Incidence of cervical kyphosis and cervical posterior translation in neck pain associated with radiological evidence of degenerative disc disease

Background: Cervical kyphosis mechanically influences the intervertebral discs, which may lead to neck, shoulder, and scapular pain.Objectives: To investigate the incidence of cervical kyphosis and posterior displacement of cervical vertebrae (cervical posterior translation index) in patients with radiologically evident degenerative disc disease.Design: Retrospective-cohort study.Methods: Ninety-five patients with radiologically evident degenerative disc disease were recruited at our clinic from 2015 to 2019. Radiography images were used to analyze the straight-line index in each patient in the upright posture. The straight-line index was calculated by drawing a reference line connecting the posterior inferior edges of C2 to C7 and normalizing the addition of the distances from the posterior inferior edges of C3, C4, C5, and C6 to the reference line, respectively. Straight-line index < 0 was defined as cervical kyphosis and & GE;0 as cervical lordosis, the cervical kyphosis. In cervical kyphosis group, the distance from the posterior inferior edges of C3, C4, C5, and C6 to the reference line was normalized by the reference line distance to determine posterior displacement. Multiple comparison tests aside from simple and multiple linear regression analysis were performed.Results: The incidence of cervical kyphosis in patients with radiologically evident degenerative disc disease was 60% (57/95 patients). Multiple comparison tests revealed that the cervical posterior translation indexes of C4 and C5 were significantly higher than those of C3, C4, and C6, in cervical kyphosis group.Conclusions: Cervical kyphosis was present in 60% of patients with radiologically evident degenerative disc disease, with C5 showing the most posterior displacement.