Frequency of Change in Assessment from Bony Union to Nonunion after Lumbar Interbody Fusion: A Multicenter Study

Hiroki Oba; Jun Takahashi; Yosuke Shibata; Tetsuro Ohba; Tomohiko Hasegawa; Yukihiro Isogai; Shugo Kuraishi; Shota Ikegami; Masashi Uehara; Takashi Takizawa; Ryo Munakata; Terue Hatakenaka; Toshiyuki Ojima; Zentaro Yamagata; Yukihiro Matsuyama; Hirotaka Haro

doi:10.22603/ssrr.2020-0032

Frequency of Change in Assessment from Bony Union to Nonunion after Lumbar Interbody Fusion: A Multicenter Study

Spine Surg Relat Res. 2021 Jun 30;6(1):63-70. doi: 10.22603/ssrr.2020-0032. eCollection 2022.

Authors

Hiroki Oba¹, Jun Takahashi¹, Yosuke Shibata², Tetsuro Ohba³, Tomohiko Hasegawa⁴, Yukihiro Isogai⁵, Shugo Kuraishi¹, Shota Ikegami¹, Masashi Uehara¹, Takashi Takizawa¹, Ryo Munakata¹, Terue Hatakenaka¹, Toshiyuki Ojima², Zentaro Yamagata⁶, Yukihiro Matsuyama⁴, Hirotaka Haro³

Affiliations

¹ Department of Orthopaedic Surgery, Shinshu University, School of Medicine, Matsumoto, Japan.
² Departments of Community Health and Preventive Medicine, Hamamatsu University School of Medicine, Hamamatsu, Japan.
³ Department of Orthopaedic Surgery, University of Yamanashi, School of Medicine, Chuo, Japan.
⁴ Department of Orthopaedic Surgery, Hamamatsu University School of Medicine, Hamamatsu, Japan.
⁵ Medical Affairs Department, Pharmaceutical Business Administration Division, Asahi Kasei Pharma Corporation, Tokyo, Japan.
⁶ Departments of Health Science for Clinical Medicine, Graduate School of Medicine, University of Yamanashi, Chuo, Japan.

Abstract

Introduction: Assessments of early postoperative bony union after posterior lumbar interbody fusion via computed tomography (CT) have revealed cases in which interbody fixation by bony union resulted in nonfusion due to bone absorption. The apparent bone union state reverted to a nonunion state several months later, exhibiting a so-called "fake union" phenomenon. Additionally, few reports have evaluated the effect of teriparatide on bony union. The present study aimed to evaluate the frequency of change in assessment from fusion to nonfusion in the postoperative follow-up of lumbar interbody fusion, compare the late postoperative bony union rates in groups with or without early postoperative fusion, and examine the effect of postoperative teriparatide in those groups.

Methods: Sixty-nine subjects enrolled from multiple hospitals were prospectively evaluated following single-level lumbar interbody fusion. The patients were randomly allocated into treatment with or without weekly postoperative teriparatide. The subjects were then classified as having bony union or nonfusion at 2 months postoperatively, and fusion rates at 6 months were compared. For the evaluation of bony union, blinded radiological examinations were performed via CT. Additional comparisons were made according to teriparatide use.

Results: The rate of nonunion at 6 months postoperatively in patients with fusion at 2 months postoperatively was 27.8%. Among subjects with bony union at 2 months postoperatively, the fusion rate at 6 months in those who received teriparatide was 93.3% (p=0.027) versus 57.1% in those who did not.

Conclusions: The rate of nonunion at 6 months postoperatively in patients exhibiting union at 2 months after surgery was 27.8%. Postoperative weekly teriparatide treatment significantly reduced the rate of fake union.

Keywords: bone resorption; bony union; delayed fusion; posterior lumbar interbody fusion; transforaminal lumbar interbody fusion; weekly teriparatide.