Radiological cervical foraminal stenosis severity and morphology as a predictor of pre-operative function and functional surgical outcome.

Background: Cervical foraminal stenosis on MRI may be assessed using the Kim, modified Kim or Siller methods. This study aimed to investigate which morphological features of cervical foraminal stenosis in patients with cervical radiculopathy correlated best with pre-operative and post-operative surgical outcome following Anterior Cervical Discectomy (ACD) or a Posterior Cervical Foraminotomy (PCF).

Methods: Pre-operative MRIs of adults with cervical radiculopathy were assessed by six raters. The following measurements were made; uncompressed nerve root diameter, maximal compressed nerve root diameter, anterior & posterior compression, length of the neuroforaminal canal where the diameter was less than the uncompressed nerve root diameter and the distance of maximum compression from the apex of the ligamentum flavum. The Kim, modified Kim and Siller grades were calculated. Neck Disability Index (NDI) was measured pre-operatively and six weeks post-operatively. The radiological measurements and grades were compared to the pre-operative and change in NDI.

Results: Mean NDI was higher in female (58.2) than male patients (45.6) p = 0.05. No other baseline, operative or radiological factors where significantly associated with the pre-operative NDI. The mean [±SD] post-operative NDI was 14.3 [±22.5]. This represents a change of 37.8 (p < 0.001). The pre-operative NDI correlated strongly with the post-operative NDI but no other patient, operation or radiological factors correlated significantly. Neither pre-operative NDI or change in NDI was statistically different in those treated with ACD and those treated with PCF.

Conclusion: There was no association between pre-operative NDI and any of the radiological measurements or radiological grades. Furthermore, whilst surgery significantly improved NDI, for those patients with anterior compression, there was no difference in outcome between those treated with an ACD and those treated with a PCF. Current axial MRIs do not adequately assess the cervical nerve root foramina or predict surgical approach, 3D isotropic acquisition and DTI should be explored.