The Anteroposterior Positioning of Viscoelastic Cervical Disc Prosthesis Does Not Alter the Outcomes

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Figure 1
Measurement of anteroposterior positioning. The distance between the center of the prosthesis (red arrow) and the center of the endplate of the inferior vertebra (green arrow reference), relative to the total length of the inferior endplate (distance b, blue line). When the ratio was <50%, the prosthesis was positioned anteriorly (image on the left). When the ratio was >50%, the prosthesis was positioned posteriorly (image on the right).
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Figure 2
Distribution of the patients. The distribution was given for the anteroposterior positioning in percentage (top) and the crude offset distance from the center, in millimeters (bottom).

Table 1

Characteristics of the cohort.

Characteristic	Mean (95% CI)
Crude offset distance from vertebral endplate center, mm, median (IQR)	0.4 (−1.5 to +2)
APP
Overall	49.4% (47.5%–51.4%)
Anterior positioning group (n = 15)	45.2% (43.2%–47.1%)
Posterior positioning group (n = 10)	54.1% (51.4%–55.3%)
Translation at LFU	1.6% (−1.6% to 4.9%)
Neck Disability Index
Preoperative	36.4% (28.9%–36.4%)
LFU	13.9% (9.4%–17%)
Visual analog scale for neck pain score
Preoperative	8.1 (7.2–8.9)
LFU	2.7 (2.1–3.3)
Visual analog scale for radicular pain score
Preoperative	7.2 (6.7–7.6)
LFU	2.5 (2.1–2.9)
Range of Motion
Preoperative	-
LFU	10.8° (8.8°–12.9°)
Cobb angle C2–C7
Preoperative	11.6° (8.6°–14.5°)
LFU	15.6° (11.2°–18.8°)
Spinocranial angle
Preoperative	79° (75.1°–83.7°)
LFU	74° (70.9°–77.9°)

Table 2

The difference in the functional outcomes, ROM, and sagittal alignment parameters according to the 2 groups.