Osteophytes: relevance and biology

Computed tomography is superior to radiography for detection of feline elbow osteoarthritis

Elbow osteoarthritis (OA) is common in cats and radiography is typically used for diagnosis. However computed tomography (CT), with its multiplanar three-dimensional characteristics, could have significant advantages for assessment of OA compared to radiography, particularly early in the disease process. The study objectives were to compare radiography and CT to histologic OA changes, investigate the stage of OA that radiography and CT detect, and search for specific changes in CT images strongly predictive for feline elbow OA. Right elbows from 29 cats were evaluated by radiography and CT, and articular cartilage lesions graded histologically and macroscopically. Three further joints were sampled to specifically evaluate the morphology of the anconeal process. Macroscopic, radiographic and CT OA diagnosis were compared to the reference standard histologic OA that was divided into mild, moderate and severe. Osteophytic spurs on the lateral margin of the anconeal process could be reliably measured in CT images (intra-class correlation 0.79) and when ≥0.5 mm had high sensitivity for moderate/severe histologic OA, moderate sensitivity for mild histologic OA and high specificity for all stages of OA. In moderate/severe histologic OA both radiography and CT subjective OA diagnosis had moderate to very high sensitivity. However, in mild histologic OA CT grading had low sensitivity and radiography did not detect OA. In conclusion, CT of the feline elbow including measurement of osteophytes on the anconeal process lateral margin is superior to radiography for OA detection and should be considered for OA diagnosis, particularly when mild OA changes are of interest.

Increased uptake of 68Ga-DOTA-FAPI-04 in bones and joints: metastases and beyond

PURPOSE

To describe the uptake of ⁶⁸Gallium-labelled fibroblast activation protein inhibitor (⁶⁸Ga-FAPI) in the bones and joints for better understanding of the role of ⁶⁸Ga-FAPI PET in benign and malignant bone lesions and joint diseases.

METHODS

All 129 ⁶⁸Ga-FAPI PET/MR or PET/CT scans from June 1, 2020, to February 20, 2021, performed at our PET center were retrospectively reviewed. Foci of elevated ⁶⁸Ga-FAPI uptake in the bones and joints were identified. All lesions were divided into malignant and benign diseases. Benign lesions included osteofibrous dysplasia, periodontitis, degenerative bone diseases, arthritis, and other inflammatory or trauma-related abnormalities. The number, locations, and SUVmax of all lesions were recorded and analyzed. The detectability of ⁶⁸Ga-FAPI PET and ¹⁸F-FDG PET in patients who had two scans was also compared.

RESULTS

Elevated uptake of ⁶⁸Ga-FAPI in/around the bones and joints was found in 82 cases (63.57%). A total of 295 lesions were identified, including 94 (31.9%) malignant lesions (all were metastases) and 201 (68.1%) benign lesions. The benign lesions consisted of 13 osteofibrous dysplasia, 48 degenerative bone disease, 33 periodontitis, 56 arthritis, and 51 other inflammatory or trauma-related abnormalities. The spine, shoulder joint, alveolar ridge, and pelvis were the most commonly involved locations. Bone metastases were mainly distributed in the spine, pelvis, and ribs. Among benign diseases, periodontitis and arthritis are site-specific. The mean SUVmax of bone metastases was significantly higher than that of benign diseases (7.14 ± 4.33 vs. 3.57 ± 1.60, p < 0.001), but overlap existed. The differences in SUVmax among subgroups of benign diseases were statistically significant (p < 0.001), with much higher uptake in periodontitis (4.45 ± 1.17). ⁶⁸Ga-FAPI PET identified much more lesions than ¹⁸F-FDG PET (104 vs. 48) with higher uptake value.

CONCLUSION

⁶⁸Ga-FAPI accumulated in both bone metastases and some benign diseases of the bones and joints. Although the uptake of ⁶⁸Ga-FAPI was often higher in bone metastases, this finding cannot be used to distinguish between benign and malignant lesions. ⁶⁸Ga-FAPI PET also has the potential to locate and evaluate the extent of both malignant tumor and benign diseases in bones and joints.

TRIAL REGISTRATION

NCT04554719, NCT04605939. Registered September 8, 2020 and October 25, 2020-retrospectively registered, http://clinicaltrails.gov/show/NCT04554719 ; http://clinicaltrails.gov/show/NCT04605939.

Age-related alterations and senescence of mesenchymal stromal cells: Implications for regenerative treatments of bones and joints

The most common clinical manifestations of age-related musculoskeletal degeneration are osteoarthritis and osteoporosis, and these represent an enormous burden on modern society. Mesenchymal stromal cells (MSCs) have pivotal roles in musculoskeletal tissue development. In adult organisms, MSCs retain their ability to regenerate tissues following bone fractures, articular cartilage injuries, and other traumatic injuries of connective tissue. However, their remarkable regenerative ability appears to be impaired through aging, and in particular in age-related diseases of bones and joints. Here, we review age-related alterations of MSCs in musculoskeletal tissues, and address the underlying mechanisms of aging and senescence of MSCs. Furthermore, we focus on the properties of MSCs in osteoarthritis and osteoporosis, and how their changes contribute to onset and progression of these disorders. Finally, we consider current treatments that exploit the enormous potential of MSCs for tissue regeneration, as well as for innovative cell-free extracellular-vesicle-based and anti-aging treatment approaches.

The role of inflammation in mesenchymal stromal cell therapy in osteoarthritis, perspectives for post-traumatic osteoarthritis: a review

OA is a complex and highly prevalent degenerative disease affecting the whole joint, in which factors like genetic predisposition, gender, age, obesity and traumas contribute to joint destruction. ∼50-80% of OA patients develop synovitis. OA-associated risk factors contribute to joint instability and the release of cartilage matrix fragments, activating the synovium to release pro-inflammatory factors and catabolic enzymes in turn damaging the cartilage and creating a vicious circle. Currently, no cure is available for OA. Mesenchymal stromal cells (MSCs) have been tested in OA for their chondrogenic and anti-inflammatory properties. Interestingly, MSCs are most effective when administered during synovitis. This review focusses on the interplay between joint inflammation and the immunomodulation by MSCs in OA. We discuss the potential of MSCs to break the vicious circle of inflammation and describe current perspectives and challenges for clinical application of MSCs in treatment and prevention of OA, focussing on preventing post-traumatic OA.

Assessment of quantitative [18F]Sodium fluoride PET measures of knee subchondral bone perfusion and mineralization in osteoarthritic and healthy subjects

OBJECTIVE

Molecular information derived from dynamic [18F]sodium fluoride ([18F]NaF) PET imaging holds promise as a quantitative marker of bone metabolism. The objective of this work was to evaluate physiological mechanisms of [18F]NaF uptake in subchondral bone of individuals with and without knee osteoarthritis (OA).

METHODS

Eleven healthy volunteers and twenty OA subjects were included. Both knees of all subjects were scanned simultaneously using a 3T hybrid PET/MRI system. MRI MOAKS assessment was performed to score the presence and size of osteophytes, bone marrow lesions, and cartilage lesions. Subchondral bone kinetic parameters of bone perfusion (K1), tracer extraction fraction, and total tracer uptake into bone (Ki) were evaluated using the Hawkins 3-compartment model. Measures were compared between structurally normal-appearing bone regions and those with structural findings.

RESULTS

Mean and maximum SUV and kinetic parameters Ki, K1, and extraction fraction were significantly different between Healthy subjects and subjects with OA. Between-group differences in metabolic parameters were observed both in regions where the OA group had degenerative changes as well as in regions that appeared structurally normal.

CONCLUSIONS

Results suggest that bone metabolism is altered in OA subjects, including bone regions with and without structural findings, compared to healthy subjects. Kinetic parameters of [18F]NaF uptake in subchondral bone show potential to quantitatively evaluate the role of bone physiology in OA initiation and progression. Objective measures of bone metabolism from [18F]NaF PET imaging can complement assessments of structural abnormalities observed on MRI.

