The purpose of this study was to determine the effect of varying insertion angles
on the fixation strength of screw-in devices placed in the glenoid rim.
Type of study
Cadaveric biomechanical analysis.
Eighteen cadaveric glenoids had 3.0-mm cannulated screws inserted for a depth of 10
mm in all 4 quadrants: anterior superior (AS), anterior inferior (AI), posterior superior
(PS), posterior inferior (PI). Screws were inserted along the orthogonal to the glenoid
rim at the point of insertion or at angles that deviated from this vector by 20° and
40°. Load to failure was performed at 10 mm/s along the orthogonal to the point of
For screws inserted orthogonal to the glenoid rim, the average load to failure was
highest for the PS quadrant (733 ± 369 N) and lowest for the AI quadrant (272 ± 69
N). The AS and PI quadrants showed intermediate values (549 ± 334 N and 484 ± 141
N, respectively). Deviation from orthogonal correlated with decreased fixation strength.
This decrease was statistically significant in the AS and PI quadrants, with deviation
of 40°, and in the AI quadrant, with deviation of 20°, as well as 40°.
Insertion angles for screw-in fixation devices should be orthogonal to the glenoid
rim at the point of insertion to maximize strength. Deviation of 40° from orthogonal
compromises fixation in most quadrants and deviation as little as 20° can compromise
fixation in the AI quadrant.
To maximize strength of labral reattachment to the bony glenoid, screw-in type fixation
devices should be inserted as orthogonal to the glenoid rim as possible. This is especially
true for Bankart repairs, because device pullout occurs at significantly lower loads
in the anteroinferior quadrant compared with the other 3 quadrants. Deviating as little
as 20° further decreases fixation strength significantly.