# CT-Mapped Fusion Patterns After 360° Transforaminal Lumbar Interbody Fusion (TLIF) for Degenerative Spondylolisthesis: High Facet and Interbody Fusion Rates With Limited Clinical Correlates

## TL;DR

This study found that transforaminal lumbar interbody fusion (TLIF) leads to high fusion rates in specific spinal areas, but these rates do not significantly affect patient disability outcomes after one year.

## Contribution

The study provides new insights into the anatomical fusion patterns and their limited clinical impact after 360° TLIF for degenerative spondylolisthesis.

## Key findings

- High interbody and facet joint fusion rates were observed after 360° TLIF.
- Fusion location and number did not correlate with improvements in disability scores.
- Complications were uncommon, and female patients showed higher fusion success in some cases.

## Abstract

Introduction: Degenerative spondylolisthesis is a common cause of low back pain and disability. We evaluated fusion rates across predefined lumbar regions and their association with clinical outcomes after transforaminal lumbar interbody fusion (TLIF). We aimed to compare CT-confirmed fusion across predefined anatomical zones and to assess baseline-to-12-month changes in Oswestry Disability Index (ODI) and Roland-Morris Disability Questionnaire (RMDQ).

Methods: We retrospectively analyzed 88 patients who underwent 360° TLIF at the Mexican National Rehabilitation Institute (January 2017-May 2022). Fusion at seven anatomical zones was assessed on a 12-month follow-up CT. Patient-reported outcomes at 12 months included the ODI and the RMDQ.

Results: Operations most commonly involved L4-L5 (38; 43.1%), followed by L4-L5+L5-S1 (31; 35.3%), L3-L4+L4-L5 (12; 13.7%), L5-S1 (5; 5.9%), and L2-L3+L3-L4+L4-L5 (2; 2.0%). Fusion success was high, particularly for interbody fusion (79; 89.6%, p < 0.0001) and facet joint fusion. Complications were uncommon (8; 9.1%): pedicle fracture (2; 2.3%), durotomy (1; 1.1%), dural injury (1; 1.1%), transient nerve alteration on neuromonitoring (2; 2.3%), L4 spinous-process fracture (1; 1.1%), and screwdriver breakage with retained fragment (1; 1.1%). Fusion location/number did not correlate with postoperative ODI (p = 0.7124) or RMDQ (p = 0.4255). Several fusion types were more often successful in female patients (p < 0.01).

Discussion: TLIF achieved high CT-confirmed fusion-especially interbody and facet-yet the anatomical distribution/number of fused zones did not influence 12-month disability (ODI/RMDQ). Results likely reflect surgical technique and patient optimization rather than fusion location. Interpretation should be cautious given the retrospective single-center design, 12-month follow-up, lack of bone-quality data, and exploratory multiple comparisons.