Bone microstructure is significantly altered in CRPS-affected distal tibiae as detected by HR-pQCT: a retrospective cross-sectional study

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

PURPOSE OF REVIEW

This review presents the most current information about the epidemiology of complex regional pain syndrome (CRPS), classification and diagnostic criteria, childhood CRPS, subtypes, pathophysiology, conventional and less conventional treatments, and preventive strategies.

RECENT FINDINGS

CRPS is a painful disorder with multifactorial pathophysiology. The data describe sensitization of the central and peripheral nervous systems, inflammation, possible genetic factors, sympatho-afferent coupling, autoimmunity, and mental health factors as contributors to the syndrome. In addition to conventional subtypes (type I and type II), cluster analyses have uncovered other proposed subtypes. Prevalence of CRPS is approximately 1.2%, female gender is consistently associated with a higher risk of development, and substantial physical, emotional, and financial costs can result from the syndrome. Children with CRPS seem to benefit from multifaceted physical therapy leading to a high percentage of symptom-free patients. The best available evidence along with standard clinical practice supports pharmacological agents, physical and occupational therapy, sympathetic blocks for engaging physical restoration, steroids for acute CRPS, neuromodulation, ketamine, and intrathecal baclofen as therapeutic approaches. There are many emerging treatments that can be considered as a part of individualized, patient-centered care. Vitamin C may be preventive. CRPS can lead to progressively painful sensory and vascular changes, edema, limb weakness, and trophic disturbances, all of which substantially erode healthy living. Despite some progress in research, more comprehensive basic science investigation is needed to clarify the molecular mechanisms of the disease so that targeted treatments can be developed for better outcomes. Incorporating a variety of standard therapies with different modes of action may offer the most effective analgesia. Introducing less conventional approaches may also be helpful when traditional treatments fail to provide sufficient improvement.

Senso-Immunologic Prospects for Complex Regional Pain Syndrome Treatment

Complex regional pain syndrome (CRPS) is a chronic pain syndrome that occurs in tissue injuries as the result of surgery, trauma, or ischemia. The clinical features of this severely painful condition include redness and swelling of the affected skin. Intriguingly, it was recently suggested that transient receptor potential ankyrin 1 (TRPA1) is involved in chronic post-ischemia pain, a CRPS model. TRPA1 is a non-selective cation channel expressed in calcitonin gene-related peptide (CGRP)-positive primary nociceptors that becomes highly activated in ischemic conditions, leading to the generation of pain. In this review, we summarize the history of TRPA1 and its involvement in pain sensation, inflammation, and CRPS. Furthermore, bone atrophy is also thought to be a characteristic clinical sign of CRPS. The altered bone microstructure of CRPS patients is thought to be caused by aggravated bone resorption via enhanced osteoclast differentiation and activation. Although TRPA1 could be a target for pain treatment in CRPS patients, we also discuss the paradoxical situation in this review. Nociceptor activation decreases the risk of bone destruction via CGRP secretion from free nerve endings. Thus, TRPA1 inhibition could cause severe bone atrophy. However, the suitable therapeutic strategy is controversial because the pathologic mechanisms of bone atrophy in CRPS are unclear. Therefore, we propose focusing on the remission of abnormal bone turnover observed in CRPS using a recently developed concept: senso-immunology.

Prospective Study Evaluating Changes in Bone Quality in Premenopausal Women With Breast Cancer Undergoing Adjuvant Chemotherapy

BACKGROUND

Ovarian suppression from chemotherapy results in bone loss in premenopausal women with breast cancer (BC). Less is known about bone microarchitecture changes. We used high-resolution peripheral quantitative computed tomography (HR-pQCT) to measure volumetric bone density and trabecular and cortical microarchitecture in this population.

MATERIALS AND METHODS

The primary endpoint was to assess changes in cortical thickness and trabecular bone density by HR-pQCT. Premenopausal women with stage I to III BC undergoing adjuvant chemotherapy underwent a bone mineral density (BMD) dual energy x-ray absorptiometry scan and HR-pQCT (voxel size, 82 microns) at baseline and 12 months. Paired t tests were used to observe the change over time in bone microarchitecture and areal and volumetric density.

RESULTS

Eighteen patients were evaluated, of which 12 patients had baseline and matched 12-month imaging. The mean age was 45.2 years (range, 35-51 years), 17 (94%) patients had hormone receptor-positive BC, and 16 (89%) initiated tamoxifen. At 12 months, there was a significant decrease in femoral neck (P < .05) and lumbar spine and total hip (P < .01) BMD. Changes detected by HR-pQCT at 12 months included significant decreases in cortical thickness and area at the tibia (P < .05), and total and cortical volumetric BMD at the radius and tibia (P < .01), as well as an increase in tibial trabecular area (P < .05).

CONCLUSION

Premenopausal women undergoing chemotherapy experience BMD decline and trabecular and cortical bone microarchitecture deterioration. In this population, future efforts should focus on therapy-induced bone loss and optimizing bone density-related management.