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J Shoulder Elbow Surg. 2013 Jul;22(7):963-70. doi: 10.1016/j.jse.2012.10.035. Epub 2013 Jan 16.

The impact of scapular notching on reverse shoulder glenoid fixation.

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1
Exactech, Gainesville, FL, USA.

Abstract

BACKGROUND:

Scapular notching is a well-documented complication of reverse shoulder arthroplasty. The effect of scapular notching on glenoid fixation is unknown.

MATERIALS AND METHODS:

This study dynamically evaluated reverse shoulder glenoid baseplate fixation and assessed the effect of scapular notching on fixation in composite scapulae. A cyclic test was conducted to simulate 55° of humeral abduction in the scapular plane as a 750-N axial load was continuously applied to induce a variable shear and compressive load. Before and after cyclic loading, a displacement test was conducted to measure glenoid baseplate displacement in the directions of the applied static shear and compressive loads.

RESULTS:

For the scapulae without a scapular notch, glenoid baseplate displacement did not exceed the generally accepted 150-μm threshold for osseous integration before or after cyclic loading in any component tested. 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 (P = .003) and after (P = .023) cyclic loading.

CONCLUSIONS:

Adequate glenoid baseplate fixation was achievable in most cases in scapulae with a severe scapular notch; however, the fact that this micromotion threshold was not met in all scapulae with a notch is concerning and implies that severe notching may play a role in initial glenoid baseplate stability.

PMID:
23333170
DOI:
10.1016/j.jse.2012.10.035
[Indexed for MEDLINE]

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