Efficacy of a short plate with an oblique screw trajectory for anterior cervical plating

Abstract

Study Design: A retrospective case-control study. Background Context: It has been reported that adjacent segment ossification development (ASOD) commonly occurs after anterior cervical arthrodesis. Objective: The aim of this study was to compare the efficacy of the short plate and oblique screw trajectory with the traditional long plate and parallel screw trajectory by investigating the incidence of ASOD and graft subsidence. Materials and Methods: We retrospectively reviewed the patients who underwent single-level anterior cervical discectomy and fusion (ACDF) with plate augmentation in our institute between June 2003 and August 2011. The patients were divided into 2 groups according to the plating technique, which was determined by the distances between the tips of the plate and the cranial and caudal adjacent endplates (plate-to-endplate distance, PED). Group L included the patients with a long plate (PED shorter than 5 mm), and group S contained the patients with a short plate (PED longer than 5 mm). Vertebral body height, distribution of ACDF level, incidence of cranial and caudal ASOD, ASOD grade, screw-to-endplate angle, vertebral body diameter, screw length, screw-to-body ratio, disk space height, subsidence, and cervical range of motion were measured and compared between the 2 groups. Results: The incidences of both cranial and caudal ASOD at least 2 years after surgery in group S were significantly lower than in group L (17.6% vs. 53.8%, P = 0.001 and 31.4% vs. 65.4%, P = 0.004, respectively). The incidence of severe ASOD at the caudal adjacent disk space was significantly lower in group S (2.0% vs. 23.0%, P = 0.002). The incidence of the subsidence was significantly lower in group S ( 2.0% vs. 25.9, P = 0.001). Changes in the cervical range of motion showed no significant differences regardless of group, ASOD, and graft subsidence. Conclusions: Techniques using a short plate with an oblique screw trajectory resulted in significantly reduced incidence and severity of ASOD and prevented graft subsidence.