What a pain in the back: a review of current treatment options with a focus on naproxen sodium.

Non-specific low back pain (LBP) represents a challenging and prevalent condition that is one of the most common symptoms leading to primary care physician visits. While established guidelines recommend prioritizing non-pharmacological approaches as the primary course of action, pharmacological treatments are advised when non-pharmacological approaches are ineffective or based on patient preference. These guidelines recommend non-steroidal anti-inflammatory drugs (NSAIDs) or skeletal muscle relaxers (SMRs) as the first-line pharmacological options for acute or subacute LBP, while NSAIDs are the exclusive first-line pharmacological option for chronic LBP. Although SMRs are generally effective for acute LBP, the available evidence does not support the view that they improve functional recovery, and their comparative efficacy to NSAIDs and other analgesics remains unknown, while studies have shown them to introduce adverse events without significantly reducing LBP. Moreover, opioids continue to be widely prescribed for LBP, despite limited evidence for effectiveness and known risks of addiction and overdose. Broader use of non-opioid pharmacotherapy, including the appropriate use of OTC options, is critical to addressing the opioid crisis. The balance of evidence indicates that NSAIDs have a favorable benefit-risk profile when compared to other available pharmacological treatment options for non-specific LBP, a condition that is primarily acute in nature and well-suited for self-treatment with OTC analgesics. While clinical guidelines do not differentiate between NSAIDs, evidence indicates that OTC naproxen sodium effectively relieves pain across multiple types of pain models, and furthermore, the 14-h half-life of naproxen sodium allows sustained, all day pain relief with reduced patient pill burden as compared to shorter acting options. Choosing the most appropriate approach for managing LBP, including non-pharmacological options, should be based on the patient's condition, severity of pain, potential risks, and individual patient preference and needs.

Understanding general practitioners' prescribing choices to patients with chronic low back pain: a discrete choice experiment.

BACKGROUND: Although NSAIDs are recommended as a first line analgesic treatment, opioids are very commonly prescribed to patients with low back pain (LBP) despite risks of harms. AIM: This study aimed to determine factors contributing to general practitioners' (GPs') prescribing choices to patients with chronic LBP in a primary care setting. METHOD: This discrete choice experiment (DCE) presented 210 GPs with hypothetical scenarios of a patient with chronic LBP. Participants chose their preferred treatment for each choice set, either the opioid, NSAID or neither. The scenarios varied by two patient attributes; non-specific LBP or LBP with referred leg pain (sciatica) and number of comorbidities. The three treatment attributes also varied, being: the type of opioid or NSAID, degree of pain reduction and number of adverse events. The significance of each attribute in influencing clinical decisions was the primary outcome and the degree to which GPs preferred the alternative based on the number of adverse events or the amount of pain reduction was the secondary outcome. RESULTS: Overall, GPs preferred NSAIDs (45.2%, 95% CI 38.7-51.7%) over opioids (28.8%, 95% CI 23.0-34.7%), however there was no difference between the type of NSAID or opioid preferred. Additionally, the attributes of pain reduction and adverse events did not influence a GP's choice between NSAIDs or opioids for patients with chronic LBP. CONCLUSION: GPs prefer prescribing NSAIDs over opioids for a patient with chronic low back pain regardless of patient factors of comorbidities or the presence of leg pain (i.e. sciatica).

Menopausal hormone therapy, oral contraceptives and risk of chronic low back pain: the HUNT Study.

