Risk factors associated with clinical adjacent segment pathology following multi-level cervical fusion surgery

Few clinical studies investigate risk factors associated with clinical adjacent segment pathology (CASP) following multi-level cervical fusion surgery. The aim is to record the incidence of postoperative CASP in patients after at least 2 years' follow-up and to identify possible risk factors that may be associated with the CASP after multi-level cervical surgery.We retrospectively reviewed patients who underwent multi-level cervical surgery in our hospital from January 2004 to February 2016. All patients underwent more than 2 years' follow-up. The diagnosis of CASP is according to clinical symptoms as well as image findings. Potential risk factors were collected from demographic data and radiographic images.A total of 301 patients after multi-level cervical surgery were analyzed. During follow-up, 28 patients (9.3%) were diagnosed as having CASP. Among these patients, 7 showed symptoms of CASP within 3 years after surgery, 6 showed symptoms between 3 and 5 years, 14 showed symptoms between 5 and 10 years, and the last one showed symptoms more than 10 years later. In the multivariate analysis, degeneration of adjacent segment (OR, 1.592; 95% CI, 1.113-2.277), decreased Cobb angle in fused vertebrae (OR, 2.113; 95% CI, 1.338-3.334) and decreased Cobb angle in cervical spine (OR, 1.896; 95% CI, 1.246-2.886) were correlated with the incidence of CASP during follow-up.The incidence of CASP following multi-level cervical surgery was 9.3% with a mean of about 70 months' follow-up. Patients with preoperative degeneration of adjacent segment and postoperative imbalance of sagittal alignment have a higher risk of developing CASP after multi-level cervical surgery.