Tuesday, November 17, 2015

Short stem humeral prosthesis: the risk of stress shielding. Is shorter better?

Radiologic bone adaptations on a  short-stem shoulder prosthesis.

These authors evaluated 52 patients with uncemented short-stem shoulder arthroplasties at a mean age of 71.6 years with a minimum clinical and radiologic follow-up of 2 years.

Major bone changes were present in 27 patients (51.9%). Cortical thinning and osteopenia in the medial cortex (82.7%) and spot welds in the lateral cortex (78.6%) were the most frequently occurring bone adaptations. Patients with major bone changes had significantly higher metaphyseal  and diaphyseal filling ratio at 2-year follow-up than patients with milder bone changes.

The two films below the bone appearance  immediately after operation (left) and at 26-month follow-up, showing cortical thinning and osteopenia (right).

Comment: While there is interest among some surgeons in such a short stemmed prostheses, the advantages of such a humeral component are unclear. We have previously pointed out the problems of "Shorty" (see this link). As pointed out in this paper, the short stemmed prosthesis depends for fixation on cortical contact which, of necessity, gives rise to stress shielding. Furthermore, a short stemmed prosthesis is more difficult to align with the shaft as shown by cases like this one:

In our hands the humeral side of the glenohumeral arthroplasty is solved by an impaction grafted non-ingrowth stem of standard length (see this link and this link), which minimizes cortical contact, distributes the load along the entire area of the prosthesis, enables proper alignment, avoids tip incarceration, enables full seating, and facilitates removal should that become necessary.


Check out the new Shoulder Arthritis Book - click here.

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and runreverse total shoulderCTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'