Two-Year Clinical and Radiographic Outcomes of Expandable Interbody Spacers Following Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Prospective Study

BACKGROUND

The advantages of minimally invasive surgery for transforaminal lumbar interbody fusion (MIS TLIF) are well documented and include decreased blood loss, shorter length of hospital stay, and reduced perioperative costs. Clinical evidence for the use of expandable interbody spacers in conjunction with MIS TLIF, however, is scarce. This study sought to examine the clinical and radiographic outcomes of patients undergoing MIS TLIF with an expandable spacer.

METHODS

Forty patients from 4 institutions who underwent MIS TLIF with an expandable spacer were included in this study and followed for 24 months. Investigator assessment of the surgical technique was reported. Patient self-reported outcomes included Visual Analog Scale (VAS), Oswestry Disability Index (ODI), and Short Form 36 (SF-36) physical and mental component scores. Disc height, foraminal height, segmental and lumbar lordosis, and fusion were also assessed.

RESULTS

Investigators reported that intraoperative insertion, impaction, number of passes through the neural structures, and fit were better with an expandable spacer than a static spacer. Significant improvements in VAS, ODI, and SF-36 were reported as early as 6 weeks postoperatively and maintained through 24 months. Mean intervertebral and foraminal heights improved significantly from the preoperative time interval to as early as 6 weeks postoperatively and maintained through 24 months. There were no cases of spacer migration, subsidence, or collapse.

CONCLUSIONS

The use of an expandable interbody spacer in combination with MIS TLIF resulted in positive investigator assessments, immediate and progressive symptom relief, significant radiographic improvements, and no spacer-related complications.

Clinical and radiographic analysis of expandable versus static lateral lumbar interbody fusion devices with two-year follow-up

Background

Utilization of static and expandable interbody spacers for minimally invasive lateral lumbar interbody fusion (LLIF) offers favorable clinical results. However, complications such as implant migration and/or subsidence may occur with a static implant. Expandable devices allow for in situ expansion to optimize fit and mitigate iatrogenic endplate damage during trialing and impaction. This study sought to compare clinical and radiographic outcomes of static and expandable spacers following LLIF and report device-related complications.

Methods

This study included 29 patients who underwent LLIF with a static spacer and 27 with an expandable spacer; all procedures were combined with supplemental transpedicular posterior fixation. Patient self-assessment forms and radiographic records were used to assess clinical and radiologic outcomes.

Results

Mean patient age was 62.3±10.3 years (64% female). One-level surgery was performed in 87.5% of patients, and 12.5% underwent two-level surgery. Results showed no significant differences in blood loss or length of hospital stay (P>0.05). However, operative times differed statistically between static (63.3±37.8 min) and expandable (120.2±59.6 min) groups (P=0.000). Mean visual analog scale (VAS) and Oswestry Disability Index (ODI) scores improved significantly from preoperative to 24-month follow-up in both groups (P<0.05). Preoperative intervertebral and neuroforaminal height increased significantly in both groups (P<0.01). Fusion was observed in all operative levels in the static and expandable spacer groups by 24-month follow-up. Implant subsidence was reported in 16.1% of static levels and none of the expandable levels (P<0.01). Postoperative radiographs showed no evidence of implant migration, and no cases required surgical revision at the index or adjacent levels.

Conclusions

LLIF using expandable spacers resulted in similar clinical and radiographic outcomes when compared with using static spacers, and led to a lower subsidence rate.