Abstract
Introduction
Anterior plate constructs for cervical discectomy and fusion have been linked to postoperative dysphagia, increased operative times, and wider surgical exposures. Several “low profile” integrated stand-alone spacers (SAS) have been developed. While these spacers have demonstrated successful clinical outcomes and similar biomechanical stability to anterior plate constructs in single-level fusions, their biomechanical stability in multi-level constructs has not yet been established.
Methods
Twelve human cadaveric cervical spines (C2-T2) were nondestructively tested with a six-degree-of-freedom simulator under axial rotation (AR), flexion-extension (FE), and lateral bending (LB) loading. After intact analysis, each specimen underwent sequential instrumentation and testing: (A) C5-6 spacer/plate with C6-7 SAS; (B) C5-7 SAS; (C) C5-7 spacer/plate. Range of motion (ROM) data was obtained and analyzed with paired t-tests and Bonferroni correction.
Results
The 2-level plate construct significantly reduced flexion-extension ROM compared to the 2-level SAS (5.6 ± 3.4 degrees versus 11.6 ± 4.6 degrees, respectively; p < 0.05). There was a significantly increased segmental ROM in the 2-level SAS construct compared to the 2-level hybrid construct in flexion-extension as well (11.6 ± 4.6 degrees versus 7.2 ± 2.4 degrees, respectively, p < 0.05). There was no significant difference in lateral bending and axial rotation (p > 0.05) between the three different 2-level constructs.
Conclusions
Our study found that hybrid and 2-level SAS constructs are comparable to conventional anterior plate constructs in lateral bending and axial rotation, but there was an increase in flexion-extension motion allowed with constructs that incorporated a SAS. Stand-alone cervical spacers with integrated screws for hybrid and 2-level SAS constructs are reasonable alternatives to two-level plate fixation; however, clinical trials are necessary to determine if the increased ROM in flexion-extension noted in the SAS constructs translates to clinical outcome.