Multidisciplinary management of chronic refractory pain in autosomal dominant polycystic kidney disease.

BACKGROUND: Chronic pain is often difficult to manage in autosomal dominant polycystic kidney disease (ADPKD) patients and sometimes even leads to nephrectomy. We analyzed the long-term efficacy of our innovative multidisciplinary protocol to treat chronic refractory pain that aims to preserve kidney function by applying among other sequential nerve blocks. METHODS: Patients were eligible if pain was present ≥3 months with a score of ≥50 on a visual analog scale (VAS) of 100, was negatively affecting quality of life and if there had been insufficient response to previous therapies, including opioid treatment. Treatment options were, in order, analgesics, cyst aspiration and fenestration, nerve blocks and nephrectomy. RESULTS: A total of 101 patients were assessed in our clinic (mean age 50 ± 11 years, 65.3% females). Eight patients were treated with medication, 6 by cyst aspiration or fenestration, 63 by nerve blocks and 6 received surgery as the first treatment option. Overall, 76.9% experienced a positive effect on pain complaints shortly after treatment. The VAS score was reduced from 60/100 to 20/100 (P < 0.001) and patients decreased their number of nonopioid and opioid analgesics significantly (P < 0.001, P = 0.01, respectively). A substantial number of the patients (n = 51) needed additional treatment. At the end of follow-up in only 13 patients (12.9%) was surgical intervention necessary: 11 nephrectomies (of which 10 were in patients already on kidney function replacement treatment), 1 liver transplantation and 1 partial hepatectomy. After a median follow-up of 4.5 years (interquartile range 2.5-5.3), 69.0% of the patients still had fewer pain complaints. CONCLUSIONS: These data indicate that our multidisciplinary treatment protocol appears effective in reducing pain in the majority of patients with chronic refractory pain, while postponing or even avoiding in most patients surgical interventions such as nephrectomy in most patients.

A guide for standardized interpretation of lumbar multifidus ultrasonography; an observational study.

BACKGROUND: Inconsistent descriptions of Lumbar multifidus (LM) morphology were previously identified, especially in research applying ultrasonography (US), hampering its clinical applicability with regard to diagnosis and therapy. The aim of this study is to determine the LM-sonoanatomy by comparing high-resolution reconstructions from a 3-D digital spine compared to standard LM-ultrasonography. METHODS: An observational study was carried out. From three deeply frozen human tissue blocks of the lumbosacral spine, a large series of consecutive photographs at 78 µm interval were acquired and reformatted into 3-D blocks. This enabled the reconstruction of (semi-)oblique cross-sections that could match US-images obtained from a healthy volunteer. Transverse and oblique short-axis views were compared from the most caudal insertion of LM to L1. RESULTS: Based on the anatomical reconstructions, we could distinguish the LM from the adjacent erector spinae (ES) in the standard US imaging of the lower spine. At the lumbosacral junction, LM is the only dorsal muscle facing the surface. From L5 upwards, the ES progresses from lateral to medial. A clear distinction between deep and superficial LM could not be discerned. We were only able to identify five separate bands between every lumbar spinous processes and the dorsal part of the sacrum in the caudal anatomical cross-sections, but not in the standard US images. CONCLUSION: The detailed cross-sectional LM-sonoanatomy and reconstructions facilitate the interpretations of standard LM US-imaging, the position of the separate LM-bands, the details of deep interspinal muscles, and demarcation of the LM versus the ES. Guidelines for electrode positioning in EMG studies should be refined to establish reliable and verifiable findings. For clinical practice, this study can serve as a guide for a better characterisation of LM compared to ES and for a more reliable placement of US-probe in biofeedback.

Inconsistent descriptions of lumbar multifidus morphology: A scoping review.

