Neuroarthropathy in diabetes: pathogenesis of Charcot arthropathy

Cartilage Damage Pathological Characteristics of Diabetic Neuropathic Osteoarthropathy

Background

Diabetic neuropathic osteoarthropathy (DNOAP) is a rare and easily missed complication for diabetes that leads to increased morbidity and mortality. DNOAP is characterized by progressive destruction of bone and joint, but its pathogenesis remains elusive. We herein aimed to investigate the pathological features and pathogenesis of the cartilages damage in DNOAP patients.

Methods

The articular cartilages of eight patients with DNOAP and eight normal controls were included. Masson staining and safranine O/fixed green staining (S-O) were used to observe the histopathological characteristics of cartilage. The ultrastructure and morphology of chondrocytes were detected by electron microscopy and toluidine blue staining. Chondrocytes were isolated from DNOAP group and control group. The expression of receptor activator of nuclear factor kappaB ligand (RANKL), osteoprotegerin (OPG), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and Aggrecan protein was evaluated by western blot. Reactive oxygen species (ROS) levels were measured using a 2',7'-dichlorofluorescin diacetate (DCFH-DA) probe. The percentage of apoptotic cells was determined by flow cytometry (FCM). The chondrocytes were cultured with different glucose concentrations to observe the expression of RANKL and OPG.

Results

Compared with the control group, the DNOAP group showed fewer chondrocytes, subchondral bone hyperplasia, and structural disorder, and a large number of osteoclasts formed in the subchondral bone area. Moreover, mitochondrial and endoplasmic reticulum swellings were observed in the DNOAP chondrocytes. The chromatin was partially broken and concentrated at the edge of nuclear membrane. The ROS fluorescence intensity of chondrocyte in DNOAP group was higher than that in normal control group (28.1 ± 2.3 vs. 11.9 ± 0.7; P < 0.05). The expression of RANKL, TNF-α, IL-1β, and IL-6 protein in DNOAP group was higher than that in normal control group, whereas OPG and Aggrecan protein were lower than that in normal control group (both P < 0.05). FCM showed that the apoptotic rate of chondrocyte in DNOAP group was higher than that in normal control group (P < 0.05). The RANKL/OPG ratio showed significant upward trend when the concentration of glucose was over than 15 mM.

Conclusions

DNOAP patients tend to have severe destruction of articular cartilage and collapse of organelle structure including mitochondrion and endoplasm reticulum. Indicators of bone metabolism (RANKL and OPG) and inflammatory cytokines (IL-1β, IL-6, and TNF-α) play an important role in promoting the pathogenesis of DNOAP. The glucose concentration higher than 15 mM made the RANKL/OPG ratio change rapidly.

Nondiabetic Charcot Neuroarthropathy: Evaluation and Treatment

There are many similarities between nondiabetic and diabetic Charcot neuroarthropathy (CN) but many of the underlying causes causing nondiabetic neuropathy and CN are associated with poor bone quality. Patient workup for nondiabetic CN should include the underlying cause of the neuropathy and optimization of bony healing, such as vitamin D supplementation and bisphosphonate or calcitonin administration. Surgical reconstruction should include the most robust fixation possible, as nondiabetic patients with CN are more prone to delayed union.

The Charcot Foot Reflects a Response to Injury That Is Critically Distorted by Preexisting Nerve Damage: An Imperfect Storm

It has been recognized since comprehensive descriptions by Jean-Martin Charcot in 1868 and 1883 that development of what is usually known as neuropathic osteoarthropathy (or the Charcot foot) requires the coincidence of neuropathy and inflammation. Despite this, detailed understanding of the causes has remained remarkably limited in the succeeding century and a half. The aim of this descriptive account is to draw particular attention to the processes involved in both the onset and resolution of the inflammation that is an essential component of active disease. The principal observation is that while neuropathy is common in people with diabetes, the inflammation and secondary skeletal damage that characterize neuropathic osteoarthropathy are observed in only a small minority of people with diabetes and with neuropathy. We therefore argue that the key to understanding the causes of the Charcot foot is to focus equally on those who have active disease as well as those who do not. Although neuropathy is essential for development of the disorder, neuropathy also has an adverse impact on the mechanisms involved in the onset of inflammation, and these may be critically affected in the majority of those who are susceptible. The Charcot foot is uncommon in people with diabetes (or any other cause of neuropathy) because the large majority of those with neuropathy may have also lost the capacity to mount the specific inflammatory reaction that is essential for its development.

