Thursday, July 2, 2015

Shoulder arthroplasty - what advantage does a stemless humeral prosthesis offer; is less more?

Midterm results of stemless shoulder arthroplasty: a prospective study.

These authors evaluated 78 patients having shoulder arthroplasty using a stemless humeral head implant with a minimum follow-up of 5 years. 39 patients had a hemiarthroplasty,and 39 had total shoulder arthroplasty.

The overall complication rate was 12.8%, with an overall revision rate of 9%. None of the stemless implants were revised for loosening. Rotator cuff tears occurred in 6 patients (7.7%). Revision surgery to reverse shoulder arthroplasty was performed in 3 patients. Loosening of a cementless metal backed glenoid component was observed in 2 patients (8.3%). Both patients represented a type B glenoid according to the Walch classification. One patient required secondary implantation of a glenoid component due to secondary glenoid wear. One late infection was treated by a 2-stage revision. Another patient fell on the shoulder leading to a proximal humeral fracture.  Some cases showed proximal humeral bone loss from stress shielding.

Comment: The advantages of stemless humeral fixation include suggested by the authors include 
(a)  "anatomic reconstruction of the center of rotation of the humeral head independent
from the shaft axis and to avoid an additional osteotomy of the greater tuberosity". 
(b) "a standard approach to the glenoid for glenoid resurfacing (compared with
surface replacement of the humeral head)", 
(c) "avoidance of stress shielding at the lateral humeral cortex", 
(d) "preservation of an intact humeral shaft for revision arthroplasty",
(e) "theoretic risk reduction of periprosthetic humeral shaft fractures".
(f) "preservation of an intact humeral shaft for later revision to a stemmed humeral head replacement"
(g) no change in the "metaphyseal geometry of the humerus"

They suggest that this prosthesis is not indicated for rheumatoid arthritis, osteoporosis,
and the presence of large subchondral cysts.

The results presented here are comparable to many other series of shoulder arthroplasty. The article does not comment on the ease or difficulty of removing this prosthesis should revision become necessary.

Our approach to the humeral side of shoulder arthroplasty continues to be the use of an impaction grafted stemmed humeral component. This approach optimizes glenoid exposure with minimal sacrifice of humeral bone stock, minimal risk of stress shielding, minimal risk of fracture, no alteration of humeral metaphyseal or diaphyseal geometry, versatility in the selection of humeral head prostheses to optimize both mobility and stability, and the ability to use the same approach and implants for essentially all anatomic arthroplasties.


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