BACKGROUND: The incidence of symptomatic adjacent segment disease (ASD) after anterior cervical discectomy and fusion (ACDF) was reported as 2.9% per year in a previous cohort of 374 patients. Few other data corroborate the incidence and natural history of ASD.
OBJECTIVE: To calculate the incidence of ASD after ACDF that required secondary fusion surgery.
METHODS: The retrospective study used an 11-year nationwide database to analyze the incidences. All patients who underwent ACDF for cervical disc diseases were identified through diagnostic and procedure codes. Kaplan-Meier and Cox regression analyses were performed.
RESULTS: From 1997 to 2007, covering 241800725.8 person-years, 19385 patients received ACDF and 568 had two or more ACDF operations. The incidence of secondary ACDF operations was 7.6 per 1,000 person-years. At the end of the ten-year cohort, 94.4% of patients who had received one ACDF remained free from secondary ACDF. The average time interval between the first and second ACDF was 23.3 months. After adjusting for comorbidities and socio-economic status, secondary ACDF operations were more likely performed on males (HR= 1.27, p=0.008) aged 15-39 and 40-59 years (HR= 1.45 and 1.41, p=0.009 and 0.002, respectively).
CONCLUSION: Repeat ACDF surgery for ASD cumulated steadily in an annual incidence of ~0.8%, much lower than the reported incidence of symptomatic ASD. However, at the end of this ten-year cohort, a considerable portion of patients (5.6%) received a second operation. Younger and male patients are more likely to receive such second operations.
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