Facet joint injection and facet nerve block: a randomised comparison in 86 patients with chronic low back pain

Pain, 49 (1992) 325-328

325

0 1992 Elsevier Science Publishers B.V. All rights reserved 0304-3959/92/$05.00

PAIN 02046

Facet joint injection and facet nerve block: a randomised comparison in 86 patients with chronic low back pain Robert Cornelius Marks a, Thomas Houston b and Terry Thulbourne

a

aDepartment of Orthopaedic Surgery, Dundee Royal Infirmary, Dundee DDl9ND,

Scotland (UK) and b Department of Anaesthetics, Ninewells Hospital, Dundee DDI 9SV, Scotland (UK)

(Received 21 November 1990, accepted 20 December 1991)

Eighty-six patients with refractory chronic low back pain were randomly assigned to receive either Summary facet joint injection or facet nerve block, using local anaesthetic and steroid. There was no significant difference in the immediate response. The duration of response after facet joint injection was marginally longer than after facet nerve block (P < 0.05 1 month after infiltration), but for both groups the response was usually short-lived; by 3 months only 2 patients continued to report complete pain relief. Patients who had complained of pain for more than 7 years were more likely to report good or excellent pain relief than those with a shorter history (P < O.OOS>, but no other clinical feature was of value in predicting the response to infiltration. Facet joint injections and facet nerve blocks may be of equal value as diagnostic tests, but neither is a satisfactory treatment for chronic back pain. Key words:

Spine; Back pain; Facet joint

Introduction

In the majority of patients with mechanical-type back pain, a correlation between the pain and pathological or radiological changes has not been established (Nachemson 1985; Volinn et al. 1988; Haldeman 1990). Thus, like many other therapies for chronic back pain, facet joint treatments remain scientifically unproven, with uncertainty surrounding both their indications (Jackson et al. 1989) and effectiveness (Lilius et al. 1989). Nevertheless, the theoretical basis for the origin of pain from these synovial joints is unassailable (Eisenstein and Parry 19871, and facet-related injections remain a valid approach to the identification of the anatomical pain source in an individual patient, provided such injections are performed under radiological control and with small volumes of infiltrate. Despite worries regarding the safety of injections of steroid preparations in proximity to the dural sheath (Bogduk and Cherry 19851, the clinical safety of facet-related

Correspondence to: R.C. Marks, Dept. of Orthopaedic Surgery, Dundee Royal Infirmary, Dundee DDl 9ND, Scotland, UK. Tel.: (03-82) 23125.

injections is good, with only 2 cases of complications reported (Goldstone and Pennant 1987). Facet treatments, whether simple injections (Lippitt 1984; Lewinnek and Warfield 1986; Lynch and Taylor 19861, percutaneous radiofrequency denervation (Privat et al. 1980; Rashbaum 19831, or surgery (Maigne et al. 1978; Eisenstein and Parry 1987) are still widely used in pain clinics and specialised back clinics. Since there are probably no reliable clinical or radiological features specific to facet joint pain (Jackson et al. 1989), the diagnosis is usually based on the response to an injection of local anaesthetic, often combined with a corticosteroid in the hope of prolonging any beneficial effect. Two basic diagnostic techniques have been described: facet joint injection and facet nerve block. Intra-articular facet joint injection has been presented as a treatment as well as an investigation (Mooney and Robertson 1976) and has the advantages of a simple technique and localised containment of the infiltrate within the joint. However, its effect is dependent on adequate diffusion of drugs into the capsule of the joint, and any anterior ruptures of the joint will introduce infiltrate into the intervertebral foramen and may confuse the diagnosis. Facet nerve block was introduced as a diagnostic test prior to facet denervation

326

(Bogduk and Long 1979) and has the advantage of directly simulating the effect of a radiofrequency medial branch neurotomy (Bogduk and Long 1980). However, the medial branch of the posterior primary ramus also supplies muscle, and the ligaments and periosteum of the neural arch, in addition to the facet joint capsule (Bogduk and Long 1979); thus pain relief after facet nerve block cannot be regarded as specific to the facet joint. It might also be anticipated that a sustained response to steroid injection would be less likely than with intra-articular placement. Facet joint injection and facet nerve block have not previously been compared. We present a prospective randomised comparison of their effects in patients with severe, chronic low back pain.

