Complex Regional Pain Syndrome: Evidence-Based Advances in Concepts and Treatments

The pharmacology of vitamin C

Ascorbic acid, the reduced form of vitamin C, is a ubiquitous small carbohydrate. Despite decades of focused research, new metabolic functions of this universal electron donor are still being discovered and add to the complexity of our view of vitamin C in human health. Although praised as an unsurpassed water-soluble antioxidant in plasma and cells, the most interesting functions of vitamin C seem to be its roles as specific electron donor in numerous biological reactions ranging from the well-known hydroxylation of proline to cofactor for the epigenetic master regulators ten-eleven translocation enzymes and Jumonji domain-containing histone-lysine demethylases. Some of these functions may have important implications for disease prevention and treatment and have spiked renewed interest in, eg, vitamin C's potential in cancer therapy. Moreover, some fundamental pharmacokinetic properties of vitamin C remain to be established including if other mechanisms than passive diffusion governs the efflux of ascorbate anions from the cell. Taken together, there still seems to be much to learn about the pharmacology of vitamin C and its role in health and disease. This review explores new avenues of vitamin C and integrates our present knowledge of its pharmacology. SIGNIFICANCE STATEMENT: Vitamin C is involved in multiple biological reactions of which most are essential to human health. Hundreds of millions of people are considered deficient in vitamin C according to accepted guidelines, but little is known about the long-term consequences. Although the complexity of vitamin C's physiology and pharmacology has been widely disregarded in clinical studies for decades, it seems clear that a deeper understanding of particularly its pharmacology holds the key to unravel and possibly exploit the potential of vitamin C in disease prevention and therapy.

An unresolving painful condition following a trivial peripheral fracture

A 58-yr-old woman presented to our mineral metabolism center, complaining of localized and continuous pain, which worsened with movements, and weakness of the right foot. The patient reported having had a fracture of the fifth metatarsal bone of the right foot about 4 mo ago. She was initially treated with a cast that she did not tolerate and then with an orthopedic brace. After about 1 mo, she noticed swelling of the right foot and started complaining of continuous pain. The physical examination when came to our center seemed partly improved in respect to the initial one referred by the patient even though she still presented with a mild swelling, reddish skin color, and mild sweating on the right foot. Allodynia and hyperalgesia still persisted but at a lower grade. Main biochemical parameters of calcium metabolism were in the normal range. After excluding other clinical conditions, a diagnosis of complex regional pain syndrome type I was made. She was treated with neridronate iv with resolution of symptoms while continuing with physical therapy and pain relievers. Similar milder episodes were reported by the patient in the following months. However, they were immediately resolved by prompt neridronate infusion. No further complaints have been reported during the next 3 yr follow-up.

Efficacy of Immunotherapy for Complex Regional Pain Syndrome: A Narrative Review

PURPOSE OF REVIEW

Complex regional pain syndrome (CRPS) is a chronic condition characterized by disproportional pain typically affecting an extremity. Management of CRPS is centered around specific symptomatology, which tends to be a combination of autonomic dysfunction, nociceptive sensitization, chronic inflammation, and/or motor dysfunction. Targeting the autoimmune component of CRPS provides a way to both symptomatically treat as well as minimize progression of CRPS.

RECENT FINDINGS

Understanding the physiology of CRPS and strategies for treating and targeting immunophysiology behind CRPS allows examination of the efficacy of such treatments. IL-1 receptor antagonism, glucocorticoid administration, IVIG infusion, and TNFα inhibitors are treatments that target the immune response and decrease inflammation, thereby reducing pain and enhancing function in patients with CRPS. IL-1 receptor antagonism is thought to inhibit the inflammatory effects of IL-1, a key player in the inflammatory process in CRPS. Glucocorticoids have anti-inflammatory properties and can reduce inflammation in affected tissues. IVIG infusion involves administering immunoglobulins, which may modulate the immune response and reduce autoimmunity in CRPS. TNFα inhibitors block the action of TNFα, a pro-inflammatory cytokine associated with CRPS development. These therapies are further discussed at the extent of mechanism of action as well as advantages and limitations of such therapies. The present investigation provides a detailed summary of the mechanism of action, advantages, and limitations of novel immunomodulatory therapies and recent studies and trials that investigated these therapies for CRPS. Future studies are warranted related to the role of immunomodulators in the treatment of CRPS.