Osseous Pathology on Wrist Magnetic Resonance Imaging

Advanced imaging of the osseous structures of the wrist by magnetic resonance imaging (MRI) yields powerful information regarding marrow composition and overall bone structure. Various forms of pathology, both benign and malignant, have unique marrow signal abnormalities that can be easily detected by MRI given its high sensitivity to radiographically occult processes. In particular, osseous pathology can be seen in the setting of traumatic, degenerative, congenital, infectious, and neoplastic conditions. The acuity or chronicity of these conditions can often be determined by imaging to aid in appropriate therapy. A thorough understanding of the breadth of pathology and corresponding MRI appearances can allow the interpreting radiologist to formulate a concise and accurate assessment of an examination.

The physiopathology of osteoarthritis: Paleopathological implications of non-articular lesions from a modern surgical sample

OBJECTIVES

This research focused on osteoarthritis (OA) lesions on modern patients to 1) identify consistently observed lesions not included within current paleopathological measures of OA, 2) assess the correspondence of bone and cartilage lesions with clinical OA diagnostic criteria, and 3) discuss the correspondence of bone lesions with sources of pain reported in clinical literature.

MATERIALS

Tibial plateaus from 62 patients undergoing total knee replacement surgery due to OA were examined.

METHODS

Plateaus were scored for several non-standard OA criteria, including non-articular and X-ray visible lesions and pre-maceration cartilage lesions, as well as articular surface criteria standard in paleopathology.

RESULTS

Proliferative bone in the intercondylar region was present in 95 % of specimens, while areas of dense trabecular bone and lytic defects, both on the inferior side of the plateaus, were present in 98 % and 83 %, respectively.

CONCLUSIONS

The inferior lytic defects may be physical evidence of bone marrow lesions (BML), a clinical OA indicator visible via MRI. Previous research has linked BML to pain, inflammation, and ligament pathology. The latter conditions have also been associated with intercondylar enthesophytes and third intercondylar tubercle of Parsons (TITP), both of which were observed in the intercondylar regions.

SIGNIFICANCE

Several non-articular lesions not currently included in paleopathological measures of OA were consistently observed.

SUGGESTIONS FOR FUTURE RESEARCH

A similar analysis of a control sample of non-OA tibial plateaus would better contextualize these results.

LIMITATIONS

The sample's high average age (65.8 years) and severe OA stage may hamper generalizability to archaeological collections.

Multivariable modeling of biomarker data from the phase 1 Foundation for the NIH Osteoarthritis Biomarkers Consortium

OBJECTIVE

To determine the optimal combination of imaging and biochemical biomarkers to predict knee osteoarthritis (OA) progression.

METHODS

Nested case-control study from the FNIH OA Biomarkers Consortium of participants with Kellgren-Lawrence grade 1-3 and complete biomarker data (n=539 to 550). Cases were knees with radiographic and pain progression between 24-48 months from baseline. Radiographic progression only was assessed in secondary analyses. Biomarkers (baseline and 24-month changes) with p<0.10 in univariate analysis were selected, including MRI (quantitative (Q) cartilage thickness and volume; semi-quantitative (SQ) MRI markers; bone shape and area; Q meniscal volume), radiographic (trabecular bone texture (TBT)), and serum and/or urine biochemical markers. Multivariable logistic regression models were built using three different step-wise selection methods (complex vs. parsimonious models).

RESULTS

Among baseline biomarkers, the number of locations affected by osteophytes (SQ), Q central medial femoral and central lateral femoral cartilage thickness, patellar bone shape, and SQ Hoffa-synovitis predicted progression in most models (C-statistics 0.641-0.671). 24-month changes in SQ MRI markers (effusion-synovitis, meniscal morphology, and cartilage damage), Q central medial femoral cartilage thickness, Q medial tibial cartilage volume, Q lateral patellofemoral bone area, horizontal TBT (intercept term), and urine NTX-I predicted progression in most models (C-statistics 0.680-0.724). A different combination of imaging and biochemical biomarkers (baseline and 24-month change) predicted radiographic progression only, with higher C-statistics (0.716-0.832).

CONCLUSION

This study highlights the combination of biomarkers with potential prognostic utility in OA disease-modifying trials. Properly qualified, these biomarkers could be used to enrich future trials with participants likely to progress.

Ultrasound Findings were Associated With Radiographic Changes, But Not Clinical and Functional Outcomes in Hand Osteoarthritis

Objective

There is a debate over the relevance of ultrasound abnormalities to the pain, functional impairment, and radiologic severity in hand osteoarthritis (OA) This study aims to determine the association between ultrasound abnormalities and clinical, functional, and radiographic measures in hand OA.

Methods

A total of 66 patients was consecutively enrolled All patients with gray-scale synovitis, joint effusion, and osteophytes were examined by ultrasound for 20 hand joints Radiographic changes in both hands were evaluated by the Kellgren-Lawrence (K-L) grading system and were described as total radiographic severity score and number of affected joints Other measures were also assessed, including each patient's visual analogue scale for pain, the Functional Index for Hand Osteoarthritis for functional disability, and grip and pinch strength for hand muscle strength.

Results

In total, 10 patients with gray-scale synovitis, 35 with joint effusion, and 66 with osteophytes were detected in hand OA scans on ultrasound Osteophytes on ultrasound were significantly associated with total radiographic severity score and number of affected joint (r=0293, p=0003 and r=0336, p<0001, respectively) In addition, there were weak associations of synovitis and joint effusion with radiographic changes Patients with higher total radiographic severity score showed larger number of ultrasound-detected abnormalities, such as synovitis, joint effusion, and osteophytes (p=0011, p=0002, and p<0001, respectively).

Conclusion

This study shows that ultrasound findings, especially osteophytes, were associated with radiographic changes based on K-L grade, but not clinical and functional status in hand OA.

Progression of acromegalic arthropathy in long-term controlled acromegaly patients: 9 years of longitudinal follow-up

CONTEXT

Joint complaints in patients with acromegaly are common, although the long-term disease course is largely unknown.

OBJECTIVE

This study aims to evaluate the long-term course of acromegalic arthropathy.

DESIGN AND SETTING

A prospective longitudinal cohort study was conducted in controlled acromegaly patients followed at a tertial referral center, with 3 study visits: at baseline and after a median of 2.6 and 9.1 years.

PATIENTS

We included 31 patients with biochemically controlled acromegaly for 2 or more years (49% female; median age, 60 years) at baseline.

MAIN OUTCOME MEASURES

Radiographic arthropathy of the knee, hip, hand, and cervical and lumbar spine were evaluated using Kellgren and Lawrence (KL) scores, developed for assessment of primary osteoarthritis (OA). Radiographic progression was defined as a KL increase above the smallest detectable change. Joint symptoms were assessed using self-reported questionnaires. Progression was defined using existing clinically important cutoff values. Risk factors for progression were investigated using a multivariable model.

RESULTS

All patients had definite radiographic OA at 1 or more joints at baseline. Radiographic progression was observed in 29%, 48%, 84%, and 94% of patients in the knees, hips, hands, and axial joints, respectively. Deterioration in hand-related pain and function was observed in 10 (32.3%) and 11 patients (35.5%), respectively. Solely baseline KL scores of the hip were associated with hip OA progression (OR 1.88; 95% CI, 1.09-3.16).

CONCLUSIONS

Acromegalic arthropathy showed significant radiographic progression over 9.1 years of follow-up in patients in remission, whereas clinical progression was observed less frequently. Future studies should focus on adequate prevention and treatment strategies of acromegalic arthropathy.