Risk Factors and Outcomes After Surgical Reconstruction of Charcot Neuroarthropathy in Fracture Versus Dislocation Patterns

The primary aim of this study is to compare the preoperative risk factors and postoperative outcomes between Charcot neuroarthropathy patients with dislocation versus purely fracture pattern breakdown. The secondary aim is to compare the same factors between Charcot neuroarthropathy patients with dislocation versus fracture-dislocation pattern breakdown. A total of 55 patients with forefoot, midfoot, or hindfoot Charcot Neuroarthopathy were assessed at a mean follow up of 2.99 years. Bivariate analysis compared preoperative risk factors and postoperative outcomes, and segmented multivariable regression analysis was performed. Dislocation pattern Charcot had statistically significant higher rates of broken hardware (p = .05), mean age (p = .01), and revisional exostectomy (p = .01) compared to pure fracture pattern Charcot. Dislocation pattern Charcot was 12 times more likely to have revisions exostectomy (odds ratio [OR] 12.0, 95% confidence interval [CI] 1.84-78.37), and was 8 times more likely to have osteomyelitis (OR 7.8, 95% CI 1.4-42.7, p = .02) compared to the fracture-dislocation pattern Charcot. The patients with pure fracture pattern Charcot were 58.8 times more likely to have Charcot breakdown involvement of the talonavicular joint compared to the dislocation pattern cohort (OR 58.83, 95% CI 1.1-3220.3). Involvement of the talonavicular joint, in the fracture pattern Charcot associate with medial column collapse occurring at the onset of Charcot breakdown. The dislocation pattern in Charcot Neuroarthropathy demonstrated a higher propensity for residual collapse as demonstrated by the higher rates of broken hardware, osteomyelitis, and need for revisional exostectomy.

Pathogenesis, diagnosis and clinical management of diabetic sensorimotor peripheral neuropathy

Diabetic sensorimotor peripheral neuropathy (DSPN) is a serious complication of diabetes mellitus and is associated with increased mortality, lower-limb amputations and distressing painful neuropathic symptoms (painful DSPN). Our understanding of the pathophysiology of the disease has largely been derived from animal models, which have identified key potential mechanisms. However, effective therapies in preclinical models have not translated into clinical trials and we have no universally accepted disease-modifying treatments. Moreover, the condition is generally diagnosed late when irreversible nerve damage has already taken place. Innovative point-of-care devices have great potential to enable the early diagnosis of DSPN when the condition might be more amenable to treatment. The management of painful DSPN remains less than optimal; however, studies suggest that a mechanism-based approach might offer an enhanced benefit in certain pain phenotypes. The management of patients with DSPN involves the control of individualized cardiometabolic targets, a multidisciplinary approach aimed at the prevention and management of foot complications, and the timely diagnosis and management of neuropathic pain. Here, we discuss the latest advances in the mechanisms of DSPN and painful DSPN, originating both from the periphery and the central nervous system, as well as the emerging diagnostics and treatments.

