Anterior cervical discectomy and fusion (ACDF) is one of the most commonly performed cervical spine procedures by both orthopaedic and neurosurgeons to manage radicular symptoms that can result from degenerative disk disease (DDD) of the cervical spine. Since the first description by Cloward (1) and subsequent modification by Smith and Robinson (2), the technique has been fairly standard with extremely satisfactory results. Although high fusion rates and good clinical outcomes have been reported without the use of supplemental anterior plating (3), most studies have established that anterior instrumentation improves the results in multilevel fusions (4,5).

In the early 1980s, Caspar et al. (6) popularized anterior cervical plating in collaboration with Aesculap. The Caspar plates were unrestricted backout plates. These constructs did not have a fixed-moment arm and, furthermore, had limited fixation at the screw-plate interface. This facilitated greater exposure of the graft to compressive forces, allowing for a higher rate of fusion. The plate, however, required placement of bicortical screws. The locking plates that locked the screws to the plate (CSLP) were introduced in the United States in 1991 by Synthes. The Synthes CSLP did not require a bicortical purchase because a titanium expansion screw was used to affix the screw rigidly to the plate (7).

The next generation of anterior cervical plating systems was the dynamic plates that allowed motion of the construct. The dynamic plate is supposed to allow for axial settling to accommodate a potential biologic or mechanical shortening of the anterior graft (8). Dynamic plates have been classified into rotational plates, which allow rotation at the screw-plate interface, and translational plates, which allow axial translation and possibly rotation (9). Movement at the screw-plate interface was planned to avoid stress shielding so that, theoretically, fusion rates would increase and time to fusion would decrease. This concept follows Wolff’s law, which suggests that loading alters bone integrity and bone healing, that is, bone heals more optimally when exposed to a compressive load.

Until recently, the majority of the published series with multilevel ACDF have used the fixed plate system (5,10). It is accepted universally that static or fixed plating systems provide rigid internal fixation, but this also reduces the load sharing across the bone-graft interface. Reidy et al. (11) studied the characteristics of cervical spine loading in a cadaveric corpectomy model and showed that dynamic plating allows significantly higher load transmission by the graft, and Brodke et al. (12) suggested that in vitro, dynamic plate allows for load sharing without apparent loss of rigidity. DuBois et al. (13) in 2007 have published the most recent clinical data comparing the outcome of patients undergoing ACDF with either static or dynamic plates. The authors found a higher rate of nonunion (5%) in the group with dynamic plates and hypothesize the higher incidence to increased motion at the bone-graft interface. This was a retrospective data collection study for patients operated by two different surgeons. The bone grafts used for patients were structural allograft or iliac crest grafts depending upon surgeon’s preference. The authors acknowledge that 80% of the nonunion patients had used allografts, thus adding bias to the analysis. Furthermore, there were no specific clinical parameters for quantitatively comparing the results except for Odom’s criteria, which is a very objective outcome parameter.

In order to obtain class I unbiased data comparing the efficacy of static versus dynamic plate, the authors conceived a prospective randomized trial at their center for patients
receiving ACDF for cervical DDD. The trial was designed to enroll the patients that satisfied the following inclusion and exclusion criteria cited in Table 127.1.