Background: As arthroplasty leads to bone loss, we hypothesized that humeral bone mineral density (BMD) is lower after total shoulder arthroplasty (TSA) in the operative versus non-operative arm. However, there is no clinical approach to measure humeral BMD with dual-energy x-ray absorptiometry (DXA). The purposes of this pilot study were to develop DXA methodology to measure humerus BMD, propose humerus regions of interest (ROIs), compare TSA BMD to the non-operative arm, correlate humeral BMD with standard sites, and evaluate measurement reproducibility. Methodology: Thirty-eight adults 1-5 years post-TSA had standard clinical DXA scans plus full humerus scans using the atypical femur fracture feature; precision was assessed in a subset (n = 32). Six custom ROIs were used to measure BMD throughout the humerus. Radius and humeral BMD were compared between arms by paired t-test and correlated ipsilaterally using Pearson's Correlation. Custom ROI BMD precision was assessed using the International Society for Clinical Densitometry (ISCD) advanced precision calculator. Results: Study included 38 subjects (24M/14F), with mean (SD) age and time post-surgery of 69.6 (7.7) years and 2.5 (1.3) years respectively. BMD was lower (p < 0.01) at all custom humerus sites (3.8% to 8.2%) on the surgical side but not different at radius sites. Humeral BMD correlated positively with ipsilateral ultra-distal and 1/3 radius (r = 0.54 to 0.86; p < 0.05). Custom BMD precision (%CV) ranged from 6.0-16.0%. Conclusions: Humerus BMD can be measured using DXA and is lower in the TSA arm. Radius BMD correlated with humeral BMD but was not lower in the surgical arm. BMD precision was worse than usual clinical sites; use of software optimized for the femur is a notable limitation and likely contributes to suboptimal precision. Further study to assess the clinical utility of humeral BMD is needed. Automation and optimization of these measurements should improve precision.

背景：由于关节置换术导致骨质流失，我们假设全肩关节置换术(TSA)后的肱骨骨密度 (BMD)与非手术臂相比较低。然而，目前还没有用双能 X 射线骨密度测定法 (DXA) 测量肱骨 BMD 的临床方法。本试点研究的目的是开发 DXA 方法来测量肱骨 BMD，提出肱骨感兴趣区域 (ROI)，将 TSA BMD 与非手术手臂进行比较，将肱骨 BMD 与标准部位相关联，并评估测量的可重复性。方法：38 名 TSA 后 1-5 年的成年人使用非典型股骨骨折进行了标准临床 DXA 扫描和全肱骨扫描特征; 在一个子集中评估精度 (n = 32)。六个自定义 ROI 用于测量整个肱骨的 BMD。通过配对 t 检验比较手臂和肱骨 BMD，并使用 Pearson 相关性进行同侧相关。使用国际临床密度测定学会 (ISCD) 高级精度计算器评估自定义 ROI BMD 精度。结果：研究包括 38 名受试者 (24M/14F)，平均 (SD) 年龄和术后时间分别为 69.6 (7.7) 岁和 2.5 (1.3) 岁。手术侧所有自定义肱骨部位 (3.8% 至 8.2%) 的 BMD 均较低 (p < 0.01)，但桡骨部位没有差异。肱骨 BMD 与同侧超远端和 1/3 半径呈正相关（r = 0.54 至 0.86；p < 0.05）。自定义 BMD 精度 (%CV) 范围为 6.0-16.0%。结论：肱骨 BMD 可以使用 DXA 测量，并且在 TSA 臂中较低。桡骨 BMD 与肱骨 BMD 相关，但在手术臂中并不低。BMD 精度低于通常的临床站点；使用针对股骨优化的软件是一个显着的限制，可能会导致精度不佳。需要进一步研究来评估肱骨 BMD 的临床效用。这些测量的自动化和优化应该会提高精度。