An In Vitro Biomechanical Study Evaluating Cervical Extension Plates for Stabilizing Degenerated Adjacent Levels

Area of Science:

• Spine biomechanics
• Orthopedic surgery
• Biomedical engineering

Background:

• Adjacent level degeneration is a common complication after cervical spine fusion.
• Traditional treatment involves removing existing instrumentation and extending fusion, risking neurovascular damage.
• Cervical extender plates were developed to address these challenges by augmenting existing implants.

Purpose of the Study:

• To evaluate the biomechanical stability of two types of cervical extender plates.
• To compare the stability of extender plates with traditional two-level fusion techniques.
• To assess extender plate performance in a human cadaveric model.

Main Methods:

• Fourteen human cadaver cervical spines (C2-C7) were used.
• Two groups tested: Group 1 (primary plate-attached extender) and Group 2 (universal extender).
• Constructs tested included intact, single-level plate, single-level plate with extender, and two-level plate under ±1.5 Nm moments.

Main Results:

• All instrumented constructs significantly reduced range of motion compared to intact specimens.
• Single-level plates with extender plates demonstrated comparable stability to two-level plates across all loading modes.
• Both extender plate types proved effective in stabilizing the cervical spine.

Conclusions:

• Cervical extender plates allow treatment of adjacent level degeneration without removing primary implants.
• This approach may reduce the risk of damage to vital neurovascular structures.
• Both evaluated extender plate designs are viable options for managing adjacent level degeneration.