High-Density Mineralized Protrusions and Central Osteophytes: Associated Osteochondral Junction Abnormalities in Osteoarthritis

The aim of this study was to determine the association between high-density mineralized protrusions (HDMPs) and central osteophytes (COs), and describe the varying appearance of these lesions using advanced clinical imaging and a novel histological protocol. Seventeen consecutive patients with clinically advanced knee osteoarthritis undergoing knee arthroplasty were included. Surgical tissues containing the osteochondral region were investigated using computed tomography (CT); a subset was evaluated using confocal microscopy with fluorescence. Tissues from seven subjects (41.2%) contained HDMPs, and tissues from seven subjects (41.2%) contained COs. A significant association between HDMPs and COs was present (p = 0.003), with 6 subjects (35.2%) demonstrating both lesions. In total, 30 HDMPs were found, most commonly at the posterior medial femoral condyle (13/30, 43%), and 19 COs were found, most commonly at the trochlea (5/19, 26.3%). The HDMPs had high vascularity at their bases in cartilaginous areas (14/20, 70%), while the surrounding areas had elevated levels of long vascular channels penetrating beyond the zone of calcified cartilage (p = 0.012) compared to HDMP-free areas. Both COs and HDMPs had noticeable bone-resorbing osteoclasts amassing at the osteochondral junction and in vascular channels entering cartilage. In conclusion, HDMPs and COs are associated lesions in patients with advanced knee osteoarthritis, sharing similar histologic features, including increased vascularization and metabolic bone activity at the osteochondral junction. Future studies are needed to determine the relationship of these lesions with osteoarthritis progression and symptomatology.

Identification of the skeletal progenitor cells forming osteophytes in osteoarthritis

OBJECTIVES

Osteophytes are highly prevalent in osteoarthritis (OA) and are associated with pain and functional disability. These pathological outgrowths of cartilage and bone typically form at the junction of articular cartilage, periosteum and synovium. The aim of this study was to identify the cells forming osteophytes in OA.

METHODS

Fluorescent genetic cell-labelling and tracing mouse models were induced with tamoxifen to switch on reporter expression, as appropriate, followed by surgery to induce destabilisation of the medial meniscus. Contributions of fluorescently labelled cells to osteophytes after 2 or 8 weeks, and their molecular identity, were analysed by histology, immunofluorescence staining and RNA in situ hybridisation. Pdgfrα-H2BGFP mice and Pdgfrα-CreER mice crossed with multicolour Confetti reporter mice were used for identification and clonal tracing of mesenchymal progenitors. Mice carrying Col2-CreER, Nes-CreER, LepR-Cre, Grem1-CreER, Gdf5-Cre, Sox9-CreER or Prg4-CreER were crossed with tdTomato reporter mice to lineage-trace chondrocytes and stem/progenitor cell subpopulations.

RESULTS

Articular chondrocytes, or skeletal stem cells identified by Nes, LepR or Grem1 expression, did not give rise to osteophytes. Instead, osteophytes derived from Pdgfrα-expressing stem/progenitor cells in periosteum and synovium that are descendants from the Gdf5-expressing embryonic joint interzone. Further, we show that Sox9-expressing progenitors in periosteum supplied hybrid skeletal cells to the early osteophyte, while Prg4-expressing progenitors from synovial lining contributed to cartilage capping the osteophyte, but not to bone.

CONCLUSION

Our findings reveal distinct periosteal and synovial skeletal progenitors that cooperate to form osteophytes in OA. These cell populations could be targeted in disease modification for treatment of OA.

An evaluation of the relationship between the degree of entheseal changes and the severity of osteodegenerative processes at fibrocartilaginous entheses

An enthesis refers to the interface at which a tendon or a ligament integrates into the periosteum. Its morphology can be influenced by intrinsic factors such as sex, age, and extrinsic factors such as levels of activity, which will in turn impact on bone remodeling and lead to morphological changes. In bioarcheology, entheseal changes have had a long tradition of being used for the reconstruction of past activities. The literature has shown that in some cases of osteoarthritis, entheseal changes are associated with osteoarthritic manifestations. This work aims to evaluate the relationship between the degree of entheseal changes and the severity of osteodegenerative processes. The studied materials consisted of 30 humeri and 30 femora from the osteological collection at St George's University of London. Intensities of both entheseal changes and osteodegenerative processes were macroscopically assessed and scored. The difference in scores of entheseal changes between osteoarthritic groups and nonosteoarthritic groups is statistically significant at a confidence level of 95% (α = .05) for both the humeri and femora. Results show a positive correlation between the degree of entheseal changes and the severity of osteodegenerative processes in the femora, suggesting that enthesis may play a role in osteoarthritis. Findings from this work supports the proposed hypothesis that the degree of entheseal changes and the severity of osteoarthritic manifestation are related. This work contributes to current knowledge that osteoarthritis is a disease involving the whole joint; the enthesis could potentially be a target for the diagnosis of osteoarthritis.

Histomorphometric case-control study of subarticular osteophytes in patients with osteoarthritis of the hip

Objective

The objective of this cross-sectional case-control study was to determine the prevalence and size of marginal and subarticular osteophytes in patients with osteoarthritis (OA), and to compare these to that of a control group.

Design

We investigated femoral heads from 25 patients with OA following hip replacement surgery, and 25 femoral heads from a control group obtained post-mortem. The area and boundary length of the femoral head, marginal osteophytes, and subarticular osteophytes were determined with histomorphometry. Marginal osteophytes were defined histologically as bony projections at the peripheral margin of the femoral head, while subarticular osteophytes were defined as areas of bone that expanded from the normal curvature of the femoral head into the articular cartilage.

Results

The prevalence of OA patients with marginal- and subarticular osteophytes were 100 and 84%, respectively. Whereas the prevalence of the participants in the control group with marginal- and subarticular osteophytes were 56 and 28%, respectively.

The area and boundary length of marginal osteophytes was (median (Interquartile range)) 165.3mm² (121.4–254.0) mm² and 75.1 mm (50.8–99.3) mm for patients with OA compared to 0 mm² (0–0.5) mm² and 0 mm (0–0.5) mm for the control group (P <  0.001). For the subarticular osteophytes, the area and boundary length was 1.0 mm² (0–4.4) mm² and 1.4 mm (0–6.5) mm for patients with OA compared to 0 mm² (0–0.5) mm² and 0 mm (0–0.5) mm for the control group (P <  0.001).

Conclusion

As expected, both marginal- and subarticular osteophytes at the femoral head, were more frequent and larger in patients with OA than in the control group. However, in the control group, subarticular osteophytes were more prevalent than expected from the minor osteophytic changes at the femoral head margin, which may suggest that subarticular osteophytes are an early degenerative phenomenon that ultimately might develop into clinical osteoarthritis.

Arthritis and the role of endogenous glucocorticoids

Rheumatoid arthritis and osteoarthritis, the most common forms of arthritis, are chronic, painful, and disabling conditions. Although both diseases differ in etiology, they manifest in progressive joint destruction characterized by pathological changes in the articular cartilage, bone, and synovium. While the potent anti-inflammatory properties of therapeutic (i.e., exogenous) glucocorticoids have been heavily researched and are widely used in clinical practice, the role of endogenous glucocorticoids in arthritis susceptibility and disease progression remains poorly understood. Current evidence from mouse models suggests that local endogenous glucocorticoid signaling is upregulated by the pro-inflammatory microenvironment in rheumatoid arthritis and by aging-related mechanisms in osteoarthritis. Furthermore, these models indicate that endogenous glucocorticoid signaling in macrophages, mast cells, and chondrocytes has anti-inflammatory effects, while signaling in fibroblast-like synoviocytes, myocytes, osteoblasts, and osteocytes has pro-inflammatory actions in rheumatoid arthritis. Conversely, in osteoarthritis, endogenous glucocorticoid signaling in both osteoblasts and chondrocytes has destructive actions. Together these studies provide insights into the role of endogenous glucocorticoids in the pathogenesis of both inflammatory and degenerative joint disease.

Systemic iron overload exacerbates osteoarthritis in the strain 13 guinea pig

OBJECTIVE

Iron is emerging as a key player in aging-associated diseases due to its propensity for driving free radical formation. Studies examining the role of iron in the pathogenesis of primary osteoarthritis (OA) are limited. Our objective was to establish a direct relationship between excess iron and OA by administering iron dextran to a guinea pig strain with decreased propensity for developing this disease.