BACKGROUND: There are indications that use of menopausal hormone therapy (MHT) and oral contraceptives (OC) increases the risk of low back pain (LBP), with higher oestrogen levels involved in the underlying mechanisms. The purpose of the present study was to investigate associations between use of systemic MHT or OC and risk of chronic LBP in a large population-based data set. METHODS: Data were obtained from two surveys in the Trøndelag Health Study in Norway, HUNT2 (1995-1997) and HUNT3 (2006-2008). A cross-sectional study of association between use of systemic MHT and prevalence of chronic LBP comprised 12,974 women aged 40-69 years in HUNT2, with 4007 women reporting chronic LBP. A cohort study involving MHT comprised 6007 women without chronic LBP at baseline in HUNT2, and after 11 years 1245 women reported chronic LBP at follow-up in HUNT3. The cross-sectional study of association with use of OC included 23,593 women aged 20-69 years in HUNT2, with 6085 women reporting chronic LBP. The corresponding cohort study included 10,586 women without chronic LBP at baseline in HUNT2, of whom 2084 women reported chronic LBP in HUNT3. Risk of chronic LBP was examined in both study designs in generalised linear models with adjustment for potential confounders. RESULTS: In the cohort study, current users of systemic MHT at baseline showed a greater risk of chronic LBP (relative risk (RR) 1.30; 95% CI: 1.14-1.49; compared with never users). The risk increased according to duration of MHT use (P for linear trend = 0.003). Known users of systemic MHT based exclusively on oestrogen experienced the highest risk (RR 1.49; 95% CI: 1.16-1.91), but an increased risk was also seen among known users of oestrogen-progestin combination MHT (RR 1.35; 95% CI: 1.16-1.57). A slight increase in risk of chronic LBP was found in the cohort study among former users of OC (RR 1.17; 95% CI: 1.06-1.30; compared with never users). CONCLUSIONS: Long-lasting use of systemic MHT, in particular therapy based on oestrogen only, is associated with greater risk of chronic LBP. Having been a user of OC most likely entails a minor increase in risk.

Different Dosage Regimens of Tanezumab for the Treatment of Chronic Low Back Pain: A Meta-analysis of Randomized Controlled Trials.

OBJECTIVE: The aim of this study was to assess the efficacy of different dosage regimens of tanezumab among individuals living with chronic low back pain (CLBP). METHODS: PubMed, Embase, The Cochrane Library, and other databases were searched from inception until August 2021. Randomized controlled trials investigating the efficacy and safety of tanezumab in individuals with CLBP were included. Data were extracted independently by 2 investigators and assessed the study quality by the Cochrane risk-of-bias tool. The measurements include low back pain intensity and Roland-Morris Disability Questionnaire. The incidence of adverse events and serious adverse events was set to assess the safety of tanezumab for CLBP. RESULTS AND DISCUSSION: Three high-quality randomized controlled trials with 3414 patients were finally included in our analysis. Tanezumab, respectively, led to a notable decrease compared with placebo in low back pain intensity (mean difference, -0.62; 95% confidence interval [CI], -0.77 to -0.46; P < 0.01) and Roland-Morris Disability Questionnaire (mean difference, -0.64; 95% CI, -0.80 to -0.47; P = 0.01). In addition, no significant difference existed between tanezumab and placebo groups (risk ratio, 1.10; 95% CI, 0.81-1.49; P = 0.55) in the adverse events and (risk ratio, 1.06; 95% CI, 0.34-3.27; P = 0.93) serious adverse events. CONCLUSIONS: Intravenous and subcutaneous tanezumab injections as treatment for improving CLBP have promising clinical application as its great improvement on all efficacy and its controllable safety issues. Furthermore, intravenous and subcutaneous tanezumab injections were proved to achieve excellent and long-term curative effect on CLBP through our subgroup analysis and comparison.

Acute Lower Back Pain after Intralesional Injection of Collagenase Clostridium histolyticum for Peyronie's Disease.

