Standard of Care Cervical Spine Flexion/Extension Radiograph Measurements Do Not Predict Multiplanar Intervertebral Motion

Evaluation of patients with neck pain often relies on end-range flexion and extension radiographs that do not capture mid-range or multiplanar motion. The purpose of this study was to determine if end-range flexion/extension range of motion (ROM) predicts axial rotation ROM or mid-range ROM during either flexion/extension or axial rotation in patients with neck pain or in asymptomatic controls. It was hypothesized that end-range flexion/extension ROM would predict mid-range flexion/extension ROM, but not mid-range or end-range axial rotation ROM. Dynamic flexion/extension and axial rotation were performed by 75 patients prior to surgery and 71 asymptomatic controls, while synchronized biplane radiographs were collected at 30 images per second. Intervertebral motion from C2 to C7 was tracked using a validated volumetric model-based tracking process that matched subject-specific computed tomography (CT)-based bone models to the radiographs. The main findings were that intervertebral end-range flexion/extension ROM is a strong to very strong predictor of mid-range flexion/extension at all subaxial motion segments of the cervical spine (all r = 0.61 to 0.91), but, in general, a weak to moderate predictor of axial rotation mid-range (all ρ = 0.002 to 0.50) and end-range (all r = 0.2 to 0.68) ROM. This study suggests that the current standard of care end-range flexion/extension ROM is not sufficient to characterize the multiplanar motion that occurs in the cervical spine during activities of daily living.