Outcome evaluation of the zero-profile device comprising two integrated variable angle screws used for single-level...

Zero-P VA device is a unique zero-profile device comprising only two integrated variable-angle screws which may provide inferior mechanical stability compared with other types of devices. There is a lack of comprehensive clinical and radiological evidence comparing the plate-cage construct (PCC) and the Zero-P VA device in single-level anterior cervical discectomy and fusion (ACDF).

We retrospectively reviewed consecutive patients who underwent single-level ACDF using either the Zero-P VA device (50 cases) or the PCC (51 cases). Clinical outcomes were evaluated using the Visual Analogue Scale (VAS) and Japanese Orthopaedic Association (JOA) scores. Radiological outcomes were assessed using standard lateral cervical x-ray films. Data were recorded preoperatively, immediately postoperatively, and at 3- and 12-month follow-up visits.

VAS and JOA scores, cervical alignment, segmental angle, and surgical segment height were all significantly improved postoperatively in both groups. However, in the Zero-P VA group, the segmental angle and anterior height of the surgical segment at 3 and 12 months decreased significantly compared with immediate postoperative values and were significantly lower than those observed in the PCC group. The rate of segmental kyphosis was significantly higher in the Zero-P VA group at the 12-month follow-up (12% vs. 0%, p < 0.05), while fusion rates were comparable.

The Zero-P VA device provides short-term clinical outcomes comparable to those of the PCC for single-level ACDF. However, it is associated with inferior radiological outcomes, specifically greater loss of segmental lordosis and anterior surgical segment height. The surgeon's choice of implant therefore involves a clinical trade-off between the established surgical advantages of a zero-profile system and the superior radiological stability offered by the PCC.