Charcot Reconstruction: Outcomes in Patients With and Without Diabetes

The objective of this study is to compare risk adjusted matched cohorts of Charcot neuroarthropathy patients who underwent osseous reconstruction with and without diabetes. The 2 groups were matched based on age, body mass index, hypertension, history of end-stage renal disease, and peripheral arterial disease. Bivariate analysis was performed for preoperative infection, location of Charcot breakdown, and post reconstruction outcomes, in patients with a minimum of 1 year follow-up period. Through bivariate analysis, presence of preoperative ulceration (p = .0499) was found to be statistically more likely in the patients with diabetes; whereas, delayed osseous union (p = .0050) and return to ambulation (p ≤ .0001) was statistically more likely in patients without diabetes. The nondiabetic Charcot patients were 17.6 folds more likely to return to ambulation (odds ratio [OR] 17.6 [95% confidence interval {CI} {3.5-87.6}]), and 16.4 folds more likely to have delayed union (OR 16.4 [95% CI {1.9-139.6)]). Subanalysis compared well-controlled diabetic and nondiabetic Charcot neuroarthropathy patients for same factors. Multivariate analysis, in the subanalysis, found return to ambulation was 15.1 times likely to occur in the nondiabetic CN cohort (OR 15.1 [95% CI 1.3-175.8]) compared to the well-controlled diabetic CN cohort.

Ocular Manifestations and Neuropathy in Type 2 Diabetes Patients With Charcot Arthropathy

OBJECTIVE

Diabetes can affect the eye in many ways beyond retinopathy. This study sought to evaluate ocular disease and determine any associations with peripheral neuropathy (PN) or cardiac autonomic neuropathy (CAN) in type 2 diabetes (T2D) and Charcot arthropathy (CA) patients.

DESIGN

A total of 60 participants were included, 16 of whom were individuals with T2D/CA, 21 of whom were individuals with T2D who did not have CA, and 23 of whom were healthy controls. Ocular surface evaluations were performed, and cases of dry eye disease (DED) were determined using the Ocular Surface Disease Index (OSDI) questionnaire, ocular surface staining, Schirmer test, and Oculus Keratograph 5M exams. All variables were used to classify DED and ocular surface disorders such as aqueous deficiency, lipid deficiency, inflammation, and ocular surface damage. Pupillary and retinal nerve fiber measurements were added to the protocol in order to broaden the scope of the neurosensory ocular evaluation. PN and CAN were ascertained by clinical examinations involving the Neuropathy Disability Score (for PN) and Ewing's battery (for CAN).

RESULTS

Most ocular variables evaluated herein differed significantly between T2D patients and controls. When the controls were respectively compared to patients with T2D and to patients with both T2D and CA, they differed substantially in terms of visual acuity (0.92 ± 0.11, 0.73 ± 0.27, and 0.47 ± 0.26, p=0.001), retinal nerve fiber layer thickness (96.83 ± 6.91, 89.25 ± 10.44, and 80.37 ± 11.67 µm, p=0.03), pupillometry results (4.10 ± 0.61, 3.48 ± 0.88, and 2.75 ± 0.81 mm, p=0.0001), and dry eye symptoms (9.19 ± 11.71, 19.83 ± 19.08, and 24.82 ± 24.40, p=0.03). DED and ocular surface damage also differed between individuals with and without CA, and were associated with PN and CAN.

CONCLUSION

CA was found to be significantly associated with the severity of ocular findings. DED in cases of CA was also associated with PN and CAN. These findings suggest that intrinsic and complex neurosensory impairment in the eyes, peripheral sensory nerves, and the autonomic nervous system are somehow connected. Thus, a thorough ocular evaluation may be useful to highlight neurological complications and the impact of diabetes on ocular and systemic functions and structures.

Novel FEMASK-score, a histopathologic assessment for destructive Charcot neuropathic arthropathy, reveals intraneural vasculopathy and correlates with progression and best treatment

BACKGROUND

Charcot neuropathic arthropathy is a debilitating, rapidly destructive degenerative joint disease that occurs in diabetic, neuropathic midfoot. Clinicoradiologic assessment for Charcot neuropathic arthropathy previously relied on Eichenholtz stage. There is limited histopathologic data on this entity. We wanted to independently develop a histopathologic scoring system for Charcot neuropathic arthropathy.