BACKGROUND: Lumbar multifidus (LM) is regarded as the major stabilizing muscle of the spine. The effects of exercise therapy in low back pain (LBP) are attributed to this muscle. A current literature review is warranted, however, given the complexity of LM morphology and the inconsistency of anatomical descriptions in the literature. METHODS: Scoping review of studies on LM morphology including major anatomy atlases. All relevant studies were searched in PubMed (Medline) and EMBASE until June 2019. Anatomy atlases were retrieved from multiple university libraries and online. All studies and atlases were screened for the following LM parameters: location, imaging methods, spine levels, muscle trajectory, muscle thickness, cross-sectional area, and diameter. The quality of the studies and atlases was also assessed using a five-item evaluation system. RESULTS: In all, 303 studies and 19 anatomy atlases were included in this review. In most studies, LM morphology was determined by MRI, ultrasound imaging, or drawings - particularly for levels L4-S1. In 153 studies, LM is described as a superficial muscle only, in 72 studies as a deep muscle only, and in 35 studies as both superficial and deep. Anatomy atlases predominantly depict LM as a deep muscle covered by the erector spinae and thoracolumbar fascia. About 42% of the studies had high quality scores, with 39% having moderate scores and 19% having low scores. The quality of figures in anatomy atlases was ranked as high in one atlas, moderate in 15 atlases, and low in 3 atlases. DISCUSSION: Anatomical studies of LM exhibit inconsistent findings, describing its location as superficial (50%), deep (25%), or both (12%). This is in sharp contrast to anatomy atlases, which depict LM predominantly as deep muscle. Within the limitations of the self-developed quality-assessment tool, high-quality scores were identified in a majority of studies (42%), but in only one anatomy atlas. CONCLUSIONS: We identified a lack of standardization in the depiction and description of LM morphology. This could affect the precise understanding of its role in background and therapy in LBP patients. Standardization of research methodology on LM morphology is recommended. Anatomy atlases should be updated on LM morphology.

Novel treatment protocol for ameliorating refractory, chronic pain in patients with autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) patients can suffer from chronic pain that can be refractory to conventional treatment, resulting in a wish for nephrectomy. This study aimed to evaluate the effect of a multidisciplinary treatment protocol with sequential nerve blocks on pain relief in ADPKD patients with refractory chronic pain. As a first step a diagnostic, temporary celiac plexus block with local anesthetics was performed. If substantial pain relief was obtained, the assumption was that pain was relayed via the celiac plexus and major splanchnic nerves. When pain recurred, patients were then scheduled for a major splanchnic nerve block with radiofrequency ablation. In cases with no pain relief, it was assumed that pain was relayed via the aortico-renal plexus, and catheter-based renal denervation was performed. Sixty patients were referred, of which 44 were eligible. In 36 patients the diagnostic celiac plexus block resulted in substantial pain relief with a change in the median visual analogue scale (VAS) score pre-post intervention of 50/100. Of these patients, 23 received a major splanchnic nerve block because pain recurred, with a change in median VAS pre-post block of 53/100. In 8 patients without pain relief after the diagnostic block, renal denervation was performed in 5, with a borderline significant change in the median VAS pre-post intervention of 20/100. After a median follow-up of 12 months, 81.8% of the patients experienced a sustained improvement in pain intensity, indicating that our treatment protocol is effective in obtaining pain relief in ADPKD patients with refractory chronic pain.

Different Approaches to Ultrasound-guided Thoracic Paravertebral Block: An Illustrated Review.

Given the fast development and increasing clinical relevance of ultrasound guidance for thoracic paravertebral blockade, this review article strives (1) to provide comprehensive information on thoracic paravertebral space anatomy, tailored to the needs of a regional anesthesia practitioner, (2) to interpret ultrasound images of the thoracic paravertebral space using cross-sectional anatomical images that are matched in location and plane, and (3) to briefly describe and discuss different ultrasound-guided approaches to thoracic paravertebral blockade. To illustrate the pertinent anatomy, high-resolution photographs of anatomical cross-sections are used. By using voxel anatomy, it is possible to visualize the needle pathway of different approaches in the same human specimen. This offers a unique presentation of this complex anatomical region and is inherently more realistic than anatomical drawings.

