Advancements in Inlay Glenoid Components for Anatomic Total Shoulder Arthroplasty: A Review

Abstract

While anatomic total shoulder arthroplasty is a successful procedure that provides reliable pain relief and restoration of function in most patients, its success has been limited by glenoid component loosening. While series reporting the outcomes of inlay glenoid components have demonstrated excellent clinical outcomes with low rates of component loosening and need for revision, surgeons have been hesitant to adopt these implants due to concerns of inadequate pain relief secondary to the remaining glenoid rim contacting the humeral head implant. The inset glenoid component, a variant of the traditional inlay components, has gained interest because its design aims to achieve similar stability to traditional inlay components through implantation within strong subchondral bone, reduce the amount of glenoid vault removed compared to inlay components, and has a glenoid face designed to limit the rocking-horse phenomenon. In limited series, the inset glenoid component has demonstrated superior biomechanical and clinical performance compared to traditional onlay glenoid components. Although there have been minimal clinical studies investigating the inset glenoid in comparison to onlay and inlay components to date, a subset of case series with short-term follow-up have demonstrated favorable outcomes. The purpose of this article was to review the design rationale, biomechanical evidence, and clinical performance of the inset glenoid component.

Keywords: inlay glenoid; inset glenoid; inverted shoulder; total shoulder arthroplasty.

Figure 1

Glenoid designs in anatomic total shoulder arthroplasty can be classified according to their interface with glenoid bone as onlay (A) or inlay (B). The new Inset glenoid includes characteristics of both onlay and inlay glenoid components with one central peg and two peripheral pegs (C).

Figure 2

The inset glenoid is comprised of three different zones [40]. The central zone provides contact with the polyethylene at a location where the humeral head is typically placed at rest. The second zone is designed to conform during abduction. The outer zone provides a larger radial mismatch for when the humeral head translates without catching the ends of the implant, a typical issue in onlay glenoids.