An 85-year-old man with diffuse idiopathic skeletal hyperostosis underwent total hip arthroplasty (THA) through a direct anterior approach. Postoperatively, persistent blood loss and worsening abdominal and back pain prompted computed tomography, which identified an L1 hyperextension fracture-dislocation. The patient underwent staged posterior and anterior instrumented fusion. At the 5-year follow-up, he had persistent dorsal column dysfunction.Conclusion:
Fracture-dislocation of the ankylosed spine is a rare complication following THA. We recommend lateral decubitus positioning, pelvic and back support, careful limb manipulation, and an in situ femoral neck osteotomy to avoid excessive loads on the stiff spine during THA.