# Does adding an interbody cage in L4–L5 posterolateral fusion for degenerative spondylolisthesis and stenosis improve clinical outcome?

## TL;DR

Adding an interbody cage during L4–L5 spinal fusion for elderly patients with spondylolisthesis did not improve long-term outcomes but increased complications and surgery time.

## Contribution

This study provides evidence that adding interbody cages in spinal fusion for elderly patients does not improve disability outcomes and increases peri-operative risks.

## Key findings

- Functional improvement was similar between groups with and without interbody cages.
- Cage use increased complications, transfusions, and hospital stay.
- Reoperation rates were similar over five years regardless of cage use.

## Abstract

As the population ages, L4–L5 degenerative spondylolisthesis is increasingly common. Posterolateral fusion was long standard; interbody cages are widely used for perceived higher fusion rates.

Does adding an interbody cage to posterolateral fusion improve outcomes or reduce complications in elderly patients with grade I spondylolisthesis and severe stenosis?

We retrospectively studied 319 adults aged 60–85 who underwent single-level L4–L5 fusion (2011–2018) after failed conservative care. Patients received posterior lumbar fusion (PLIF, n = 155) or posterolateral lumbar fusion (PLF, n = 164). Primary outcomes were Oswestry Disability Index (ODI) change and complications over a median five-year follow-up; secondary outcomes were operative time, hospital stay, and transfusions. Multivariable analyses adjusted for age, sex, BMI, year of surgery, and sagittal alignment.

Functional improvement was similar (median ODI reduction ≈22 points; p = 0.97), and implant-related revision and revision-free survival did not differ. Cage use increased overall complications (24.5 % vs 7.9 %), prolonged surgery (125 vs 95 min) and hospital stay (4 vs 3 days), and raised transfusions (9.7 % vs 1.8 %), dural tears (11.6 % vs 2.4 %), and radicular deficits (6.5 % vs 1.2 %). The association between cage use and complications persisted after adjustment.

In this elderly, low-grade L4–L5 degenerative spondylolisthesis cohort, adding a posterior interbody cage to instrumented posterolateral fusion did not improve 5-year disability but was associated with higher peri-operative morbidity and greater resource use.

•Adding an interbody cage did not improve 5-year disability after L4–L5 fusion.•Cage use increased complications, blood transfusions, and hospital stay.•Operations with a cage were longer and had more dural tears and nerve deficits.•Reoperation rates were similar with and without a cage over five years.•Fusion without an interbody cage may be a safer, simpler option for older patients.

Adding an interbody cage did not improve 5-year disability after L4–L5 fusion.

Cage use increased complications, blood transfusions, and hospital stay.

Operations with a cage were longer and had more dural tears and nerve deficits.

Reoperation rates were similar with and without a cage over five years.

Fusion without an interbody cage may be a safer, simpler option for older patients.