466 - What Are Correlated Factors Affecting the Cage Subsidence and Implant...

#466 What Are Correlated Factors Affecting the Cage Subsidence and Implant Failure in Anterior Cervical Fusion Using Zero-profile Implant?

Cervical Therapies and Outcomes

Poster Presented by: H. Oh


H.S. Oh (1)
B.W. Hwang (1)
S.J. Park (1)
S.J. Lee (1)
S.H. Shin (1)
J.H. Cho (1)
S.H. Lee (2)

(1) Busan Wooridul Spine Hospital, Neurosurgery, Busan, Korea, Republic of
(2) Wooridul Hospital, Seoul, Korea, Republic of


Purpose: The zero-profile implant(Zero-p) was recently introduced in anterior cervical discectomy and fusion (ACDF). Its radiological and clinical outcomes have not been reported and concerns remain regarding its complications, especially cage subsidence and implant failure. This study was undertaken to investigate radiological and clinical outcomes of the Zero-p and to evaluate the incidence of cage subsidence and implant failure in relation to the clinical outcomes in the surgical treatment of degenerative cervical disc disease.

Methods: We prospectively followed 52 patients with radiculopathy/myelopathy undergoing ACDF using zero-profile implant. All patients checked postoperative bone densitometry(BMD) and 3D reconstructed CT. Radiologic parameters, clinical features (Neck Disability Index, visual analog scale score) were recorded. Mean follow-up period was 10.4 months (range 6-15 months). Eleven patients had two level ACDF using Zero-p.

Results: There was good maintenance in postoperative segmental height and lordosis(P< 0.005). And anterior segmental height was more increased than posterior height, so lordosis was increased postoperatively(P=0.001). We evaluated the fusion grade with postoperative CT reconstruction, considering segmental interspinous distance, trabecular bone contact, and bone bridge formation. This fusion grade was correlated to BMD (P=0.046), age (P=0.023), subsidence (P=0.000). And it was not affected by clinical outcome and lordosis. Among 3 cases of pseduoarthosis, there were two hardware failures as screw pull out. In two level fusion, compared to one level fusion, there was no difference in radiological outcome difference. One underwent operative removal and the other showed spontaneous reposition.

Conclusion: The zero-profile implant for ACDF allows decompression and fusion with low complication rates. There was good maintenance in postoperative segmental height and lordosis. Two level fusion using zero-p showed good radiological outcome. Long-term follow-up with more patients should be necessary to confirm these observations.