Does Humeral Component Lateralization in Reverse Shoulder Arthroplasty Affect Rotator Cuff Torque? Evaluation in a Cadaver Model

Abstract

The results of this preliminary in vitro cadaveric study suggest that the lateral offset of the RTSA humeral component plays an important role in the torque generated by the anterior and posterior rotator cuff. However, further studies are needed before clinical application of these results. Increasing humeral offset may have adverse effects, such as the increased risk of implant modularity, increasing tension of the cuff and soft tissues, increased costs often associated with design modifications, and other possible as yet unforeseen negative consequences.

Development and Application of a Novel Metric to Characterize Comprehensive Range of Motion of Reverse Total Shoulder Arthroplasty

“…Previous studies related to ROM of rTSA generally characterize ranges of motions that are contained within a subset of single paths (i.e., abduction, flexion, axial rotation, etc.) . However, conclusions pertaining to implant performance drawn from a subset of investigated motions may be misleading, as it has been shown that differing implant designs maximize different motions .…”

“…Previous studies related to ROM of rTSA generally characterize ranges of motions that are contained within a subset of single paths (i.e., abduction, flexion, axial rotation, etc.). [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]33,34,36,37 However, conclusions pertaining to implant performance drawn from a subset of investigated motions may be misleading, as it has been shown that differing implant designs maximize different motions. 13,36 GC-ROM, which condenses the analysis of a broader ROM, provides a single, generalized performance metric.…”

“…Several experimental studies have used biomechanical models, with cadavers or bone substitutes, to identify relationships between implant design parameters and ROM . In a study utilizing artificial shoulder bones, Gutierrez et al found that increasing lateral offset of the center of rotation increased impingement‐free abduction ROM.…”

“…Several experimental studies have used biomechanical models, with cadavers or bone substitutes, to identify relationships between implant design parameters and ROM. [1][2][3][4][5][6][7][8][9][10] In a study utilizing artificial shoulder bones, Gutierrez et al 1 found that increasing lateral offset of the center of rotation increased impingement-free abduction ROM. However, cadaveric studies by Henninger et al 5 and Giles et al 9 showed that by increasing the center of rotation lateralization also increased the deltoid force required to abduct the arm, which could negatively impact ROM if deltoid strength was insufficient.…”

The biomechanics of subscapularis repair in reverse shoulder arthroplasty: The effect of lateralization and insertion site

“…The effect of implant lateralization on SSc function and clinical outcomes following SSc repair also remains controversial . Lateralization of the center of rotation in RSA is shown to reduce intra‐articular impingement and scapular notching and increase range of motion (ROM), but it can also reduce the deltoid lever arm, which results in increased glenohumeral shear forces and bending moments on the glenosphere fixation, which is a risk for glenoid loosening.…”