Purpose:

To explore the characteristics of spontaneous facet joint fusion (SFJF) in patients after oblique lateral lumbar interbody fusion combined with lateral single screw-rod fixation (OLIF-LSRF).

Methods:

We randomly selected 300 patients from 723 patients treated with OLIF-LSRF into a cross-sectional study based on the pilot study results. A novel fusion classification system was designed to evaluate the fusion status of the facet joints at three time points. Ultimately, the prevalence, characteristics, and significance of SFJF were analyzed.

Results:

A total of 265 (333 levels) qualified cases were included in our study. The novel classification for SFJF has excellent reliability (kappa > 0.75). The rate of SFJF was 15.20% (45/296 levels) at 3 months postoperatively, 31.34% (89/284 levels) at 6 months postoperatively, and 33.63% (112/333 levels) at the last follow-up. The circumferential fusion rate was 31.53% (105/333 levels) at the last follow-up. The location of SFJF was mostly on the right facet joint (P < 0.001), and the rate of SFJF increased significantly from 3 to 6 months after the operation (P < 0.001). The average age of patients with SFJF was older than that of patients without SFJF (P < 0.001). There was no significant difference in Visual Analog Scale or Oswestry Disability Index scores between patients with and without SFJF.

Conclusion:

In the OLIF-LSRF procedure, SFJF occurs mostly at 3-6 months postoperatively, especially in elderly patients and at the right facet joint. OLIF-LSRF has the potential for circumferential fusion.