Spinal endoscopy for chronic sciatica

Editor—We congratulate Dr Dashfield and colleagues¹ on a well conducted clinically relevant study. Caudal epidural placement of steroid and spinal endoscopic placement of steroid were found to be effective in patients with sciatica of 6–18 months. Superior, but not significantly superior results were found in the caudal epidural group. The conclusion must be that putting a patient through the longer, more uncomfortable, more costly and potentially more hazardous procedure of spinal endoscopy is difficult to justify on symptomatic grounds. We would tentatively accept this conclusion, but wish to emphasize some important caveats.

We refer particularly to a prospective observational study,² two prospective case series,³⁴ two retrospective evaluations⁵⁶ and a randomized double-blind controlled trial,⁷ which have shown positive results with spinal endoscopy in patients with chronic low-back pain with radiculopathic leg pain who had previously obtained inadequate pain relief with traditionally placed caudal or lumbar epidural steroids. The reasons for this discrepancy are relevant to those who manage these patients on a day-to-day basis.

Firstly, all of these studies^2–7 involved different populations from those of the Dashfield and colleagues' study where no patients had undergone back surgery and mean symptom duration was about 10 months for both groups (range 6–18 months). In their spinal endoscopy group very little scar tissue was encountered. In the study of Geurts and colleagues,² symptom duration was a mean of 5.5 yr (range 2–10 yr), with 12 of 20 patients having had a total of 26 back operations between them. Adhesions were found in 19 patients, being dense in 12. In the case series of Richardson and colleagues³ symptom duration was 10.9 yr (range 2–26 yr). Nineteen patients out of 38 had failed back surgery syndromes. Epidural adhesions were found in all patients with dense fibrosis being present in 14. All patients in the Igarashi study⁴ had spinal stenosis, a significant amount of narrowing being caused by fibrous tissue encroachment on the spinal canal.⁵ Manchikanti and colleagues published two studies: one involving post-lumbar laminectomy patients and one including a heterogeneous group of patients, which included both post laminectomy and non-laminectomy patients, all additionally non-responsive to fluoroscopically directed, but non-spinal endoscopic, epidural percutaneous adhesiolysis.⁶⁷ The majority of patients in Manchikanti and colleagues prospective randomized double-blind trial had moderate or extensive epidural fibrosis and again all had failed to obtain adequate pain relief with non-spinal endoscopic, percutaneous adhesiolysis.⁸ Fewer pathological changes were found in the Dashfield group.

Secondly, deliberate attempts were made in all the other quoted publications to carry out adhesiolysis. Indeed, this was felt to be an integral, important part of the procedure. Efficacy of adhesiolysis is hard to establish scientifically, but postoperative epidurography had improved (compared with preoperative epidurography) in approximately half the patients in the Geurts and Richardson case series.²³ Positive effects of deliberately carried out adhesiolysis involving spinal endoscopy have been found in all publications in terms of pain relief and physical function. The recent prospective randomized double-blind trial of Manchikanti and colleagues specifically studying this aspect showed that spinal endoscopic adhesiolysis reduced pain and improved physical, functional, psychological and behavioural status in a significant number of patients, without adverse effects.⁸

We would agree that in patients with relatively short case histories with probably less epidural chronic pathological changes spinal endoscopic placement of steroid has little to offer over and above caudal steroid placement and this has been elegantly shown in the Dashfield and colleagues study. If specific nerve roots require to be targeted the simpler method of selective nerve root approach may be preferable.

For patients with more chronic symptoms, particularly with epidural fibrosis shown on MRI scanning corresponding with the side and presumed site of symptoms, we would contend that effective delivery of steroid to the required nerve roots is highly unlikely to be effective through non specific (caudal or translaminar lumbar) delivery. Spinal endoscopy is a safe undertaking, as demonstrated in these publications as well as others. Its usefulness in patients with chronic severe radiculopathic symptoms especially in association with epidural fibrosis, as in, for example, failed back surgery syndromes and spinal stenosis, remains unchallenged. We accept completely that better and more scientific studies are required.

A. K. Dashfield*

A. K. Dashfield*

M. B. Taylor

M. B. Taylor

Plymouth, UK

Editor—We would like to thank Drs Richardson, Kallewaard and Groen for their interest in our study. We agree that our prospective randomized double-blind study¹ population differed from the populations studied in previously published case series, observational studies and a preliminary report of a randomized double-blind controlled trial.^2–8 We limited our study population to exclude patients who had previous spinal surgery and chronic lumbar spinal stenosis who are likely to have large amounts of scar tissue around nerve roots. All the other studies and case series included patients with longstanding chronic back pain with radiculopathy many of whom had had spinal surgery once or more. Our study was designed to answer the question whether the site of epidural corticosteroid placement within the epidural space was important in patients with little or no epidural scar tissue. We did not investigate the role of epiduroscopic adhesiolysis in patients with epidural scar tissue.

Having said this, we did use a constant flow of normal saline through the video-guided catheter enabling distension of the epidural space and allowing a good visual field during the procedure. This constant flow of normal saline itself can achieve a degree of adhesiolysis, although this was not our primary objective. Very little scar tissue was encountered in our population. We did not attempt mechanical dissection of scar tissue on the few occasions where it was encountered. The pain generator was identified in all patients in the epiduroscopy group and corticosteroid sited. We agree that selective nerve root block may be simpler and more cost effective than epiduroscopy in a population similar to ours.

Spinal endoscopy is a safe procedure. The usefulness of this procedure where adhesiolysis is undertaken in patients with chronic epidural fibrosis causing radiculopathic symptoms will need to investigated by a well designed prospective randomized study producing high quality evidence rather than the relatively low quality evidence available at present.

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