Radiographic Robustness of Lumbar Interbody Fusion Techniques

Introduction:

Lumbar interbody fusion (LIF) can be achieved with various techniques, each with its own advantages and disadvantages. Differences in long-term radiographic outcomes remain unclear.

Aims/

Objectives:

The purpose of this study was to (1) evaluate the changes in sagittal parameters in the preoperative, immediate post-operative, and latest follow-up phase, and (2) to evaluate the radiographic maintenance of these parameters over time.

Materials and

Methods:

Patients who had undergone single level anterior (ALIF), lateral (LLIF), posterior (PLIF), or transforaminal (TLIF) lumbar interbody fusion in an integrated health system from 2007 to 2022 were identified. Orthopaedic spine and neurosurgical patients were included. Exclusion criteria included a non-degenerative diagnosis, inadequate radiographs, multilevel and revision surgery, and postoperative follow-up less than one month. Retrospective chart review was conducted to collect patient demographics and diagnosis at time of surgery. Upright lumbar radiographs taken prior to surgery, at the time of surgery, and at most recent follow-up were analyzed. Each radiograph was measured for pelvic incidence (PI), lumbar lordosis (LL), segmental lordosis (SL), posterior disc height (PDH), and foraminal height (FH).


Results:

A total of 194 patients met inclusion criteria. There were 28 ALIFs (follow-up=23.6mon), 19 LLIFs (follow-up=11.2mon), 96 TLIFs (follow-up=10.4mon) and 51 PLIFs (follow-up=24.1mon). Differences were found in patient age, gender, and BMI between cohorts.

PDH and FH spinal parameters increased immediately following ALIF (ΔPDH= +5.3mm ΔFH= +4.4mm p< 0.0001), LLIF (ΔPDH= +4.5mm ΔFH= +4.1mm p< 0.0001), TLIF (ΔPDH= +3.4mm ΔFH= +3.5mm p< 0.0001), and PLIF (ΔPDH= +4.5mm ΔFH= +4.0mm p< 0.0001). SL changed immediately for ALIF (ΔSL= +5.0deg, p=0.002) and LLIF (ΔSL= +3.3deg, p=0.0007).

Compared to the immediate post-operative phase, PDH and FH decreased at latest follow-up for ALIF (ΔPDH= -1.9mm p=0.002, ΔFH= -1.7mm p=0.03), LLIF (ΔPDH= -1.6mm ΔFH= -2.5mm p< 0.003), TLIF (ΔPDH= -0.9mm ΔFH= -1.9mm p< 0.001), and PLIF (ΔPDH= -1.0mm ΔFH= -1.7mm p< 0.005). SL decreased for ALIF (ΔSL= -4.6deg, p=0.0008), TLIF (ΔSL= -0.9deg, p=0.02), and PLIF (ΔSL= -1.2deg, p=0.07). LL did not change at any time point postoperatively across techniques.

Accounting for interobserver reliability, no significant differences in the change in radiographic parameters was noted across all techniques at final follow up (p>0.05).


Conclusion:

Lumbar interbody fusion, regardless of technique, was shown to provide significant radiographic changes in posterior disc height and foraminal height. Techniques utilizing larger intervertebral cage sizes (ALIF and LLIF) improved segmental lordosis. Single level LIF did not affect overall lumbar lordosis.

Over time, all LIF techniques demonstrated a degree of loss of correction and radiographic settling. No LIF technique demonstrated superior radiographic robustness over time. A limitation of this study was that ALIF and LLIF were not subdivided into standalone LIF versus LIF supplemented with posterior instrumentation. Further studies are warranted to study the relationship of these parameters to the degree of indirect decompression, as well as its relationship to clinical outcomes.