Shoulder arthroplasty with anchor peg implant may promote bone growth, reduce pain
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Anatomic total shoulder arthroplasty with a partially cemented polyethylene glenoid component, or anchor peg implant, may yield “in between fin” bone growth and decreased pain, according to recently presented results.
“Anchor peg [DePuy, Wright Medical Technology] anatomic glenoid designs were made to avoid central peg cement, enhancing primary stability of the central peg and component and increasing the potential for bone growth in between the fins of the component,” Armodios M. Hatzidakis, MD, a shoulder and elbow specialist at Western Orthopaedics, said in his presentation at the American Shoulder and Elbow Surgeons Annual Meeting, which was held as a virtual event.
“Typically, the Wirth method has been used to analyze these implants radiographically, with grade 1 showing osteolysis, grade 2: bone in contact with periphery events and grade three: increased radio density between the fins,” Hatzidakis said. “The purpose of our study was to evaluate the clinical results at 48 months or greater follow-up of this type of implant and to critically evaluate the radiological results and better understand the reaction of the glenoid bone with a central peg over time.”
In their retrospective review, Hatzidakis and colleagues included 83 patients who underwent 150 consecutive total shoulder arthroplasties from November 2008 to January 2012. The peripheral pegs of the anchor peg implants were cemented, and glenoid and humeral head bone reaming was applied to the central peg. All procedures were performed by Hatzidakis.
According to the study, clinical outcome measures included ASES scores, constant scores, VAS pain scores, single assessment numeric evaluation (SANE) scores, subjective shoulder value (SSV), active range of motion (AROM) and patient-reported outcome (PRO) scores.
Five shoulder specialists evaluated radiographic results using a quadrant score, the Wirth radiodensity scale to determine in between fin growth, or interdigitation, and the Lazarus radiolucency scale to determine radiolucency.
AROM and PRO scores improved significantly; however, the radiographic results were surprising, Hatzidakis said.
“19% of patients had in between fin optimal growth – a score greater than six. Conversely, 28% of patients had a radiolucency score greater than six of the central peg, indicating an expansile lucency or ‘balloon sign,’” he said. “Optimal bone interdigitation nor expansile lucency affected AROM or PRO scores. However, a high in between growth score correlated to decreased pain scores. Conversely, patients with a radiolucency score that was high, trended toward higher VAS scores than patients with interdigitation.”
Hatzidakis and colleagues concluded the total quadrant score for bone growth and radiolucency showed a more detailed assessment of reaction to the central peg with improved interobserver reliability compared with Wirth and Lazarus scores.
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Hatzidakis AM, et al. Paper 7. Presented at: American Shoulder and Elbow Surgeons Annual Meeting; Oct. 2-3, 2020 (virtual meeting).
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