Reliability of the assessment of scapular posterior tilt angle using the smartphone and scapular movement during arm elevation in healthy individuals and patients with frozen shoulder: a cross-sectional study

BACKGROUND: Frozen shoulders are associated with abnormal scapular movements. However, scapular posterior tilt movement in frozen shoulders has not been investigated using simple clinical methods. This study aimed to clarify the reliability of scapular posterior tilting movement using a smartphone and scapular posterior tilting movement in healthy individuals and patients with frozen shoulder. METHODS: The participants were 22 healthy young (age 25.9 ± 4.1 years), 22 healthy middle-aged (age 52.6 ± 4.4 years), and 37 individuals with frozen shoulder (age 56.0 ± 7.0 years). Scapular posterior tilting movement was measured at shoulder flexion 0° (0° posterior tilt), shoulder flexion 90° (90° posterior tilt), and scapular tilt excursion using a smartphone. The intrarater reliability was calculated using the intraclass correlation coefficient (1, 3). RESULTS: Intrarater reliability at 0° posterior tilt and 90° posterior tilt was 0.76 and 0.84, respectively. The 0° posterior tilt was not significantly different among the three groups (P = .90). The 90° posterior tilt was not significantly different among the three groups (P = .06). The scapular tilt excursions were significantly greater in the frozen shoulder group than in the middle-aged group (P = .03). CONCLUSION: Measurement of scapular posterior tilting movement using a smartphone was highly reliable. The frozen shoulder might compensate for the limited arm elevation of the glenohumeral joint by scapular posterior tilting movement.