DESIGN

Twenty, 12-week-old Strain 13 guinea pigs received either iron dextran or dextran control intraperitoneally once weekly for 4 weeks; termination occurred at 16 weeks of age. Iron levels were determined systemically (serum and liver) and within diarthrodial joints [femoral head articular cartilage and infrapatellar fat pads (IFPs) of knee joints]. One knee was collected to score structural changes associated with OA via microcomputed tomography (microCT) and histology using published grading schemes. Articular cartilage and IFPs were harvested from contralateral knees for gene expression analyses.

RESULTS

Iron overload was confirmed systemically via increased serum iron and liver iron concentration. Articular cartilage and IFPs in the iron dextran group also had higher levels of iron. Excess iron worsened knee OA using both microCT and histologic scoring systems. Gene analyses revealed that exogenous iron altered the expression of iron trafficking proteins, select cytokines, and structural components of cartilage.

CONCLUSION

These results demonstrate that systemic iron overload caused cellular iron accumulation in the knee joint. This excess iron is associated with increased expression of local inflammatory mediators and early onset and progression of knee joint OA in Strain 13 animals.

Differential patterns of pathology in and interaction between joint tissues in long-term osteoarthritis with different initiating causes: phenotype matters

OBJECTIVE

To determine if osteoarthritis (OA) progression and joint tissue-pathology associations link specific animal models to different human OA phenotypes.

DESIGN

Male 11-week-old C57BL6 mice had unilateral medial-meniscal-destabilization (DMM) or antigen-induced-arthritis (AIA). Joint tissue histopathology was scored day-3 to week-16. Tissue-pathology associations (corrected for time and at week-16) were determined by partial correlation coefficients, and odds ratios (OR) calculated for likelihood of cartilage damage and joint inflammation by ordinal-logistic-regression.

RESULTS

Despite distinct temporal patterns of progression, by week-16 joint-wide OA pathology in DMM and AIA was equivalent. Significant pathology associations common to both models included: osteophyte size and maturity (r > 0.4); subchondral bone (SCB) sclerosis and osteophyte maturity (r > 0.25); cartilage erosion and chondrocyte hypertrophy/apoptosis (r > 0.4), SCB sclerosis (r > 0.26), osteophyte size (r > 0.3), and maturity (r > 0.32). DMM-specific associations were between cartilage proteoglycan loss and structural damage (r = 0.56), osteophyte maturity (r = 0.49), size (r = 0.45), and SCB sclerosis (r = 0.28). AIA-specific associations were between SCB sclerosis and chondrocyte hypertrophy/apoptosis (r = 0.40) and osteophyte size (r = 0.37); and synovitis with cartilage structural damage (r = 0.18). No tissue-pathology associations were common to both models at week-16. Increased likelihood of cartilage structural damage was associated with: chondrocyte hypertrophy/apoptosis (OR>1.7), and osteophyte size (OR>2.3) in both models; SCB sclerosis (OR = 2.0) and proteoglycan loss (OR = 2.4) in DMM; and synovitis (OR = 1.2) in AIA. Joint inflammation was associated positively with cartilage proteoglycan loss (OR = 1.4) and inversely with osteophyte size (OR = 0.21) in AIA only.

CONCLUSION

This study highlights the importance of defining OA-models by initiating mechanisms and progression, not just end-stage joint-tissue pathology.

Management of Osteoarthritis During the COVID-19 Pandemic

The pandemic spread of the new coronavirus disease 2019 (COVID‐19) infection in China first, and all over the world at present, has become a global health emergency due to the rapidly increasing number of affected patients. Currently, a clear relationship between COVID‐19 infection incidence and/or complications due to chronic or occasional treatments for other pathologies is still not clear, albeit the COVID‐19 pandemic may condition the treatment strategy of complex disorders, such as osteoarthritis (OA). Importantly, OA is the most common age‐related joint disease, affecting more than 80% of people older than the age of 55, an age burden also shared with the highest severity in COVID‐19 patients. OA patients often show a large array of concomitant pathologies, such as diabetes, inflammation, and cardiovascular diseases that are again shared with COVID‐19 patients and may therefore increase complications. Moreover, different OA treatments, such as NSAIDs, paracetamol, corticosteroids, opioids, or other molecules have a wide array of iatrogenic effects, potentially increasing COVID‐19 secondary infection incidence or complications. In this review we critically analyze the evidence on either negative or positive effects of drugs commonly used to manage OA in this particular scenario. This would provide orthopedic surgeons in particular, and physicians, pharmacologists, and clinicians in general, a comprehensive description about the safety of the current pharmacological approaches and a decision‐making tool to treat their OA patients as the coronavirus pandemic continues.

Mechanically-induced osteophyte in the rat knee

OBJECTIVES

Osteophytes are common anatomical signs of advanced osteoarthritis. It remains unclear whether they develop from physio-molecular, and/or mechanical stimuli. This study examined the effects of mechanical impact on the knee joint periosteum leading to osteophyte formation.

DESIGN

Eighteen mature rats received one single impact load of 53 N (30 MPa) to the periosteum of the experimental medial femoral condyles. Contralateral knees were used as controls. Animals were sacrificed at 24 h, 3, 6 and 9 weeks post-impact. Distal femurs were harvested and prepared for histology. Hematoxylin and Eosin, and Masson's trichrome stained slides were examined by light microscopy. Nuclear density was quantified to assess the tissue reaction.

RESULTS

24 h: The synovium membrane, fibrous and cambium periosteum were damaged. Blood infiltration pooled in the impacted medial collateral ligament (MCL) region. Week 3: A cartilaginous tissue spur, chondrophyte, was found in every rat at the impacted site of the MCL. Chondrophytes were composed of fibrocartilage and cartilage matrix, with signs of cartilage mineralization and remodelling activity. Week 6: Chondrophytes presented signs of more advanced mineralisation, recognized as osteophytes. Week 9: Osteophytes appeared to be more mineralized with almost no cartilage tissue.

CONCLUSIONS

Osteophytes can be induced with a single mechanical impact applied to the periosteum in rat knees. These data indicate that a moderate trauma to the periosteal layer of the joint may play a role in osteophyte development.

Osteophyte volume calculation using dissimilarity-excluding Procrustes registration of archived bone models from healthy volunteers

Osteophytes are associated with later stage osteoarthritis and are most commonly described using semiquantitative radiographic grading systems. A detailed understanding of osteophyte formation is, in part, limited by the ability to quantify bone pathology. Osteophytes can be quantified relative to pre-osteoarthritic bone, or to the contralateral bone if it is healthy; however, in many cases, neither are available as references. We present a method for computing three-dimensional (3D) osteophyte models using a library of healthy control bones. An existing data set containing the computed tomography scans of 90 patients with first carpometacarpal osteoarthritis (OA) and 46 healthy subjects were utilized. A healthy bone that best fit each OA subject's bone was determined using a dissimilarity-excluding Procrustes registration technique (DEP) that minimized the influence of dissimilar features (ie, osteophytes). The osteophyte model was then computed through Boolean subtraction of the reference bone model from the OA bone model. DEP reference bones conformed significantly better to the OA bones (P < .0001) than by finite difference iterative closest point registration (root mean squared distances, 0.33 ± 0.05 and 0.41 ± 0.16 mm, respectively). The effect of library size on dissimilarity measure was investigated by leave-k-out cross-validation randomly reducing k from 46 to 1. A library of n ≥ 31 resulted in less than 10% difference from the theoretical minimum value. The proposed method enables quantification of osteophytes when the disease-free bone or the healthy contralateral bone is not available for any 3D data set. Quantifying osteophyte formation and growth may aid in understating the associated mechanisms in OA.

