Cervical pedicle screw fixation at C6 and C7: A cadaveric study

Area of Science:

• Spine surgery
• Orthopedic surgery
• Anatomical studies

Background:

• Cervical pedicle screw fixation is crucial for spinal injuries but faces challenges with pedicle penetration.
• Previous anatomical studies lacked a clearly defined entry point for cervical pedicle screw placement.
• A preliminary method for C3-C5 vertebrae proved safe and feasible, prompting this study for C6-C7.

Purpose of the Study:

• To establish a precise entry point for C6 and C7 cervical pedicle screw fixation.
• To determine optimal screw insertion angles and measure critical anatomical parameters for safe fixation.

Main Methods:

• Fifteen cervical spine specimens were used for manual pedicle screw insertion into C6 and C7 vertebrae.
• A specific anatomical landmark was defined as the entry point: the intersection of transverse process root and isthmus planes.
• Axial and sagittal sections were analyzed to measure pedicular width (PW), height (PH), screw channel length (LSC), and angles (E, F).

Main Results:

• C6 pedicle width (PW) averaged 6.12 mm and height (PH) 7.48 mm; C7 PW was 6.85 mm and PH 8.03 mm.
• The average screw channel length (LSC) was 30.83 mm.
• Transverse angles (E1, E2) were 89.61° and 59.71°, and the sagittal angle (F) was 75.86°.

Conclusions:

• The defined intersection point serves as a reliable entry point for C6 and C7 pedicle screw fixation.
• Optimal screw insertion involves angles of 60° or 90° in the transverse plane and 75° in the sagittal plane.
• The screw channel length should not exceed 30 mm to ensure safe fixation.