الفهرس 
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Abstract
Failed-back-surgery syndrome is a condition, in which patients who have undergone lumbar disc surgery have persistent symptoms or experience, after a brief asymptomatic period, recurrence of symptoms equivalent or similar to their preoperative symptoms. Nowadays MRI is establishing itself as the modality of choice for imaging the postoperative spine. Its major advantages are its multi-planar capability, superior soft tissue contrast resolution and excellent tissue characterization. The intravenous administration of gadolinium compounds is an important adjunct to MRI in clarifying the probable cause of the postsurgical syndrome.
This study aimed at illustrating the abnormal MRI findings encountered in the lumbosacral spine following surgery for intervertebral disc disease.
The review of literature included the following considerations about the postoperative lumbar spine :
• Anatomy and magnetic resonance imaging features of the normal lumbar spine.
• Surgical procedures for the lumbar spine and the MRI features of the non complicated postoperative lumbar spine.
• Pathological considerations including different causes of failed back surgery and their MRI findings.
• MRI technical considerations including types of coils, pulse sequences, contrast material, limitations and common artifacts.
This study has been accomplished in the Radiology Department of Assiut University Hospitals. It was carried out from December 2001 to March 2004.
Patients have been referred from the Orthopaedics and Neurosurgery Departments outpatient clinics and inpatient ward for MRI study of the lumbosacral spine.
Over all 100 patients, who had been previously operated upon for lumbosacral intervertebral disc disease and who presented with either persistant low back pain, with or without sciatica, or limitation of movement were included into this study.
All patients with complicated postoperative lumbar spine were subjected to full history taking, thorough clinical evaluation, and complete radiological examination including, plain x-rays, dynamic views, oblique views and MRI.
Magnetic Resonance Imaging studies were performed with a 1.5 T super-conducting MRI system (Gyroscan NT Power Track 6000, Philips, Netherlands). Phased array (Synergy) spine coil was used for examination of the lumbosacral spine in all patients. The examination time was about 18 minutes.
Stastical analysis were done including descriptive analysis like; mean ± standard deviation, number and percentage, frequencies, sensitivity and significant tests ... etc.
Part of the analysis required statistical significance tests as follows:
Chi-Square test (x2) for qualitative variables. Relations and differences were considered significant according to the level of significance as follows:
A P-value more than 0.05 was considered to indicate statistical insignificance.
A P-value less than 0.05 was considered to indicate statistical significance.
A P-value less than 0.01 was considered to indicate high statistical significance.
Seventy-three (73%) of the patients included were males and the remaining 27 (27%) were females. Their age ranged from 21 up to 76 (range of age of affection), with a mean age ± S.D. 44.25 ± 10.69 years, and with the peak age of affection between 40-49 years (33%) of patients.
Three patients had undergone surgery three times, three patients twice, and the rest of the patients once.
All patients were subjected to axial and sagittal planes study of the lumbosacral spine with T1-WI, T2-WI and post contrast T1-WI sequences. The current MRI examination was done 17 days up to 20 years following the previous surgery.
Eighteen patients were subjected to revision surgery of the lumbosacral spine in the Orthopaedic Surgery Department, Assiut University Hospital and their findings were correlated to those of the MRI examination. They were similar in eighteen patients. The ability of the MRI for the detection of the different lesions in comparison with the surgical findings (valid test) in 18 patients was highly sensitive (sensitivity = 100%).
Post contrast fat-suppression sequences, done in 50 patients, improved the visualization of enhancing scar, helped in distinguishing scar from recurrent disc prolapse and showed more clearly the relationship of scar to the nerve roots and thecal sac.
In patients diagnosed as spondylodiscitis, lateral spinal canal stenosis, instability, fractures, pseudomeningocele, malignancy, arachnoiditis and patients with no significant abnormality, enhanced conventional T1W sequences correlated well with the fat suppression findings. However, in patients with epidural fibrosis and disc lesions the findings of enhanced conventional T1W images and fat suppression did not correlate.