Tuesday, June 17, 2014

Massive press fit humeral stems and proximal humeral bone loss from stress shielding

Patterns of proximal humeral bone resorption after total shoulder arthroplasty with an uncemented rectangular stem

These authors assessed the timing and location of cortical bone resorption after total shoulder arthroplasty with an uncemented rectangular stem and investigate its effect on shoulder function up to 5 years after implantation.

They evaluated 133 arthroplasties performed between June 2003 and September 2006.
Twenty-two patients (17%) showed full-thickness cortical bone resorption, 21 of whom were diagnosed with zone 2 resorption. The maximum craniocaudal distance of full resorption averaged 19.1 mm (range, 5.6-46.7 mm). The median distance progressed significantly from 9.6 mm to 13.8 mm between 6 and 12 months (P . .005). The risk of bone resorption was 3.1 times higher for posttraumatic OA patients than for those with primary OA. The occurrence of bone resorption increased significantly
with increasing stem diameters relative to the humeral diameter. 

Comment: The authors concluded that bone resorption is a "radiographic phenomenon without significant impairment of function or need for revision within 5 years after surgery" there can be no question that loss of humeral bone stock can be a problem with respect to risk of fracture, loosening and increased difficulty of revision. 

The desire to achieve cement less fixation of the humeral stem has led implant companies to develop porous surfaces, trabecular metal, and large stems (such has that shown below).

The difficulties associated with bone resorption with such a prosthesis can be envisioned on this film showing the absence of lateral cortical bone three years after prosthesis implantation. It would be difficult to remove this stem without fracturing the humerus.


To see the topics covered in this Blog, 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'

To see other similar posts, click on the label of interest below.