Prediction of Clinical Results of Laminoplasty for Cervical Myelopathy Focusing on Spinal Cord Motion in Intraoperative Ultrasonography and Postoperative Magnetic Resonance Imaging

Study Design. Retrospective analysis of preoperative imaging and clinical data from patients undergoing cervical expansive laminoplasty for cervical myelopathy. Objective. To investigate preoperative parameters that predict the floating status of the spinal cord at the anterior elements of the cervical spine in both intraoperative ultrasonography (US) and postoperative magnetic resonance imaging (MRI), and to evaluate the association between clinical outcome and spinal cord floating. Summary of Background Data. Intraoperative US has been used to evaluate the status of the spinal cord after cervical laminoplasty for cervical myelopathy. Few studies have evaluated the predictive preoperative parameters for intraoperative US results. Methods. Imaging and clinical outcome data were collected from 101 consecutive patients who underwent cervical expansive laminoplasty for cervical myelopathy at Kaikoukai Nagoya Kyouritsu Hospital, Japan, from April 2004 to April 2008. The preoperative parameters associated with spinal cord floating in intraoperative US and postoperative MR images were investigated. Predictive parameters for the rate of recovery according to the Japanese Orthopedic Association score for cervical myelopathy at each follow-up session were also investigated. Results. Predictive parameters for spinal cord floating after decompression in intraoperative US were the cervical vertebrae 2 to 7 (C2-C7) sagittal alignment in the standing neutral position on preoperative plain radiograph radiography (cut-off value = 3 degrees) and the C5/6 "beak angle" in preoperative MRI (cut-off value = 20 degrees). A predictive parameter for spinal cord floating in postoperative MRI was the C5/6 beak angle in preoperative MRI (cut- off value = 21 degrees). The preoperative Japanese Orthopedic Association score and spinal cord floating at anterior elements of the cervical spine in intraoperative US were predictive parameters for clinical outcome. Conclusion. Intraoperative US was more useful than postoperative MRI for predicting the clinical outcome of cervical expansive laminoplasty. Knowledge of the predictive parameters for spinal cord floating after cervical expansive laminoplasty could help evaluate the limitations of posterior decompression.