Computed tomography of the asymptomatic postsurgical lumbar spine: analysis of the physiologic scar

CT Five Years after Myelographic Diagnosis of Lumbar Disk Herniation

Fifty-seven patients were examined with CT 5 years after primary myelography for disabling sciatica and suspected herniated lumbar disk. Forty were in an operated group, 22 with good and 18 with poor results evaluated by occupational handicap (21) 5 years after surgery. Seventeen patients had myelography indicating disk herniation, but were treated conservatively, 9 with good and 8 with poor result. Various spinal dimensions measured at CT did not correlate with outcome. Operated patients had narrower canals than others, and male canals were broader than those in females. Increased amount of scar tissue at L4 level correlated with poor result (p = 0.008). Operated patients with poor result had more advanced lateral stenosis than those treated conservatively (p < 0.001). Patients with good result after operation had more degeneration observed on CT of erector spinae muscle than those treated conservatively with good outcome. Only 9% of operated patients did not have muscle degeneration. A tendency for more frequent recurrent disk herniations could be seen for conservatively treated patients. The narrowing of the spinal canal 5 years after operation did not correlate with the 5-year outcome.

Magnetic resonance image changes and clinical outcome after microdiscectomy or nucleotomy for ruptured disc

Preoperative and postoperative magnetic resonance imaging (MRI) of the lumbar spine was performed on 41 patients treated either microsurgically or with percutaneous nucleotomy for lumbar disc herniation. On the first postoperative day, MRI revealed an edematous mass effect at the level of surgery in 25 (61%) patients. The mass effect caused compression of the anterior dural sac mimicking preoperative disc herniation. After the follow-up of 6 months, the mass effect had disappeared in all patients, and the MRI finding in the operated disc space was that of a prolapse in six (15%) patients and that of a protrusion in 16 (39%) patients. Postoperative scarring was detected in 23 (56%) patients. The amount of the epidural scar tissue was significantly (p = 0.0002) associated with the extent of the early postoperative hemorrhagic changes detected in these patients with MRI. No association was observed between these MRI findings (mass effect, disc herniation, epidural scarring) and the clinical outcome of the patients.

Postoperative hematomas after successful lumbar microdiscectomy or percutaneous nucleotomy: a magnetic resonance imaging study

We evaluated the incidence of postoperative extradural hematomas by means of magnetic resonance imaging (MRI) technique in 44 patients who underwent successful surgery for a virgin lumbar disc herniation. Of these patients, 28 were treated with microdiscectomy and 16 with percutaneous nucleotomy. Postoperative hematoma proved to be a universal MRI finding in the microsurgically treated patients: hematomas were found in all patients in the microdiscectomy group. In 12 (43%) patients the hematoma extended into the dural sack. The incidence of hematomas was significantly (p = 0.001) lower in the patients treated with percutaneous nucleotomy: hematomas were detected in only 10 (63%) of the 16 patients in the nucleotomy group. The hematomas in these patients were also smaller in size and none of them connected with the dural sac. Correlation between the hematomas and clinical findings showed that the presence of a hematoma had no obvious effect on the immediate postoperative recovery of a patient.

The postoperative lumbar spine: imaging considerations

MRI with intravenous contrast has recently become the imaging modality of choice in the evaluation of patients developing recurrent back pain or symptoms following laminectomy and/or discectomy. The normal postoperative appearance is important to recognize because a number of changes occur normally throughout the healing period. The difference between epidural scar and recurrent disc herniation can usually be determined on MRI. Postoperative fluid collections may also develop. Disc space infection, although uncommon, is a critical diagnosis, but can be confused with degenerative end plate changes. Arachnoiditis and spinal stenosis also show characteristic imaging findings.

The role of early postoperative CT scan following surgery for herniated lumbar disc

40 patients underwent lumbosacral microdiscectomy in a 12 months period covering the years 1988-1989 in our center. For the purpose of the present study, we considered the 30 cases who underwent CT control of the operated interspaces and of the adjacent vertebral endplates. This was routinely carried out on the 3rd post-operative day. The present study failed to show correlations between early post-operative CT data and subsequent clinical results in this unselected series of patients. In fact an image suggesting persistent disc herniation was as a rule observed in spite of satisfactory clinical results, and other CT findings that have been considered of clinical significance, such as intraspinal air and low attenuation of disc space, were commonly observed in patients with an uncomplicated post-operative course. The present study suggests that early post-operative CT appears to be of no value in the management of potential early complications of low-back surgery. The introduction of MRI appears to offer other possibilities in the evaluation and management of failed back surgery syndrome (FBSS).

CT-diskography in the evaluation of the postoperative lumbar spine. Preliminary results

Thirty-three patients with recurrent sciatica after lumbar-disk surgery were studied for recurrent herniated nucleus pulposus (HNP) by CT alone and CT-diskography (CTD). Twenty-six patients underwent surgical reexploration allowing correlation with CTD. CTD made a correct diagnosis of recurrent HNP in twenty-one patients showing an extravasation of the contrast medium from the disk space into the medullary canal. In two cases CTD was positive for recurrent HNP but surgery showed only fibrosis. The amount of contrast leak was very small in these two cases along the posterior common longitudinal ligament, and the junction with the disk was very narrow. Because of their clinical presentation three patients with negative studies were operated upon. One showed only fibrosis and the two others showed an associated disk fragment. Among the twenty-one true-positive cases, seven showed a combination of recurrent HNP and scarring. Contamination of CSF by the contrast medium through the dura was observed in two patients. Although a prospective comparative study between CTD and IV-contrast-enhanced CT is necessary, CTD appears to be a useful diagnostic procedure for recurrent HNP after surgery of the lumbar spine.

Computed tomography after lumbar disc surgery: a comparison between symptomatic and asymptomatic patients

The evaluation of patients with recurrent symptoms after lumbar disc surgery, is a difficult diagnostic problem. The causes of failure may include recurrent disc herniation, postoperative scarring, arachnoiditis, spinal stenosis, infection and mechanical instability. The most common causes are recurrent herniation and postoperative scarring; the routine x-ray and myelographic differentiation between them is difficult or impossible. High resolution CT has shown some results in the evaluation of the postoperative patients. It requires some knowledge of CT findings of "normal" pictures of the physiologic healing and scarring after disc surgery. We scanned 30 asymptomatic operated patients and 30 patients with recurrent sciatic nerve pain after disc surgery. From our observations result that it is quite impossible to distinguish "normal" scar from asymptomatic fibrosis. The degree and type of fibrosis are not related to recurrent symptoms.

Contrast-enhanced computed tomography scanning of the postoperative spine

A prospective study of contrast-enhanced computed tomography (CT) scanning was undertaken for 17 levels previously operated upon in the lumbosacral spine in 14 patients. All levels with prior operations were scanned before and after the administration of intravenous contrast medium. A standardized technique for contrast enhancement using high doses of intravenous contrast medium was employed and a specialized technique for measuring enhancement with corrections for scan artifacts was used. Results indicated that measurable contrast enhancement occurred in 16 of 17 postoperative scars up to 12 years after surgery. Enhanced scans provided more accurate delineation of the size and margins of postoperative scarring than precontrast scans. No instances of enhancement of normal disk or recurrent herniated disk were observed. In six instances recurrent herniated disks were predicted on the basis of contrast-enhanced CT scans and subsequently confirmed at reoperation. Contrast-enhanced CT scans meticulously performed appear to permit differentiation between scarring and disk herniation in patients with recurring symptoms after operations for lumbosacral disk disease.