The goal of fixation surgery for atlantoaxial instability is to achieve solid bony fusion. Achieving bony fusion as early as possible is beneficial for patients. Although placement of a transverse cross-link connector (XL) provides greater biomechanical strength, XLs have not been able to be placed when performing the Goel/Harms procedure. Recently, placing a XL on the screw head (on-the-head XL [OH-XL]) has become a viable option during the Goel/Harms procedure. However, there is little evidence demonstrating whether applying an OH-XL achieves early solid bony union. A matched-control study was conducted to investigate whether placing an OH-XLs in C1/2 fixation surgery provides earlier bone union or not. Eighteen patients who underwent atlantoaxial fusion with OH-XLs (X-group), and 17 age and sex-matched patients without OH-XLs (NX-group) were compared. Bony union was assessed using reconstructed sagittal and coronal computed tomography images. Six months after surgery, six patients in the X-group and one patient in the NX-group achieved bony union (p = .0338). One year after surgery, 14 patients in the X-group and 4 patients in the NX-group achieved bone union (p = .0010). Two years after surgery, 17 patients in the X-group and 9 patients in the NX-group achieved bony union (p = .0011). This is the first report of the clinical application of OH-XLs for the Goel/Harms procedure. OH-XLs yield earlier bony fusion; thus, placing OH-XLs is beneficial for atlantoaxial fixation surgery using lateral mass screws of the atlas.
Keywords: Atlantoaxial fixation; Atlantoaxial instability; Biomechanical strength; Bone fusion; Crosslink connector; Goel/Harms technique; Lateral mass screw; On the head crosslink connector; Overhead connector; Pedicle screw; Transverse connector.
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