Impact of Interspace Distraction on Fusion and Clinical Outcomes in Anterior Cervical Discectomy and Fusion: A Longitudinal Cohort Study

Abstract

Study design: Longitudinal cohort study.

Purpose: To determine the effect of change in interspace height on fusion and postoperative neck pain.

Overview of literature: The optimal height of a cervical interbody device (cage) in anterior cervical discectomy and fusion (ACDF) is not well defined. In addition, the effect of interspace distraction on fusion and postoperative neck pain remains unclear.

Methods: We retrospectively reviewed the charts of consecutive patients who underwent one- or two-level ACDF using polyetheretherketone cages by multiple surgeons from January 2015 to June 2016. We excluded patients younger than 18 years old, patients who had prior surgery at the same level (s), those with two-stage procedures, and those with less than 3 months of followup. Fusion was determined using the "Song" criteria. Ordinal regression was used to determine predictors of fusion. Patient-reported outcomes (PRO) were analyzed.

Results: We identified 323 consecutive patients. Twenty-two patients met the exclusion criteria. A total of 435 operative levels were included in the 301 remaining patients. Interspace fusion did not significantly vary by increasing interspace height with fusion rates between 76.2% and 82.8% at a mean follow-up of 17.9±12.6 months. The effect of an increase in interspace height and neck pain PRO was available for 163 patients who underwent one-level ACDF at a mean follow-up period of 16.2±13.1 months. We found no significant difference in fusion rate or neck pain score with increasing interspace height from 1 to 8 mm. Ordinal regression demonstrated no significant predictors of fusion.

Conclusions: Interspace distraction from 1 to 8 mm did not result in significantly different pseudarthrosis rates or postoperative neck pain.

Keywords: Cage height; Cervical spine; Neck pain; Spinal fusion.

Fig. 1

A 35-year-old female patient with C6–7 disc herniation with central and right neuroforaminal stenosis causing right C7 radiculopathy failed several months of conservative management, elected to proceed with C6–7 anterior cervical discectomy and fusion. (A, B) Preoperative sagittal magnetic resonance imaging, lateral standing radiograph with neutral head position. (C, D) Flexion and extension lateral radiographs at 13 months postoperative demonstrating absence of spinous process motion at the level of arthrodesis and some posterior disc-space crossing trabeculation.