Abstract
The design and ratio of the cortico-cancellous composition of allograft spacers are associated with graft-related problems, including subsidence and allograft spacer failure. Methods: The study analyzed stress distribution and risk of subsidence according to three types (cortical only, cortical cancellous, cortical lateral walls with a cancellous center bone) and three lengths (11, 12, 14 mm) of allograft spacers under the condition of hybrid motion control, including flexion, extension, axial rotation, and lateral bending,. A detailed finite element model of a previously validated, three-dimensional, intact C3–7 segment, with C5–6 segmental fusion using allograft spacers without fixation, was used in the present study. Findings: Among the three types of cervical allograft spacers evaluated, cortical lateral walls with a cancellous center bone exhibited the highest stress on the cortical bone of spacers, as well as the endplate around the posterior margin of the spacers. The likelihood of allograft spacer failure was highest for 14 mm spacers composed of cortical lateral walls with a cancellous center bone upon flexion (PVMS, 270.0 MPa; 250.2%) and extension (PVMS: 371.40 MPa, 344.2%). The likelihood of allograft spacer subsidence was also highest for the same spacers upon flexion (PVMS, 4.58 MPa; 28.1%) and extension (PVMS: 12.71 MPa, 78.0%). Conclusion: Cervical spacers with a smaller cortical component and of longer length can be risk factors for allograft spacer failure and subsidence, especially in flexion and extension. However, further study of additional fixation methods, such as anterior plates/screws and posterior screws, in an actual clinical setting is necessary.
Highlights
The incidence of degenerative cervical spine diseases (DCSD) was varied from 1684 to 1767 per100,000 population stratified according to disease codes in the Republic of Korea from 2012 to 2016 [1].In the USA, the incidence of surgery for DCSD rose by almost 150% over the last three decades and stabilized at slightly over 70 operations/100,000 people [2]
The geometrical data of the multi-segmental cervical model were reconstructed from computed tomography (CT) images
The validated range of motion (ROM) of our intact finite element model (FEM) model was within the acceptable range, compared with cadaver studies [29,30] Upon flexion, the ROM at C4–5 was increased in all spacer models, compared with that in the intact model
Summary
The incidence of degenerative cervical spine diseases (DCSD) was varied from 1684 to 1767 per100,000 population stratified according to disease codes in the Republic of Korea from 2012 to 2016 [1].In the USA, the incidence of surgery for DCSD rose by almost 150% over the last three decades and stabilized at slightly over 70 operations/100,000 people [2]. The incidence of degenerative cervical spine diseases (DCSD) was varied from 1684 to 1767 per. 100,000 population stratified according to disease codes in the Republic of Korea from 2012 to 2016 [1]. In the USA, the incidence of surgery for DCSD rose by almost 150% over the last three decades and stabilized at slightly over 70 operations/100,000 people [2]. The mean age at surgery was 53.3 years, and women underwent 44.4% of all cervical spine surgeries [2]. Anterior cervical discectomy and fusion (ACDF) is a standard treatment for DCSD [3,4].
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