[Radiological features of degenerative cervical kyphosis and relationship between sagittal parameters]

To investigate the radiological features of degenerative cervical kyphosis (DCK) and the relationship between cervical sagittal parameters.

The quality of life scores and imaging data of 89 patients with DCK treated between February 2019 and February 2022 were retrospectively analysed. There were 47 males and 42 females, with an average age of 48.4 years (range, 25-81 years). Quality of life scores included visual analogue scale (VAS) score and neck disability index (NDI). The imaging data included C ₀-C ₂ angle, C ₂-C ₇ angle, C ₃-C ₇ inclination of zygapophyseal joints, C ₇ slope (C ₇S), cervical sagittal vertical axis (cSVA), kyphosis range, and kyphosis focal. The patients were grouped by gender, and the differences of the above parameters between the two groups were compared. Pearson correlation was used to analyze the relationship between age, quality of life scores, and cervical sagittal parameters, and the relationship between cervical sagittal parameters.

The preoperative VAS score was 0-9 (mean, 4.3); NDI was 16%-44% (mean, 30.0%). There was no significant difference in VAS score and NDI between male and female groups ( P>0.05). The kyphosis range of cervical spines was C _3-5 in 3 cases, C _3-6 in 41 cases, C _3-7 in 30 cases, C _4-6 in 4 cases, C _4-7 in 10 cases, C _5-7 in 1 case, and the kyphosis focal was mostly located between C ₄-C ₅ (78/89, 87.64%). The C ₃-C ₇ inclination of zygapophyseal joints were (60.25±5.56)°, (55.42±5.77)°, (53.03±6.33)°, (58.39±7.27)°, and (64.70±6.40)°, respectively. The C ₀-C ₂ angle, C ₂-C ₇ angle, C ₇S, and cSVA were (-23.81±6.74)°, (10.15±2.94)°, (15.31±4.59)°, and (2.37±1.19) mm, respectively. The C ₇S and cSVA of males were significantly larger than females ( P<0.05), with no significant difference in other parameters between male and female groups ( P>0.05). VAS score and NDI were negatively correlated with C ₀-C ₂ angle ( P<0.05), and positively correlated with C ₂-C ₇ angle and cSVA ( P<0.05); VAS score was negatively correlated with C ₇S ( P<0.05). Except VAS, NDI and all cervical sagittal parameters were affected by age. Age was positively correlated with NDI, C ₇S, and cSVA ( P<0.05), and negatively correlated with C ₀-C ₂ angle and C ₂-C ₇ angle ( P<0.05). The correlation analysis of cervical sagittal parameters showed that C ₀-C ₂ angle was negatively correlated with C ₂-C ₇ angle and cSVA ( P<0.05); C ₇S was negatively correlated with C ₂-C ₇ angle ( P<0.05) and positively correlated with cSVA ( P<0.05). There was no correlation among other parameters ( P>0.05).

The inclination of zygapophyseal joints of cervical spines of DCK patients is U-shaped in the kyphosis range, and the inclination at the kyphosis focal is the smallest. When cervical degenerative kyphosis occurs, in addition to the interaction of sagittal parameters, age, gender, neck pain, and dysfunction will also affect the cervical sagittal balance. Furthermore, cervical curvature and morphological changes are not purely local problems.