Diagnostic cervical and lumbar medial branch blocks

Transcription

1 Considered Judgement Form This form is a checklist of issues that may be considered by the Purchasing Guidance Advisory Group when making purchasing recommendations Meeting date: 2 November 2015 Topic: Diagnostic cervical and lumbar medial branch blocks Purpose ACC Research was asked to review the evidence for the performance of diagnostic medial branch blocks for chronic cervical and lumbar pain to determine if the body of evidence has changed since The evidence was last reviewed by ACC in 2005 as part of the Interventional Pain Management guidelines, and the following recommendations and purchasing decisions were developed: Intervention Clinical practice recommendations Purchasing recommendations IN40 Diagnostic cervical medial branch block Double-blind, comparative medial branch blocks, followed by an independent outcome assessment, may be used in the investigation of cervical pain in adults (B = recommendation supported by fair evidence). Purchase There is medium quality evidence that cervical medial branch blocks have diagnostic utility in the investigation of pain in adults. We recommend that double blind comparative medial branch blocks should be used in the investigation of cervical pain in adults. IN41 Diagnostic lumbar medial branch block Double blind comparative medial branch blocks may be used in the investigation of adults with persistent low back pain (B = recommendation supported by fair evidence). Purchase We recommend that double blind comparative medial branch blocks should be used in the investigation of adults with persistent low back pain. Good practice points In order to determine the sensitivity, specificity and reproducibility of this technique [lumbar diagnostic medial branch blocks], replication of the rigour used for medial branch blocks in the cervical spine is encouraged. This includes double-blinding, independent outcome assessment, and use of comparative, local anaesthetic block. The purpose of the current review is to review the best available evidence published since 2005 which examines the diagnostic performance of cervical and lumbar medial branch blocks. Systematic reviews and clinical guidelines based on a systematic review were included in the report. Background Cervical and lumbar facet joints (also called zygapophysial or z-joints) are recognised as a potential source of neck or low back pain, but diagnosis remains a challenge because facet joint pain cannot be reliably diagnosed from history, clinical examination, or radiological findings 1,2.

2 The facet joints receive their nerve supply from nerves called the medial branches of the dorsal rami. Diagnostic medial branch blocks involve the injection of small volumes of local anaesthetic into these nerves to see whether one or more of the related facet joints are responsible for a patient s pain. Each joint is supplied by two medial branches (except C2-3 which is innervated by the third occipital nerve), so each block involves two injections. Injections are usually performed under fluoroscopic guidance 1,2,3. If the injections temporarily relieve the pain, it can be deduced that the facet joint innervated by those medial branches is the source of pain. Following a positive diagnosis, radiofrequency neurotomy of the nerves for the affected facet joint can then be considered. Diagnostic medial branch blocks can be conducted using single block or double block protocols. Single blocks with one anaesthetic are associated with an unacceptably high false-positive rate, and for this reason are no longer recommended 1. Double, comparative block protocols involve two separate blocks with two anaesthetics of different durations of action. Commonly the two anaesthetics used are lignocaine, relatively short-lasting, and bupivacaine, longerlasting. To reduce observer bias, neither the patient, the physician administering the blocks, nor the person assessing the patient s response to the block should know the order of administration of the two anaesthetics. Ideally the length of time the pain is relieved following each block should correspond with the anaesthetic used (short-acting or long-acting), however discordant responses, where the length of pain relief does not match the anaesthetic used, are often accepted as positive responses 1,4. The lowest false-positive rate is obtainable using placebo-controlled blocks, where responses to three separate injections are assessed a saline injection and two anaesthetics, but this is considered less feasible and too costly in practice. In the New Zealand setting diagnostic MBBs are most likely to be performed by a musculoskeletal physician, anaesthetist or radiologist. The assistance of a radiographer is required during the procedure. Afterwards an independent assessor, for example a registered nurse, usually monitors the effect of the blocks. 1. Effectiveness, Volume of Evidence, Applicability /Generalisability and Consistency / Clinical impact Comment here on the extent to which the service/product/ procedure achieves the desired outcomes. Specific reference needs to be made to safety. Report number needed to treat and harm where possible, any issues concerning the quantity of evidence and its methodological quality and the extent to which the evidence is directly applicable or generalisable to the New Zealand Population, and the degree of consistency demonstrated by the available evidence. Where there are conflicting results, indicate how the group formed a judgement as to the overall direction of the evidence. Comment on the clinical impact e.g. size of population, magnitude of effect, relative benefit over other management options, resource implications, balance of risk and benefit. Effectiveness: Systematic reviews included within the evidence based review Ten systematic reviews and three clinical guidelines published since 2005 reported on the diagnostic accuracy of medial branch blocks. The reviews were of low to moderate quality (grade 2+ or 1-). Findings were based on mostly low to moderate quality primary studies, with the biggest shortcomings being the lack of a reference standard against which to compare medial branch blocks and a lack of blinding or independent observation of the results of the anaesthetic blocks. None of the reviews were able to complete a meta-analysis because of variability in the patient populations, mechanism of injury (traumatic/non-traumatic), and procedural technique. Instead, the ranges of prevalence and false-positive rates (FPR) were reported. Eight reviews included prospective and retrospective cohort studies as well as RCTs. These reviews generally concluded that there is moderate to good evidence that utilizing comparative blocks with greater than 75% criterion pain relief is a reliable method of diagnosing facet-joint mediated pain. It is important to note however, that many of these reviews were authored by the same group of researchers (Manchikanti, Boswell, Falco and colleagues). These researchers also authored a large proportion of the included primary studies. Two systematic reviews were completed by other independent groups (CADTH, American Pain Society) and Page 2 of 7

