Tuesday, June 18, 2013

Reverse total shoulder - glenosphere fixation - scapular notching

The impact of scapular notching on reverse shoulder glenoid fixation.

These authors used a plastic composite scapula model to evaluate reverse shoulder glenoid baseplate fixation and the effect of scapular notching. They used acyclic test to simulate 55° of humeral abduction in the scapular plane as a 750-N axial load was applied to induce a variable shear and compressive load. Before and after cyclic loading, a displacement test was conducted to measure glenoid baseplate displacement.

They found that scapulae without a scapular notch, glenoid baseplate displacement did not exceed 150-μm - a suggested threshold for osseous integration. For the scapulae with a scapular notch, glenoid baseplate displacement exceeded 150 μm in 2 of the 7 samples before cyclic loading and in 3 of the 7 samples after cyclic loading. The average pre-cyclic glenoid baseplate displacement in the direction of the shear load was significantly greater in scapulae with a scapular notch than those without a scapular notch both before and after cyclic loading.

We've previously posted on a related study: Radiographic analysis of the effects of glenosphere position on scapular notching following reverse total shoulder arthroplasty

Comment: Glenoid loosening rates for reverse total shoulders have been reported to range between 0% and 12%. This complication is multifactorial, depending on component design, glenosphere placement, surgical technique, the degree of glenoid bone reaming, bone quality and the loads applied by the patient. Some designs, such as the one studied here, depend on bone ingrowth for fixation - thus the attention to the described 'threshold for osseous integration'. The problem with bone ingrowth is that one cannot be sure how long it takes before good fixation is achieved and, in each case, how long the shoulder should be protected from loading to assure that the micromotion threshold is not exceeded. Other designs, such as the one shown here provide immediate fixation without need to wait for bone ingrowth. The clinical environment surrounding each patient's reverse total shoulder is unique and this variability cannot be simulated in the lab. Only long term clinical studies will reveal what designs and techniques are best suited for which patients.

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'

See from which cities our patients come.

See the countries from which our readers come on this post.