Study design:

Retrospective cohort study.

Purpose:

To assess long-term clinical outcomes of adjacent segment disease (ASD) in patients who underwent lumbar interbody fusion with percutaneous pedicle screw (PS) instrumentation.

Overview of literature:

ASD is a well-known sequela of spinal fusion, and is reported to occur at a rate of 2%-3% per year. There is debate as to whether ASD is a result of the instrumentation and fusion method or is the natural history of the patient’s disease. Minimally invasive percutaneous PS augmentation of lumbar interbody fusion aims to prevent the disruption of posterior soft tissue stabilizers.

Methods:

From 2004-2014, 419 consecutive patients underwent anterior, lateral, or minimally invasive transforaminal lumbar interbody fusion with percutaneous PS placement at a single institution. The mean follow-up was 4.5 years. The primary outcome measure was reoperation due to ASD. Patients were divided into two cohorts: those who underwent revision surgery secondary to ASD and those who did not require further surgery. Radiographic parameters were performed using postoperative radiographs. Patients with a pelvic incidence-lumbar lordosis (PI-LL) mismatch >10° were noted.

Results:

Revision proportion secondary to ASD was 4.77% (n=20). Mean time to revision surgery was 2.5 years. Revision rate secondary to ASD was 1.1% per year. Patients who developed ASD were younger than those who did not (50.5 vs. 56.9 years, p=0.015). There was no difference in number of levels fused between cohorts. Revision proportion secondary to ASD was similar between approaches (anterior, lateral, minimally invasive). There was no significant difference in PI-LL mismatch between those who underwent revision for ASD and those who did not (22.2% vs 18.8%, p=0.758).

Conclusions:

ASD rates in patients who underwent percutaneous PS placement were lower than those previously published after open PS placement, possibly related to greater preservation of the posterior stabilizing elements of the lumbar spine.