3 included only high quality studies (RCTs, systematic reviews and meta-analyses). Both of these reviews concluded that there was insufficient evidence to make a recommendation and noted that it was often difficult to see the link between the evidence and recommendations in other reviews. They suggested that the high FPRs and wide prevalence rates did not seem to support there being good or strong evidence that diagnostic MBBs are accurate. Three reviews compared the prevalence and false positive rates when different pain relief thresholds are applied for a positive diagnosis. Studies were divided into two groups: those with 50-74% pain relief thresholds and those that used a cut-off of 75% or more. There were very small numbers in some of the groups (n=1 or 2) with the majority utilising comparative blocks with at least 80% pain reduction as the threshold. No meta-analysis was performed and the prevalence and false positive rates varied widely with high upper limits in all groups. For lumbar diagnostic blocks prevalence rates ranged from 31 61% using a single block, and 15 61% with comparative blocks. False positive rates ranged from 17 66% using comparative blocks. The prevalence and false-positive rates are similar for diagnostic cervical medial branch blocks with a prevalence ranging from 36 to 67% and false positive rates between 27 and 63%. Most of the reviews since 2005 did not discuss safety or complications. Earlier reviews noted that the inherent risks of anaesthetic blocks include radiation exposure, damage to tissues from needle insertion and adverse reactions to the drugs used. For medial branch blocks performed under fluoroscopic guidance with a low volume of anaesthetic the risks of complications are considered low 1. Other jurisdictions: Most organisations approve the use of diagnostic medial branch blocks but recommend the use of double-blind comparative or placebo-controlled blocks. They also recommend that the criteria for a positive result should be set at a threshold of at least 80% pain relief plus the ability to perform previously painful activities. The Spine Intervention Society (SIS) and the Australian and New Zealand College of Anaesthetists Faculty of Pain Medicine also recommend utilizing comparative local anaesthetic blocks with at least an 80% reduction in pain and functional improvement. Validity to the New Zealand setting: In New Zealand the Australian and New Zealand College of Anaesthetists Faculty of Pain Medicine (ANZCAFPM) provides guidance for the conduct of diagnostic cervical and lumbar medial branch blocks on its website. This includes detailed information about assessments required prior to the procedure, patient selection criteria and interpretation of the patient s response to the blocks. These recommendations are derived in part from the Spinal Intervention Society (SIS) guidance. There are likely to be some differences between the protocols applied in many of the international-based primary studies and standard practice in New Zealand. For instance many of the primary studies included in the systematic reviews use 0.5ml of local anaesthetic for each block where SIS recommends 0.3ml. Groups which have adopted the technique and protocol recommended by SIS should match the New Zealand setting fairly well. External peer-review comments: The external peer reviewer was overall positive about the findings of the current ACC evidence report with no major changes recommended. The reviewer did however comment on the overall low quality of the evidence base and suggested that ACCs recommendation should reflect this. In addition, the reviewer made several comments about the procedure itself and best practice regarding the type and volume of local anaesthetic, imaging alternatives, use of placebo blocks and psychosocial assessments prior to the procedure. The full comments are included in Appendix A at the end of this summary. 2. Cost Where possible and reported in the published research literature any economic analysis of the new treatment is considered. Where possible the following will be considered; total costs of the new intervention and number of claimants likely to be affected are considered, along with comparison with the cost of current treatments or interventions, actuarial assessment of the impact of the intervention on scheme liability (including direct and indirect impact e.g. other services and access), expected accrued benefit in terms of quality of life, longer life or Page 3 of 7

