Flexion Dysfunction of Atlanto-Occipital Joint Associated with Cervical Spondylosis.

OBJECTIVE: To investigate the association between atlanto-occipital radiographic alignment in flexion and cervical spondylosis (CS). METHODS: This is a retrospective case-control study. CS patients were recruited from our hospital, and the age/gender/body mass index (BMI)-matched healthy controls were selected from the subjects in health examinations at the same hospital between January 2015 and May 2019. A total of 464 subjects was included in the study. There are 282 males and 182 females. The ages of patients were 20 to 67 years, and the mean age was 33.9 years. CS patients were considered the case group. Based on surgical treatments, they were subdivided into non-operation group and operation group. The operation group and non-operation group had 45 and 187 patients, respectively, while 232 subjects were included in the control group. The angle between McGregor's line and C1 line (O-C1 angle) was evaluated on images taken in flexion (F-OC) and neutral positions (N-OC) independently. The relationship between the FOC (FOC=F-OC-N-OC) and Neck Disability Index (NDI) was examined, and the involvement of the FOC in the onset of CS was analyzed. Receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cut-off for detecting an increased risk of CS. RESULTS: The median follow-up time was 51.6 months (25-115 months). The case groups, especially the operation group, tended to be older (55.8 ± 11.2 vs 41.6 ± 13.8 vs 23.5 ± 5.5 years, P < 0.001), have a higher NDI score (12.2 ± 4.5 vs 6.2 ± 2.1 vs 3.2 ± 1.2, P < 0.001), and longer medical history (10.5 ± 9.5 vs 6.8 ± 11.2 years, P < 0.001). One-way analysis of variance showed statistically significant differences in FOC between the control and case groups (1.4° ± 1.2° vs 3.6° ± 1.9° vs 7.2° ± 2.0°, P < 0.001). Besides, a post-hoc Tukey test showed a lower FOC in the operation group compared with that in the non-operation group (1.4° ± 1.2° vs 3.6° ± 1.9°, P < 0.001). Using FOC as a radiological predictive model to predict CS, the cut-off value was 4.2°. Using FOC as a radiological predictive model to predict CS, the area under the curve (AUC) was 0.86 (95% CI: 0.78-0.92, P < 0.001). In the univariable risk analysis model, conditional logistic regression showed that the FOC level was an independent factor with an important role in the risk of CS. The odds rose to 8.2 times when FOC reached the level under 4.2° (OR = 8.2; 95% CI: 6.4-10.0; P < 0.001). There existed a significant negative correlation between FOC levels and NDI (r = -0.451, P = 0.016). CONCLUSIONS: Stiff O-C1 , which is defined as FOC ≤ 4.2°, represented decreased flexion dysfunction of atlanto-occipital joint and is closely associated with high risk for the occurrence of CS. This finding could show a possible relationship between upper and lower cervical spine and help spine surgeons to understand the pathological process of CS and implement appropriate management.

Thoracolumbar flexion dysfunction and thoracolumbar compression fracture in postmenopausal women: a single-center retrospective study.

OBJECTIVE: To investigate whether thoracolumbar flexion dysfunctions increase the risk of thoracolumbar compression fractures in postmenopausal women. METHODS: The records of postmenopausal women with thoracolumbar vertebral compression fractures and without vertebral compression fractures were surveyed. Demographic data, clinical data, and quantitative computed tomography (QCT) findings were compared between the groups. Chi-squared tests, unpaired t-tests, Spearman, and Mann-Whitney U were used to assess the group characteristics and proportions. The relationship between the risk of fracture and the difference of Cobb's angle of thoracolumbar segment (DCTL) was evaluated by logistic regression. DCTL was calculated by subtracting thoracolumbar Cobb's angles (TLCobb's) from thoracolumbar hyperflexion Cobb's angles (TLHCobb's). Quantitative computed tomography (QCT) values and spinal osteoarthritis (OA) of postmenopausal women in the two groups were compared. RESULTS: 102 of 312 were enrolled to the study group of postmenopausal women with the fracture, and 210 of 312 were enrolled to the control group of postmenopausal women without the fracture. There were significant differences in QCT values and spinal OA including disc narrowing (DSN) and osteophytes (OPH) between the two groups (p < 0.001 for all four). The risk of thoracolumbar compression fractures in the postmenopausal women with DCTL ≤ 8.7° was 9.95 times higher (95% CI 5.31-18.64) than that with > 8.7° after adjusting for age, BMI, and QCT values. CONCLUSION: Low DCTL may be a risk factor of thoracolumbar compression fractures in postmenopausal women, and a DCTL ≤ 8.7° can be a threshold value of thoracolumbar compression fractures.