Lateralized RSA: The US Experience

The design of the reverse total shoulder arthroplasty (RTSA) has been in evolution since the initial designs by Dr. Grammont. The unique characteristic of the initial design was to create more medial center of rotation (COR) of the glenoid component so that shear forces across the baseplate–glenoid bone interface reduced and thereby decrease glenoid component failure rates. Subsequent designs were created which did not medialize the COR as much as the initial Grammont prosthesis to decrease the notching and dislocation rates seen in the Grammont prosthesis. These prostheses were called “lateralized” although the COR was actually just less medial than popular Grammont type of designs. This chapter will summarize the effects of a “lateralized” (i.e., less medial) COR used initially in the United States in terms of the biomechanics, the effect upon baseplate loosening and clinical results. This chapter will also address the biomechanics and clinical results in terms of inlay versus onlay humeral components as they relate to the experience of using lateralized RTSA.