Abstract
Purpose Bioabsorbable Mg-based implants were previously assessed due to their intrinsic advantages, but Mg-based cage related research is limited. The specific blood supply and stress of the intervertebral environment can affect the function of Mg-based implants. The objective of this study was to investigate the performance of a bioabsorbable Mg-Zn alloy cage in anterior cervical discectomy and fusion (ACDF) and evaluate the control of degradation of the Mg-Zn cage surface modified by microarc oxidation (MAO) technology containing Si under an intervertebral microenvironment. Methods Twenty-four goats were divided into four groups according to the experimental period and all underwent ACDF at C2-3 and C4-5 with porous Mg-Zn cage covered with a MAO/Si-containing coating in one intervertebral space and with autologous iliac bone in another space. After 3, 6, 12, or 24 weeks after operation, the cervical spine specimens were harvested to evaluate the biocompatibility, fusion status, and degradation conditions using blood analysis, radiology, biomechanical testing, histology, and micro-CT. Results The Mg-Zn cages showed ideal biocompatibility and biomechanical characterization; however, the fusion state, as evaluated with radiology and histology, was not acceptable. Modified by the MAO/Si-containing coating, the degradation rate of the Mg-Zn cages was controllable but slower than expected. Conclusion MAO/Si-containing coating Mg-Zn alloy cages demonstrated excessive control of degradation and fusion failure after 24 weeks postoperatively. We conclude that further studies should be designed to improve the using of Mg-based materials at the intervertebral space.
Highlights
Anterior cervical discectomy and fusion (ACDF) was first described in 1958 using a graft of autogenous bone from the iliac crest [1, 2]
We developed a newly designed porous Mg-Zinc (Zn) alloy cage treated with a microarc oxidation (MAO)/silicon(Si-) containing coating as the experimental implant based on previous research conclusions from Mg-based materials applied in long bones
After 6 weeks postoperatively, subsidence of the intervertebral space was observed in the segments with the autogenous iliac graft
Summary
Anterior cervical discectomy and fusion (ACDF) was first described in 1958 using a graft of autogenous bone from the iliac crest [1, 2]. As the gold standard for intervertebral fusion, iliac autograft demonstrated a series of complications such as infection, fractures, and prolonged pain at the donor site [3, 4]. Bioabsorbable implants can effectively avoid longterm complications, which include stress shielding effects, implant shifts, and foreign body reactions. Complete intervertebral bony fusion is accomplished as the degradation space can be continuous replaced by osteosis. Among the types of bioabsorbable materials, magnesium (Mg) is considered a potential orthopedic material due to its favorable characteristics, such as biocompatibility, similar mechanical properties to natural bone, osteoconductive activity, and radiolucency [5, 6] (Table 1)
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