A stepwise approach for effective management of chronic pain in autosomal-dominant polycystic kidney disease.

Chronic pain, defined as pain existing for >4-6 weeks, affects >60% of patients with autosomal-dominant polycystic disease (ADPKD). It can have various causes, indirectly or directly related to the increase in kidney and liver volume in these patients. Chronic pain in ADPKD patients is often severe, impacting physical activity and social relationships, and frequently difficult to manage. This review provides an overview of pathophysiological mechanisms that can lead to pain and discusses the sensory innervation of the kidneys and the upper abdominal organs, including the liver. In addition, the results of a systematic literature search of ADPKD-specific treatment options are presented. Based on pathophysiological knowledge and evidence derived from the literature an argumentative stepwise approach for effective management of chronic pain in ADPKD is proposed.

Ultra-high-definition (22 MHz) ultrasound of the ulnar nerve: additional value and normative data.

We studied 30 healthy volunteers (60 arms), categorized into three age groups with equal numbers to verify if a 22 MHz compared with a 15 MHz ultrasound transducer has additional value for studying the intraneural architecture of the ulnar nerve throughout its course. At six sites, there were no differences in cross-sectional area measurements between the two transducers. With both, the cross-sectional area was significantly larger at the medial epicondyle compared with the other sites and smaller at the mid-forearm and Guyon's canal compared with the mid-upper arm. With higher age the cross-sectional area significantly increased. Significantly more fascicles were visible distal to the medial epicondyle compared with more proximal sites, as well as in men compared with women. Finally, higher body weight was related to a significantly smaller number of fascicles being seen. A 22 MHz transducer depicts more details of the intraneural architecture than a 15 MHz transducer. Our data can be used as normative data or reference values in analysing ulnar nerve pathology.Level of evidence: II.

Human assumed central sensitisation (HACS) in patients with chronic low back pain radiating to the leg (CLaSSICO study).

INTRODUCTION: Patients with chronic low back pain radiating to the leg (CLBPr) are sometimes referred to a specialised pain clinic for a precise diagnosis based, for example, on a diagnostic selective nerve root block. Possible interventions are therapeutic selective nerve root block or pulsed radiofrequency. Central pain sensitisation is not directly assessable in humans and therefore the term 'human assumed central sensitisation' (HACS) is proposed. The possible existence and degree of sensitisation associated with pain mechanisms assumed present in the human central nervous system, its role in the chronification of pain and its interaction with diagnostic and therapeutic interventions are largely unknown in patients with CLBPr. The aim of quantitative sensory testing (QST) is to estimate quantitatively the presence of HACS and accumulating evidence suggest that a subset of patients with CLBPr have facilitated responses to a range of QST tests.The aims of this study are to identify HACS in patients with CLBPr, to determine associations with the effect of selective nerve root blocks and compare outcomes of HACS in patients to healthy volunteers. METHODS AND ANALYSIS: A prospective observational study including 50 patients with CLBPr. Measurements are performed before diagnostic and therapeutic nerve root block interventions and at 4 weeks follow-up. Data from patients will be compared with those of 50 sex-matched and age-matched healthy volunteers. The primary study parameters are the outcomes of QST and the Central Sensitisation Inventory. Statistical analyses to be performed will be analysis of variance. ETHICS AND DISSEMINATION: The Medical Research Ethics Committee of the University Medical Center Groningen, Groningen, the Netherlands, approved this study (dossier NL60439.042.17). The results will be disseminated via publications in peer-reviewed journals and at conferences. TRIAL REGISTRATION NUMBER: NTR NL6765.

Functional and morphological lumbar multifidus characteristics in subgroups with low back pain in primary care.

