Surgical Results in Hidden Lumbar Spinal Stenosis Detected by Axial Loaded Computed Tomography and Magnetic Resonance Imaging

STUDY DESIGN: An outcome study of patients with neurogenic claudication and/or sciatica with hidden stenosis, detected only by axial loading of the lumbar spine (ACE) but not at the traditional unloaded examination (psoas relaxed position) during computed tomography (CT) myelography or magnetic resonance imaging (MRI), followed up after surgery. OBJECTIVE: To estimate the clinical effect of decompression with or without fusion in patients with hidden stenosis in the lumbar spine. SUMMARY OF BACKGROUND DATA: A number of patients with neurogenic claudicatio with or without sciatica do not have corresponding imaging abnormalities. Axial loaded CT and MRI have disclosed hidden stenosis in certain cases. The surgical effect in patients with hidden stenosis has never been described. METHODS AND MATERIALS: Axial loading of the lumbar spine during CT and MRI was performed in 250 patients with neurogenic claudication and sciatica. All fulfilled the inclusion criteria for ACE, i.e., suspected but not verified spinal stenosis in 1 to 3 levels. In 125 patients (50%), a significant narrowing of the spinal canal occurred. Out of these 125 patients, 101 had a clear stenosis besides the stenosis only detected at ACE. In 24 patients, a hidden stenosis was detected in 1 to 3 levels only at the ACE. These patients were observed for 1 to 6 years after decompression with or without fusion regarding subjective improvement of leg and back pains, walking capacity, satisfaction, and health related quality of life. RESULTS: At follow-up, 76% of the patients had leg pain less than 25/100 on a VAS scale and 62% had back pain less than 25/100. Ninety-six percent were improved or much improved regarding leg and back pains The ability to walk increased significantly after surgery. Walking capacity to more than 500 m increased from 4% to 87%. Twenty-two patients were subjectively satisfied with the surgical results. The ODI score, the SF-36 and the EQ-5D score corresponded well to the above mentioned improvements at follow-up. CONCLUSION: According to this study, the results of surgery in hidden lumbar stenosis only detected by axial compression in extension during CT or MRI, are convincing and comparable with the results of surgical treatment for stenoses diagnosed by unloaded examinations.