Transpedicle osteotomy positioning in pedicle-lengthening laminoplasty

Pedicle-lengthening laminoplasty is a new minimally invasive technique for surgical treatment of lumbar spinal stenosis. The procedure is performed with the assistance of fluoroscopy and involves creating a pedicle passage, transpedicle osteotomy from inside the pedicle passage and lengthening it by using an implant bilaterally to enlarge the spinal canal and neural foramen. A critical component of the procedure is the precise determination of the osteotomy site on the pedicle. The objective of this study was to examine in vitro whether fluoroscopic positioning could be used to guide the osteotomy and to define the cutting site in the pedicle-lengthening laminoplasty in relation to the posterior vertebral line. It was found that the osteotomy site was from 2.0 to 3.5 mm posterior to the posterior vertebral line. The maximum difference between the measured value and that theoretically simulated on 3-dimensional (3D) computed tomography reconstruction was 0.3 mm. The spinal canal cross-sectional area was significantly enlarged after pedicle-lengthening. Accurate placement of the osteotomy is critical in pedicle-lengthening laminoplasty. Guiding the positioning of the osteotomy based on the posterior vertebral line images provides satisfactory accuracy, suggesting a possible clinical application for our technique; however, further verification in vivo is needed.