Subcortical brain anatomy as a potential biomarker of persistent pain after total knee replacement in osteoarthritis

The causal role of brain circuits in osteoarthritis pain

Osteoarthritis (OA) is a leading cause of chronic pain worldwide, resulting in substantial disability and placing a substantial burden on patients and society. The hallmark symptom of OA is joint pain. Despite extensive research, new treatments for OA pain remain limited, partly owing to a lack of understanding of underlying pain mechanisms. For a long time, OA pain was seen as a reflection of nociceptive activity at the joint level, and the brain has been viewed as a passive recipient of such information. In this Review, we challenge these concepts and discuss how, over time, the activation of peripheral nociceptors leads to adaptations in the brain that dictate the properties and experience of OA pain. These adaptations are further influenced by the inherent properties of the brain. We review general concepts that distinguish pain from nociception, present evidence on the incongruity between joint injury and experience of OA pain, and review brain circuits that are crucial in the perception of OA pain. Finally, we propose a model that integrates nociception, spinal-cord mechanisms, and central nervous system dynamics, each contributing uniquely to pain perception. This framework has the potential to inform the development of personalized treatment strategies.

Brain functional imaging contributions in osteoarthritis-related pain: A viewpoint

Objective

Neuroimaging investigations are critical to provide a more direct assessment of brain disturbances associated with osteoarthritis (OA)-related pain, and to better understand its pathophysiology to develop new treatment strategies. This viewpoint aims to summarize the importance of the brain in OA pain.

Method

A European working group on pain in osteoarthritis GO-PAIN (Going Inside Osteoarthritis-related Pain Phenotyping) has been created to work on a global assessment of the OA-related pain. Relevant scientific literature was evaluated, summarized and discussed to expose advances in functional brain alterations related-to OA pain.

Results

Findings of neuroimaging studies are highly heterogenous and based on small sample size, but some key brain alterations associated with OA pain can be identified across experiments. A systematic literature review conducted by Hall and colleagues (2023) found lower activity, connectivity, and grey matter volume in the right anterior insula in patients with OA than in healthy controls. Other works also pointed out that activity of specific brain regions could serve as a potential surrogate biomarker, but several limitations and confounding factors needs to be addressed.

Conclusions

Brain functional imaging provides opportunities to accurately address an OA-related pain endophenotype. To encompass limitations and fill the gaps from the previous studies, we propose a blueprint for the next 5 years and stimulate ideas for others working in the field.

Relationship between preoperative and discharge evaluations in patients receiving around-the-knee osteotomy

[Purpose] This study aimed to determine the relationship between preoperative and discharge assessments in patients undergoing around-the-knee osteotomy. [Participants and Methods] We enrolled patients admitted to our hospital who underwent around-the-knee osteotomy. We measured knee joint range of motion, pain numeric rating scale, pain catastrophizing scale, hospital anxiety and depression scale, and 10-m walk time were measured preoperatively and before discharge. Pre-post comparisons and correlation testing were performed. [Results] A total of 18 patients were analyzed. Resting and exercise pain numeric rating scale, knee flexion and extension range of motion, and pain catastrophizing scale were significantly better during discharge. A significant correlation was observed between the preoperative pain catastrophizing scale total score and 10-m walking time, knee flexion and extension range of motion, pain catastrophizing scale total score, and hospital anxiety and depression scale-depression subscale preoperatively. [Conclusion] Appropriate postoperative rehabilitation after around-the-knee osteotomy improved physical function and cognitive/psychological evaluation at discharge. The correlation between the preoperative pain catastrophizing scale total score and 10-m walking time at discharge suggests that the prolonged walking pain that occurred preoperatively may have affected the cognitive and psychological evaluation of pain.

Cells and circuits for amygdala neuroplasticity in the transition to chronic pain

Maladaptive plasticity is linked to the chronification of diseases such as pain, but the transition from acute to chronic pain is not well understood mechanistically. Neuroplasticity in the central nucleus of the amygdala (CeA) has emerged as a mechanism for sensory and emotional-affective aspects of injury-induced pain, although evidence comes from studies conducted almost exclusively in acute pain conditions and agnostic to cell type specificity. Here, we report time-dependent changes in genetically distinct and projection-specific CeA neurons in neuropathic pain. Hyperexcitability of CRF projection neurons and synaptic plasticity of parabrachial (PB) input at the acute stage shifted to hyperexcitability without synaptic plasticity in non-CRF neurons at the chronic phase. Accordingly, chemogenetic inhibition of the PB→CeA pathway mitigated pain-related behaviors in acute, but not chronic, neuropathic pain. Cell-type-specific temporal changes in neuroplasticity provide neurobiological evidence for the clinical observation that chronic pain is not simply the prolonged persistence of acute pain.

A causal effect study of cortical morphology and related covariate networks in classical trigeminal neuralgia patients

Structural covariance networks and causal effects within can provide critical information on gray matter reorganization and disease-related hierarchical changes. Based on the T1WI data of 43 classical trigeminal neuralgia patients and 45 controls, we constructed morphological similarity networks of cortical thickness, sulcal depth, fractal dimension, and gyrification index. Moreover, causal structural covariance network analyses were conducted in regions with morphological abnormalities or altered nodal properties, respectively. We found that patients showed reduced sulcal depth, gyrification index, and fractal dimension, especially in the salience network and the default mode network. Additionally, the integration of the fractal dimension and sulcal depth networks was significantly reduced, accompanied by decreased nodal efficiency of the bilateral temporal poles, and right pericalcarine cortex within the sulcal depth network. Negative causal effects existed from the left insula to the right caudal anterior cingulate cortex in the gyrification index map, also from bilateral temporal poles to right pericalcarine cortex within the sulcal depth network. Collectively, patients exhibited impaired integrity of the covariance networks in addition to the abnormal gray matter morphology in the salience network and default mode network. Furthermore, the patients may experience progressive impairment in the salience network and from the limbic system to the sensory system in network topology, respectively.

