Sunday, October 7, 2018

Total shoulder - does a hybrid glenoid component with a central porous titanium post provide a benefit?

Five-year minimum clinical and radiographic outcomes of total shoulder arthroplasty using a hybrid glenoid component with a central porous titanium post

These authors evaluated clinical and radiographic outcomes at a minimum 5-year followup in 45 shoulders that underwent total shoulder arthroplasty (TSA) using a glenoid with a central porous titanium post to augment the cemented peripheral pegs.

While the average clinical scores were improved, radiographs showed glenoid component radiolucency in 29 of 45 (64%) of the shoulders. Radiolucencies were confined to the area under the glenoid faceplate in 6 and were only around the central post in 13. Nine TSAs (20%) demonstrated 2 or more columns of involvement.

Some implants had secure fixation of the central peg, but evidence of stress-shielding in the bone beneath the face of the component (see below)

Some had incomplete bone healing to the central peg (see below)

One had fracture of the central peg 

Comment: Each of the three observations can be attributed to the different material properties of the central peg (which is stiff) and the polyethylene (which is more flexible). Loads applied to the glenoid component deform the two materials differently.

In contrast, all polyethylene components have uniform material properties more closely resembling those of bone.

See below such a component two years after implantation without stress shielding and with bone ingrowth into the flutes on the central peg.

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