Biomechanical Analysis of Cervical Artificial Disc Replacement Using Cervical Subtotal Discectomy Prosthesis

Area of Science:

• Spine Biomechanics
• Orthopedic Biomaterials
• Surgical Innovation

Background:

• Anterior cervical discectomy and fusion (ACDF) leads to adjacent segment degeneration due to lost mobility.
• Cervical artificial disc replacement (CADR) presents alternatives but introduces issues like hypermobility and wear.
• A new cervical subtotal discectomy prosthesis (CSDP) was designed to control motion and reduce subsidence.

Purpose of the Study:

• To biomechanically assess the novel CSDP using finite element analysis, in vitro friction-wear testing, and non-human primate implantation.
• To compare CSDP's biomechanics against an intact spine and a commercial prosthesis (Prestige LP).
• To evaluate the impact of implantation errors on CSDP's biomechanical performance.

Main Methods:

• Finite element (FE) analysis of C2-C7 spinal models with CSDP implantation (C5-C6) and comparison with Prestige LP.
• Calculation of range of motion (ROM), bone-implant stress, and facet joint forces under various loading conditions.
• In vitro friction-wear testing and implantation in non-human primates for durability and radiographic evaluation.

Main Results:

• CSDP FE models exhibited ROM close to intact models, with minimal changes in facet joint forces.
• Improper CSDP implantation (1 mm elevation) increased ROM and altered biomechanical parameters.
• Friction-wear tests showed minimal wear, and primate studies reported no subsidence, dislocation, or loosening.

Conclusions:

• CSDP demonstrates biomechanical parameters comparable to intact spines and superior to the Prestige LP prosthesis.
• Implantation accuracy is crucial for optimal CSDP performance, affecting ROM, stress, and joint forces.
• The CSDP shows promising durability and effectiveness, validated through in vitro and in vivo studies.