Behavioral Smartphone Orientation Is Associated with Upper Limb Dysfunction Among University Students: A...

Background: Excessive smartphone use has been associated with musculoskeletal disorders; however, the relationship between smartphone orientation and objective measures of upper limb function remains insufficiently explored. The aim of this study was to determine whether smartphone orientation is associated with upper limb disability, grip strength, pain intensity and clinical signs of musculoskeletal dysfunction in university students. Materials and methods: The study involved 84 students including women (n = 74) and men (n = 10), with an age of 21 ± 2.6 years. This cross-sectional study utilized the Smartphone Orientation Scale (SOS) to assess behavioral smartphone orientation. Functional disability was assessed using the QuickDASH questionnaire and the intensity of pain was measured using the Numeric Rating Scale (NRS). Objective assessments included hand grip strength measurements via an electronic dynamometer and clinical evaluation using the Finkelstein test. Because the analyzed variables did not follow a normal distribution, Spearman's rank correlation analysis was performed to assess the relationship between variables across the study group with statistical significance set at p < 0.05. Results: Higher SOS scores were associated with lower left- and right-hand grip strength (ρ = -0.391 and -0.395, respectively; Holm-adjusted p = 0.001 for both) and greater upper-limb disability measured by QuickDASH (ρ = 0.387; Holm-adjusted p = 0.001). SOS score was also associated with a positive right Finkelstein test (ρ = 0.294; Holm-adjusted p = 0.020), but not with the left Finkelstein test. Longer daily smartphone-use duration was associated with lower grip strength and higher SOS and QuickDASH scores after Holm correction. Conclusions: Screening using the Smartphone Orientation Scale may help identify young adults presenting with behavioral patterns associated with upper limb dysfunction. Smartphone orientation may represent a more clinically relevant behavioral marker of early upper limb dysfunction than self-reported daily smartphone use.