A new technique for reduction of atlantoaxial subluxation using a simple tool during posterior segmental screw fixation

Clinical article

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Object

The authors introduce a simple technique and tool to facilitate reduction of atlantoaxial subluxation during posterior segmental screw fixation.

Methods

Two types of reduction tool have been designed: T-type and L-type. A T-shaped levering tool was used when a pedicle or pars screw was used for C-2, and an L-shaped tool was used when a laminar screw was used for C-2. Twenty-two patients who underwent atlantoaxial segmental screw fixation and fusion for the treatment of anteroposterior instability or subluxation, using either of these new types of reduction tool, were enrolled. Demographic, clinical, and surgical data, which had been prospectively collected in a database, were analyzed. The atlantodens interval was measured on lateral radiographs, and the space available for the spinal cord was measured on CT scans.

Results

The authors could attain reduction of the atlantoaxial subluxation without difficulty using either type of tool. The preoperative atlantodens interval ranged from −16.9 to 10.9 mm in a neutral position, and the postoperative interval ranged from −2.8 to 3.0 mm, with negative values due to extension-type or mixed-type instability. The mean space available for the spinal cord significantly increased, from 9.5 mm preoperatively to 15.4 mm postoperatively (p < 0.001).

Conclusions

This technique allowed for controlled manipulation and reduction of the atlantoaxial subluxation without difficulty.

Abbreviations used in this paper:ADI = atlantodens interval; JOA = Japanese Orthopaedic Association; NDI = Neck Disability Index; SAC = space available for the spinal cord; VAS = visual analog scale.

Article Information

Address correspondence to: Jin S. Yeom, M.D., Spine Center and Department of Orthopaedic Surgery, Seoul National University College of Medicine and Seoul National University Bundang Hospital, 166 Gumiro, Bundang-ku, Sungnam 463-707, Republic of Korea. email: highcervical@gmail.com.

Please include this information when citing this paper: published online June 21, 2013; DOI: 10.3171/2013.5.SPINE12859.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Photograph of 2 newly designed types of reduction tool: the T-type (upper) and the L-type (lower).

  • View in gallery

    Schematic of a technique for reducing anterior subluxation of C-1 on C-2 using a T-type tool for a C-2 pedicle screw. Upper: The tool is loosely secured to the heads of C-1 and C-2 screws with set screws before reduction. Lower: During reduction, the handle is levered caudally, such that the C-1 screw is pulled up as the C-2 screw is pushed down.

  • View in gallery

    Images of a technique for reducing anterior subluxation of C-1 on C-2 using two T-type tools for two C-2 pedicle screws. A: A lateral radiograph shows anterior subluxation of C-1 on C-2 in a patient with os odontoideum. B–D: In lateral fluoroscopic images, the subluxation was slightly under-reduced (B); over-reduced so that C-1 was posteriorly displaced on C-2 (C); and after a reverse reduction maneuver, slightly over-reduced (D), which was accepted by the operating surgeon. E: A lateral fluoroscopic image shows that the two T-type tools were replaced with two final rods. F: A postoperative lateral radiograph shows acceptable reduction.

  • View in gallery

    Images of a technique for reducing anterior subluxation of C-1 on C-2 using two L-type tools for two C-2 laminar screws. A: A lateral radiograph shows anterior subluxation of C-1 on C-2 in a patient with idiopathic atlantoaxial instability. B: A lateral fluoroscopic image shows that the subluxation was under-reduced so that C-1 was still anteriorly displaced on C-2. C: This lateral fluoroscopic image was taken after a further caudal leverage maneuver that involved pushing the C-2 spinous process anteriorly, and replacement of the tools with final rods. It shows slight under-reduction, which was accepted by the operating surgeon. D: A postoperative lateral radiograph shows acceptable reduction. E and F: Reconstructed CT scans taken 6 months after surgery show a well-maintained ADI (E) and solid union of the intraarticular arthrodesis (F, arrowhead).

  • View in gallery

    An intraoperative photograph taken after posterior release of the right C1–2 facet joint capsule shows the articular cartilages (arrowheads) of C-1 and C-2. The right C-2 root (asterisk) had been retracted cranially.

  • View in gallery

    Graphs of preoperative and postoperative ADI and SAC. A and B: Preoperative ADI in neck flexion, extension, and neutral positions, and postoperative ADI in the neutral position, of 14 patients with positive (A) and 8 patients with negative (B) preoperative ADIs in the neutral position. C: Preoperative and postoperative SAC measured on CT scans.

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