Cervical transfacet versus lateral mass screws: a biomechanical comparison

Area of Science:

• Orthopedics
• Spine Surgery
• Biomechanics

Background:

• Posterior cervical fixation using lateral mass plates is a standard technique for cervical spine fusions.
• Anatomical variations or complications can limit traditional screw placement options.
• Transfacet screw placement, validated in the lumbar spine, presents a potential alternative for cervical fusion.

Purpose of the Study:

• To compare the biomechanical pullout strength of cervical transfacet screws versus lateral mass screws.
• To evaluate the efficacy of transfacet screw placement as an alternative fixation method in the cervical spine.

Main Methods:

• Ten human cadaveric cervical spines were used.
• Transfacet screws and lateral mass screws were placed on contralateral sides at specified cervical levels.
• Axial pullout testing was performed using a servohydraulic testing machine to determine screw strength.

Main Results:

• Transfacet screws demonstrated significantly greater mean pullout strength (467 N) compared to lateral mass screws (360 N) (p = 0.008).
• This difference was particularly pronounced at the C7-T1 level.
• All transfacet screw placements showed higher pullout resistance than lateral mass placements.

Conclusions:

• Cervical transfacet screw placement offers biomechanical pullout resistance comparable to or exceeding that of lateral mass screw placement.
• Transfacet screw fixation is a viable alternative for posterior cervical fusion, especially in cases with challenging anatomy or fixation failures.