PURPOSE: The safety label for collagenase Clostridium histolyticum was updated to include postinjection acute lower back pain as an adverse event observed with intralesional therapy for Peyronie's disease. Incidence and causality are unknown. We assessed frequencies and temporal associations for this adverse event in a large cohort. MATERIALS AND METHODS: Data on all men undergoing collagenase injections for Peyronie's disease at our institution from October 2015 through December 2020 were retrospectively assessed. The study included 330 patients, 300 completing at least 1 full course (8 injections). Measured outcomes included incidence and timing of back pain, and associations with demographics and comorbidities. RESULTS: Of 330 patients, 19 (5.8%) experienced at least 1 episode of postinjection acute lower back pain. Of 300 who completed at least 1 full course of 8 injections, 4 (1.3%) reported back pain within the 8-injection course. A subset underwent additional rounds (16 or 24 injections). Back pain increased to 8.7% (13/149) during a second round, 6.9% (3/43) during a third. No association was found with age, diabetes or back pain history. Most cases occurred shortly after injection; all were self-limited or resolved with a single dose of ketorolac. CONCLUSIONS: This single-center, retrospective analysis suggests that intralesional collagenase injections for Peyronie's disease may cause acute lower back pain in up to 6% of patients. Patients may benefit from counseling regarding this risk. Incidence rises with additional rounds of treatment. Prospective safety data regarding >8 injections do not exist. No patient had long-term sequelae of back pain.

Dolor lumbar persistente tras la administración de [131I]Iodo-6-beta-iodometil-19-norcolesterol: a propósito de un caso / Lower back pain after iodine-131-6-Beta-iodomethyl-19-norcholesterol injection: a case report

El [131I]Iodo-6-Beta-iodometil-19-norcolesterol ([131I]Norcolesterol), radiofármaco indicado en el diagnóstico del estado funcional de tejido cortical suprarrenal, en la detección del tejido funcional en el hiperadrenocorticalismo así como en el aldosteronismo primario. Presentamos el caso de una mujer de 54 años de edad, remitida para la evaluación de una sospecha de aldosteronismo, y que inmediatamente después de la administración intravenosa de [131I]Norcolesterol sufrió una fuerte reacción adversa al medicamento, con mareo, rubor, aumento de la presión arterial, opresión en el pecho, dolor lumbar y sarpullido eritematoso hasta 9 días postinyección. Los síntomas se resolvieron satisfactoriamente tras la administración de antihistamínicos y corticoides. Se sospechó que esta reacción estuviera relacionada con la administración del [131I]Norcolesterol causada por una reacción alérgica de tipo I (AU)

The [131I]Iodine-6-Beta-iodomethyl-19-norcholesterol ([131I]Norcholesterol; NP-59), is indicated in the diagnosis of the functional state of adrenal cortical tissue, in the detection of functional tissue in hyperadrenocorticalism as well as in primary aldosteronism. We present the case of a 54-year-old woman, referred for evaluation of suspected aldosteronism, and who immediately after intravenous administration of [131I]Norcholesterol suffered a strong adverse drug reaction, with dizziness, flushing, increased blood pressure, chest tightness, low back pain and erythematous rash up to 9 days after injection. Symptoms resolved satisfactorily after administration of antihistamines and corticosteroids. This reaction was suspected to be related to the administration of [131I]Norcholesterol caused by a type I allergic reaction.(AU)

Somatosensory behavioral alterations in a NGF-induced persistent low back pain model.

