The significance of cervical sagittal alignment for nonrecovery after whiplash injury

BACKGROUND CONTEXT Whiplash-associated disorder is a common cause of chronic neck pain. Several radiological cervical angular variables are suggested to have constitutional characteristics, that is, them being minimally influenced by body positioning. However, the association between these variables and pain conditions remains poorly understood. To our knowledge, no previous studies have investigated the association between constitutional angular variables and the outcome after whiplash trauma. PURPOSE Our objectives were (1) to study the inter-rater agreement of sagittal radiologic variables between 2 raters and (2) to investigate any association between these variables and self-perceived nonrecovery after whiplash injury. STUDY DESIGN Prospective cohort study. PATIENT SAMPLE Forty-six patients aged 16 to 70 years, attending an emergency department after a motor vehicle accident resulting in neck pain were recruited. OUTCOME MEASURES Self-perceived nonrecovery (yes/no) was the primary outcome measure. The secondary outcome measure was pain level on a numeric rating scale. METHODS The participants underwent computed tomography scans in a supine position. Sagittal alignment variables (T1 slope, neck tilt, thoracic inlet angle [TIA], and C2–C7 angle) on the computed tomography scans were measured by 2 independent raters. Inter-rater agreement was tested with a paired sample t test and Bland-Altman plots for each variable. The patients were followed up after 6 months. RESULTS No systematic differences for the assessed variables were found between the 2 raters. The overall nonrecovery rate was 28%. For the group with low neck tilt, the nonrecovery rate was 50% (95% CI: 36%–78%) and for the group with high neck tilt, 8% (95% CI: 3%–25%). The nonrecovery rate for the group low TIA was 50% (95% CI 29%–72%) and for those with high TIA 14% (95% CI 4%–26%). The associations remained significant after adjustments for possible confounders. The inter-rater analysis shows satisfactory agreement without proportional bias. CONCLUSIONS This study indicates the existence of an association between the constitutional sagittal alignment of the cervical spine and the outcome after whiplash injuries.