Use of Anterior Plates in Anterior Cervical Discectomy and Fusion After Traumatic Fracture Dislocations Lead to Early Adjacent-Level Degeneration.

Objectives Adjacent-level disc degeneration after anterior cervical discectomy and fusion (ACDF) is established in degenerative cervical disease. Plate-to-disc distance (PDD) <5 mm is a known cause of this complication. Our aim was to assess the likelihood of disc degeneration of adjacent levels in patients with traumatic fracture dislocation within two years of surgery. Methods We retrospectively reviewed scans of patients who underwent ACDF surgery using an anterior plate for fracture dislocation of the cervical spine in the Royal London Hospital, London, UK. ACDF for indications other than trauma and fusions without an anterior plate were excluded. The distance between the edges of the plate and the superior and inferior intervertebral discs was measured on scans before and after surgery, with six months to two years of follow-up. Degeneration of the adjacent intervertebral discs was assumed if there was a difference in height equal to or greater than 30% and signs of ossification. Results Twenty-five patients with 50 discs were included. We investigated a PDD cutoff of 5 mm. Adjacent discs with PDD >5 mm were in group A (n = 14) while those with PDD <5 mm were in group B (n = 36). The mean age was 38 and 43 years, respectively. There was significantly lower incidence of radiological evidence of disc degeneration in group A compared to group B (43.24% vs. 15.38%; p = 0.03). More patients had PDD <5 mm in cephalad adjacent discs compared to caudal adjacent discs (84.62% vs. 58.33%; p = 0.03). No significant difference was found comparing the proportion of caudal and cephalad adjacent discs that underwent degeneration (37.50% vs. 34.62%; p = 0.41). We further analysed the impact of different PDD cutoffs, varying from 2 mm to 6 mm, and found that a PDD of at least 4 mm significantly decreases the likelihood of adjacent disc degeneration (p = 0.03). Conculsion There was a significant increase in adjacent disc degeneration in patients undergoing ACDF when PDD was <5 mm. There was no difference in patient outcome between patients with two discs <5 mm away from the plate or patients with only one. A PDD of at least 4 mm decreased the likelihood of adjacent disc degeneration.