DESIGN

Retrieval of surgical pathology midfoot specimens from Charcot patients (2012-2019) were analyzed to evaluate joint soft tissue and bone. Considering progression from large (≥half 40× hpf) to small (<half 40× hpf) periarticular bone fragments to resolution, we devised and applied a Charcot neuropathic arthropathy novel FEMASK-score (named after coauthors: Fanburg-Smith, Frauenhoffer, Flemming, Fritsche, Elfar, Murie, Aynardi, Stauch, Smith, King, and Klein): 0 (initial) = the observed intraneural arteriolosclerosis in all diabetic neuropathic patient specimens (not observed in other diabetic nerves); and finally scored with the most destruction observed: 1 = large bone fragments without host histiocytic response; 2 = mixed bone fragments with host histiocytic response; 3 = small minute bone spicules resorption to fibrosis. Eichenholtz stage and outcome were then compared.

RESULTS

Forty-eight cases of Charcot neuropathic arthropathy included 34 males and 14 females, mean age 60.3 and age range 28-83 years, with clinical diabetes mellitus (predominantly Type II) and longstanding neuropathy. Elevated HbA1C, Eichenholtz stage, American Society of Anesthesia score, and Charlson comorbidity index indicated initial clinical amputation. Pathologic specimens varied from fixation tissue to amputation. In addition to neurotraumatic, neurovascular and inflammatory findings, a distinctive intraneural hyalinized arteriolosclerosis was observed. FEMASK-scores: 1 = 10%, 2 = 58%, and 3 = 32%. Score comparisons were 98% accurate compared with Eichenholtz and 98% reproducible among pathologists. FEMASK 2 and 3 correlate with clinical need for amputation.

CONCLUSIONS

Our novel Charcot neuropathic arthropathy FEMASK-score classification, derived from the largest cohort of diabetic neuropathic specimens, is reproducible, explains pathophysiologic progression of destructive phase of Charcot, correlates with Eichenholtz, and predicts progression to or clinical need for amputation. The unique intraneural vasculopathy observed contributes to Charcot neuropathic arthropathy etiology.

Charcot Neuroarthropathy Advances: Understanding Pathogenesis and Medical and Surgical Management

Understanding new theories of the epidemiology of Charcot neuroarthropathy is practice changing. Treatment of Charcot neuroarthropathy is evolving from a passive approach to one that sees the urgency of proactive, early recognition, thereby avoiding the cascading events that lead to the complex, limb-threatening deformities. Preventive medicine is the most efficient at avoiding severe deformity, with prolonged offloading and immobilization as the current mainstay of treatment. However, with recent advancements in medical and surgical modalities, this may become the treatment of the past as clinicians begin to favor medical management and early surgical intervention.

Microscopic study of chronic charcot arthropathy foot bones contributes to understanding pathogenesis - A preliminary report

INTRODUCTION

Charcot arthropathy (CA) is non-infective, chronic destructive condition affecting the pes architecture of long standing diabetic patients with neuropathy. Even though several theories have emerged to disclose its pathogenesis, inflammatory cytokine induced osteoclastogenesis stands as the chief culprit. Studies on micro-architecture of foot bones of acute stage CA patients, describes mainly destructive phase of bone remodelling. Increased osteoclast cell activity is reported in all studies communicated. No study has to the best of our knowledge detailed the microscopic structure of chronic stage CA foot bones.

AIM

To study the microscopic structure of foot bones in patients with chronic CA.

MATERIALS AND METHODS

Foot bones were collected from the feet of chronic CA patients (six in number) who underwent corrective foot surgery in the Department of Podiatric Surgery of a tertiary care hospital. Control samples were collected from the feet of age matched non-diabetic controls (2 in number). The samples were fixed in formalin, decalcified in 10% nitric acid, processed, sectioned and stained with haematoxylin and eosin. Histopathology and histomorphometry analysis were performed by two different pathologists.

RESULTS

Trabeculae of chronic CA foot bones exhibited mainly a lamellar architecture, with reduced number of osteocytes and plenty of empty lacunae. Trabecular connectivity was lost and trabeculae showed considerable thinning. Trabecular osteoids lined by active osteoblast cells was a remarkable observation. Bone area was also considerably reduced in chronic CA foot bones.

CONCLUSION

Chronic stage CA foot bones presented features of both healing and fragile bone. The compromised bone quality may be due to thin and fragmented trabecular structure and reduced cellularity.