Low back pain (LBP) is a major global burden in part due to the underlying pathophysiological mechanisms being poorly understood. A LBP rat model involving two injections of nerve growth factor (NGF, an endogenous pain-related neurotrophin) into trunk musculature was recently developed. Additional behavioral work in this NGF-LBP rat model is required to better characterize local and remote somatosensory alterations related to NGF-induced peripheral and central sensitization. This work characterizes the time-dependent development of hypersensitivity to trunk and hindpaw cutaneous mechanical stimulation and deep muscle mechanical hyperalgesia in adult male Sprague-Dawley rats (n = 6/group). Behavioral assays were performed at baseline (Day 0, D0), D2, D5 (pre- and 4 h post-2nd NGF or control injection), D7, D10, and D14 in NGF and control groups. Trunk and hindpaw cutaneous mechanical hypersensitivity were tested using von Frey filaments. Deep trunk mechanical hyperalgesia was determined using a small animal algometer. NGF rats demonstrated increased cutaneous sensitivity to ipsilateral trunk mechanical stimuli at D7, D10, and D14. NGF rats also demonstrated ipsilateral deep mechanical hyperalgesia on D2, D5 + 4 h, D7, D10, and D14. Cutaneous hypersensitivity was delayed compared to deep hyperalgesia in NGF rats. No additional sensory changes were noted. Together, these results indicate that male mechanical somatosensory changes develop primarily locally in the ipsilateral trunk following unilateral NGF injections. These findings contrast with a previous report in female rats using this NGF-LBP model showing more widespread (bilateral) hyperalgesia and remote mechanical hypersensitivity. Future studies will examine potential sex-related pain behavioral differences in the NGF model.

Pain-related anxiety, sex, and co-use of alcohol and prescription opioids among adults with chronic low back pain.

BACKGROUND: Both alcohol and prescription opioid use/misuse are highly prevalent among individuals with chronic pain. Co-use of alcohol and prescription opioids is also common, despite contraindications due to increased risk of negative health effects and mortality. There is evidence that pain-related anxiety (i.e., the tendency to respond to pain with anxiety or fear) may be associated with heavier drinking and prescription opioid use/co-use, and that these associations may be especially salient among men. METHODS: This study is the first examination of pain-related anxiety in relation to hazardous alcohol use, prescription opioid use/misuse, and alcohol-opioid co-use. Participants included 1812 adults with chronic low back pain (69 % female, Mage = 43.95) who completed an online survey assessing health behaviors. RESULTS: Pain-related anxiety was positively associated with indices of alcohol (i.e., alcohol-related consequences) and opioid use (i.e., prescription opioid use/misuse, daily opioid consumption). Of note, sex moderated associations between pain-related anxiety and both alcohol-related consequences and prescription opioid misuse. In addition to being associated with alcohol and prescription opioid use, independently, pain-related anxiety was also associated with greater likelihood of endorsing co-use of alcohol and opioids and engaging in concurrent hazardous drinking and prescription opioid misuse. CONCLUSIONS: These findings contribute to a growing literature suggesting that pain-related anxiety is an important transdiagnostic factor in pain and alcohol and prescription opioid use/co-use, perhaps especially among males.

Effect of Serum 25 Hydroxy Vitamin D Level on Isotretinoin-Induced Musculoskeletal Symptoms: A Cross-Sectional Study.

Isotretinoin (ISO) is a drug which is used for the treatment of severe and refractory acne vulgaris (AV), over the last few decades. The drug has various musculoskeletal side effects. The aim of this study was to investigate relationship between serum 25 hydroxy (OH) vitamin D levels and the ISO-induced musculoskeletal side effects in patients with AV. We included 87 patients receiving ISO and had musculoskeletal symptoms as adverse effect (AE) group. Another 90 patients receiving ISO for AV and had any musculoskeletal complaints were recruited as control (C) group. Locomotor system examination of the patients was performed by the same clinician. Serum 25 OH vitamin D levels of the all participants were measured. Patients in the AE group were divided into three subgroups by serum 25 OH vitamin D levels. Patients with serum 25 OH vitamin D level lower than 10 ng/ml was classified as Group I, the ones between 10-20 ng/ml as Group II and those higher than 20 ng/ml were classified as Group III. AE and C groups were similar in terms of age and sex (p > 0.05). There was no statistically significant difference in the mean serum vitamin D levels between two groups (p = 0.17). Also, there was no significant difference in number of arthralgia (p = 0.30), myalgia (p = 0.29), low back pain (p = 0.10) and sacroiliitis (p = 0.17) between three subgroups in AE group. In addition, we found no statistically significant correlation between the serum vitamin D levels and age, cumulative dose of ISO, arthralgia, myalgia and sacroiliitis parameters in AE group (p > 0.05). Serum 25 OH vitamin D levels between the AE and C groups were similar. We also found that no significant difference in musculoskeletal adverse events between AE subgroups. Therefore, it can be concluded that vitamin D deficiency has no effect on the musculoskeletal adverse events in patients receiving ISO.

