Does the novel artificial cervical joint complex resolve the conflict between stability and mobility after anterior cervical surgery? a finite element study

Abstract

Background and objective: Our group has developed a novel artificial cervical joint complex (ACJC) as a motion preservation instrument for cervical corpectomy procedures. Through finite element analysis (FEA), this study aims to assess this prosthesis's mobility and stability in the context of physiological reconstruction of the cervical spine.

Materials and methods: A finite element (FE)model of the subaxial cervical spine (C3-C7) was established and validated. ACJC arthroplasty, anterior cervical corpectomy and fusion (ACCF), and two-level cervical disc arthroplasty (CDA) were performed at C4-C6. Range of motion (ROM), intervertebral disc pressure (IDP), facet joint stress (FJS), and maximum von Mises stress on the prosthesis and vertebrae during loading were compared.

Results: Compared to the intact model, the ROM in all three surgical groups demonstrated a decline, with the ACCF group exhibiting the most significant mobility loss, and the highest compensatory motion in adjacent segments. ACJC and artificial cervical disc prosthesis (ACDP) well-preserved cervical mobility. In the ACCF model, IDP and FJS in adjacent segments increased notably, whereas the index segments experienced the most significant FJS elevation in the CDA model. The ROM, IDP, and FJS in both index and adjacent segments of the ACJC model were intermediate between the other two. Stress distribution of ACCF instruments and ACJC prosthesis during the loading process was more dispersed, resulting in less impact on the adjacent vertebrae than in the CDA model.

Conclusion: The biomechanical properties of the novel ACJC were comparable to the ACCF in constructing postoperative stability and equally preserved physiological mobility of the cervical spine as CDA without much impact on adjacent segments and facet joints. Thus, the novel ACJC effectively balanced postoperative stability with cervical motion preservation.

Keywords: anterior cervical corpectomy and fusion; artificial cervical joint complex; biomechanical; cervical disc arthroplasty; finite element analysis.

FIGURE 1

(A) The structure of the novel ACJC prosthesis: (a) the “L” shape endplate component; (b) the anti-pullout endplate teeth; (c) the UHMWPE joint socket; (d) the vertebral body component; (e) the porous titanium structure; (f) the external joint; (g) the Co–Cr–Mo alloy joint ball; (h) vertebral screws. (B) Three-dimensional geometric model; (C) the implanted view.

FIGURE 2

Three-dimensional finite element models of Intact subaxial cervical spine (C3-C7) and three anterior cervical surgery were established. (A) Front and lateral view of intact C3-C7 model; (B) The artificial cervical joint complex (ACJC) prosthesis; (C) ACJC implanted after C5 corpectomy; (D) Prestige-LP prostheses; (E) Two-level CDA at the C4-C6 level. (F) The titanium mesh cage (TMC) with plate and screws; (G) Anterior cervical corpectomy and fusion (ACCF) at the C4-C6 level.

FIGURE 3

Loading and boundary conditions of the C3–C7 cervical model.

FIGURE 4

Validation of the intact cervical model. (a) Values of lateral bending and axial rotation summate both right and left motion. (b) Values of lateral bending and axial rotation are unilateral.

FIGURE 5

Comparison of segmental ROM between intact model and different surgical models under loading directions of FL, EX, LB, RB, LAR, and RAR (FL, flexion; EX, extension; LB, left bending; RB, right bending; LAR, left axial rotation; RAR, right axial rotation).

FIGURE 6

Comparison of intervertebral disc pressure and its increment between intact model and different surgical models under loading directions of FL, EX, LB, RB, LAR, and RAR (FL, flexion; EX, extension; LB, left bending; RB, right bending; LAR, left axial rotation; RAR, right axial rotation).

FIGURE 7

Comparison of FJS and its increment between intact model and different surgical models under loading directions of FL, EX, LB, RB, LAR, and RAR (FL, flexion; EX, extension; LB, left bending; RB, right bending; LAR, left axial rotation; RAR, right axial rotation).

FIGURE 8

Comparison of the maximum von Mises stress and the stress distribution of vertebrae between intact and different surgical models under loading directions of FL, EX, LB, RB, LAR and RAR (FL, flexion; EX, extension; LB, left bending; RB, right bending; LAR, left axial rotation; RAR, right axial rotation), the arrow points to the area of maximum stress.

FIGURE 9

Comparison of the maximum von Mises stress and the stress distribution between different instruments models under loading directions of FL, EX, LB, RB, LAR, and RAR (FL, flexion; EX, extension; LB, left bending; RB, right bending; LAR, left axial rotation; RAR, right axial rotation), the arrow points to the area of maximum stress.