4 speedier return to the workforce, implications of cost to the wider health sector. Since 2008 ACC has made service payments for 468 cervical and 476 lumbar diagnostic medial branch blocks at a current cost of $960 per procedure. It is difficult to tell from the data whether each service payment is for a single block (two injections) or includes both blocks where comparative blocks have been used. Of those claims with a diagnostic medial branch block service payment, 24% of cervical MBBs and 21% of lumbar MBBs also have a service payment for RFN. 3. Equity The extent to which the intervention reduces disparities in health status; in particular equity of access and health outcome. The extent to which the intervention supports the objectives of the Maori access strategy and will encourage access to assessment, treatment and rehabilitation services for those groups where there is evidence of that access is problematic. No issues identified 4. Consistency with the intent of the Accident Compensation Act 2001 Purchasing decisions made by ACC must be consistent with and reflect consideration of factors described in the AC Act, Schedule 1, clause 2 (1 and 2) and these decisions must be defensible against this statutory requirement in respect of individual claimants. 5. Possible purchasing options The options are: 1. Purchase, 2. Don t purchase, or 3. Purchase on a case by case basis on the decision of the Corporate Medical Advisor (or equivalent). 6. Evidence statements Summarise the advisory group s synthesis of evidence relating to this service, product or procedure, taking the above factors into account, and indicate the evidence level that applies. The guidelines and systematic reviews mostly report that there is moderate evidence that comparative diagnostic medial branch blocks are safe and reasonably accurate if a minimum pain reduction threshold of at least 75% is applied. Although the evidence base is not strong, several studies, including two New Zealand case series, have demonstrated that cervical and lumbar diagnostic medial branch blocks can be valid and reliable diagnostic tools. There is considerable variation in outcomes from primary studies and it appears that good patient selection criteria, robust criteria for a positive diagnosis and a rigorous technique are essential for obtaining good outcomes. 7. Purchasing recommendations What recommendation(s) does the advisory group draw from this evidence? It is suggested that the 2005 recommendations be amended slightly to reflect the current evidence regarding pain relief thresholds and the importance of patient selection criteria and technique. A proposed change to the recommendations to purchase cervical and lumbar diagnostic medial branch blocks follows (updated recommendations & good practice points are in bold text): Page 4 of 7

