Does Interbody Cage Lordosis and Position Affect Radiographic Outcomes After Single-level Transforaminal Lumbar Interbody Fusion?

Abstract

Study Design: This was a retrospective cohort study. Objective: The objective of this study was to determine if the degree of interbody cage lordosis and cage positioning are associated with changes in postoperative sagittal alignment after single-level transforaminal lumbar interbody fusion (TLIF). Summary of Background Data: Ideal sagittal alignment and lumbopelvic alignment have been shown to correlate with postoperative clinical outcomes. TLIF is one technique that may improve these parameters, but whether the amount of cage lordosis improves either segmental or lumbar lordosis (LL) is unknown. Methods: A retrospective review was performed on patients who underwent single-level TLIF with either a 5-degree or a 12-degree lordotic cage. LL, segmental lordosis (SL), disk height, center point ratio, cage position, and cage subsidence were evaluated. Correlation between center point ratio and change in lordosis was assessed using the Spearman correlation coefficient. Secondary analysis included multiple linear regression to determine independent predictors of change in SL. Results: A total of 126 patients were included in the final analysis, with 51 patients receiving a 5-degree cage and 75 patients receiving a 12-degree cage. There were no differences in the postoperative minus preoperative LL (∆LL) (12-degree cage: −1.66 degrees vs. 5-degree cage: −2.88 degrees, P=0.528) or ∆SL (12-degree cage: −0.79 degrees vs. 5-degree cage: −1.68 degrees, P=0.513) at 1-month follow-up. Furthermore, no differences were found in ∆LL (12-degree cage: 2.40 degrees vs. 5-degree cage: 1.00 degrees, P=0.497) or ∆SL (12-degree cage: 1.24 degrees vs. 5-degree cage: 0.35 degrees, P=0.541) at final follow-up. Regression analysis failed to show demographic factors, cage positioning, or cage lordosis to be independent predictors of change in SL. No difference in subsidence was found between groups (12-degree cage: 25.5% vs. 5-degree cage: 32%, P=0.431). Conclusion: Lordotic cage angle and cage positioning were not associated with perioperative changes in LL, SL, or cage subsidence after single-level TLIF. Level of Evidence: Level III.

The impact of cage positioning on lumbar lordosis and disc space restoration following minimally invasive lateral lumbar interbody fusion

“…A recent analysis of 126 single-level TLIFs demonstrated no association between cage lordosis or cage placement in sagittal parameters or disc height. 17 Another study of 45 single-level TLIFs found that anterior cage placement contributed to greater posterior disc height but did not affect LL. 13 This finding is counterintuitive and contrary to the findings of our study, as we found that cage positioning increases the height in the area wherein it is placed.…”

“…Multiple other studies that also evaluated lordosis in LLIF and TLIF found that cage lordosis did not independently predict radiographic improvement. 14,17 Moreover, surgeons should feel comfortable with cage choice without attempting to place progressively larger or more lordotic cages and instead focus on cage placement. Cages should be appropriately sized to a patient's anatomy rather than to impact radiographic outcomes, which may significantly reduce vertebral endplate disruption and increase the chance of subsequent cage subsidence.…”

“…7,[12][13][14][15][16] However, recent studies have not demonstrated an association between degree of cage lordosis and correction of sagittal parameters following interbody fusion. 13,14,17 The role of cage geometry and placement during LLIF procedures continues to remain unclear. Therefore, the primary objective of our study was to evaluate patient and surgical factors that predict increased overall lumbar lordosis (LL) and segmental lordosis correction following LLIF procedures, specifically evaluating cage geometry and positioning.…”

“…Cage placement was defined by measuring the center point ratio (CPR) on the initial postoperative standing lateral radiograph. 17,18 CPR is the distance between the midpoint of the cage and the posterior edge of the superior endplate of the inferior vertebral body divided by the entire length of the superior endplate of the inferior vertebral body. In effect, cages with a greater CPR were placed more anteriorly, while those with a lower CPR were located more posteriorly; a CPR of 0.50 represented a cage placed exactly in the middle of the inferior vertebral body.…”

Radiographic and Patient-Reported Outcomes in Anteriorly Placed Transforaminal Lumbar Interbody Fusion Cage Versus Anterior Lumbar Interbody Fusion With Posterior Instrumentation

“…CPR is calculated by dividing the distance between the cage center point and the posterior extent of the superior endplate of the inferior vertebra by the entire length of the superior endplate of the inferior vertebra. Patients with a TLIF were only included if the cage was anterior (CPR > 0.6), a cutoff used in recent literature investigating anterior cage positioning 14,20 …”