BACKGROUND: Since the contribution of the lumbar multifidus(LM) is not well understood in relation to non-specific low back pain(LBP), this may limit physiotherapists in choosing the most appropriate treatment strategy. OBJECTIVES: This study aims to compare clinical characteristics, in terms of LM function and morphology, between subacute and chronic LBP patients from a large clinical practice cohort compared to healthy controls. DESIGN: Multicenter case control study. METHOD: Subacute and chronic LBP patients and healthy controls between 18 and 65 years of age were included. Several clinical tests were performed: primary outcomes were the LM thickness from ultrasound measurements, trunk range of motion(ROM) from 3D kinematic tests, and median frequency and root mean square values of LM by electromyography measurements. The secondary outcomes Numeric Rating Scale for Pain(NRS) and the Oswestry Disability Index(ODI) were administered. Comparisons between groups were made with ANOVA, p-values<0.05, with Tukey's HSD post-hoc test were considered significant. RESULTS: A total of 161 participants were included, 50 healthy controls, 59 chronic LBP patients, and 52 subacute LBP patients. Trunk ROM and LM thickness were significantly larger in healthy controls compared to all LBP patients(p < 0.01). A lower LM thickness was found between subacute and chronic LBP patients although not significant(p = 0.11-0.97). All between-group comparisons showed no statistically significant differences in electromyography outcomes (p = 0.10-0.32). NRS showed no significant differences between LBP subgroups(p = 0.21). Chronic LBP patients showed a significant higher ODI score compared to subacute LBP patients(p = 0.03). CONCLUSIONS: Trunk ROM and LM thickness show differences between LBP patients and healthy controls.

Persistent cortical blindness after a thoracic epidural test dose of bupivacaine.

Thoracic epidural anesthesia is considered as an essential component of the perioperative care for patients undergoing lung resection. Although neurologic adverse events have been associated with this technique, permanent injury is rare. These events primarily involve the peripheral nervous system; for example, nerve root injury. We present a case of persistent cortical blindness after a test dose of bupivacaine was administered into an uneventfully placed thoracic epidural catheter.

15. Discogenic low back pain.

An estimated 40% of chronic lumbosacral spinal pain is attributed to the discus intervertebralis. Degenerative changes following loss of hydration of the nucleus pulposus lead to circumferential or radial tears within the annulus fibrosus. Annular tears within the outer annulus stimulate the ingrowth of blood vessels and accompanying nociceptors into the outer and occasionally inner annulus. Sensitization of these nociceptors by various inflammatory repair mechanisms may lead to chronic discogenic pain. The current criterion standard for diagnosing discogenic pain is pressure-controlled provocative discography using strict criteria and at least one negative control level. The strictness of criteria and the adherence to technical detail will allow an acceptable low false positive response rate. The most important determinants are the standardization of pressure stimulus by using a validated pressure monitoring device and avoiding overly high dynamic pressures by the slow injection rate of 0.05 mL/s. A positive discogram requires the reproduction of the patient's typical pain at an intensity of > 6/10 at a pressure of < 15 psi above opening pressure and at a volume less than 3.0 mL. Perhaps the most important and defendable response is the failure to confirm the discus is symptomatic by not meeting this strict criteria. Various interventional treatment strategies for chronic discogenic low back pain unresponsive to conservative care include reduction of inflammation, ablation of intradiscal nociceptors, lowering intranuclear pressure, removal of herniated nucleus, and radiofrequency ablation of the nociceptors. Unfortunately, most of these strategies do not meet the minimal criteria for a positive treatment advice. In particular, single-needle radiofrequency thermocoagulation of the discus is not recommended for patients with discogenic pain (2 B-). Interestingly, a little used procedure, radiofrequency ablation of the ramus communicans, does meet the (2 B+) level for endorsement. There is currently insufficient proof to recommend intradiscal electrothermal therapy (2 B±) and intradiscal biacuplasty (0). It is advised that ozone discolysis, nucleoplasty, and targeted disc decompression should only be performed as part of a study protocol. Future studies should include more strict inclusion criteria.