Isotretinoin-induced sacroiliitis in patients with hidradenitis suppurativa: a case-based review.

Hidradenitis suppurativa (HS) is a chronic, suppurative skin disease characterized by painful nodules, particularly in the axillae and groin. Isotretinoin can be used in the treatment of HS; however, it may paradoxically lead to skin lesions or worsen the existing lesions. Isotretinoin, which is commonly used in the treatment of severe acne, is associated with several side effects, including rheumatic side effects and rarely sacroiliitis. In this study, we discussed two cases who presented with low back pain after isotretinoin was used for the treatment of acne vulgaris. The patients did not have low back pain before isotretinoin use and did not have enthesitis, dactylitis, uveitis, psoriasis, recent infection, trauma, and family history spondylitis. HLA-B27 was negative. Bone-marrow edema was detected at the sacroiliac joint on magnetic resonance imaging. Because of these findings, sacroiliitis related to the drug was considered in our patients and isotretinoin treatments were discontinued. Because the patients' low back pain continued when they administered non-steroidal anti-inflammatory drugs, biological drug treatments were started. Both cases presented had a simultaneous HS lesion. After the treatment, both low back pain and HS lesions regressed. Patients with isotretinoin therapy should be alerted for inflammatory low back pain and HS lesions that may develop. We should note that biologic agents should be considered in the treatment of resistant cases.

Are radio-contrast agents commonly used in discography toxic to the intact intervertebral disc tissue cells?

In the literature, there have been no studies showing clear results on how radio-contrast pharmaceuticals would affect intact disc tissue cells. In this context, it was aimed to evaluate the effects of iopromide and gadoxetic acid, frequently used in the discography, on intact lumbar disc tissue in pharmaco-molecular and histopathological level. Primary cell cultures were prepared from the healthy disc tissue of the patients operated in the neurosurgery clinic. Except for the control group, the cultures were incubated with the indicated radio-contrast agents. Cell viability, toxicity and proliferation indices were tested at specific time intervals. The cell viability was quantitatively analysed. It was also visually rechecked under a fluorescence microscope with acridine orange/propidium iodide staining. Simultaneously, cell surface morphology was analysed with an inverted light microscope, while haematoxylin and eosin (H&E) staining methodology was used in the histopathological evaluations. The obtained data were evaluated statistically. Unlike the literature, iopromide or gadoxetic acid did not have any adverse effects on the cell viability, proliferation and toxicity (P < 0.05). Although this study reveals that radio-contrast pharmaceuticals used in the discography, often used in neurosurgical practice, can be safely used, it should be remembered that this study was performed in an in vitro environment.

The prevalence of sacroiliitis in patients with acne vulgaris using isotretinoin.

