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

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

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To compare outcomes in anteriorly placed transforaminal lumbar interbody fusions (TLIFs) and anterior lumbar interbody fusions (ALIFs).

SUMMARY OF BACKGROUND DATA

TLIF and ALIF are surgical techniques that have become more prevalent in recent years. Although studies have compared the two, none have considered TLIFs with anteriorly placed cages, which may serve as a better comparison to ALIFs.

PATIENTS AND METHODS

Patients undergoing TLIF or ALIF with posterior instrumentation from 2010 to 2020 at a tertiary care institution were retrospectively identified. TLIF cage position was assessed and those with anterior placement were included. Electronic medical records were reviewed to identify patient characteristics and patient-reported outcomes. Radiographic outcomes included posterior disc height (DH), lumbar lordosis (LL), sacral slope, pelvic incidence, and pelvic tilt. Statistical analysis was performed to compare the two groups.

RESULTS

Of the 351 patients, 108 had ALIF with posterior instrumentation and 207 had a TLIF. Preoperatively, patients undergoing TLIF had less LL (53.7° vs . 60.6°, P < 0.001), sacral slope (38.3° vs . 43.7°, P < 0.001), and pelvic incidence (60.1° vs . 66.1°, P < 0.001), all of which remained significant at 1-year and long-term follow-up ( P < 0.001). The TLIF group had less ∆DH (1.51° vs . 5.43°, P < 0.001), ∆LL (1.8° vs . 2.97°, P = 0.038), and ∆segmental lordosis (0.18° vs . 4.40°, P < 0.001) at 1 year postoperatively. At 2 to 3 years, ∆DH ( P < 0.001) and ∆segmental lordosis ( P = 0.001) remained significant, but ∆LL ( P = 0.695) did not. Patients in the TLIF group had higher Visual Analog Scale-Back scores 1 year postoperatively (3.68 vs . 2.16, P = 0.008) and experienced less improvement in Oswestry Disability Index (-17.1 vs . -28.6, P = 0.012) and Visual Analog Scale-Back (-2.67 vs . -4.50, P = 0.008) compared with patients undergoing ALIF.

CONCLUSIONS

Our findings suggest that ALIF with posterior instrumentation performed superiorly in radiographic outcomes and patient-reported outcomes compared with anteriorly placed TLIFs. Anteriorly placed TLIF cages may not achieve the same results as those of ALIF cages.

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

OBJECTIVE

The objective of this study was to evaluate patient and surgical factors that predict increased overall lumbar lordosis (LL) and segmental lordosis correction following a minimally invasive lateral lumbar interbody fusion (LLIF) procedure.

METHODS

A retrospective review was conducted of all patients who underwent one- or two-level LLIF. Preoperative, initial postoperative, and 6-month postoperative measurements of LL, segmental lordosis, anterior disc height, and posterior disc height were collected from standing lateral radiographs for each patient. Cage placement was measured utilizing the center point ratio (CPR) on immediate postoperative radiographs. Spearman correlations were used to assess associations between cage lordosis and radiographic parameters. Multivariate linear regression was performed to assess independent predictors of outcomes.

RESULTS

A total of 106 levels in 78 unique patients were included. Most procedures involved fusion of one level (n = 50, 64.1%), most commonly L3-4 (46.2%). Despite no differences in baseline segmental lordosis, patients with anteriorly or centrally placed cages experienced the greatest segmental lordosis correction immediately (mean anterior 4.81° and central 4.46° vs posterior 2.47°, p = 0.0315) and at 6 months postoperatively, and patients with anteriorly placed cages had greater overall lordosis correction postoperatively (mean 6.30°, p = 0.0338). At the 6-month follow-up, patients with anteriorly placed cages experienced the greatest increase in anterior disc height (mean anterior 6.24 mm vs posterior 3.69 mm, p = 0.0122). Cages placed more posteriorly increased the change in posterior disc height postoperatively (mean posterior 4.91 mm vs anterior 1.80 mm, p = 0.0001) and at 6 months (mean posterior 4.18 mm vs anterior 2.06 mm, p = 0.0255). There were no correlations between cage lordotic angle and outcomes. On multivariate regression, anterior cage placement predicted greater 6-month improvement in segmental lordosis, while posterior placement predicted greater 6-month improvement in posterior disc height. Percutaneous screw placement, cage lordotic angle, and cage height did not independently predict any radiographic outcomes.

CONCLUSIONS

LLIF procedures reliably improve LL and increase intervertebral disc space. Anterior cage placement improves the lordosis angle greater than posterior placement, which better corrects sagittal alignment, but there is still a significant improvement in lordosis even with a posteriorly placed cage. Posterior cage placement provides greater restoration in posterior disc space height, maximizing indirect decompression, but even the anteriorly placed cages provided indirect decompression. Cage parameters including cage height, lordosis angle, and material do not impact radiographic improvement.