Prevalence, Features, and Predictive Factors of Spontaneous Spinal Arthrodesis in Posttraumatic Thoracolumbar Kyphosis.

ABSTRACT

OBJECTIVE: Spontaneous spinal arthrodesis (SSA) is a phenomenon of spontaneous fusion, and SSA is not rare in posttraumatic thoracolumbar kyphosis (PTK). However, few reports have focused on SSA in patients with PTK. The objective of this study was to investigate the prevalence, features, and predictive factors of SSA in patients with PTK. METHODS: In this retrospective study, 70 patients with PTK were included. Data on the clinical and radiologic parameters were obtained and evaluated. According to whether there was SSA or not, patients were divided into an SSA group (n = 45) or a non-SSA group (n = 25). A binary logistic regression analysis was used to identify the predictive factors for SSA. RESULTS: The incidence of SSA in PTK was 64%. Among 45 patients with PTK with SSA, SSA was present as a solid bridging anterior osteophyte along the vertebral bodies in 11 patients, posterior contiguous bony growth through the facet joints bilaterally in 13 patients, bony formation in both anterior and posterior elements in 18 patients, and direct contiguous bony formation from the injured vertebral body to the adjacent one in 3 patients. Patients with longer disease duration, larger local Cobb angle, and anterior wall height loss (AWHL) ratio of injured vertebral body, and less kyphosis flexibility index were significantly more likely to develop SSA. The parameter of AWHL remained significant in binary logistic regression analysis. CONCLUSIONS: SSA in PTK was common, and the SSA sign presented in various patterns, which might have implications for surgical decisions. AWHL was the independent predictor for SSA.