Pedicle Screw System May Not Control Severe Spinal Rotational Instability.

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Spinal Fusion

Background:

• Previous deer models suggested pedicle screw systems with crosslinking fail to control spinal rotational instability after facetectomy.
• This prior research indicated limitations in using pedicle screw systems for severe rotational instability.

Purpose of the Study:

• To investigate the efficacy of pedicle screw systems in controlling spinal rotational instability.
• To evaluate biomechanical performance in human lumbar functional spinal units with total facetectomy.

Main Methods:

• An in vitro biomechanical study using 10 human cadaveric lumbar functional spinal units (L3-L4).
• Four models were prepared sequentially: intact, damaged, pedicle screw fixation, and crosslink (CL) fixation.
• Rotational range of motion (ROM) was measured and compared across all models.

Main Results:

• Rotational ROM was significantly higher in the crosslink model compared to the intact model.
• The order of rotational ROM was: damaged model >> pedicle screw model > CL model > intact model.
• Statistical analysis confirmed significant differences (P < 0.001) between all tested models.

Conclusions:

• Pedicle screw systems may be insufficient for managing severe spinal rotational instability in human lumbar cadavers with bilateral total facetectomy.
• This finding highlights a potential biomechanical drawback of current pedicle screw systems in specific clinical scenarios.