Deciphering the potential pharmaceutical mechanism of Guzhi Zengsheng Zhitongwan on rat bone and kidney based on the "kidney governing bone" theory

BACKGROUND

Guzhi Zengsheng Zhitongwan (GZZSZTW) is an effective Chinese medicinal formulation for the treatment of osteoarthritis (OA) designed according to the "kidney governing bone" theory, which has been widely used as a golden guide for treating bone and cartilage diseases in traditional Chinese medicine. The aim of this study was to explore the molecular mechanism underlying its effects on the bone and kidney.

METHODS

Preparation and quality control were performed as previously described. Since GZZSZTW is orally administered in the form of pills prepared in boiled water, the Chinese materia medica (CMM) mixture of this formula was extracted with distilled water by a reflux method and was then filtered through a 0.45-μm Hollow Fiber Cartridge (GE Healthcare, USA). The filtrate was freeze-dried by a Heto PowerDry LL3000 Freeze Dryer (Thermo, USA) and stored at - 80 °C. The effects of GZZSZTW on gene expression and regulation of both kidney and bone tissues were investigated using a state-of-the-art RNA-seq technology.

RESULTS

We demonstrated that GZZSZTW could enhance kidney function and suppress bone formation and resorption by modulating the activities of osteoblast and osteoclast, and might subsequently contribute to the inhibition of osteophyte formation during the process of OA. These effects might be achieved by the synergistic interactions of various herbs and their active components in GZZSZTW, which increased the expression levels of functional genes participating in kidney function, regulation, and repair, and then decreased the expression levels of genes involved in bone formation and resorption. Thus, our findings were consistent with the "kidney governing bone" theory, which has been widely used as a guide in clinical practice for thousands of years.

CONCLUSIONS

This study has deepened the current knowledge about the molecular effects of GZZSZTW on bone and kidney regulation. Furthermore, this study might be able to provide possible strategies to further prevent and treat joint diseases by using traditional Chinese medicinal formulations following the "kidney governing bone" theory.

Biomechanical pathways of dentoalveolar fibrous joints in health and disease

Spatial and temporal adaptations within periodontal tissues and their interfaces result from functional loads. Functional loads can be physiologic and/or pathologic in nature. The prolonged effect of these loads can alter the overall biomechanics of a dentoalveolar fibrous joint (dentoalveolar joint) by changing the form of the tooth root and its socket. This "sculpting" of the tooth root and alveolar bony socket is a consequence of several mechano-biological changes that occur within the periodontal complex of a load-bearing dentoalveolar joint. These include changes in biochemical expressions, structure, elemental composition, and mechanical properties of alveolar bone, the underlying tissues of the roots of teeth, and their interfaces. These physicochemical changes in tissues continue to prompt mechano-responsive biochemical activities at the attachment sites of periodontal ligament (soft) with bone (hard), and ligament with cementum (hard), which are the entheses of a load-bearing dentoalveolar joint. Forces at soft-hard tissue attachment sites between disparate materials with different stiffness values theoretically generate strain singularities or discontinuities. These discontinuities under prolonged functional loading increase the probability for failure to occur specifically at the enthesial zones. However, in a normal dentoalveolar joint, gradual stiffness gradients exist from ligament to bone, and from ligament to cementum. The gradual transitions in stiffness from softer ligament (lower stiffness) to harder bone or cementum (higher stiffness) or vice versa optimize tissue and interfacial strains. Optimization of tissue and ligament-enthesial physical and chemical properties facilitates transmission of cyclic forces of varying magnitudes and frequencies that collectively maintain the overall biomechanics of a dentoalveolar joint. The objectives of this review are 3-fold: (i) to illustrate physicochemical adaptations at the periodontal ligament entheses of a human periodontal complex affected by subgingival calculus; (ii) to demonstrate how to "program" the hallmarks of periodontitis in small-scale vertebrates in vivo to generate spatiotemporal maps of physicochemical adaptations in a diseased dentoalveolar joint; and (iii) to correlate dentoalveolar joint biomechanics in healthy and diseased states to spatiotemporal maps of physicochemical adaptations within respective periodontal tissues. This interdisciplinary approach demonstrates that physicochemical adaptations within periodontal tissues using the mechanics of materials (tissue mechanics), materials science (tissue composition), and mechano-biology (matrix molecules) can help explain the mechano-adaptation of dentoalveolar joints in normal and diseased functional states. Multiscale biomechanics and mechano-biology approaches can provide insights into the functional competence of a diseased relative to a normal dentoalveolar joint. Insights gathered from interdisciplinary and multiscale biomechanics approaches include the following: (i) physiologic loads related to chewing maintain a balance between mineral-forming and-resorbing biochemical cellular events, resulting in gradual stiffness gradients at the periodontal ligament entheses, and, in turn, sustain the overall biomechanics of a normal "healthy" dentoalveolar joint; (ii) pathologic loads resulting from tissue degradation and physical changes to the periodontal complex promote an abrupt stiffness gradient at the periodontal ligament entheses. The shift from gradual to an abrupt stiffness gradient could prompt a shift in the biochemical cascades, exacerbate mechano-responsive biochemical expressions at periodontal ligament entheses farther away from the site of insult, and culminate in joint degradation; (iii) sustained pathologic function on periodontally diseased joints exacerbates degradation of periodontal ligament entheses providing insights into "rescue therapy", such as the use of an adequate "mechanocal dose" to regain joint function; and (iv) spatiotemporal maps of changes in biochemical expressions, and physicochemical properties of strain-dominated affected sites, including the periodontal ligament entheses, can guide anatomy-specific therapeutics for tissue regeneration and/or disease control with the purpose of regaining dentoalveolar joint function. Modulation of occlusal loads could minimize disease progression and potentially assist in regaining functional attachment of ligament to bone and/or ligament to cementum of the dentoalveolar joint. Elucidating mechanisms that drive the breakdown of the functionally active periodontal complex burdened with microbes will provide the required critical insights into regenerative medicine and/or biomimetic approaches that would facilitate rescue/regain of dentoalveolar joint function.

A novel elastic and controlled-release poly(ether-ester-urethane)urea scaffold for cartilage regeneration

In the tissue engineering of cartilage, scaffolds with appropriate elasticity and controlled-release properties are essential. Herein, we synthesized a poly(ether-ester-urethane)urea scaffold with a pendant amino group (PEEUUN) through a de-protection process from PEEUU-Boc polymers and grafted kartogenin (KGN) onto the PEEUUN scaffolds (PEEUUN-KGN). Characterization, performance tests, scaffold biocompatibility analysis, and chondrogenesis evaluation both in vitro and in vivo were conducted. The results revealed that the PEEUUN-KGN scaffolds were degradable and three-dimensional (3D) with interconnected pores, and possessed good elasticity, as well as excellent cytocompatibility. Meanwhile, KGN on the PEEUUN-KGN scaffolds underwent stable sustained release for a long time and promoted human umbilical cord mesenchymal stem cells (HUCMSCs) to differentiate into chondrocytes in vitro, thus enhancing cartilage regeneration in vivo. In conclusion, the present PEEUUN-KGN scaffolds would have application potential for cartilage tissue engineering.

Assessment of Intra- and Inter-observer Measurement Variability in a Radiographic Metacarpophalangeal Joint Osteophytosis Scoring System for the Horse

The study evaluated the intra- and inter-observer measurement variability of an osteophytosis metacarpophalangeal joint scoring system. Ten (n = 10) dorso/palmar, latero/medial, and oblique views of equine metacarpophalangeal joints affected by osteoarthritis were examined. Nine assessment points were graded (scale: 0–3) twice by five veterinary students (inexperienced group, I) and four equine veterinary surgeons (expert group, E). The grades for each of the nine factors were summed to obtain the osteophytosis score. The variability between the two measurements was −2.04 ± 3.5, 95% CI −3.04 to −1.03 for the I group. For the E group, they were 0 ± 1.43, 95% CI −0.45 to 0.45. In the evaluation of the same radiographs, the I group had a coefficient of variability (CV) of 37.29%. The correlation was r = 0.90%. The CV between groups was 28.85%. The mean difference between the two observations was -0.03 ± 0.29 in the E group and 0.22 ± 0.77 in the I group. The I group showed a greater CV when the score was low (r = −0.78) compared to the E group, where the CV was independent of severity of osteophytosis (r = −0.47). The osteophytosis scoring system is an easily applicable and feasible system to be used by observers with different levels of experience, but inexpert observers may need additional training or may need to be helped by reference images. These data are validated by the low inter- and intra-observer measurement variability results in the E group. Therefore, the scoring system proposed seems to be a repeatable instrument applicable to the radiographic score of the severity of metacarpophalangeal joint osteoarthritis.

