AMERICAN JOURNAL OF PHYSICAL MEDICINE & REHABILITATION

Objective The aim of this study was to assess flexor pollicis longus tendon by using ultrasound imaging in frequent mobile phone texters. Subjects In total, 149 subjects, aged 18-40 yrs, were recruited as frequent mobile phone texters (n = 71) and infrequent texters (n = 78). Methods Demographic data and estimate frequency of texting were noted. Thumb pain during activity, range of motion for thumb joints, grip and pinch strengths, and Quick Disabilities of arm, shoulder, and hand were evaluated. Standardized bilateral ultrasound evaluations were performed using a linear array probe, and tendon area measurements were done with axial imaging at midthenar region and midproximal phalangeal region with manual trace technique. Results The groups were similar except for the mean estimate number of messages/month (P = 0.001). Whereas grip and pinch strength values were significantly higher (frequent texter group, P = 0.001; infrequent texter group, grip strength P = 0.018; pinch strengths, P = 0.001) on the texting side in both groups, flexor pollicis longus tendons were larger (P = 0.001) and the activity pain was higher (P = 0.005) on the texting sides only in the frequent texter group. Flexor pollicis longus thickness significantly correlated with messages/month only in the frequent texter group (r = 0.592, P = 0.001). Conclusions Flexor pollicis longus tendons seem to be thicker at the midthenar level in subjects who frequently use mobile phone texting. Because this increase in thickness parallels the number of messages per day, the authors believe that further studies are needed to elucidate whether such changes become problematic later on in life