Anatomic shoulder arthroplasty with metal head linked with proximal humeral osteolysis
After anatomic shoulder arthroplasty with the same glenoid component, patients who received stemless ceramic-head implants had fewer radiolucent lines and less osteolysis than patients who received long-stem metal-head humeral implants.
Researchers retrospectively studied 59 patients who underwent anatomic total shoulder replacement (TSR) during a 6-year period and received two types of modular humeral implants. Either the press-fit Affinis prosthesis (Mathis) – which was implanted uncemented and had a tapered, long titanium humeral stem – and a cobalt chromium head was used (group A; 39 TSRs in 36 patients) or the uncemented Affinis short humeral stem and a ceramic head was used, which is classified as stemless in the Australian Orthopaedic Association National Joint Replacement Registry (group B; 23 TSAs in 23 patients).
Regarding surface finish, the stem in group A was two-thirds grit blasted with the distal one-third polished, whereas the stem in group B was coated with osteoconductive calcium phosphate.
Prospective analysis of both groups was done at 2-year clinical follow-up, and 5.5-year radiographic follow-up showed the extent of glenoid osteolysis was greater in group A than group B based on the Lazarus score and cement/bone radiolucent lines assessment.
“No glenoid in group B (ceramic-head group) had more than a partial radiolucent line (none higher than Lazarus grade 1),” the authors wrote.
Proximal humerus osteolysis was seen in 56% of all patients, specifically 72% of group A and 30% of group B.
Researchers also found clinical outcomes were similar in patients at 2-year follow-up regardless of the presence of humeral osteolysis or radiolucent lines in the glenoid regions. “The study showed that there was more glenoid and humeral osteolysis with a long-stem metal-head construct than with a stemless ceramic-head construct,” they wrote.
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This well-written paper shares the authors’ experience with two different humeral implants in 62 shoulder arthroplasties; one with a stem and cobalt chrome head and the other a stemless ceramic head, both with the same glenoid. The ceramic head did better radiographically with less glenoid radiolucent lines and humeral osteolysis. With an average 5.5-year follow-up, however, this study joins the vast majority of the clinical literature leaving us unclear on what happens at 10 years plus.
The exclusion criteria offered by the authors, “revision surgery within 5 years of initial arthroplasty …”, also need elaboration. Were the excluded cases unfavorable to the ceramic implant or otherwise inconsistent with their findings? Additionally, as 62 shoulder arthroplasties were done on 59 patients, are there patients who have a ceramic head on one side and cobalt chrome on the other?
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