Osteoarthritis, Osteophytes, and Enthesophytes Affect Biomechanical Function in Adults With X-linked Hypophosphatemia

CONTEXT

X-Linked hypophosphatemia (XLH) is a lifelong metabolic disease with musculoskeletal comorbidities that dominate the adult clinical presentation.

OBJECTIVE

The adult XLH disorder has yet to be quantified on the basis of the physical and functional limitations that can affect activities of daily living. Our goal was to report the impact of the musculoskeletal manifestations on physical function.

DESIGN AND SETTING

Musculoskeletal function was evaluated by validated questionnaires and in an interdisciplinary clinical space where participants underwent full-body radiologic imaging, goniometric range of motion (ROM) measurements, general performance tests, and kinematic gait analysis.

PATIENTS

Nine adults younger than 60 years with a diagnosis of XLH and self-reported musculoskeletal disability, but able to independently ambulate, were selected to participate. Passive ROM and gait analysis were also performed on age-approximated controls to account for differences between individual laboratory instrumentation.

RESULTS

Enthesophytes, degenerative arthritis, and osteophytes were found to be consistently bilateral and diffusely present at the spine and synovial joints across participants, with predominance at weight-bearing joints. Passive ROM in adults with XLH was decreased at the cervical spine, hip, knee, and ankle compared to controls. Gait analysis relative to controls revealed increased step width, markedly increased lateral trunk sway, and physical restriction at the hip, knees, and ankle joints that translated into limitations through the gait cycle.

CONCLUSIONS

The functional impact of XLH musculoskeletal comorbidities supports the necessity for creating an interprofessional health-care team with the goal of establishing a longitudinal plan of care that considers the manifestations of XLH across the lifespan.

Improvement of bone-erosive temporomandibular joint (TMJ) abnormalities in adolescents undergoing non-surgical treatment: a longitudinal study

OBJECTIVES

To investigate the longitudinal changes of the imaging temporomandibular joint (TMJ) characteristics in young patients with TMJ-related symptoms and treated with non-surgical methods. The severity of self-reported symptoms at follow-up was also investigated.

METHODS

A cone beam CT (CBCT)/CT follow-up examination [median follow-up 4.1 (1.3-6.4) years] was performed in 22 patients with erosive TMJ abnormalities [baseline median age 16 (12-18) years]. Imaging characteristics were analyzed and the changes between the examinations were categorized as (A) improvement, (B) no change, or (C) worsening. Severity of follow-up symptoms was evaluated using Jaw Functional Limitation Scale (JFLS-8) and Graded Chronic Pain Scale (Grade 0-IV). Analyses were performed separately for left and right TMJ. Findings at baseline and follow-up were compared using McNemar test to account for dependencies. Changes in proportions of hard tissue findings between examinations were assessed using Wilcoxon signed ranks test.

RESULTS

A significant reduction in the proportion of patients with erosive abnormalities was found [59.1%, 95% CI (36.4-79.3) %]. Baseline erosions improved in 9/12 (75%) right and 14/15 (93%) left TMJs. About half repaired; developed an intact cortical outline. Number of joints with osteophytes increased (right: p < 0.04, left: p < 0.003). New osteophytes were mostly found in joints with erosive findings. Low or no limitation of jaw function (Jaw Functional Limitation Scale) was found in 12/22 (55%) and no or low intensity of pain (Graded Chronic Pain Scale Grade 0 or I) in 19/22 (86%) at follow-up.

CONCLUSION

We found a high potential for repair of erosive TMJ abnormalities. However, the patient series was small. The majority of patients assessed their symptom severity at follow-up as low.

Associations of serum citrate levels with knee structural changes and cartilage enzymes in patients with knee osteoarthritis

OBJECTIVE

The aim of this study was to investigate cross-sectional associations between serum levels of citrate and knee structural changes and cartilage enzymes in patients with knee osteoarthritis (OA).

METHOD

A total of 137 subjects with symptomatic knee OA (mean age 55.0 years, range 34-74, 84% female) were included. Knee radiography was used to assess knee osteophytes, joint space narrowing (JSN) and radiographic OA assessed by Kellgren-Lawrence (K-L) grading system. T2-weighted fat-suppressed fast spin echo magnetic resonance imaging (MRI) was used to determine knee cartilage defects, bone marrow lesions (BMLs) and infrapatellar fat pad (IPFP) signal intensity alternations. Colorimetric fluorescence was used to measure the serum levels of citrate. Enzyme-linked immunosorbent assay was used to measure the serum cartilage enzymes including matrix metalloproteinase (MMP)-3 and MMP-13.

RESULTS

After adjustment for potential confounders (age, sex, body mass index), serum citrate was negatively associated with knee osteophytes at the femoral site, cartilage defects at medial femoral site, total cartilage defects, and total BMLs (odds ratio [OR] 0.17-0.30, all P < .05). Meanwhile, serum citrate was negatively associated with IPFP signal intensity alteration (OR 0.30, P = .05) in multivariable analyses. Serum citrate was significantly and negatively associated with MMP-13 (β -3106.37, P < .05) after adjustment for potential confounders. However, citrate was not significantly associated with MMP-3 in patients with knee OA.

CONCLUSION

Serum citrate was negatively associated with knee structural changes including femoral osteophytes, cartilage defects, and BMLs and also serum MMP-13 in patients with knee OA, suggesting that low serum citrate may be a potential indicator for advanced knee OA.

COL2A1 and Caspase-3 as Promising Biomarkers for Osteoarthritis Prognosis in an Equus asinus Model

Osteoarthritis (OA) is one of the most degenerative joint diseases in both human and veterinary medicine. The objective of the present study was the early diagnosis of OA in donkeys using a reliable grading of the disease based on clinical, chemical, and molecular alterations. OA was induced by intra-articular injection of 25 mg monoiodoacetate (MIA) as a single dose into the left radiocarpal joint of nine donkeys. Animals were clinically evaluated through the assessment of lameness score, radiographic, and ultrasonographic findings for seven months. Synovial fluid and cartilage samples were collected from both normal and diseased joints for the assessment of matrix metalloproteinases (MMPs) activity, COL2A1 protein expression level, and histopathological and immunohistochemical analysis of Caspase-3. Animals showed the highest lameness score post-induction after one week then decreased gradually with the progression of radiographical and ultrasonographic changes. MMP activity and COL2A1 and Caspase-3 expression increased, accompanied by articular cartilage degeneration and loss of proteoglycan. OA was successfully graded in Egyptian donkeys, with the promising use of COL2A1and Caspase-3 for prognosis. However, MMPs failed to discriminate between early and late grades of OA.

