Pathophysiology

Goal of the Study?

In this paper, [Pathophysiology of musculoskeletal pain: a narrative review], the authors provide a review of the various pathophysiology mechanisms of musculoskeletal pain and how they interact to promote the transition from acute to chronic pain. 

 

Why are they doing this review?

Chronic musculoskeletal pain is defined as pain felt in the musculoskeletal tissues that last for more than 3 months and is characterized by functional disability and emotional distress. It is a secondary type of pain caused by different conditions such as infection or auto-inflammatory processes that lead to systemic inflammation or structural changes to joints, muscles or tissues. 

Chronic musculoskeletal pain is prevalent in the general population, with approximately 37% of the US population impacted and an economic burden of $635 billion per year. Outside of the US, the prevalence ranges from 18.6% in Switzerland to over 45% in Italy and France.

 

What did they find?

In the review, the authors illustrate how many factors and processes interact to produce musculoskeletal pain. Research illustrates that bones, joints and muscles, including the ligaments, capsules and menisci, are innervated by a network of sensory nerve fibres including, Aδ and C fibres. These fibres’ stimulation can drive musculoskeletal pain through mechanical distortion, local acidosis, and increased bone medullary pressure. This then drives the promotion of inflammatory mediators such as nerve growth factor (NGF), pro-inflammatory cytokines interleukin (IL) 1ß, IL-6, tumour necrosis factor- α chemokines. Moreover, the interaction between immune and nervous systems and glial stimulation further promotes these inflammatory mediators that magnify and sensitize pain signals and lead to cortical remodelling.

Bone pain can also be caused by the increase in sensory nerve fibres where there are injuries. During bone healing, nerves sprout around the injury site and then pull back when it is healed. However, when bones don’t heal (as in osteoarthritis), the injured area remains hyper-innervated, and heightened pain sensitivity occurs. 

Finally, research has indicated that sex, age, psychosocial factors, beliefs and thoughts influence gene expression and the experience of musculoskeletal pain. For example, women experience higher pain sensitivity than men and have a different biologic response to tissue damage with higher cytokine production than men, which means a stronger inflammatory response and higher pain levels. 

 

Why do these findings matter?

Understanding the pathophysiology of musculoskeletal pain, which includes biological and demographic and psychological factors, is critical to developing pain management treatments and strategies for patients.

facet osteoarthritis, facet joint pain

Goal of the Study?

The objective of this study 1 evaluates the feasibility of sensory mapping of lumbar facet joint pain in patients scheduled to undergo radiofrequency (RF) denervation. 

 

Why are they doing this study?

Lower back pain (LBP) is a widespread condition that can result in chronic pain.  While there are many treatment approaches, one of the most established interventions uses diagnostic blocks to identify the source of nociception. Though many parts of the back can be involved in LBP, facet joints are among the most common sources contributing to back pain. Most often, for treatment in clinical practice, the medial branches are anesthetized to establish the diagnosis of facet joint pain. RF denervation of these nerves, which is a process to stop nerves from transmitting pain, is used as pain management. 

The authors argue that while this approach has been well established, the use in a clinical setting has been questioned due to the high rates of false-positive (30%), cost-effectiveness and lack of standardization and anatomical variation. For this reason, the authors hope to develop a strategy for a more precise identification of the nerves involved in LBP.

facet capsule nerves, facet joint pain

 

What was done?

In total, they had 15 participants for this study. After written consent, participants completed a pre-procedure pain diagram and rated their pain on a scale of 1-10. The researchers used a standard procedure for RF denervation, including a single diagnostic block and imaging in determining cannula placement. To reproduce the pain in patients with chronic back pain, medial branches were stimulated using 50Hz electrical stimulation to determine the threshold. This was then increased threefold to achieve the suprathreshold stimulation, after which participants were asked to map their pain and compare this against the initial pre-procedure pain diagram.

 

What did they find?

A total of 71 nerves were scheduled for RF denervation. Sensory stimulation was successful in 68 out of 71 nerves using 50Hz electrical stimuli. All 15 participants reported either pain or paraesthesia (tingling or prickling) during suprathreshold stimulation, and 14 (93%) reported complete coverage of their usual painful area. In one participant, the upper lumbar pain was not covered by suprathreshold stimulation. For 60% of the participants, they reported pain/paraesthesia outside of their normal pain area during suprathreshold. Overall, in their population, 7.5% of the denervated nerves did not contribute to pain transmission. The average sensory detection threshold was 0.3V, with the suprathreshold was 0.6V.

 

Why do these findings matter?

Using suprathreshold stimulation, lumbar facet joint pain can be mapped and offers objectivity by reproducing patients’ back pain. This approach can also improve patient safety and experience by limiting RF denervation to nerves involved in pain transmission. This can improve patient safety and experience. 

pathology & pain in Peripheral Joint

A review 1 published in Arthritis Research & Therapy decided to cover the link between subchondral bone features, pain, and structural pathology during peripheral joint OA (osteoarthritis). The review concluded that the subchondral OA bone does seem to have relevance when it comes to therapeutic measures.

The Context

According to research, OA (or osteoarthritis) is the most common form of arthritis is human beings. It leads to disability and chronic pain. Also, during the process of this review, the market didn’t necessarily have licensed DMOADs (disease-modifying osteoarthritis drugs). Take note; multiple tissues are usually involved in clinical OA. Gaining a better understanding regarding the intricate relationships that exist between these tissues and structural progression (along with the symptoms) might help with identifying potential tissue targets. The subchondral bone is of particular interest because it’s significantly associated with the hyaline cartilage.

The current review was conducted to comprehensively go over the available literature on subchondral bone structure which has been assessed using non-conventional radiographic imaging modalities. The said literature, used in this review, had examined common sites of peripheral OA as well as had described the relationships between joint replacement, structural progression, subchondral bone features, and pain.

The Method

The required original articles were found using Medline, EMBASE, and the Cochrane library databases. The articles reported an association between non-conventional radiographic imaging-assessed subchondral bone pathologies and joint replacement, pain or structural progression in the knee, hip, hand, ankle and foot OA.

A total of 2456 abstracts were screened for this review. Take note; 139 papers were included (70 of which were cross-sectional, 71 were longitudinal analyses).

The Results

The results of this review showed that there was an independent association when it came to the link between BMLs (bone marrow lesions), osteophytes and bone shape with structural progression or joint replacement. Furthermore, there was an independent association between BMLs and bone shape with longitudinal change in pain as well as incident frequent knee pain (respectively).

What was Concluded?

The review concluded that there are independent associations between subchondral bone features and structural progression, pain as well as joint replacement when peripheral OA is concerned; in the hand and hip, however, particularly in the knee. Furthermore, more in-depth research needs to be conducted to collect data about other associations (namely with the ankle and foot). Also, a better understanding of the subchondral OA bone might open doors for better therapeutic strategies.