Dynamic risk factors for complex regional pain syndrome after distal radius fracture surgery: multivariate analysis and prediction

BACKGROUND

Distal radius fractures are a common orthopedic injury, particularly prevalent among elderly and osteoporotic patients. Although surgical treatment effectively restores fracture alignment and stabilizes the bone, Complex Regional Pain Syndrome (CRPS) can occur as a postoperative complication, severely impacting patients' rehabilitation and quality of life. Therefore, assessing the risk factors for postoperative CRPS is crucial for early clinical intervention, aiming to improve recovery outcomes and overall patient well-being.

OBJECTIVE

This study aims to dynamically evaluate the risk factors for CRPS following distal radius fracture surgery through a retrospective analysis. The goal is to provide scientific evidence for early clinical identification and intervention.

METHODS

A retrospective analysis was conducted on 191 adult patients who underwent distal radius fracture surgery between January 2021 and December 2022, comprising 89 males and 102 females, with an average age of 59.7 ± 11.6(18-75) years. Baseline and follow-up data, including demographic information, clinical characteristics, and psychological assessments, were collected. Descriptive statistics, univariate, and multivariate logistic regression analyses were used to identify independent risk factors and assess their dynamic changes over time.

RESULTS

Age, gender, occupation, fracture type, surgical method, osteoporosis, pain score (VAS), functional disability score (DASH), anxiety score (GAD-7), depression score (PHQ-9), physical therapy, and occupational therapy significantly affected the incidence of CRPS. Age and VAS scores were consistent risk factors. Female gender, internal fixation surgery, and high DASH scores posed higher risks in the early postoperative period but decreased over time. Occupation and fracture type were more significant in the mid to late postoperative period. Psychological factors were most significant in the midterm, while physical and occupational therapy were protective factors early on.

CONCLUSION

The occurrence of CRPS is the result of many factors. Elderly patients, females, and manual laborers had higher risks, with complex fractures and internal fixation surgery patients showing increased risk later on. Osteoporotic patients had higher risks in the mid to late postoperative period. VAS, DASH, GAD-7, and PHQ-9 scores were significantly associated with CRPS. Early physical and occupational therapy can effectively prevent CRPS, but further research is needed to evaluate their long-term effects.

Chronic post-ischemic pain (CPIP) a model of complex regional pain syndrome (CRPS-I): Role of oxidative stress and inflammation

Complex regional pain syndrome (CRPS) presents as a persistent and distressing pain condition often stemming from limb trauma or ischemia, manifesting as either CRPS-I (without initial nerve injury) or CRPS-II (accompanied by nerve injury). Despite its prevalence and significant impact on functionality and emotional well-being, standard treatments for CRPS remain elusive. The multifaceted nature of CRPS complicates the identification of its underlying mechanisms. In efforts to elucidate these mechanisms, researchers have turned to animal models such as chronic post-ischemic pain (CPIP), which mirrors the symptoms of CRPS-I. Various mechanisms have been proposed to underlie the acute and chronic pain experienced in CRPS-I, including oxidative stress and inflammation. Traditional treatment approaches often involve antidepressants, non-steroidal anti-inflammatory drugs (NSAIDs), and opioids. However, these methods frequently fall short of providing adequate relief. Accordingly, there is a growing interest in exploring alternative treatments, such as antioxidant supplementation, anti-inflammatory agents, and non-pharmacological interventions. Future research directions should focus on optimizing treatment strategies and addressing remaining gaps in knowledge to improve patient outcomes. This review aims to delve into the pathophysiological mechanisms implicated in the CPIP model, specifically focusing on oxidative stress and inflammation, with the ultimate goal of proposing innovative therapeutic strategies for alleviating the symptoms of CRPS-I.

