A Critical Review on Prosthetic Features Available for Reversed Total Shoulder Arthroplasty

Abstract

Reversed total shoulder arthroplasty is a popular treatment in rotator cuff arthropathy and in displaced proximal humeral fractures in elderly. In 2016, 29 models of commercially available designs express this popularity. This study describes all the different design parameters available on the market. Prosthetic differences are found for the baseplate, glenosphere, polyethylene, and humeral component and these differences need to be weighed out carefully for each patient knowing that a gain in one mechanical parameter can balance the loss of another. Patient specific implants may help in the future.

Figure 1

29 models of commercially available reverse prosthesis designs: (1) Aequalis Tornier; (2) Aequalis Fracture Tornier; (3) Anatomical Zimmer; (4) Trabecular Zimmer; (5) Titan Integra; (6) Equinoxe Exactech; (7) Equinoxe Fracture Exactech; (8) TESS Biomet; (9) Verso Biomet; (10) Comprehensive Biomet; (11) SMR Lima; (12) Encore DJO; (13) Promos Smith&Nephew; (14) Affinis Fracture Mathys; (15) Affinis Mathys; (16) Duocentric Aston Med; (17) Arrow FH; (18) Scultra Euros; (19) NGRi Wright; (20) Unic Evolutis; (21) Géo Biotechni; (22) Univers Arthrex; (23) Delta Xtend Depuy-Synthes; (24) Vaios JRI; (25) Ascend Tornier; (26) Seviin Ingen; (27) Agilon Implantcast; (28) Ulys Ceraver; and (29) Humelock FX Solution.

Figure 2

Baseplates can ben oval or circular, flat-backed or curved-backed, and with or without inferior extension.

Figure 3

The differences in glenosphere placement between a (a) flat base plate and a (b) convex base plate are shown. Both have the same center of rotation [28].

Figure 4

Different designs of glenospheres: from (a) to (d) 36 mm concentric, 36 mm eccentric, 44 mm polyethylene concentric glenosphere, and 44 mm polyethylene eccentric glenosphere [43]. Note the inferior extension to prevent impingement.

Figure 5

Two types of polyethylene inlay: (a) a horseshoe-shaped inlay [75]; (b) a wedged inlay [76].

Figure 6

(a) Traditional inlay Grammont RSA with a straight stem and a 155° inclination. (b) Example of a new design with a curved stem and an onlay humeral tray in a 135° inclination. The red line passes through the center of the stem. Note that the center of the polyethylene is more medial with the curved stem which results in lateralization of the humerus (red arrow) [62].

Figure 7

Normal shoulder (a), nonoffset rTSA (b), and posterior-superior offset rTSA (c) [72].