Humeral-sided Radiographic Changes Following Reverse Total Shoulder Arthroplasty

Abstract

Background: We sought to characterize humeral-sided radiographic changes at a minimum of 2 years after reverse<br />shoulder arthroplasty (RSA) to determine their association with specific implantation techniques.<br />Methods: The immediate and most recent postoperative anteroposterior radiographs of 120 shoulders with primary RSA<br />and a minimum of 2-years of radiographic follow-up were analyzed (mean follow-up 35.2 months). Stress shielding was<br />evaluated by measuring cortical thickness at 4 different locations. Three independent examiners evaluated radiographs<br />for humeral osteolysis, radiolucent lines, stress shielding, stem loosening, and scapular notching.<br />Results: The cortical diameter, marker of external stress shielding, significantly decreased from initial to most<br />recent measurement (P<0.001), but did not differ between cemented and uncemented groups. Cemented stems had<br />significantly more osteolysis and radiolucent lines; uncemented stems had significantly more internal stress shielding<br />(P<001). The presence of scapular notching was significantly correlated with the presence of humeral osteolysis<br />(P<0.001). Three (2.5%) stems were deemed “at risk" for loosening and 2 (1.7%) were loose.<br />Conclusion: Cemented humeral stems were associated with an increased rate of radiolucent lines and osteolysis,<br />whereas uncemented stems were associated with more internal stress shielding. Humeral cortical thickness significantly<br />decreased over time regardless of fixation. There was an association between scapular notching and increased<br />humeral osteolysis.<br />Level of evidence: III