Allograft Subsidence Decreases Postoperative Segmental Lordosis With Minimal Effect on Global Alignment Following ACDF

Zachariah W. Pinter, Anthony Mikula, Matthew Shirley, Ashley Xiong, Scott Wagner, Benjamin D. Elder, Brett A. Freedman, Ahmad Nassr, Mohamad Bydon, Bradford Currier, I. David Kaye, Christopher Kepler, Arjun S. Sebastian

Research output: Contribution to journalArticlepeer-review

Abstract

Study Design: Retrospective cohort study. Objective: Studies investigating the impact of interbody subsidence in ACDF suggest a correlation between subsidence and worse radiographic and patient-reported outcomes. The purpose of this study was to assess whether allograft subsidence assessed on CT is associated with worse cervical alignment. Methods: We performed a retrospective review of a prospective cohort of patients undergoing 1 to 3 level ACDF. Cervical alignment was assessed on standing radiographs performed preoperatively, less than 2 months postoperatively, and greater than 6 months postoperatively. Allograft subsidence was assessed on CT scan performed at least 6 months postoperatively. Patients with at least 1 level demonstrating greater than 4mm of cage subsidence were classified as severe subsidence. Student’s t-test was used to compare all means between groups. Results: We identified 66 patients for inclusion, including 56 patients with non-severe subsidence and 10 patients with severe subsidence. For the entire cohort, there was a significant increase in C2-7 Lordosis (p = 0.005) and Segmental Lordosis (p < 0.00 001) from preoperative to early postoperative. On comparison of severely and non-severely subsided levels, severely subsided levels demonstrated a significantly greater loss of segmental lordosis from early to mid-term follow-up than non-severely subsided levels (-4.89 versus -2.59 degrees, p < 0.0001), manifesting as a significantly lower segmental lordosis at >6 months postoperative (0.54 versus 3.82 degrees, p < 0.00 001). There were no significant differences in global cervical alignment parameters between patients with severe and non-severe subsidence. Conclusions: Severe subsidence is associated with a significant increase in loss of segmental lordosis, but has minimal effect on global cervical alignment parameters.

Original languageEnglish (US)
JournalGlobal Spine Journal
DOIs
StateAccepted/In press - 2021

Keywords

  • allograft
  • cervical alignment
  • interbody
  • segmental lordosis
  • subsidence

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine
  • Clinical Neurology

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