These authors evaluated clinical and radiographic outcomes at a minimum 5-year followup in 45 shoulders that underwent total shoulder arthroplasty (TSA) using a system with a central porous titanium post to augment the cemented peripheral pegs as shown below
The mean American Shoulder and Elbow Surgeons score improved from 40.4 to 83.7 (P < .0001). Radiographs showed glenoid component radiolucency in 29 of 45 shoulders. Radiolucencies were confined to the area under the glenoid faceplate in 6 and were around the central post in 13. Nine TSAs (20%) demonstrated 2 or more columns of involvement but were not judged to be at-risk. One implant (2.2%) had glenoid component failure and was revised to a hemiarthroplasty.
The authors point out that previous hybrid glenoid designs have manifested problems with fatigue fracture of the titanium (Results of total shoulder arthroplasty with a monoblock porous tantalum glenoid component: a prospective minimum 2-year follow-up study).
Comment: There are two potential issues with hybrid glenoid components. One is the risk of fatigue fracture - the breakage of the metal from repeated rocking forces applied to the glenoid face while the titanium peg or pegs are securely fixed to the bone of the glenoid. The second is the risk of stress shielding that arises because the titanium is stiffer than bone and polyethylene. Just as in the case of stress shielding in humeral component fixation, when the metal is stiffer than the bone in which it is inserted, the unloaded bone tends to lose mineral. Loss of bone beneath the polyethylene face of the component can give rise to increased rocking of the component with increased risk of fatigue fracture of the metal.
The reader may wish to look at these links regarding Young's Modulus for bone, titanium, and polyethylene. Correlation between Young's Modulus and Porosity in Porous Materials and Young's Modulus for Some Common Materials and Microstructure and Mechanical Properties of Porous Titanium Based on Controlling Young’s Modulus
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The reader may also be interested in these posts:
Consultation for those who live a distance away from Seattle.
Click here to see the new Shoulder Arthritis Book.
Click here to see the new Rotator Cuff Book
Information about shoulder exercises can be found at this link.
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 run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'
See from which cities our patients come.
See the countries from which our readers come on this post.
