Degenerative L4-L5 spondylolisthesis and stenosis surgery: does over-level flavectomy technique influence clinical outcomes and rates of cranial adjacent segment disease?

Background: One of the most dreaded long-term complications related to L4-L5 lumbar arthrodesis is the onset of adjacent segment disease, which most frequently occurs at the cranial level. Few studies have compared the rates of cranial adjacent segment disease (CASD) in patients undergoing lumbar fusion associated with total laminectomy at the same level with those undergoing partial laminectomy. No study has examined the role of selective over-level flavectomy (OLF; i.e., L3-L4).

Methods: A total of 299 patients undergoing posterolateral arthrodesis (PLA) for L4-L5 degenerative spondylolisthesis were retrospectively analyzed with a 5-year follow-up. 148 patients underwent PLA + L4-L5 flavectomy + L4 partial laminectomy (control group), while 151 underwent PLA + L4-L5 flavectomy + total L4 laminectomy + L3-L4 flavectomy (OLF group). Rates of reoperations due to CASD were examined utilizing Cox proportional hazard models, while clinical improvement at follow-up (measured in ODI) was analyzed using generalized linear models (GLMs). Adjustments for potential confounders were made (grade of lumbar lordosis, age, sex, BMI, intervertebral disc degeneration, and presurgical cranial spinal stenosis).

Results: At 5 years from the operation, 16 patients (10.8%) in the control group had undergone revision surgery for CASD compared to 5 patients (3.3%) in the OLF group (p = 0.013). Survival analysis and GLM demonstrated that the OLF group had a significantly lower incidence of CASD and presented more favorable clinical outcome. There were no differences in the rate of discal degeneration or the onset of Meyerding's grade I degenerative spondylolisthesis at the adjacent segment. BMI was the only other significant predictor of ODI improvement and of the incidence of CASD.

Conclusions: In patients with L4-L5 degenerative spondylolisthesis and stenosis, the OLF technique may lower rates of CASD and improve clinical outcomes by preventing cranial spinal stenosis without increasing iatrogenic instability or accelerating intervertebral disc degenerative changes.