Differences in quantitative architecture of sciatic nerve may explain differences in potential vulnerability to nerve injury, onset time, and minimum effective anesthetic volume.

BACKGROUND: In sciatic nerve (SN) blocks, differences are seen in risk of nerve damage, minimum effective anesthetic volume, and onset time. This might be related to differences in the ratio neural:nonneural tissue within the nerve. For the brachial plexus, a higher proximal ratio may explain the higher risk for neural injury in proximal nerve blocks. A similar trend in risk is reported for SN; however, equivalent quantitative data are lacking. The authors aimed to determine the ratio neural:nonneural tissue within SN in situ in the upper leg. METHODS: From five consecutive cadavers, the region between the sacrum and distal femur condyle was harvested and frozen. Using a cryomicrotome, consecutive transversal sections (interval, 78 mum) were obtained and photographed. Reconstructions of SN were made strictly perpendicular to its long axis in the midgluteal, subgluteal, midfemoral, and popliteal regions. The epineurial area and all neural fascicles were delineated and measured. The nonneural tissue compartment inside and outside SN was also delineated and measured. RESULTS: The amount of neural tissue inside the epineurium decreased significantly toward distal (midfemoral/popliteal region) (P < 0.001). The relative percentage of neural tissue decreased from midgluteal (67 +/- 7%), to subgluteal (57 +/- 9%), to midfemoral (46 +/- 10%), to popliteal (46 +/- 11%). Outside the SN, the adipose compartment increased significantly toward distal (P < 0.007). CONCLUSION: In SN, the ratio neural:nonneural tissue changes significantly from 2:1 (midgluteal and subgluteal) to 1:1 (midfemoral and popliteal). This suggests a higher vulnerability for neurologic sequelae in proximal SN, and may explain differences observed in minimum effective anesthetic volume and onset time between proximal and distal SN blocks.

Extraneural versus intraneural stimulation thresholds during ultrasound-guided supraclavicular block.

BACKGROUND: A stimulation current of no more than 0.5 mA is regarded as safe in avoiding nerve injury and delivering adequate stimulus to provoke a motor response. However, there is no consistent level of stimulating threshold that reliably indicates intraneural placement of the needle. The authors determined the minimally required stimulation threshold to elicit a motor response outside and inside the most superficial part of the brachial plexus during high-resolution, ultrasound-guided, supraclavicular block. METHODS: After institutional review board approval, ultrasound-guided, supraclavicular block was performed on 55 patients. Patients with neurologic dysfunction were excluded. Criteria for extraneural and intraneural stimulation were defined and assessed by independent experts. To determine success rate and any residual neurologic deficit, qualitative sensory and motor examinations were performed before and after block placement. At 6 month follow-up, the patients were examined for any neurologic deficit. RESULTS: Thirty-nine patients met all set stimulation criteria. Median +/- SD (interquartile range) minimum stimulation threshold outside was 0.60 +/- 0.37 mA (0.40, 1.0) and inside 0.30 +/- 0.19 mA (0.20, 0.40). The difference of 0.30 mA was statistically significant (P < 0.0001). Stimulation currents of 0.2 mA or less were not observed outside the trunk in any patient. Significantly higher thresholds were observed in diabetic patients. Success rate was 100% after 20 min. Thirty-four patients had normal sensory and motor examination at 6 months. Five patients were lost to follow-up. CONCLUSION: Within the limitations of this study and the use of ultrasound, a stimulation current of 0.2 mA or less is reliable to detect intraneural placement of the needle. Furthermore, stimulation currents of more than 0.2 and no more than 0.5 mA could not rule out intraneural position.

Lack of analgesic effects of transcranial pulsed electromagnetic field stimulation in neuropathic pain patients: A randomized double-blind crossover trial.

