BackgroundRadiolucent lines (RLLs) are commonly seen on the humerus after uncemented shoulder arthroplasty. However, long-term changes to humeral reactions, including RLL, remain unclear. This study investigated long-term chronological changes around the humeral stem, including RLL, after anatomic shoulder arthroplasty. MethodsTwenty-four shoulders after anatomic total shoulder arthroplasty or humeral head replacement using an uncemented standard humeral stem conducted between 2005 and 2012 with ≥8 years of follow-up were retrospectively evaluated at 2 years, 5 years, and final follow-up. Radiographic changes including RLL, distal sclerosis, and bone resorption were evaluated. ResultsMean final follow-up was 10.7 ± 1.6 years. The number of cases showing RLL gradually decreased over time from 19 cases (79.2%) to 15 cases (62.5%), to 10 cases (41.7%) between 2 years, 5 years, and long-term follow-up >8 years. Sclerosis at the tip of the stem increased significantly from only 1 case to 15 cases between 2 years and long-term. Bone resorption exceeding grade 4 was found in 2 of 24 cases (8.2%) at a final follow-up. ConclusionRLL on the humerus around the cementless on-growth standard stem in shoulder arthroplasty at short-term follow-up did not necessarily elicit long-term loosening. In addition, distal RLL tended to improve over the long term and finally change into distal sclerosis.