BACKGROUD: Reliable scapular upward rotation and anterior-posterior tilt data are required for patients with subacromial impingement syndrome (SIS). Only a few studies have explored the reliability of such measurements derived using a modified inclinometer. OBJECTIVES: To determine the relative and absolute reliability of scapular upward rotation and anterior-posterior tilt measurements derived using a modified digital inclinometer in patients with SIS. METHOD: Seventeen SIS patients were assessed twice within 1 week. We determined the relative and absolute measurement reliability by calculating the intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimal clinically important difference (MCID). Both intra- and interrater reliability were determined. RESULTS: The intra-rater reliability (both measurements) was high (0.72–0.88), and the interrater ICC was high to excellent (0.72–0.98). Clinically acceptable SEM and MCID values were obtained for scapular upward rotation (SEM: 4.28–9.33∘, MCID: 5.1–11.3∘) and anterior-posterior tilt (SEM: 3.72–7.55∘, MCID: 2.5–10.8∘). CONCLUSIONS: Measurements of scapular upward rotation and anterior-posterior tilt using a modified digital inclinometer reliably reveal scapular position and kinematics in patients with SIS.