Bone Scintigraphy in 2 Cases of Complex Regional Pain Syndrome

ABSTRACT

A 59-year-old woman was presented to the outpatient clinic with persistent pain after a hyperextension/inversion trauma of the ankle. Six months after the incident, a 3-phase bone scan was performed. A second patient, a 54-year-old man, was referred for a 3-phase bone scan 2 months after his right hand was twisted while using a drill. In both patients, scintigraphy showed diffuse increased uptake in the affected limb in all 3 phases. The x-rays of the affected limbs showed osteopenia. These findings are consistent with (early phase) complex regional pain syndrome.

Effect duration of lumbar sympathetic ganglion neurolysis in patients with complex regional pain syndrome: a prospective observational study

Lumbar sympathetic ganglion neurolysis (LSGN) has been used for long-term pain relief in patients with complex regional pain syndrome (CRPS). However, the actual effect duration of LSGN has not been accurately measured. This prospective observational study measured the effect duration of LSGN in CRPS patients and investigated the relationship between temperature change and pain relief. After performing LSGN, the skin temperatures of both the maximum pain site and the plantar area in the affected and unaffected limbs were measured by infrared thermography, and pain intensity was assessed before and at 2 weeks, 1 month, and 3 months. The median time to return to baseline temperature was calculated using survival analysis. The skin temperature increased significantly at all-time points relative to baseline in both regions (maximum pain site: 1.4 °C ± 1.0 °C, plantar region: 1.28 °C ± 0.8 °C, all P < 0.001). The median time to return to baseline temperature was 12 weeks (95% confidence interval [CI] 7.7-16.3) at the maximum pain site and 12 weeks (95% CI 9.4-14.6) at the plantar area. Pain intensity decreased significantly relative to baseline, at all-time points after LSGN. In conclusion, the median duration of the LSGN is estimated to be 12 weeks.

Complex Regional Pain Syndrome after Distal Radius Fracture-Case Report and Mini Literature Review

This study explores the impact of the complex regional pain syndrome (CRPS) on the lives and mobility of patients, with a particular focus on its emergence as a late complication of distal radius fractures (DRFs), a common occurrence, especially among an aging population. The absence of a standardized treatment for the CRPS and the challenge of predicting its occurrence make it a complex medical issue. This research aims to shed light on the effects of treating the CRPS through a case study involving a 75-year-old woman with untreated osteoporosis who experienced a Colles fracture after a fall. The initial management involved repositioning and stabilizing the fractured forearm with a plaster cast, followed by an operation using percutaneous pinning via a Kirschner wire. Subsequently, the patient developed CRPS symptoms and was admitted to the rehabilitation department three months post-fracture. The affected forearm exhibited swelling, warmth, pain, and severely limited range of motion. Treatment involved a combination of medications, physiotherapy, and kinesiotherapy. Significantly, the patient experienced notable improvement following these interventions. This study underscores the absence of a definitive standard for CRPS treatment but suggests that proper rehabilitation and pharmaceutical interventions can contribute positively to patient outcomes. The case further highlights the potential association between DRF and CRPS development, emphasizing the need for continued research in this field.

Role of Resolvins in Inflammatory and Neuropathic Pain

Chronic pain is an unpleasant experience associated with actual or potential tissue damage. Inflammatory pain alerts the body to inflammation and promotes healing; however, unresolved inflammation can lead to chronic pain. Conversely, neuropathic pain, due to somatosensory damage, can be a disease in itself. However, inflammation plays a considerable role in the progression of both types of pain. Resolvins, derived from omega-3 fatty acids, actively suppress pro-inflammatory mediators and aid in the resolution of inflammation. Resolvins alleviate various inflammatory and neuropathic pain models by reducing hypersensitivity and regulating inflammatory cytokines and glial activation in the spinal cord and dorsal root ganglia. Thus, resolvins are a promising alternative for pain management with the potential to reduce the side effects associated with conventional medications. Continued research is crucial to unlock the therapeutic potential of resolvins and integrate them into effective clinical pain management strategies. This review aimed to evaluate the literature surrounding the resolvins in inflammatory and neuropathic pain.