Multiscale bone quality analysis in osteoarthritic knee joints reveal a role of the mechanosensory osteocyte network in osteophytes

Osteophytes - bony outgrowths on joint structures - are found in healthy individuals but are specifically present in late osteoarthritis (OA). Osteophyte development and function is not well understood, yet biomechanical stimuli are thought to be critical. Bone adapts to mechanical forces via the cellular network of osteocytes. The involvement of osteocytes in osteophyte formation and maturation has not been unravelled. Forty-three osteophytes from tibias of 23 OA patients (65 ± 9 years) were analysed. The trabecular bone structure of osteophytes presented with fewer trabeculae of lower bone mineral density compared to subchondral bone. We identified 40% early stage and 60% late stage osteophytes that significantly differed in their trabecular bone characteristics. Osteophyte bone revealed a higher number of osteocytes and a lower number of empty osteocyte lacunae per bone area than the subchondral bone. We found that OA osteophytes consist of younger bone material comprised of woven and lamellar bone with the capacity to develop into a late stage osteophyte potentially via the involvement of the osteocyte network. Our analysis of OA osteophytes implies a transition from woven to lamellar bone as in physiological bone growth within a pathological joint. Therefore, osteophyte development and growth present a valuable research subject when aiming to investigate the osteogenic signalling cascade.

Surface Replacement Arthroplasty Using a Volar Approach for Osteoarthritis of Proximal Interphalangeal Joint: Results After a Minimum 5-Year Follow-up

Background: Surface replacement arthroplasty (SRA) through a volar approach for the proximal interphalangeal (PIP) joint can preserve the integrity of the extensor tendon, which allows early range of motion (ROM) exercise postoperatively. However, a few reports have shown that the PIP ROM tends to decline with longer follow-up. The goal of this study is to assess the results of at least 5 years of follow-up of SRA through a volar approach and also to investigate the cause of deterioration of ROM with time after SRA through this approach. Methods: Eleven fingers with degenerative osteoarthritis that underwent SRA through the volar approach were examined. ROM of the PIP joint preoperation, 1 year after the surgery, and at final follow-up was measured and statistically analyzed. Also, the relationship between PIP ROM and the osteophyte developed postoperatively was examined. Results: The average follow-up period was 7.3 years. The average PIP ROM of the PIP joints was 52.3° preoperatively, 54.1° at 1 year postoperatively, and 31.1° at the final follow-up. PIP ROM at the final follow-up was significantly decreased compared with that preoperatively or at 1 year postoperatively. Also, the development of an osteophyte was negatively correlated with the ROM of the PIP joint at the final follow-up. Conclusions: PIP ROM after SRA through a volar approach has the tendency to deteriorate with a longer follow-up. Development of an osteophyte is considered to be a main risk factor of deterioration in the cases of SRA through a volar approach.

Skeletal malformations and developmental arthropathy in individuals who have fibrodysplasia ossificans progressiva

RATIONALE

Fibrodysplasia ossificans progressiva (FOP) is primarily a disease of progressive heterotopic ossification (HO) leading to impaired mobility throughout life. An additional diagnostic feature is a characteristic malformation of the great toes. The culpable gene for FOP,ACVR1 (activin A receptor type 1) has a clear effect on the induction of extra-skeletal bone formation. However, this bone morphogenetic protein (BMP) pathway receptor is expressed widely throughout skeletal development and has a seminal role in axial and appendicular chondrogenesis, prompting suspicion of widespread bone and joint defects in those with ACVR1 mutations.

MATERIALS AND METHODS

We analyzed baseline whole body (minus skull) computed tomographic (CT) scans of 113 individuals with classic clinical features of FOP and the ACVR1 (R206H) mutation who were enrolled in a non-interventional natural history study ((NCT02322255)) for skeletal malformations, atypical morphology, intra-articular synovial osteochondromatosis, developmental arthropathy, and associated degenerative joint phenotypes. Individuals were evaluated in three age groups: 4-13; 14-25; and 25-56 years old, based on historical models of FOP disease progression.

RESULTS

We found widespread evidence of developmental arthropathy throughout the axial and appendicular skeleton in all age groups (61M, 52F; ages: 4-56 years). Asymmetric narrowing and subchondral sclerosis were present throughout the joints of the normotopic skeleton and osteophytes were common in the hips and knees of individuals who have FOP in all age groups. The costovertebral joints, intervertebral facet joints, and proximal tibio-fibular joints frequently showed partial or total intra-articular ankylosis, particularly after age 13. The hips of FOP subjects are frequently malformed and dysplastic. We also found evidence of degenerative joint phenotypes after age 13, particularly in the spine, sacro-iliac joints, and lower limbs.

CONCLUSIONS

The effects of ACVR1 mutation on the normotopic skeletons of individuals who have FOP extend beyond malformation of the great toes and include both morphological defects and developmental arthropathy. Associated degenerative joint disease occurring at multiple sites starts in adolescence and progresses throughout life. These phenotypes appear to be uncoupled from heterotopic bone formation, indicating a potential role for ACVR1 in the development and progression of degenerative joint disease.

SIGNIFICANCE

FOP is a disease of not only progressive heterotopic ossification, but also widespread and extensive developmental arthropathy and associated degenerative joint disease. These findings have relevance for understanding the natural history of FOP and for designing and evaluating clinical trials with emerging therapeutics.

Cartilage Extracellular Matrix Scaffold With Kartogenin-Encapsulated PLGA Microspheres for Cartilage Regeneration

Repair of articular cartilage defects is a challenging aspect of clinical treatment. Kartogenin (KGN), a small molecular compound, can induce the differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) into chondrocytes. Here, we constructed a scaffold based on chondrocyte extracellular matrix (CECM) and poly(lactic-co-glycolic acid) (PLGA) microspheres (MP), which can slowly release KGN, thus enhancing its efficiency. Cell adhesion, live/dead staining, and CCK-8 results indicated that the PLGA(KGN)/CECM scaffold exhibited good biocompatibility. Histological staining and quantitative analysis demonstrated the ability of the PLGA(KGN)/CECM composite scaffold to promote the differentiation of BMSCs. Macroscopic observations, histological tests, and specific marker analysis showed that the regenerated tissues possessed characteristics similar to those of normal hyaline cartilage in a rabbit model. Use of the PLGA(KGN)/CECM scaffold may mimic the regenerative microenvironment, thereby promoting chondrogenic differentiation of BMSCs in vitro and in vivo. Therefore, this innovative composite scaffold may represent a promising approach for acellular cartilage tissue engineering.

Osteoarthritis from evolutionary and mechanistic perspectives

Developmental osteogenesis and the pathologies associated with tissues that normally are mineralized are active areas of research. All of the basic cell types of skeletal tissue evolved in early aquatic vertebrates. Their characteristics, transcription factors, and signaling pathways have been conserved, even as they adapted to the challenge imposed by gravity in the transition to terrestrial existence. The response to excess mechanical stress (among other factors) can be expressed in the pathologic phenotype described as osteoarthritis (OA). OA is mediated by epigenetic modification of the same conserved developmental gene networks, rather than by gene mutations or new chemical signaling pathways. Thus, these responses have their evolutionary roots in morphogenesis. Epigenetic channeling and heterochrony, orchestrated primarily by microRNAs, maintain the sequence of these responses, while allowing variation in their timing that depends at least partly on the life history of the individual.

The Roles of Indian Hedgehog Signaling in TMJ Formation

The temporomandibular joint (TMJ) is an intricate structure composed of the mandibular condyle, articular disc, and glenoid fossa in the temporal bone. Apical condylar cartilage is classified as a secondary cartilage, is fibrocartilaginous in nature, and is structurally distinct from growth plate and articular cartilage in long bones. Condylar cartilage is organized in distinct cellular layers that include a superficial layer that produces lubricants, a polymorphic/progenitor layer that contains stem/progenitor cells, and underlying layers of flattened and hypertrophic chondrocytes. Uniquely, progenitor cells reside near the articular surface, proliferate, undergo chondrogenesis, and mature into hypertrophic chondrocytes. During the past decades, there has been a growing interest in the molecular mechanisms by which the TMJ develops and acquires its unique structural and functional features. Indian hedgehog (Ihh), which regulates skeletal development including synovial joint formation, also plays pivotal roles in TMJ development and postnatal maintenance. This review provides a description of the many important recent advances in Hedgehog (Hh) signaling in TMJ biology. These include studies that used conventional approaches and those that analyzed the phenotype of tissue-specific mouse mutants lacking Ihh or associated molecules. The recent advances in understanding the molecular mechanism regulating TMJ development are impressive and these findings will have major implications for future translational medicine tools to repair and regenerate TMJ congenital anomalies and acquired diseases, such as degenerative damage in TMJ osteoarthritic conditions.

