Anatomical Feasibility and Early Radiographic Outcomes of Freehand C1 Pedicle Screw Fixation in a Malaysian Cohort: A Preliminary Single-Center Study

Introduction: The C1 pedicle screw fixation demonstrates superior biomechanical stability over lateral mass fixation. Nevertheless, the approach presents technical challenges, particularly in patients with anatomical constraints. In this study, the anatomical feasibility and early radiographic outcomes of freehand C1 pedicle screw placement in a Malaysian cohort were assessed, and a descriptive population-specific morphometric comparison was conducted. Methods: This study reviewed eight patients (n=16 pedicles) treated by a single senior surgeon for atlantoaxial instability and who underwent posterior cervical stabilisation using a freehand C1 pedicle screw technique (November 2022–November 2024). Preoperative CT scans, including evaluation of the vertebral artery course and sulcus arteriosus variants, were used for morphometric planning. Radiographic outcomes, including C1–C2 and C2–C7 Cobb’s angles, were measured at ≥ 3 months. Results: The eight patients (seven males; mean age, 29 years) underwent fixation with 16 C1 pedicle screws. The mean pedicle height was 5.07 ± 0.91 mm (right) and 4.65 ± 0.89 mm (left), where 18.8% of pedicles were < 4.00 mm. The mean pedicle width was 9.81 ± 0.55 mm, which implies that height is the primary anatomical constraint for screw accommodation instead of width. No neurovascular injuries, hardware failures, or cases of occipital neuralgia were observed. There was a significant improvement of the C1–C2 Cobb’s angle postoperatively (+7.13∘, p = 0.033). The C2–C7 did not undergo a significant change, although it was moderately negatively correlated to C1–C2 correction (r = -0.70, p = 0.053). Conclusion: These preliminary results demonstrated that freehand C1 pedicle screw fixation appeared anatomically feasible and potentially safe in this small group of Malaysian patients. The technique also showed satisfactory early radiographic alignment without the use of an assistive device or intraoperative navigation, supporting its applicability in settings with limited resources.