Patients and methods Chronic low back pain patients presenting at the Pain Clinic or the Back Clinic in Dundee over a 2-year period were considered for inclusion in this study. Patients were eligible for inclusion if they fulfilled all the following criteria: (1) lumbar or lumbosacral pain, plus some referred pain in an extra-spinal location; (2) pain present most of the time for at least 6 months; (3) unsatisfactory response to non-narcotic analgesics and physiotherapy; and (4) pain aggravated by sustained postures. Patients were excluded if they had any of the following features: (1) a precise radicular pattern of motor or sensory changes in either lower limb (ignoring changes in tendon reflexes); (2) straight leg raising limited at less than 60 o by pain felt in the lower limb(s); and (3) evidence of any progressive spinal disorder of non-degenerative origin. Psychological factors were not formally assessed, but 2 patients with gross distress were excluded at the pre-randomisation stage because it was felt that valid consent could not be obtained. Informed consent was obtained from all patients. The 2 senior authors (T.T. and T.H.) identified suitable patients and indicated the level(s) to be treated on the basis of location and extent of spinal pain and tenderness. Patients were allocated to receive either facet joint injection or facet nerve block according to a random number system; the assigned technique was concealed from the patients and from the referring clinicians throughout the study. The patients in the 2 groups were comparable in terms of demography and pain details (Table I). All infiltrations were performed by one author (R.C.M.) who also assessed their initial response 30-60 min after infiltration. Patients were then returned to the referring clinician for follow-up visits at 1 month and 3 months post-infiltration. Thus the later reviews were completed double blind for the type of infiltration used. The injections were primarily intended as diagnostic tests to identify patients suitable for subsequent percutaneous radiofrequency facet denervation, and the short follow-up period of 3 months was chosen for this reason. Assessment of pain relief was subjective but standardised. Before infiltration, the location of pain was recorded, and if the patient considered either the spinal or the referred pain to be the dominant component this was also noted. Immediately prior to infiltration a provocative test was identified whenever possible: this was spinal extension (45 cases), forward flexion (21 cases), lateral flexion + / rotation (10 cases), or a combination of activities (3 cases). In 7 patients no pain provocation was possible. At each assessment, patients were asked to select one option from (i) worsening of pain. (ii) no real change or unsure, (iii) worthwhile improvement but with

TABLE

I

COMPARABILITY

OF STUDY

No. of patients Age Median (years) Range Sex Male Female GP referral Consultant referral Previous spinal surgery Length of history (years) Median Range Dominant pain component Spinal Referred Equal Paraspinal tenderness None Lumbosacral only More extensive/other Midline tenderness None Lumbosacral only More extensive Referred pain below knee

GROUPS Facet joint injection

Facet nerve block

42

44

44 24-58

42 27-57

20 2’ I2 30 5

26 1X 6 3x 5 (11.3%)

(I 1.9%)

7 0.7-25

10

I .6-35 IX (42.8% I? (28.6%) 12 (28.6%)

)

I7 (38.6%,) I5 (34.1%) I2 (27.3%)

1 I (26.2%‘) 26 (61.9%) 5 (1 l.U%)

12 (27.3%) 2X (63.6%) 4 (9.1%)

22 I4 6 I4

14 (31.8%) I8 (40.9%) 12 (27.3%) 21 (47.7%)

(52.4%) (33.3%) (14.3%;) (33.3%)

some pain remaining, or (iv) complete relief of pain. In the initial post-infiltration assessment, 30-60 min after infiltration, changes in pain at rest and on provocative testing were recorded. If no provocative test was available, this component was recorded as ‘no change’ regardless of any change in pain at rest. At l- and 3-month review changes in spinal pain and referred pain were recorded separately.

Techniques of infiltration All injections were performed under C-arm image intensifier control with the patient in the prone position, without sedation. An aseptic technique was used, with spinal needles 8.9 cm (3.5 inches) in length. When more than one injection was given on the same side, the sequence was always from caudal to cranial. For facef joint injeaion, the C-arm was adjusted from the initial vertical position until the facet joint cavity was visualised, using the minimum obliquity in order to profile the posterior (accessible) part of the joint (Carrera 1980). The needle was then introduced in the line of the image intensifier beam. We injected at the lumbosacral level, 0.5 ml Depomedrone (20 mg methylprednisolone acetate) followed by 1.5 ml lignocaine cl%), and at every other level 0.5 ml Depomedrone, followed by 1.O ml only of lignocaine. Facet nerve block was performed using the technique and radiological targets described by Bogduk and Long (19791. From Ll to L4, the medial articular branch of the posterior primary ramus was blocked where it lies in a gutter on the dorsal surface of the transverse process just caudal to the most medial end of the superior edge of the transverse process. At the lumbosacral level, the posterior primary ramus of L5 was blocked as it runs in the groove between the ala sacri and the superior articular process of the sacrum. The C-arm was set in a vertical position and needles were introduced from entry points approximately 5 cm lateral to the midline, with a slight obliquity towards the midline in order to avoid the overhang of

327 the articular processes. Otherwise, the same volumes of Depomedrone and lignocaine were injected as for facet joint injection, using 1.5 ml of local anaesthetic for the (significantly larger) posterior primary ramus at L.5. In view of the innervation of the facet joints from at least two spinal levels (Bogduk and Long 19791, the nerve blocks were performed at two levels for each joint: at the initially targeted level, and at one level above this (e.g., L3 and U for the L4/5 facet joint).

