437 - The Formation of Extragraft Bone Bridging after Anterior Cervical Disc...

Oral Posters: Cervical

Presented by: C.H. Kim - View Audio/Video Presentation (Members Only)


C.H. Kim(1), C.K. Chung(1), T.H. Park(2), S.H. Woo(2), S.-J. Lee(3), S.B. Park(1)

(1) Seoul National University Hospital, Neurosurgery, Seoul, Korea, Republic of
(2) R&D Center, Medyssey Co., Ltd, , Hanbang expo-ro, Jecheon-si, Korea, Republic of
(3) Inje University, Biomedical Engineering, Gimhae-si, Korea, Republic of


Study Design: Finite element analysis (FEA).

Objective: The objective of the present study was to determine the minimal area of contact surface between an interbody graft and vertebra required to achieve solid fusion after single-level anterior cervical discectomy and fusion (ACDF) with a stand-alone cage by finite element analysis.

Summary of Background Data: In addition to bone bridging inside a cage or graft (intragraft bone bridging, InGBB), extragraft bone bridging (ExGBB) is commonly observed after ACDF. However, the formation of ExGBB in the spinal canal may aggravate stenosis of the spinal canal. Insufficient contact area of InGBB may be a causative factor for the formation of ExGBB.

Methods: A validated 3-dimensional, nonlinear ligamentous cervical segment (C3-7) finite element model was used. This study simulated a single-level ACDF at C5-6. The variables were the properties of the incorporated interbody graft and the contact area between vertebra and interbody graft (Graft-area). The properties of the graft ranged from cancellous bone (Young´s modulus 100 or 300 MPa) to cortical bone (10,000 MPa). The morphology of the interbody graft was cylindroid, and the Graft-area increased from 10 to 200 mm2 in intervals of 10 mm2. Interspinous motion between the flexion and extension models of less than 2 mm was considered solid fusion. The interior areas of commercial interbody cages ranged from 48.5 to 108.07 mm2.

Results: The minimal Graft-areas for solid fusion were 190 mm2, 140 mm2, and 100 mm2 with properties of 100, 300 and 10,000 MPa, respectively. The Graft-areas were not obtainable with only the formation of InGBB in most commercial cages. Moreover, the InGBB property also influenced the graft area.

Conclusion: ExGBB may be formed to compensate for insufficient Graft-area in commercial cages. The present study may be helpful for the improvement of surgical implants and materials.