5 Double-blind, comparative medial branch blocks, followed by an independent outcome assessment, may be used in the investigation of cervical or low back pain in adults (B = recommendation supported by fair evidence). A threshold of at least 80% pain relief with the ability to perform previously painful activities should be the minimum criteria for a positive diagnosis. Ideally, the VAS score should reduce to a maximum of 0.5/10 following the block (B = recommendation supported by fair evidence). Good practice points: In order to determine the sensitivity, specificity and reproducibility of lumbar diagnostic medial branch blocks, replication of the rigour used for medial branch blocks in the cervical spine is encouraged. This includes double-blinding, independent outcome assessment, and use of comparative, local anaesthetic block. The technique recommended by the Australian and New Zealand College of Anaesthetists Faculty of Pain Medicine and Spine Intervention Society for the performance of diagnostic medial branch blocks should be followed. Rigorous patient selection criteria should be applied to reduce the likelihood of false positive diagnoses. Four additional good practice points relating to patient selection were added subsequently (see PGAG Discussions section below). PGAG Discussions: The group agreed with the core recommendations and good practice points. In addition to the core recommendations, the group asked for more specific guidance around patient selection to also be included as good practice points. The Research team agreed to discuss patient selection criteria with the IPM Expert Group and report their recommendations back to PGAG. Follow-up: The IPM Expert Group discussed patient selection criteria at a meeting on 10 December 2015 and agreed to include the following good practice points: Diagnostic medial branch blocks should only be used for chronic back or neck pain i.e. at least 3 months duration Patients should have minimal central sensitisation and be able to identify one or more areas of pain in a region supplied by one or more medial branches of dorsal rami of cervical or lumbar nerves Patients should have a minimum VAS pain score of 4/10 prior to consideration for diagnostic medial branch blocks Psychosocial risk factors should be considered prior to diagnostic medial branch blocks and patients should be psychologically suitable for the procedure with no psychological distress Page 5 of 7

6 References 1. Bogduk, N. (2010). On diagnostic blocks for lumbar zygapophysial joint pain. Medicine Reports 2: International Spine Intervention Society (2004). Practice guidelines for spinal diagnostic and treatment procedures. San Francisco CA: International Spine Intervention Society. 3. Cohen S.P., S.N. Raja (2007). Pathogenesis, diagnosis and treatment of zygapophysial (facet) joint pain. Anesthesiology 106: Faculty of Pain Medicine, Australian and New Zealand College of Anaesthetists (2007). Conduct of diagnostic cervical and lumbar medial branch blocks. Page 6 of 7

7 Appendix A Peer reviewer comments Consultant Pain Physician and Clinical Leader with an interest in interventional pain management 1. I would endorse the recommendation from FPMANZCA in having a comprehensive biopsychosocial assessment of the patient. This should be done by someone who does not have a vested interest in performing the procedure and have appropriate training in pain medicine. 2. Volume used. The work of Kellgren is referred to in your reference ml of solution can spread a long way and undoubtedly accounts for the variability reported. Here is no evidence to guarantee that this volume ONLY blocks the medial branch. Fluoroscopy is not a valid imaging technique CT would be ideal and ultrasound may also have a role. This needs to be improved by the operators. 3. Local anaesthetic used. Lignocaine and bupivacaine have predictable durations of action if accurately placed on nerves (as above). These durations should be replicable and defined which they do not appear to have been. 4. Outcome should be assessed against an inert solution. Placebo response can be up to 100% particularly with interventional procedures. Ochoa did some work on this many years ago in relation to CRPS. 5. Outcome should have a measure of function. Rice (UCL) published a paper in Br J Anaesth at the end of last year demonstrating that persistent pain patients have a significant numeracy deficit making pain scores invalid. 6. As you noted there is a lot of evidence produced by the same groups who are vested the procedure. Non-vested groups (your ref 13/14) do not find this to be a procedure with huge supporting evidence. I think your recommendations should reflect more emphasis on this particularly as a procedure with minimal or lacking evidence is subsequently used to undertake another procedure which is even more lacking in evidence. Page 7 of 7