Efficiency of Long Lateral Mass Screw in Posterior Cervical Fusion

Long lateral mass screw (LLMS) technique for posterior cervical fusion has been performed in our hospital since 2019. In this study, the LLMS insertion technique, deviation rate, and insertion torque have been described. Moreover, several major concerns associated with LLMS have been adequately addressed.

This study included 58 patients (43 men and 15 women) who had undergone LLMS surgery at our hospital during the four-year period from December 2019 to December 2023, and were evaluated using postoperative CT. The evaluation parameters included the screw length at each vertebral segment, screw angle in the sagittal section, distance between the screw heads, and complications.

The median screw length at C3 was 23.0 mm (22.0-24.0 mm), the screw angle was 36.1° (31.6-41.8°), and the distance between screw heads was 13.8 mm (11.6-17.2 mm). The median screw length at C4 was 22.0 mm (21.0-24.0 mm), the screw angle was 36.2° (28.7-40.7°), and the distance between screw heads was 15.9 mm (13.0-19.0 mm). The median screw length at C5 was 21.0 mm (20.0-22.0 mm), the screw angle was 35.6° (28.0-39.7°), and the distance between screw heads was 17.6 mm (15.1-20.4 mm). The median screw length for C6 was 20.0 mm (19.0-22.0 mm), the screw angle was 29.2° (25.2-36.8°), and the distance between screw heads was 20.4 mm (16.1-24.4 mm).

The major limitations of the LLMS technique were inadequate screw angle, difficulty inserting long screws, inadequate decompression, and the inability to perform cervical laminoplasty. However, these limitations did not substantially affect the efficiency of LLMS. LLMS has fewer complications and can insert longer screws than LMS.