THE EFFECTS OF OVER-DISTRACTION ON ADJACENT SEGMENT DISEASE AND CAGE SUBSIDENCE IN ANTERIOR CERVICAL DISCECTOMY AND FUSION

Over-distraction has been identified as a risk factor for cage subsidence and postoperative neck pain following anterior cervical discectomy and fusion (ACDF). Biomechanical studies have also shown increased intradiscal pressure at adjacent segments after ACDF. This study aims to investigate whether over-distraction of the index disc affects adjacent segment pathology. A retrospective review was conducted on 145 patients who underwent primary ACDF for cervical degenerative conditions between January 2016 and December 2023. Patients were categorized into two groups: (1) Over-distraction group (postoperative–preoperative index disc height difference ≥ 2 mm), and (2) No-distraction group (postoperative–preoperative index disc height difference < 2 mm). Outcome measures included radiographic parameters, Japanese Orthopaedic Association (JOA) score, and the incidences of cage subsidence, as well as radiological and clinical adjacent segment pathologies (RASP and CASP), which were assessed preoperatively, postoperatively, and at final follow-up.