BACKGROUND/OBJECTIVE: Acne vulgaris is a chronic inflammatory disease affecting the pilosebaceous unit in the skin. Isotretinoin is a synthetic vitamin A derivative regarded as the most effective agent in the treatment of acne. There have recently been increasing reports of adverse effects of isotretinoin on the skeletal system. Our aim in this study was to evaluate the rheumatic side-effects triggered by this drug, and particularly the prevalence of sacroiliitis. MATERIALS AND METHODS: A total of 73 patients receiving isotretinoin due to moderate or severe acne vulgaris were included. All patients were questioned about inflammatory low back pain and musculoskeletal pains during the treatment process. Inflammatory low back pain was evaluated using Assessment of Spondyloarthritis International Society (ASAS) criteria. Patients meeting ASAS criteria were evaluated with radiography and when necessary with sacroiliac magnetic resonance. RESULTS: The dose range for isotretinoin was between 0.4 and 0.8 mg/kg/day (mean 0.53 mg/kg/day). Treatment lasted for 6-8 months (mean 6.8 months). Lethargy was determined in 37 (50.7%) patients, myalgia in 31 (42.5%) and low back pain in 36 (49.3%). Mechanical low back pain symptoms were present in 20 of the patients describing low back pain and inflammatory low back pain in 16. Acute sacroiliitis was determined in six patients (8.2%) following a sacroiliac magnetic resonance imaging (MRI). Five (83.3%) of the patients with sacroiliitis were female and one (16.7%) was male. No statistically significant difference was determined between male and female patients in terms of prevalence of sacroiliitis (p = 0.392). CONCLUSION: The incidence of sacroiliitis in patients using isotretinoin is quite high. Patients using isotretinoin must be questioned about sacroiliitis findings and must be subjected to advanced assessment when necessary. Further studies regarding the development of sacroiliitis under isotretinoin therapy are now needed.

Reorganized Trunk Muscle Activity During Multidirectional Floor Perturbations After Experimental Low Back Pain: A Comparison of Bilateral Versus Unilateral Pain.

UNLABELLED: Low back pain changes trunk muscle activity after external perturbations but the relationship between pain intensities and distributions and their effect on trunk muscle activity remains unclear. The effects of unilateral and bilateral experimental low back pain on trunk muscle activity were compared during unpredictable multidirectional surface perturbations in 19 healthy participants. Pain intensity and distribution were assessed using a visual analogue scale (VAS) and pain drawings. Root mean square (RMS) of the electromyographic (EMG) signals from 6 trunk muscles bilaterally after each perturbation was extracted and averaged across perturbations. The difference (ΔRMS-EMG) and absolute difference (absolute ΔRMS-EMG) RMS from baseline conditions were extracted for each muscle during pain conditions and averaged bilaterally for back and abdominal muscle groups. Bilateral compared with unilateral pain induced higher VAS scores (P < .005) and larger pain areas (P < .001). Significant correlation was present between VAS scores and muscle activity during unilateral (P < .001) and bilateral pain (P < .001). Compared with control injections ΔRMS-EMG increased in the back (P < .03) and abdominal (P < .05) muscles during bilateral and decreased in the back (P < .01) and abdominal (P < .01) muscles during unilateral pain. Bilateral pain caused greater absolute ΔRMS-EMG changes in the back (P < .01) and abdominal (P < .01) muscle groups than unilateral pain. PERSPECTIVE: This study provided novel observations of differential trunk muscle activity in response to perturbations dependent on pain intensity and/or pain distribution. Because of complex and variable changes the relevance of clinical examination of muscle activity during postural tasks is challenged.

The Effects of Experimentally Induced Low Back Pain on Spine Rotational Stiffness and Local Dynamic Stability.

Local dynamic stability, quantified using the maximum finite-time Lyapunov exponent (λ max), and the muscular contributions to spine rotational stiffness can provide pertinent information regarding the neuromuscular control of the spine during movement tasks. The primary goal of the present study was to assess if experimental capsaicin-induced low back pain (LBP) affects spine stability and the neuromuscular control of repetitive trunk movements in a group of healthy participants with no history of LBP. Fourteen healthy males were recruited for this investigation. Each participant was asked to complete three trials (baseline, in pain, and recovery) of 35 cycles of a repetitive trunk flexion/extension task at a rate of 0.25 Hz. Local dynamic stability and the muscular contributions to lumbar spine rotational stiffness were significantly impaired during the LBP trial compared to the baseline trial (p < 0.05); however, there was a trend for these measures to recover after a 1 h rest. This study provides evidence that capsaicin can effectively induce LBP, thereby altering spine rotational stiffness and local dynamic stability. Future research should directly compare the effects capsaicin-induced LBP and intramuscular/intraligamentous induced LBP on these same variables.

