The Correlation Between Smartphone Use and Compressive Ulnar Neuropathy at the Elbow: A Retrospective Study

<b>Background:</b> Cubital Tunnel Syndrome (CuTS) is the second-most common compressive neuropathy of the upper limb, traditionally associated with prolonged elbow flexion, trauma, or anatomical constraints. With the widespread adoption of smartphones, sustained upper-limb postures have emerged as potential novel risk factors for ulnar nerve compression. This retrospective study aimed to investigate the potential correlation between smartphone use patterns and the development of CuTS. <b>Methods:</b> A retrospective observational study was conducted on 100 subjects recruited between 2021 and 2024, including 50 patients with EMG-confirmed CuTS who underwent surgical decompression and 50 matched controls without clinical or electrophysiological evidence of ulnar neuropathy. Demographic variables, daily smartphone use (h/day), predominant activity type, and habitual posture during device handling were collected through clinical records and questionnaires. Group comparisons were performed using <i>t</i>-tests and Chi-square analyses, with significance set at <i>p</i> < 0.05. <b>Results:</b> Daily smartphone use was higher in the CuTS group compared with controls (4.94 ± 1.8 vs. 4.04 ± 1.5 h/day), although the difference did not reach statistical significance (<i>p</i> = 0.0716). Posture during device use showed a significant association with CuTS: 82% of affected patients reported using smartphones with the elbow flexed, compared with 56% of controls, whereas supportive postures were less frequent among CuTS patients (16% vs. 38%) (<i>p</i> = 0.019). No significant differences were found between groups regarding smartphone activity type (<i>p</i> = 0.858). <b>Conclusions:</b> Smartphone use may contribute to ulnar nerve compression primarily through ergonomically disadvantageous postures, particularly sustained elbow flexion, rather than total usage time. These findings highlight a modifiable behavioral risk factor relevant to the rising prevalence of CuTS in the digital era. Increased clinical attention to device-handling habits and public-health strategies promoting ergonomic posture may support CuTS prevention. Prospective and biomechanically informed studies are warranted to further elucidate causal mechanisms. Unmeasured confounders (e.g., occupational and sleep-related elbow flexion) may influence these associations.