Results

All cases were reviewed at 1 month, but by 3 months 1 patient from the facet joint injection group and 2 from the facet nerve block group had been lost to follow-up. Pain relief

Table II shows the subjective changes in pain intensity reported at each stage of the study. On the basis of changes reported in spinal and referred pain (or in pain at rest and on provocation in the case of the immediate post-injection review), the response to infiltration was graded as follows: none = no relief of pain, worsening of any pain component, or any vague or uncertain statement; slight = worthwhile relief of part only of the pain complex (e.g., partial relief of spinal pain but referred pain unaffected); good = worthwhile relief of all pain, or complete relief of the component of the pain previously recorded as dominant; and excellent = complete relief of all pain.

TABLE III ADVERSE EFFECTS OF INFILTRATIONS Symptom

Facet joint injection

Facet nerve block

Headache Paraesthesiae of one leg below knee, no motor signs Nausea Worsening of pain

4

3

1 1 9

1 1 13

Overall, the facet joint injections did slightly better at every stage than the facet nerve blocks. This reaches a weak statistical significance only at l-month review, comparing any positive response to infiltration with no response at all (P < 0.05). The following factors in the clinical documentation of the patients were compared with their subsequent response to infiltration, combining both study groups: age, sex, occupation, smoking habits, mode of onset of pain, duration of history of pain, distribution of spinal and referred pain, distribution of spinal tenderness, pattern of pain on spinal movements, straight leg raising, total number of injections used at infiltration, and reproduction of pain during infiltration. Of these, the only significant finding was a positive correlation between a history of pain longer than seven years and a rating of good or excellent at any stage in the first month (P < 0.005). Adverse effects

TABLE II REPORTED TION

CHANGES

IN PAIN SEVERITY

Facet joint injection (n = 42) Immediately after infiltration None 15 (35.7%) Slight 11 (26.2%) Good 5 (11.9%) Excellent 11 (26.2%) Best response in first 2 weeks None 14 (33.3%) Slight 10 (23.8%) Good 14 (33.3%) Excellent 4 (9.6%) Response at 1 month * None 18 (42.9%) Slight 9 (21.4%) Good 12 (28.6%) Excellent 3 (7.1%) Response at 3 months (n = 41) None 25 (61.0%) Slight 7 (17.1%) Good 7 (17.1%) Excellent 2 (4.8%) * P < 0.05.

AFTER INJEC-

Facet nerve block (n = 44) 20 (45.5%) 13 (29.5%) 3 (6.8%) 8 (18.2%) 17 (38.6%) 7 (15.9%) 17 (38.6%) 3 (6.9%) 29 (65.9%) 6 (13.6%) 9 (20.5%) 0 (-) (n = 42) 30 (71.4%) 6 (14.3%) 6 (14.3%) 0 (-)

There were no serious complications (Table III). All patients found the infiltrations painful and unpleasant. Headache, nausea and paraesthesiae were all transient symptoms, such that they had vanished by the morning following infiltration. No patient required overnight admission to hospital. At l-month review, of the 22 patients who described their pain as worsened immediately after infiltration, 9 reported worthwhile pain relief, 6 were unchanged, and 7 still stated that their pain was worse than before infiltration.

Discussion

We have shown no difference in the immediate effects of facet joint injection and facet nerve block. In the absence of a control group we cannot quantify the placebo effect and cannot, therefore, draw any conclusions regarding the validity of these procedures as diagnostic tests; however, we found no major differences in the characteristics of chronic back pain patients responding positively to the two types of injection. For the present these two techniques may be regarded as equally valid in the selection of patients for definitive facet treatments.

328

Neither technique was convincingly superior in terms of duration of pain relief, and neither technique produced a useful number of sustained remissions at 3 months. These are diagnostic injections and cannot be represented as worthwhile treatments in chronic back pain. If the diagnostic validity of the injections is accepted, it is essential that some definitive management, such as a specific facet treatment or a rehabilitation programme, be rapidly available for the responders to take advantage of the brief ‘window’ in their pain. The only factor which was predictive of a positive response to either type of injection was a longer duration of pain. This is in keeping with the recent report by Jackson et al. (1989) and may suggest that facet joints tend to become painful relatively later than other structures in the spinal motion segment. Thus the early period of a patient’s history might relate to anterior (discogenic) pain, followed by later pain from overstressed facet joints once the disc has lost sufficient height.

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