Shear stability of an elastomeric disk spacer within an intervertebral joint: a parametric study

Area of Science:

• Biomedical Engineering
• Orthopedic Surgery
• Materials Science

Background:

• Lumbar intervertebral disk spacers are crucial in spinal fusion surgery.
• Ensuring implant stability against shear forces is vital for successful outcomes.
• Current designs may have limitations in resisting dislodgement.

Purpose of the Study:

• To evaluate the shear force resistance of different polymeric lumbar intervertebral disk spacer designs.
• To compare the effectiveness of various surgical implantation techniques on implant stability.
• To identify endplate features that enhance resistance to lateral displacement.

Main Methods:

• A parametric study was performed on polymeric lumbar intervertebral disk spacers.
• Three distinct surgical implantation techniques were assessed.
• Three different endplate designs (pegs, inclined planes, domes) were investigated.
• Implants were subjected to axial load and pushed laterally; force at 0.3 mm displacement, initial slope, and maximum force were measured.

Main Results:

• Implants with pegs, inclined planes, or domes demonstrated significantly improved shear stability.
• These features enhanced resistance to lateral displacement under axial load.
• The tested endplate designs maintained the simplicity of a single-part device.

Conclusions:

• Endplate modifications like pegs, inclined planes, or domes are effective in increasing shear stability of lumbar disk spacers.
• These designs offer a viable solution for improving implant resistance to dislodgement.
• The findings support the use of these enhanced designs in spinal fusion procedures.