An Investigation of the Effect of Smartphone Usage Levels on Cervical Posture, Tongue Pressure, Balance, and Neck Dysability in Individuals With Rheumatoid Arthritis and Ankylosing Spondylitis

The purpose of this cross-sectional and comparative study is to investigate the impact of smartphone addiction on the cervical posture, musculoskeletal system, balance, and tongue pressure in individuals diagnosed with Rheumatoid Arthritis (RA) and Ankylosing Spondylitis (AS), and to compare these findings with a healthy control group. Smartphone addiction has become a major contributing factor to postural alterations such as text neck syndrome. This study aims to evaluate and compare the craniovertebral angle (CVA), neck extensor muscle strength, pressure pain thresholds (PPT) of the neck and shoulder, single-leg stance static balance, and tongue pressure among three distinct groups. A healthy control group will be included as a reference baseline to differentiate the postural and functional deterioration caused by rheumatological diseases from the additional mechanical load imposed by technology use. To eliminate the misleading effects of acute pain, joint swelling, and severe functional limitations during flare-ups, only patients with stable disease activity (DAS28 \< 3.2 for RA and BASDAI \< 4 for AS) will be enrolled. This approach aims to examine the pure biomechanical relationship between technological dependency and cervical functions, independent of active systemic inflammation.

Inclusion Criteria: * Aged between 18 and 65 years. * Using a smartphone for at least 2 hours daily. * Able to understand and follow postural commands during clinical measurements. * For the Rheumatoid Arthritis (RA) Group: Diagnosed with RA by a rheumatologist, with a stable disease activity score (DAS28 \< 3.2). * For the Ankylosing Spondylitis (AS) Group: Diagnosed with AS by a rheumatologist, with a stable disease activity score (BASDAI \< 4). Exclusion Criteria: * History of prior surgical intervention in the cervical region. * Presence of neurological diseases (e.g., Parkinson's disease, ALS). * Severe visual or hearing impairment. * Vestibular system disorders. * Severe limitation in jaw opening. * Presence of acute neck trauma or malignancy. * Lower extremity amputation or advanced arthritis preventing the performance of the balance test. * Active use of muscle relaxants or advanced sedative medications.