Functional changes in the spine as predictors of comorbidities in patients with ankylosing spondylitis

BACKGROUND: Advanced ankylosing spondylitis can be characterized by the formation of disabling spinal deformities. However, the effect of cervicothoracic kyphosis on the cardiovascular system is poorly understood. In routine rheumatology practice, the occiput-to-wall distance is used as a reliable method to confirm the presence of kyphosis in patients. AIM: To assess the association between kyphosis (measured by occiput-to-wall distance, the occiput-to-wall distance) and the development of comorbidities in patients with late-stage ankylosing spondylitis. METHODS: The study included men with advanced-stage ankylosing spondylitis. As part of the standard assessment of the primary disease, clinical and laboratory examinations were performed, including additional measurement of myostatin levels. Cardiovascular status was also evaluated using echocardiography and ultrasound examination of the brachiocephalic arteries. RESULTS: Forty men (33 to 67 years old) with advanced ankylosing spondylitis participated in the study. All patients were divided into 2 groups: 1) with the occiput-to-wall distance 10 cm (n = 45%), 2) with the occiput-to-wall distance ≥ 10 cm (n = 55%). The analysis of cardiovascular system status showed that all patients in the occiput-to-wall distance ≥ 10 cm group had hypertension (100% vs 66.7%, p = 0.005) with predominance of grade 2 arterial hypertension (45.5% vs 27.8%, p = 0.010) in contrast to the occiput-to-wall distance ≥ 10 cm group. Echocardiography revealed statistically significant reductions in left ventricular function values in the occiput-to-wall distance ≥ 10 cm group compared to the occiput-to-wall distance 10 cm group. Notably, the occiput-to-wall distance ≥ 10 cm group was more frequently overweight (86.23 ± 14.03 vs. 74.83 ± 14.44, p = 0.016) with a predominance of class I–II obesity (45.5% vs. 11.1%, p 0.001). Also in our patients we found a correlation between serum myostatin level and the occiput-to-wall distance (r = 0.404, p = 0.01), ASDAS (Axial Spondyloarthritis Disease Activity Score; r = 0.405, p = 0.009) and BASFI (Bath Ankylosing Spondylitis Functional Index; r = 0.344, p = 0.03). CONCLUSION: The occiput-to-wall distance increase should be considered as a predictor of the development of cardiovascular pathology, which is confirmed by echo-CG, and other comorbidities. Patients with progressive cervicothoracic kyphosis are characterised by lower values of left ventricular ejection fraction, which may be due to adaptation mechanisms caused by spinal axis displacement. In the future, myostatin measurements should be considered as a complementary method for assessing the function of the cardiovascular system and skeletal muscles.