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Abstract
Objectives
To analyze the usefulness of Zero-P® by analyzing the radiological and clinical outcomes with a minimum of 2 years of follow-up.
Summary of Literature Review
Anterior discectomy and fusion (ACDF) using Zero-P® showed excellent results. However, there is a lack of studies focusing on long-term outcomes.
Materials and Methods
Ninety-eight patients who underwent single-level ACDF using Zero-P® with more than 2 years of follow-up were included for analysis. In the radiological analysis, we evaluated disc height, segmental lordosis, and subsidence in the preoperative, postoperative, and last follow-up periods. The Neck Disability Index (NDI), Neck Visual Analogue Scale (VAS), and Arm VAS were also evaluated for clinical assessment. Radiological bony fusion was assessed, and radiological and clinical differences according to bony fusion were evaluated.
Results
Intervertebral disc height had increased 2.92 mm after surgery and subsided to 2.36 mm at the final follow-up. Subsidence of the screw was 0.58 mm at final follow-up. Segmental lordosis was 3.97° at the preoperative assessment, 8.39° in the postoperative follow-up, and 5.83° in the last follow-up. The Neck VAS score was 4.47, 2.28, and 1.27, respectively. The Arm VAS score was 5.73, 3.13, and 2.18; and NDI score was 17.8, 11.7, and 7.89, respectively. There was no association between the radiological and clinical results. Radiological nonunion was found in 18 subjects. There were no significant differences in radiological and clinical parameters according to bony union.
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Fig. 1.
(A) Measurement of intervertebral distance (A) and Cobb angle (B), (B) Subsidence of the cage screw was measured by analyzing change in distance (d) between the tip of the screws and posterior margin of the vertebral body.
Table 1.
Correlation between radiological finding and clinical outcomes
Table 2.
Comparison of the demographic, radiololocal, and clinical outcomes according to subsidence
| Non subsidence group | Subsidence group | p-value | |
|---|---|---|---|
| Age | 54.23(±10.27) | 56.10(±8.90) | 0.341 |
| Sex (M/F) | 29/15 | 37/17 | 0.503 |
| Operation level | |||
| C3-4 | 6 | 3 | |
| C4-5 | 10 | 6 | 0.065 |
| C5-6 | 20 | 28 | |
| C6-7 | 8 | 17 | |
| Distraction (Postop-preop DH∗) | 2.57(±2.19) | 3.15(±1.43) | 0.119 |
| Subsidence (FU-postop DH) | 1.06(±0.65) | 3.22(±1.10) | <0.001 |
| Lordosis (FU-preop) | 1.65(±0.83) | 3.16(±1.87) | 0.089 |
| Neck VAS (FU-preop) | −2.28(±2.37) | −2.22(±2.85) | 0.911 |
| Arm VAS (FU-preop) | −3.64(±2.14) | −3.12(±3.80) | 0.568 |
| NDI (FU-preop) | −12.4(±3.21) | −10.2(±4.5) | 0.490 |
| Fusion(Y/N) | 32/7 | 48/11 | 0.575 |
Table 3.
Comparison of the demographic, radiololocal, and clinical outcomes according to bony union
| Fusion group | Nonunion group | p-value | |
|---|---|---|---|
| Age | 54.75±9.35 | 58.16±9.75 | 0.165 |
| Sex (M/F) | 54/26 | 10/8 | 0.336 |
| Operation level | |||
| C3-4 | 7 | 2 | |
| C4-5 | 13 | 3 | 0.973 |
| C5-6 | 40 | 8 | |
| C6-7 | 20 | 5 | |
| Distraction (Postop-preop DH∗) | 2.91±1.65 | 3.03±2.34 | 0.843 |
| Subsidence (FU-postop DH) | 2.34±1.41 | 2.36±1.51 | 0.964 |
| Lordosis (FU-preop) | 2.29±1.72 | 0.09±0.21 | 0.062 |
| Neck VAS (FU-preop) | −2.60±1.22 | −2.05±1.33 | 0.503 |
| Arm VAS (FU-preop) | −3.44±1.52 | −3.23±2.39 | 0.783 |
| NDI (FU-preop) | −11.22±3.82 | −10.05±3.27 | 0.717 |
Table 4.
Summary of the studies on cage subsidence and union
| Subsidence | % | Union | % | ||
|---|---|---|---|---|---|
| Gerek et al19) | Titanium | Disc space height > 3 mm | 56 | 2° difference on flex-ext† radiographs | 100 |
| Van Jonbergen et al20) | Titanium | Segmental height > 3 mm | 9 | 2° difference on flex-ext radiographs | 100 |
| Bartels et al9) | Carbon fiber | Disc space height > 2 mm | 29.2 | Motion on flex-ext radiographs | 95.8 |
| Vavruch et al6) | Carbon fiber | Not evaluated | Bone bridge on radiographs | 62 | |
| Kast et al7) | PEEK∗ | Segmental height > 2 mm | 29 | Bone bridge on radiographs | 76 |
| Yang et al22) | PEEK | Segmental height > 2 mm | 25.5 | 2 mm difference on flex-ext radiographs | 85.1 |
| Lee at al32) | PEEK | Segmental height > 2 mm | 44.7 | 2° difference Bone bridge on radiographs | 95 |
| Ours | PEEK | Segmental height > 2 mm | 55.1 | 2mm difference Bone bridge on radiographs | 82 |
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