Clinical Outcomes and FEM Results of ACDF Performed Using H-Beam-Shaped Allospacer Versus Rim-Shaped Allospacer: A Comparative Study

Abstract

Objective: The study’s aim was to evaluate radiological outcomes and finite element method (FEM) results of anterior cervical discectomy and fusion (ACDF) performed using H-beam-shaped allospacer and compare these with the corresponding findings of ACDF with rim-shaped allospacer. Methods: From March 2011 to February 2014, 95 patients underwent anterior cervical discectomy and fusion (ACDF) with allospacers (H-beam shaped and rim shaped). Thirty-three patients diagnosed with trauma, Ossification of the posterior longitudinal ligament (OPLL), or combined posterior fusion were excluded from the study. Sixty-two eligible patients were divided into two groups: Group A comprised patients treated with H-beam-shaped allospacer (n=31) and Group B comprised those treated with rim-shaped allospacer (n=31). Clinical outcomes such as neck and arm pain, radiographical fusion rate, and adverse effects were evaluated. In the FEM study, the performance of three types of allospacers varying in shape—H-beam shaped, H-hole shaped, and rim shaped—was assessed: the effectiveness of stress distribution from these allospacers was compared by using the evaluation criteria of (a) compression, (b) shear and (c) torsion, under the same load. Results: Neck and arm pain were reduced by 63% to 73% in both the groups. Fusion rates after one year were 100% and 98% in Groups A and B, respectively. Regarding complications, the rates of breakage and displacement in Group B were 16% and 3%, respectively. Group A showed no adverse effects. The FEM study revealed that H-beam-shaped allospacer showed more effective stress distribution and diversification with respect to compression, shear, and torsion when compared with the rim-shaped allospacer. Conclusion: In ACDF with allospacer, the H-beam-shaped allospacer offered higher stable fusion rates along with lower incidence of complications when compared with the rim-shaped allospacer.