BACKGROUND: Neuromodulation is nowadays investigated as a promising method for pain relief. Research indicates that a single 30-minute stimulation with transcranial pulsed electromagnetic fields (tPEMF) can induce analgesic effects. However, it is unknown whether tPEMF can induce analgesia in neuropathic pain patients. OBJECTIVE: To evaluate the effect of tPEMF on spontaneous pain and heat pain in neuropathic pain patients. METHODS: This study had a randomized double-blind crossover design. Twenty neuropathic pain patients received 30-minutes of tPEMF and 30-minutes sham stimulation. Primary outcomes were pain intensity, pain aversion and heat pain. Secondary outcomes included affect, cognition, and motor function, to investigate safety, tolerability and putative working mechanisms of tPEMF. Outcomes were assessed before, during and after stimulation. RESULTS: No differences in analgesic effects between tPEMF and sham stimulation were found for pain intensity, pain aversion or heat pain. No differences between tPEMF and sham stimulation were observed for affect, motor, and cognitive outcomes. CONCLUSION: A single 30-minute tPEMF stimulation did not induce analgesic effects in neuropathic pain patients, compared to sham. Further study is needed to determine whether prolonged stimulation is necessary for analgesic effects.

Quantitative architecture of the brachial plexus and surrounding compartments, and their possible significance for plexus blocks.

BACKGROUND: Nerve injury after regional anesthesia of the brachial plexus (BP) is a relatively rare and feared complication that is partly attributed to intraneural injection. However, recent studies have shown that intraneural injection does not invariably cause neural injury, which may be related to the architecture within the epineurium. A quantitative study of the neural components and the compartment outside BP was made. METHODS: From four frozen shoulders, high-resolution images of sagittal cross-sections with an interval of 0.078 mm were obtained using a cryomicrotome to maintain a relatively undisturbed anatomy. From this data set, cross-sections perpendicular to the axis of the BP were reconstructed in the interscalene, supraclavicular, midinfraclavicular, and subcoracoid regions. Surface areas of both intraepineurial and connective tissue compartments outside the BP were delineated and measured. RESULTS: The nonneural tissue (stroma and connective tissue) inside and outside the BP increased from proximal to distal, being significant between interscalene/supraclavicular and midinfraclavicular/subcoracoid regions (P < 0.001 for tissue inside BP, P < 0.02 for tissue outside BP). The median amount of neural tissue remained approximately the same in the four measured regions (41.1 +/- 6.3 mm; range, 30-60 mm). The ratio of neural to nonneural tissue inside the epineurium increased from 1:1 in the interscalene/supraclavicular to 1:2 in the midinfraclavicular/subcoracoid regions. CONCLUSION: Marked differences in neural architecture and size of surrounding adipose tissue compartments are demonstrated between proximal and distal parts of the brachial plexus. These differences may explain why some injections within the epineurium do not result in neural injury and affect onset times of BP blocks.

Psychological predictors of substantial pain reduction after minimally invasive radiofrequency and injection treatments for chronic low back pain.

OBJECTIVE: In this post hoc observational study, we investigated psychological predictors of outcome after radiofrequency and injection treatments, commonly performed in the management of chronic low back pain (CLBP). DESIGN & SETTING: Data, comprising 161 patients (29 eventually lost to follow-up), were obtained from two randomized controlled trials on efficacy of radiofrequency treatment for back pain and sciatica. Subsequently patients were additionally treated in an open prospective follow-up period. Although all groups presented a significant visual analog scale reduction after 3 and 12 months, no additional pain relief after radiofrequency compared with injection treatment was found. Both trial populations showed sufficient similarities. A principal component (factor) analysis was performed on baseline psychometric tests, SF-36, and physical activity variables. We constructed five clinically relevant psychological profiles: "psychologically negative,""adaptive manager,""rigid qualities,""supporting partner," and "strong ego." These were examined as possible predictors of significant pain relief using logistic regression analysis. RESULTS: The "psychologically negative" dimension showed a negative and the "adaptive manager" dimension a positive prognostic effect on outcome. CONCLUSIONS: Minimally invasive treatment for CLBP leads to significant pain reduction, including potential placebo effects. However, psychologically vulnerable patients, characterized by, among others, reduced life control, disturbed mood, negative self-efficacy, catastrophizing, high anxiety levels, inadequacy, and poor mental health, tend not to respond to this treatment. Patients characterized by a.o. reduced pain and interference levels, positive expectations, and reasonable physical and social functioning, react more favorably. From both a clinical and a financial perspective, psychosocial evaluation and selection of patients seems appropriate, before applying minimally invasive procedures for CLBP.

