Hybrid Fixation in Anatomic Shoulder Arthroplasty: Surgical Technique and Review of the Literature
These authors reviewed the use of a cemented polyethylene glenoid component with a porous metal central peg. Such a component with a posterior augment is shown in the figure below.
They point out that glenoid loosening remains the most common long-term complication following TSA with reported rates of up to 1.2% per year.
In their review they found 5 primary investigations and 1 systematic review evaluating TSA with hybrid fixation of glenoid components.
One study revealed a 21% glenoid component failure rate specifically due to fatigue fractures at the keel-glenoid junction. This led to early implant design revisions to reduce the risk of failure.
A second study reported 45 patients having a hybrid glenoid component with a central porous titanium post, reporting a glenoid component failure rate of 2.2%.
Three retrospective, non-randomized cohort investigations compared outcomes of hybrid glenoid component fixation to cemented all-polyethylene glenoid components.
One compared 43 patients treated with a hybrid glenoid component with 40 patients who received a cemented all-polyethylene pegged glenoid component at an average of 38 months of follow-up. This study found no differences with respect to radiolucent line scoring, change in VAS score, or complications.
Another compared 46 patients treated with a hybrid cage-glenoid components to 46 patients treated with cemented all-polyethylene pegged glenoid components at a mean of 25 months of followup. They observed a significantly lower rate of radiolucent lines and similar rates of complications.
Another study reported a matched cohort study of 316 patients treated with a hybrid cage-glenoid component compared to patients treated with cemented all-polyethylene pegged glenoid components at 50 months of follow-up. They reported a lower rate of radiolucent glenoid lines, aseptic glenoid loosening, and revision rate with the hybrid fixation cohort.
A systematic review summarized and provide additional insight on the literature to date reporting pool data for hybrid glenoid component fixation with rates of postoperative radiolucent lines at a mean rate of 17.3%, complications at 7.4%, and revisions at 2.6% at "short mid-term followup".
A retrospective multi center investigation demonstrated aseptic glenoid component loosening in 5 patients at 2 year follow-up.
Comment: For perspective, a large national registry study reported by the Australian Orthopaedic Association reports a revision rate 5% at 10 years (0.5%/year) for cross-linked all polyethylene glenoid components (see below). The available data on the metal hybrid glenoid to not demonstrate superiority over the standard all polyethylene glenoid.
The hybrid glenoid component also carries the risk of fracture (as shown below), perhaps due to the differences in material properties between metal and polyethylene.
