TRANSFORAMINAL INJECTIONS OF STEROIDS AS A METHOD OF LOW BACK PAIN TREATMENT J. Les, J. Grzesiak, M. Sienkowska-Magon, A. Kwiecien - Department of Anaesthesia and Intensive Care K. Brzozowski, P. Zukowski- Department of Interventional Radiology Military Institute of the Health Services, Central Clinical Hospital of the Ministry for National Defence, Poland

Low back-pain (LBP) is defined as pain between the 12th rib and the gluteal fold, with or without radiation to the lower extremities.

INTRODUCTION

LBP can be caused by spinal stenosis, disc bulging, disc herniation, spondylolisthesis. These conditions may produce pain due to nerve root impingement and associated intraneural oedema and inflammation. LBP, however, can be present without direct nerve root compression. Chemical mediators such as phospholipase A2 escape from the nucleus pulposus in some disc. This is an enzyme involved in the metabolism of arachidonic acid, leading to the production of inflammatory mediators. The nociceptors located at the external part of the annulus fibrosus and the posterior longitudinal ligament becomes sensitized by inflammatory mediators. In vitro, phospholipase A has a neurotoxic property. The anti-inflammatory properties of steroids can reduce inflammation and pain associated with nerve root irritation. Every year, 3-4% of the population is temporarily, and 1% of the working population is permanently, unable to work due to LBP. In 90% of cases the pain lasts between 4 and 6 weeks, and has a tendency to be recurrent. The cause of the transition from acute to persistent pain is unknown. According to a survey of non-cancer pains in Europe, around 50% of the respondents had had episodes of back pain. In the majority (74%) this was LBP.

INDICATIONS

The indication for the epidural application of steroids could be sharp or persistent pain with or without stenosis of the spinal canal or nerve root compression, with subjective symptoms or with small neurological signs.According to the literature and to our own experience, epidural application of steroids should be applied as a method of treatment in patients who have not shown any improvement after non-invasive treatments such as pharmacotherapy, physiotherapy, or short periods of immobility. The effectiveness of this method lies between 40 and 70%. The best results are achieved in patients with a short span of pain, the results being less effective in recurrent hernia, or after surgical intervention.

TECHNIQUES

Transforaminal epidural injection is selective block of the nerve roots, with a spread of local anaesthetic through the neural foramen to the epidural space.In an article published in 1971, Macnab used the term “selective nerve root infiltration”. Since then many variations of this procedure have emerged. Controversial terms for similar procedures have been used: nerve root injections, transforaminal epidural, selective nerve root block, selective nerve root sleeve injection, selective epidural, selective spinal nerve block, and selective ventral ramus block.Transforaminal injections are the most specific route for epidurals. The selective administration of epidural steroids at the most symptomatic level can provide pain relief from neural irritation and inflammation. Under fluoroscopic guidance the needle tip is placed in the “safe triangle”, and the contrast solution is injected to ensure proper needle placement and visualize probable spread of medication. This technique allows the use of smaller volumes of injectant than in the classical approach to epidural space. Medication is placed close to the site of the pathology (the disc, the nerve root, the dura).In a transforaminal epidural, 1-2 ml of local anaesthetic/steroid is injected. A volume of local anaesthetic larger than 2 ml leads to a loss of its diagnostic usefulness since, the spread of medication to adjacent spinal levels and structures is likely to occur. In the “classic” (medial, paramedical) approach to the epidural space, a larger volume has to be used to reach the pathological site: this means more medication needs to be employ otherwise its concentration will be low. In some patient the appearance of septums or scars in the epidural space can give an unpredictable spread of injectant or even preclude from reaching the place of interest. With multi-level pathology, an interlaminar epidural approach is usually performed.

COMPLICATIONS

Bleeding, local or systemic infections, post-puncture headache, nausea, vomiting, vasovagal reaction, vertigo, epidural haematoma, nerve root damage, meningitis, adrenal insufficiency.

ABSOLUTE CONTRAINDICATIONS

Local or general infections, anti-thrombolytic therapy, and documented anaphylactic reactions to given substances (e.g. contrast medium).

DURATION OF AILMENT

<3 months 3 - 6 months >1 year After surgical treatment

EFFICIENCY

90% 70% 50% <30%

APPLIED MEDICATIONS

Betamethasone acetate: dose 2-6 mg Methylprednisolone acetate: dose 20-60 mg

FLUOROSCOPY

Radiological control is recommended during the use of all methods of epidural blocking. Research shows that the use of fluoroscopy with contrast medium increases the effectiveness of blocks to between 60 and 70%. Incorrect positioning of the needle, and a resulting ineffective block, occurs in about 30% of cases, and does not depend on the operator’s experience.

CONCLUSIONS

So far, there are no strict criteria for qualifying patients for epidural application of steroids. In our opinion, the main criterion should be short-lasting pain, optimally less than three months, with a lack of neurological disorders requiring immediate neurosurgical intervention. Despite a number of reports on the positive effects of this method on LBP, there are no standards for patient qualification.

Further, different techniques and different types of steroids in different doses and concentrations have been proposed. It is normally suggested to carry out no more than three blocks per year, never less than two weeks apart.

According to some authors, if there is no improvement after the first technically correct epidural block, the initial diagnosis and the patient’s qualification should be reviewed. Although epidural application of steroids as a method of LBP treatment requires the development of defined indications and technical detailing, it is worth recommending as one of the choices for non-surgical treatment.