Cervical facet force analysis after disc replacement versus fusion.

Area of Science:

• Spine biomechanics
• Orthopedic surgery
• Degenerative spine disease

Background:

• Cervical total disc replacement aims to preserve motion and reduce adjacent-level degeneration compared to fusion.
• Concerns exist regarding potential facet joint loading alterations and arthrosis after cervical disc replacement.

Purpose of the Study:

• To evaluate changes in facet contact force, pressure, and surface area.
• Assess these changes at treated and adjacent levels after discectomy, disc replacement, and fusion.

Main Methods:

• Ten human cadaveric cervical spines (C2-C7) were used.
• Pressure sensors were placed in C3-C4 and C4-C5 facet joints.
• Moments were applied to simulate axial rotation, lateral bending, and extension.

Main Results:

• Facet contact force increased at the treated level post-discectomy and disc replacement under extension.
• Facet contact pressure and area remained largely unchanged post-discectomy and disc replacement.
• Facet contact force and area decreased at the treated level after fusion across all loading conditions.

Conclusions:

• Cervical disc replacement maintained facet contact force except during extension, influenced by the anterior disco-ligamentous complex.
• This preserved force during extension may contribute to facet joint disease at the treated level.