Degenerative cervical myelopathy: Surgical treatment, imaging evaluation, and outcome

Abstract

Degenerative cervical myelopathy (DCM) is the most common cause of spinal cord impairment in adults worldwide. The overall aims of this thesis were to compare patient-reported clinical outcomes, adverse events, and cost-effectiveness between decompression alone and decompression with fusion; evaluate magnetic resonance imaging (MRI)-based sagittal alignment measurements; determine postoperative improvement rates and potential predictors of surgical outcome; and compare the patient-derived modified Japanese Orthopaedic Association (P-mJOA) scale with the European Myelopathy Score (EMS) for the assessment of DCM.

Through five papers based on three patient cohorts, patients surgically treated for DCM were assessed using prospectively collected data from the national Swedish Spine Register and preoperative MRI examinations.

In paper I, laminectomy alone (LAM) was not associated with inferior clinical outcomes 5 years postoperatively compared with laminectomy plus fusion (LAM+F). For each propensity score-matched patient treated with fusion, the cost increase was estimated to $4,700 US, without any observed benefit regarding long-term efficacy, complications, or reoperation rates. In paper II, muscle-preserving selective laminectomy (SL) provided similar clinical improvement 2 years postoperatively compared with anterior decompression and fusion. Reoperation rates were similar, but SL was associated with significantly fewer overall complications and fewer serious adverse events, as well as higher cost-effectiveness. In paper III, spondylolisthesis and kyphosis measurements on supine static MRI were measured with high interobserver reliability. In paper IV, improvement rates 2 years and 5 years after LAM or LAM+F were approximately 40%. More severe baseline myelopathy, older age, treatment with LAM+F, and more operated levels were predictors of worse surgical outcome. In paper V, the P-mJOA and the EMS had similar mean scores, and varying intra-rater agreement levels, ranging from ‘fair’ to ‘high’. Compared with the P-mJOA, the EMS has a low sensitivity for detecting severe myelopathy but shows an increasing agreement with the P-mJOA for milder disease severity.

In conclusion, laminectomy techniques and fusion techniques offer comparable clinical outcomes. Laminectomy with muscle-preservation might however be safer and more cost-effective. Despite high interobserver reliability, MRI-based sagittal alignment measurements may be misleading if measurement errors are not adequately considered when defining narrow surgical criteria. The predictor analysis suggests that intervention at an earlier myelopathy stage might be beneficial. Finally, the continued use of the P-mJOA as a patient-reported, gold standard assessment tool for DCM is recommended.