Clinical Research Directory

Inclusion Criteria: * Adults aged 18 to 65 years * Availability of standing lateral cervical radiograph or supine cervical MRI performed during the registry period * No structural cervical pathology affecting sagittal alignment * Images of adequate quality for radiographic measurement * Neutral standing radiograph position for X-ray group * Standard supine acquisition for MRI group Exclusion Criteria: * Prior cervical spine surgery * Cervical fracture, dislocation, or whiplash history * Primary or metastatic cervical malignancy * Congenital vertebral anomaly including Klippel-Feil syndrome, os odontoideum, hemivertebra, block vertebra, or atlantoaxial instability * Spinal deformity or postural disorder likely to affect cervical alignment, including scoliosis, hyperkyphosis, or Scheuermann disease * Advanced degenerative cervical disease, including severe spondylosis, cervical spinal stenosis, OPLL, or DISH * Inflammatory or autoimmune rheumatologic disease affecting the spine * Neuromuscular or neurologic disorders affecting posture or alignment * Inadequate image quality, major artifact, or improper positioning