Effect of plate position on clinical outcome after anterior cervical spine surgery

Abstract

Background context Anterior cervical plates are commonly used to provide immediate stabilization after a variety of cervical spine procedures. It has been assumed that the ideal position for anterior cervical spine plates is centered in the horizontal plane without significant angulation and without overlap of adjacent unfused levels. Nevertheless, postoperative radiographs often demonstrate actual plate position to be lateralized, rotated, or encroaching on the adjacent disc space. There have been no reported systematic studies examining the effect of variations in plate position in a large clinical population. Purpose To evaluate the association between plate position and short-term clinical outcomes after anterior cervical discectomy and instrumented fusion (ACDF). Study design/setting Review of prospectively collected clinical outcomes measures and radiographs. Patient sample Patients undergoing ACDF surgery by a group of spine surgical specialists at a single institution. Outcome measures Direct and calculated plain radiographic measurements, visual analog scores for neck and arm pain, and SF-36 scores. Methods The study population included 200 patients undergoing a one-, two-, or three-level ACDF with instrumentation. Thirteen separate direct measurements and two calculated values of plate position on immediate postoperative radiographs, including lateralization, rotation, and proximity to adjacent disc spaces, were performed in blinded fashion by 3 independent reviewers. Statistical correlation with prospectively collected patient outcomes measures, including VAS for neck and arm pain and SF-36 scores, was performed. Results In the study population, average plate position was 3.3 mm from the cephalad disc space, 6.4 mm from the caudal disc space, 3.9° angulation in the frontal plate, and 26% laterally displaced from the midline. At average 18.6 months of follow-up, no significant association was identified between any plate position measure and clinical outcomes. Conclusions The use of anterior cervical plating by experienced spine surgeons is associated with variation in terms of plate position on postoperative radiographs. Within the range of positions analyzed in this study, no significant association was found between lateralized or rotated plates or plates placed in proximity to adjacent disc spaces and worse short-term clinical outcomes. It should be emphasized that these results and conclusions are based on relatively short-term clinical follow-up and that the long-term effects of variation in implant position remain unknown.