Influence of needle position on lumbar segmental nerve root block selectivity.

BACKGROUND AND OBJECTIVES: In patients with chronic low back pain radiating to the leg, segmental nerve root blocks (SNRBs) are performed to predict surgical outcome and identify the putative symptomatic spinal nerve. Epidural spread may lead to false interpretation, affecting clinical decision making. Systematic fluoroscopic analysis of epidural local anesthetic spread and its relationship to needle tip location has not been published to date. Study aims include assessment of epidural local anesthetic spread and its relationship to needle position during fluoroscopy-assisted blocks. METHODS: Patients scheduled for L4, L5, and S1 blocks were included in this prospective observational study. Under fluoroscopy and electrostimulation, they received 0.5 mL of a mixture containing lidocaine 5 mg and iohexol 75 mg. X-rays with needle tip and contrast were scored for no epidural spread (grade 0), local spread epidurally (grade 1), or to adjacent nerve roots (grade 2). RESULTS: Sixty-five patients were analyzed for epidural spread, 62 for needle position. Grade 1 epidural spread occurred in 47% of L4 and 28% of L5 blocks and grade 2 spread in 3 blocks (5%; L5 n = 1, S1 n = 2). For lumbar blocks, the needle was most frequently found in the lateral upper half of the intervertebral foramen. Epidural spread occurred more frequently with medial needle positions (P = .06). CONCLUSION: The findings suggest (P = .06) that the risk of grade 1 and 2 lumbar epidural spread, which results in decreased SNRB selectivity, is greater with medial needle positions in the intervertebral foramen. The variability in anatomic position of the dorsal root ganglion necessitates electrostimulation to guide SNRB in addition to fluoroscopy.

Intensity mapping of pain referral areas in sacroiliac joint pain patients.

OBJECTIVE: To identify differences in pain referral areas, using intensity maps, between responders and nonresponders to a double diagnostic sacroiliac joint injection with a short- and long-acting local anesthetic in patients with chronic low back pain. METHODS: From a group of 140 consecutive patients with chronic low back pain, 60 patients who met clinical criteria were included in the study. Twenty-seven demonstrated a positive response to a double diagnostic fluoroscopically guided intra-articular sacroiliac joint block and were compared with 33 patients with a negative response. Each patient's preinjection pain diagram was used to determine areas of pain referral. The summation of these pain referral zones for both groups was used to construct intensity maps. RESULTS: No major differences were observed between responders and nonresponders with regard to mean size and distribution of referral pain areas. Intensity maps, however, showed differences in pain referral at the buttock in the areas overlying the sacroiliac joint (100% of the responders vs 80% of the nonresponders) and the ischial tuberosity (10% of the responders vs 100% of the nonresponders). CONCLUSIONS: Overall referred pain maps appeared not to be useful to discriminate patients with an identified sacroiliac joint pain from chronic low back pain patients with pain from other sources. Differences were only found using intensity maps. By implementing these data, it could be concluded that patients with sacroiliac joint pain are less likely to experience pain in both the 'Fortin' and 'tuber' areas. This knowledge can be used as additional selection criterion for putative sacroiliac joint patients, next to sacroiliac joint pain provocation tests.