In vitro evaluation of translating and rotating plates using a robot testing system under follower load

Area of Science:

• Spinal biomechanics
• Orthopedic implant technology
• Surgical outcomes research

Background:

• Standard rigid anterior cervical plates may not optimize load sharing with bone grafts.
• Semi-constrained plates (translating or rotating) were developed to improve graft fusion.
• Previous studies lacked analysis of simulated muscle loading effects on plate designs.

Purpose of the Study:

• To compare the biomechanical performance of rigid, translating, and rotating anterior cervical plates.
• To evaluate load sharing and graft support under simulated muscle loading conditions.
• To assess the influence of plate design on cervical spine stability after corpectomy.

Main Methods:

• In-vitro biomechanical testing of 15 human cervical spine specimens (C3-7).
• Application of a simulated muscle load (follower load) up to 100 N.
• Testing of randomized rigid, translating, and rotating plate groups under various motion conditions (flexion, extension, etc.) to a 2.0 Nm moment.

Main Results:

• Translating plates maintained graft load during flexion, unlike rigid and rotating plates.
• No significant difference in neutral position load sharing or C4-6 range of motion between translating and rigid plates.
• Rotating plates exhibited less neutral position load sharing and failed to maintain graft load during flexion.

Conclusions:

• Translating anterior cervical plates demonstrate superior load sharing compared to rigid and rotating plates under simulated muscle loading.
• The findings suggest potential benefits of translating plates for improving fusion rates in anterior cervical spine surgery.
• Simulated muscle loading is a critical factor in evaluating the performance of cervical spine fixation devices.