Centralizing the Knowledge and Interpretation of Pain in Chemotherapy-Induced Peripheral Neuropathy: A Paradigm Shift towards Brain-Centric Approaches

Chemotherapy-induced peripheral neuropathy (CIPN) is a side effect of cancer treatment, often linked with pain complaints. Patients report mechanical and thermal hypersensitivity that may emerge during chemotherapy treatment and may persist after cancer remission. Whereas the latter situation disturbs the quality of life, life itself may be endangered by the appearance of CIPN during cancer treatment. The causes of CIPN have almost entirely been ascribed to the neurotoxicity of chemotherapeutic drugs in the peripheral nervous system. However, the central consequences of peripheral neuropathy are starting to be unraveled, namely in the supraspinal pain modulatory system. Based on our interests and experience in the field, we undertook a review of the brain-centered alterations that may underpin pain in CIPN. The changes in the descending pain modulation in CIPN models along with the functional and connectivity abnormalities in the brain of CIPN patients are analyzed. A translational analysis of preclinical findings about descending pain regulation during CIPN is reviewed considering the main neurochemical systems (serotoninergic and noradrenergic) targeted in CIPN management in patients, namely by antidepressants. In conclusion, this review highlights the importance of studying supraspinal areas involved in descending pain modulation to understand the pathophysiology of CIPN, which will probably allow a more personalized and effective CIPN treatment in the future.

Prognostic value of preoperative mechanical hyperalgesia and neuropathic pain qualities for postoperative pain after total knee replacement

BACKGROUND

Total knee replacement (TKR) is the gold standard treatment for end-stage chronic osteoarthritis pain, yet many patients report chronic postoperative pain after TKR. The search for preoperative predictors for chronic postoperative pain following TKR has been studied with inconsistent findings.

METHODS

This study investigates the predictive value of quantitative sensory testing (QST) and PainDETECT for postoperative pain 3, 6 and 12 months post-TKR. We assessed preoperative and postoperative (3 and 6 months) QST measures in 77 patients with knee OA (KOA) and 41 healthy controls, along with neuropathic pain scores in patients (PainDETECT). QST parameters included pressure pain pressure threshold (PPT), pain tolerance threshold (PTT), conditioned pain modulation (CPM) and temporal summation (TS) using cuff algometry, alongside mechanical hyperalgesia and temporal summation to repeated pinprick stimulation.

RESULTS

Compared to healthy controls, KOA patients at baseline demonstrated hyperalgesia to pinprick stimulation at the medial knee undergoing TKR, and cuff pressure at the calf. Lower cuff algometry PTT and mechanical pinprick hyperalgesia were associated with preoperative KOA pain intensity. Moreover, preoperative pinprick pain hyperalgesia explained 25% of variance in pain intensity 12 months post-TKR and preoperative neuropathic pain scores also captured 30% and 20% of the variance in postoperative pain at 6 and 12 months respectively. A decrease in mechanical pinprick hyperalgesia from before surgery to 3 months after TKR was associated with lower postoperative pain at the 12 months post-TKR follow-up.

CONCLUSION

Our findings suggest that preoperative pinprick hyperalgesia and neuropathic-like pain symptoms show predictive value for the development of chronic post-TKR pain.

SIGNIFICANCE STATEMENT

This study's findings hold significant implications for chronic pain management in knee osteoarthritis patients, particularly those undergoing total knee replacement surgery (TKR). Mechanical hyperalgesia and neuropathic pain-like characteristics predict postoperative pain 1 year after TKR, emphasizing the importance of understanding pain phenotypes in OA for selecting appropriate pain management strategies. The normalization of hyperalgesia after surgery correlates with better long-term outcomes, further highlighting the therapeutic potential of addressing abnormal pain processing mechanisms pre- and post-TKR.

Mechanical hyperalgesia and neuropathic pain qualities impart risk for chronic postoperative pain after total knee replacement

Total knee replacement (TKR) is the gold-standard treatment for end-stage chronic osteoarthritis pain, yet many patients report chronic postoperative pain after TKR. The search for preoperative predictors for chronic postoperative pain following TKR has been studied with inconsistent findings. This study investigates the predictive value of quantitative sensory testing (QST) and PainDETECT for postoperative pain 3, 6, and 12 months post-TKR. We assessed baseline and postoperative (3- and 6-months) QST measures in 77 patients with knee OA (KOA) and 41 healthy controls, along with neuropathic pain scores in patients (PainDETECT). QST parameters included pressure pain pressure threshold (PPT), pain tolerance threshold (PTT), conditioned pain modulation (CPM), and temporal summation (TS) using cuff algometry, alongside mechanical hyperalgesia, and mechanical temporal summation to repeated pinprick stimulation. Compared to healthy controls, KOA patients at baseline demonstrated hyperalgesia to pinprick stimulation at the medial OA-affected knee and cuff pressure on the ipsilateral calf. Lower cuff algometry PTT and mechanical pinprick hyperalgesia were associated with baseline KOA pain intensity. Moreover, baseline pinprick pain hyperalgesia explained 25% of variance in pain intensity 12 months post-TKR and preoperative neuropathic pain scores also captured 30% and 20% of the variance in postoperative pain at 6- and 12-months, respectively. A decrease in mechanical pinprick hyperalgesia from before surgery to 3 months after TKR was associated with lower postoperative pain at the 12 months post-TKR follow-up, and vice-versa. Our findings suggest that preoperative pinprick hyperalgesia and PainDETECT neuropathic-like pain symptoms show predictive value for the development of chronic post-TKR pain.