Unilateral C1 Lateral Mass and C2 Pedicle Screw Fixation for Atlantoaxial Instability in Rheumatoid Arthritis Patients: Comparison with the Bilateral Method

Abstract

ObjectiveBilateral C1 lateral mass and C2 pedicle screw fixation (C1LM-C2P) is an ideal technique for correcting atlantoaxial instability (AAI). However, the inevitable situation of vertebral artery injury or unfavorable bone structure may necessitate the use of unilateral C1LM-C2P. This study compares the fusion rates of the C1 lateral mass and C2 pedicle screw in the unilateral and bilateral methods.MethodsOver five years, C1LM-C2P was performed in 25 patients with AAI in our institute. Preoperative studies including cervical X-ray, three-dimensional computed tomography (CT), CT angiogram, and magnetic resonance imaging were performed. To evaluate bony fusion, measurements of the atlanto-dental interval (ADI) and CT scans were performed in the preoperative period, immediate postoperative period, and postoperatively at 1, 3, 6, and 12 months.ResultsUnilateral C1LM-C2P was performed in 11 patients (44%). The need to perform unilateral C1LM-C2P was due to anomalous course of the vertebral artery in eight patients (73%) and severe degenerative arthritis in three patients (27%). The mean ADI in the bilateral group was 2.09 mm in the immediate postoperative period and 1.75 mm in 12-months postoperatively. The mean ADI in the unilateral group was 1.82 mm in the immediate postoperative period and 1.91 mm in 12-months postoperatively. Comparison of ADI measurements showed no significant differences in either group (p=0.893), and the fusion rate was 100% in both groups.ConclusionAlthough bilateral C1LM-C2P is effective for AAI from a biomechanical perspective, unilateral screw fixation is a useful alternative in patients with anatomical variations.

Comparison of the clinical efficacy of unilateral and bilateral pedicle screw short-segment fixation and fusion in the treatment of atlantoaxial fracture-dislocation

“…A study by Paik et al [15] reported that from the perspective of biomechanics, unilateral C1 lateral mass screw combined with C2 pedicle screw fixation was also an effective technique for patients with atlantoaxial instability and an anatomical variation for whom the screws could not be placed bilaterally.…”

Unilateral facet cyst at the atlantoaxial joint leading to cervical myelopathy: A case report and review of literature

“…The patient successfully underwent a left-sided C1/C2 pedicle screw fusion alone. [ 6 ] The authors determined that decompression alone was warranted as the cyst did not significantly compress the cord and the mild “short-term” myelopathy would likely resolve with spontaneous cyst regression. Following the unilateral C1–C2 fusion, the patient neurologically improved and remained stable/fused 3 months later [ Figures 2 and 3 ].…”

Novel unilateral C1 double screw and ipsilateral C2 pedicle screw placement combined with contralateral laminar screw–rod fixation for atlantoaxial instability

“…The rate of VAI during C1 LMS placement has been reported up to 5.8% [14,15]. When asymmetry or unilateral occlusion is present or in the inevitable situation of VAI or in the case of unfavorable bone structures in upper cervical surgery, C1 LMS-C2 PS fixation cannot be performed using the bilateral method even though it results in greater rigidity than the unilateral method [8]. Then, unilateral fixation may be acceptable, but the patient requires an external orthosis until a fusion or bone union achieved [9].…”

“…However, they still carry potential risks of injuring the surrounding neurovascular tissue, especially vertebral artery injury (VAI). Furthermore, in the inevitable situation of VAI or in the case of unfavorable bone structures, C1 LMS-C2 PS fixation cannot be performed using the bilateral method [8]. Then, unilateral fixation is generally acceptable, but the patient requires an external orthosis until fusion or bone union is achieved [9].…”