
(2) the resumption of passive and active loading of aged tendons that have been inactive for years prior to the arthroplasty
(3) Insertion of the glenoid component in a superiorly angulated position
(4) Non anatomic selection or positioning of the humeral prosthesis.
Any of these factors individually or in combination can put the cuff at risk after arthroplasty.
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You may be interested in some of our most visited web pages arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'
