Introduction
There have been considerable changes in Lumbar Interbody Fusion (LIF) interbody cages from autograft blocks to modern cages with and without integral screw fixation. However, issues remain with reportedly high re-operation rates (18-23%), pseudoarthrosis, and cage subsidence. In the present study, we perform a systematic review of the literature to analyse how cage developments have impacted clinical outcomes (VAS back pain).
Methods
We performed a literature search following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. The search was conducted using PubMED, Embase and CENTRAL. We reviewed Randomized Controlled Trials (RCT) and considered studies published as full texts.
Results
The literature search yielded 4272 results. 14 studies met the inclusion criteria. Across the 14 studies, there were results for 860 patients. These were categorized into four groups for patients receiving: Femoral Ring Allografts (FRA); BAK style cages; and non-integral fixation cages. There were insufficient data from the 14 RCT to create a meaningful integral fixation group, and so cohort studies were also included for this group (410 patients).
All cohorts demonstrated statistically significant improvement in mean VAS (all post-op time points compared to pre-operative baseline). BAK style cages demonstrated the largest improvement (4.21), and integral screw fixation cages had the lowest mean VAS score (2.93) two years postoperatively.
Conclusion
Devices that increase stabilisation through mechanical fixation (e.g. BAK-style cages or integral screw fixation cages) resulted in lower mean VAS scores 24-months post-operatively compared to the FRA group (p<0.05).
There were no significant differences between 6-month, 1-year and 2-year time points for each group. This may suggest that VAS (back pain) results at 6-months post-op are indicative of patient scores at the 2-year follow-up time point.