Lateralized versus nonlateralized reverse total shoulder arthroplasty

Abstract

Throughout the history of reverse total shoulder arthroplasty, the extent of lateral offset has changed considerably from "too lateral" to "too medial" and has been lately swinging back towards a point somewhere in between. Nonlateralized designs minimize shear forces on the glenoid and decrease force required by the deltoid. Glenoid lateralization decreases impingement and scapular notching and improves range of motion. Humeral lateralization achieves a more anatomic position of the tuberosities while maintaining a nonlateralized center of rotation. Several factors play a role in choosing the extent of lateral offset and method of lateralization.

Keywords: Glenoid lateralization; humeral lateralization; lateral offset; lateralization; reverse shoulder arthroplasty.

Figure 1.

Components of the lateral offset in RTSA. Republished from Werthel et al. with permission from Springer Nature.

Figure 2.

(a) Compressive (Fc) and shear (Fs) components of the resultant force vector (Fv), which act through a fixed center of rotation (COR). (b) COR lateralization increases the lever arm length which decreases compressive forces, increases destabilizing shear forces, and creates a new moment (M) at the glenoid-implant interface. Republished from Berliner et al. with permission from Elsevier.

Figure 3.

Illustration showing how eccentricity of an onlay humeral tray can lateralize the humerus. Republished from Lädermann et al. with permission from Springer Nature.

Figure 4.

Illustration showing how a curved stem can lateralize the humerus relative to the center of polyethylene. Republished from Lädermann et al. with permission from Springer Nature.