Camptocormia: resultados de la rehabilitación en tres casos / Camptocormia: results of rehabilitation in three cases

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Comparison of nerve growth factor-induced sensitization pattern in lumbar and tibial muscle and fascia.

INTRODUCTION: Nerve growth factor (NGF) induces profound hyperalgesia. In this study we explored patterns of NGF sensitization in muscle and fascia of distal and paraspinal sites. METHODS: We injected 1 µg of NGF into human (n = 8) tibialis anterior and erector spinae muscles and their fasciae. The spatial extent of pressure sensitization, pressure pain threshold, and mechanical hyperalgesia (150 kPa, 10 s) was assessed at days 0.25, 1, 3, 7, 14, and 21. Chemical sensitization was explored by acidic buffer injections (pH 4, 100 µl) at days 7 and 14. RESULTS: The mechanical hyperalgesia area was larger in tibial fascia than in muscle. Pressure pain thresholds were lower, tonic pressure pain ratings, and citrate buffer evoked pain higher in fascia than in muscle. CONCLUSIONS: Spatial mechanical sensitization differs between muscle and fascia. Thoracolumbar fasciae appear more sensitive than tibial fasciae and may be major contributors to low back pain, but the temporal sensitization profile is similar between paraspinal and distal sites. Muscle Nerve 52: 265-272, 2015.

Acute epigastric and low back pain during amiodarone infusion; is it the drug or the vehicle to blame?

Amiodarone is a Class III antiarrhythmic agent used for cardioversion and prevention of recurrences of atrial fibrillation. However, its use is limited due to its side-effects resulting from the drug's long-term administration. We have described acute epigastric pain following treatment with intravenous amiodarone for atrial fibrillation in a previous report. Hereby, we describe a second patient who suffered acute epigastric pain, as well as one who suffered acute low back pain. Intravenous amiodarone has been related to a series of minor and major adverse reactions, indicating other constituents of the intravenous solution as the possible cause, possibly polysorbate-80. A possible correlation between acute epigastric and low back pain after intravenous amiodarone loading is unproven; however it is of crucial importance for clinicians to be aware of this phenomenon, and especially since an acute epigastric pain is implicated in the differential diagnosis of cardiac ischemia.

Sensory findings after stimulation of the thoracolumbar fascia with hypertonic saline suggest its contribution to low back pain.

Injection of hypertonic saline into deep tissues of the back (subcutis, muscle, or the surrounding fascia) can induce acute low back pain (LBP). So far, no study has analyzed differences in temporal, qualitative, and spatial pain characteristics originating from these tissues. The current study aimed to investigate the role of the thoracolumbar fascia as a potential source of LBP. In separate sessions, 12 healthy subjects received ultrasound-guided bolus injections of isotonic saline (0.9%) or hypertonic saline (5.8%) into the erector spinae muscle, the thoracolumbar fascia (posterior layer), and the overlying subcutis. Subjects were asked to rate pain intensity, duration, quality, and spatial extent. Pressure pain thresholds were determined pre and post injection. Injections of hypertonic saline into the fascia resulted in significantly larger area under the curve of pain intensity over time than injections into subcutis (P<0.01) or muscle (P<0.001), primarily based on longer pain durations and, to a lesser extent, on higher peak pain ratings. Pressure hyperalgesia was only induced by injection of hypertonic saline into muscle, but not fascia or subcutis. Pain radiation and pain affect evoked by fascia injection exceeded those of the muscle (P<0.01) and the subcutis significantly (P<0.05). Pain descriptors after fascia injection (burning, throbbing, and stinging) suggested innervation by both A- and C-fiber nociceptors. These findings show that the thoracolumbar fascia is the deep tissue of the back that is most sensitive to chemical stimulation, making it a prime candidate to contribute to nonspecific LBP but not to localized pressure hyperalgesia.