BACKGROUND Surgical procedures on atlantoaxial dislocation combined with osteoporosis remain controversial. This study was established to assess the mid-term clinical outcomes of atlantoaxial dislocation combined with osteoporosis using posterior atlantoaxial rod, screw fixation and posterior interfacet fusion. MATERIAL AND METHODS From January 2017 to January 2020, 21 patients (4 males and 17 females) with coexisting atlantoaxial dislocation and osteoporosis who underwent posterior atlantoaxial rod and screw fixation were included in our study with an average age of 64±8.1 years (range, 57-74 years). The subjective and objective symptoms, together with the neurological function of the patients were measured. Radiography and magnetic resonance imaging (MRI) were performed, Japanese Orthopaedic Association (JOA) score for spinal cord function and VAS score for pain recovery was assessed. RESULTS JOA and visual analog scale (VAS) score were significantly improved at 14±5.9 month follow-up compared with pretreatment values. Complete or almost complete anatomical reduction was observed in all 21 patients. All patients had good bony fusion at the final follow-up. No screw-loosening or atlantoaxial redislocation occurred in 21 cases. The only complication was mild numbness in the C2 innervation area of the posterior occipital region in 6 cases, which had no effect on life. CONCLUSIONS The results suggested that posterior atlantoaxial rod, screw fixation system, and posterior interfacet fusion could achieve satisfactory initial results for the treatment of atlantoaxial dislocation combined with osteoporosis.