Study design <p>A retrospective cohort study.</p> Objective <p>The aim of the study is to investigate the radiographic changes of the spinal canal, intervertebral foramina, and spinal cord after cervical laminectomy with posterior instrumented fusion (LF), and to determine the correlation with the length of decompression levels, clinical symptoms, and C5 palsy (C5P).</p> Summary of background data <p>LF is an effective procedure for the treatment of cervical stenosis caused by various reasons. However, the radiographic changes of the spinal canal, intervertebral foramina and spinal cord after the surgery have been poorly reported, and the relationship with clinical prognosis is controversial.</p> Methods <p>We retrospectively analyzed consecutive cases that underwent cervical LF with at least 1-year follow-up. The radiographic measurements included the spinal canal, intervertebral foramina, and spinal cord use image parameters. The clinical results were evaluated using the Japanese Orthopedic Association (JOA) score. The patients were divided into two groups according to length of decompression levels, the recovery rate of the JOA score, or the C5P complication. The correlation between changes in image parameters and these three factors was analyzed.</p> Results <p>A total of 125 patients met the inclusion criteria (M: F = 74:51, mean age 57.8&#xa0;year, mean follow-up 18.76 months). C5P observed in 21 patients (16.8%). Statistical analyses revealed that there was a statistical difference in the postoperative cervical lordosis angle between the long and short segment groups. In terms of neurological improvement, patient satisfaction was positively correlated with postoperative spinal cord cross-sectional area (SAS) and pre- and postoperative ratio of spinal cord expansion (SCE), but not with other spinal cord and spinal canal morphology parameters. C5P was negatively correlated with preoperative superior articular process projection (SAP), and the smaller the SAP, the greater the likelihood of C5P. No significant correlation was found with other morphologies of the foramen magnum, vertebral canal, and spinal cord.</p> Conclusion <p>In LF, long-segment and short-segment decompression did not produce significant differences in intervertebral foraminal, spinal canal, or spinal cord morphology pre- and postoperative. Neurological improvement was correlated with the postoperative SAS and SCE, but not with other spinal cord, intervertebral foraminal, or spinal canal morphologies. The incidence of postoperative C5P was significantly correlated with preoperative SAP in the spinal canal morphology, making it a potential predictive factor for C5P.</p>