A cadaveric feasibility study of the LM-B screw as a novel posterolateral C1 lateral mass to C2 vertebral body fixation trajectory.

This cadaveric anatomical feasibility study defines and evaluates a novel posterior C1–C2 fixation trajectory with a posterolateral entry point, termed the C1 lateral mass–C2 body (LM-B) screw.The trajectory did not traverse the spinal canal or the VA canal in the specimens examined. Four formalin-fixed adult cervical specimens were instrumented bilaterally under fluoroscopic guidance (8 screws total). Post-instrumentation computed tomography with three-dimensional reconstruction was used to assess cortical integrity, intrabony course, and spatial relationship to the VA canal.Medial and caudal angulations were quantified using standardized multiplanar reference planes. All screws originated from the same anatomical entry point at the junction of the C1 posterior arch, transverse process, and lateral mass, and reached the C2 vertebral body without violation of the VA canal (0/8).The mean medial and caudal angulations were 33.1° ± 5.1° and 32.8° ± 9.7°, respectively.The mean intraosseous screw length was 37.3 ± 5.5 mm. Within the anatomical conditions examined, the LM-B pathway demonstrated a fully intrabony posterior corridor, defining an anatomically feasible posterolateral C1–C2 screw trajectory under standard cadaveric conditions.