Radiolucent lines about the glenoid component of a total shoulder
replacement are a common finding, even on initial postoperative
radiographs. The achievement of complete osseous support of the
component has been shown to decrease micromotion. We evaluated the
ability of a group of experienced shoulder surgeons to achieve complete
cementing and support in a series of patients managed with keeled
and pegged glenoid components.
We reviewed the initial postoperative radiographs of 493 patients
with primary osteoarthritis who had been managed with total shoulder
arthroplasty by seventeen different surgeons. One hundred and sixty-five
patients were excluded because of inadequate radiographs, leaving
328 patients available for review. Of these, thirty-nine patients
had a keeled component and 289 had a pegged component. The method
of Franklin was used to grade the degree of radiolucency around the
keeled components, and a modification of that method was used to
grade the degree of radiolucency around the pegged components. The
efficacy of component seating on host subchondral bone was evaluated
with a newly constructed five-grade scale based on the percentage
of the component that was supported by subchondral bone. Each radiograph
was graded four times, by two separate reviewers on two separate
Radiolucencies were extremely common, with only twenty of the 328
glenoids demonstrating no radiolucencies. On a numeric scale (with
0 indicating no radiolucency and 5 indicating gross loosening),
the mean radiolucency score was 1.8 ± 0.9 for keeled
components and 1.3 ± 0.9 for pegged components (p = 0.0004).
After defining categories of "better" and "worse" cementing, we
found that pegged components more commonly had "better cementing"
than did keeled components (p = 0.0028). Incomplete seating was
also common, particularly among patients with keeled components.
Ninety-five of the 121 pegged components that had been inserted
by the most experienced surgeon had "better cementing," compared
with eighty-five of the 168 pegged components that had been inserted
by the remaining surgeons (p < 0.00001).
Perfectly cementing and seating a glenoid replacement is a difficult
task. Radiolucencies and incomplete component seating occur more
frequently in association with keeled components compared with pegged
components. Surgeon experience may be an important variable in the
achievement of a good technical outcome.