Longitudinal MRI structural findings observed in accelerated knee osteoarthritis: data from the Osteoarthritis Initiative

OBJECTIVE

To analyze structural, longitudinal MRI findings during the development of accelerated knee osteoarthritis (AKOA) over 4 years.

MATERIALS AND METHODS

From the Osteoarthritis Initiative (OAI), knees with no radiographic osteoarthritis (KL 0/1) developing advanced-stage osteoarthritis (KL 3/4; AKOA) within a 4-year (y) timeframe were selected. MRIs were graded using the modified Whole-Organ Magnetic Resonance Imaging Score (WORMS) at the beginning of the 4-year timeframe (index visit), at 2-year, and 4-year follow-up. Morphological and clinical findings associated with KL 3/4 onset within 2 years compared to 4 years were assessed using generalized estimating equations.

RESULTS

AKOA was found in 162 knees of 149 subjects (age 63.25 ± 8.3; 103 females; BMI 29.4 ± 3.9). Moderate to severe meniscal lesions WORMS ≥ 3 were present in 25% (41/162) at the index visit, 64% (104/162) at 2-year and 93% (151/162) at 4-year follow-up. Meniscal extrusion was the most prevalent finding (ranging from 18% at the index visit, 45% at 2-year and 94% at 4-year follow-up) and root tears were the most common types of tears (9% at the index visit; 22% at 2 years and 38% at 4 years). Risk factors associated with KL 3/4 onset within 2 years included root tears at the index visit (adjusted OR, 2.82; 95% CI: 1.33, 6.00; p = 0.007) and incident knee injury (42%, 49/116 vs. 24%, 11/46, p = 0.032).

CONCLUSIONS

Meniscal abnormalities, in particular extrusion and root tears, were the most prevalent morphological features found in subjects with AKOA. These results suggest that meniscal abnormalities have a significant role in accelerated progression of OA.

Association between cervical degeneration and self-perceived nonrecovery after whiplash injury

BACKGROUND CONTEXT

Pre-existing radiological degenerative changes have not previously been considered a risk factor for nonrecovery from neck pain due to motor vehicle accidents (MVA). Results from previous studies are however often based on assessment of plain radiography or MRI and little consideration has been given to facet joints. Furthermore, previous studies have often lacked a validated scoring system for degenerative changes.

PURPOSE

To investigate the association between cervical degeneration on computed tomography (CT) and nonrecovery after whiplash trauma.

STUDY DESIGN

Longitudinal cohort study.

PATIENT SAMPLE

One hundred twenty-one patients attending the Emergency Department because of neck pain after MVA, 2015-2017, with a valid CT-scan of the cervical spine and completion of follow up after 6 months.

OUTCOME MEASURES

The primary outcome measure was self-perceived nonrecovery (yes/no) after 6 months. A secondary outcome measure was self-reported pain level (Numeric Rating Scale).

METHODS

Baseline data regarding demographics and health factors were gathered through a web-based questionnaire. Degeneration of facet joints and intervertebral discs was assessed on CT-scans according to a validated scoring system. Binary logistic regression was used to study the association between cervical degeneration and nonrecovery.

RESULTS

Moderate facet joint degeneration was associated with nonrecovery. In the group with moderate degree of facet joint degeneration, 69.6% reported nonrecovery compared with 23.6% among patients without any signs of degeneration (adjusted odds ratio 6.7 [95% confidence interval: 1.9-24.3]). There was no association between disc degeneration and nonrecovery. Combined facet joint degeneration and disc degeneration were associated with nonrecovery (adjusted odds ratio 6.2 [2.0-19.0]).

CONCLUSIONS

These results suggest that cervical degeneration, especially facet joint degeneration, is a risk factor for nonrecovery after whiplash trauma. We hypothesize that whiplash trauma can be a trigger for painful manifestation of previously asymptomatic facet joint degeneration.

Visualization and quantification of the degenerative pattern of the talus in unilateral varus ankle osteoarthritis

The aim of this study was to quantify and visualize the degenerative patterns of the talus in ankle osteoarthritis (OA). The differences in talar morphology between sides of patients with unilateral varus ankle OA (medial talar tilt > 4°) were compared. Computed tomography images of both feet of 35 patients (OA: 22 patients, control: 13 patients) were analyzed. Each surface model of the right and left tali was registered to the opposite talus via a mirror-image technique and an iterative closest point algorithm. The surface deviation between the two models was quantified and visualized by deviation color maps. The results quantitatively demonstrated that osteophytes are generated in the area under the antero-medial margin of the trochlea in OA tali. In severe OA tali, bone resorption of more than 2 mm in the medial portion of the trochlea, as well as a similar degree of osteophyte formation on the lateral surface, was also seen. Stereotypical patterns of degeneration occurring in OA tali were successfully visualized and quantified by left-right comparison of patients with unilateral ankle OA. Such information would contribute to better understanding of the development of ankle OA and preoperative planning of total ankle arthroplasty and arthrodesis.

A Jack of All Trades: Impact of Glucocorticoids on Cellular Cross-Talk in Osteoimmunology

Glucocorticoids (GCs) are known to have a strong impact on the immune system, metabolism, and bone homeostasis. While these functions have been long investigated separately in immunology, metabolism, or bone biology, the understanding of how GCs regulate the cellular cross-talk between innate immune cells, mesenchymal cells, and other stromal cells has been garnering attention rather recently. Here we review the recent findings of GC action in osteoporosis, inflammatory bone diseases (rheumatoid and osteoarthritis), and bone regeneration during fracture healing. We focus on studies of pre-clinical animal models that enable dissecting the role of GC actions in innate immune cells, stromal cells, and bone cells using conditional and function-selective mutant mice of the GC receptor (GR), or mice with impaired GC signaling. Importantly, GCs do not only directly affect cellular functions, but also influence the cross-talk between mesenchymal and immune cells, contributing to both beneficial and adverse effects of GCs. Given the importance of endogenous GCs as stress hormones and the wide prescription of pharmaceutical GCs, an improved understanding of GC action is decisive for tackling inflammatory bone diseases, osteoporosis, and aging.

Characterization of bony changes localized to the cervical articular processes in a mixed population of horses

The objectives of this observational, cross-sectional study were to characterize and establish the prevalence of osseous proliferation of articular surfaces, joint margins and adjacent soft tissue attachments (i.e., joint capsule and deep spinal muscles) in a mixed population of horses of variable ages, sizes, and breeds to better capture the full spectrum of disease affecting the cervical articular processes. Cranial and caudal articular processes of the cervical and first three thoracic vertebrae (C2-T3) from 55 horses without a primary complaint of neck pain were evaluated for the presence and severity of abnormal bony changes. Data were analyzed to compare alterations in joint margin quadrants, paired articular surfaces within a synovial articulation, left-right laterality, and vertebral level distributions and to determine associations with age, wither height and sex. Seventy-two percent of articular processes had bony changes that were considered abnormal. Osteophyte formation was the most common bony change noted. Overall grades of severity included: normal (28%), mild (45%), moderate (22%), and severe (5%). The highest prevalence of mild changes was localized to the C3-C6 vertebral levels; moderate changes to C6-T2; and severe changes to C2-C3 and C6-T2. Most paired articular surfaces and left-right grades of severity were not significantly different. The grade of osseous pathology was positively associated with both age and wither height. A high prevalence and wide variety of abnormal bony changes of varying severity were found in articular processes across all vertebral levels. The clinical significance of the described lesions is unknown, but the findings are expected to enhance the reporting of articular process and periarticular changes noted on advanced diagnostic imaging of the equine cervical and cranial thoracic vertebral regions.

Features of the Femoral Proximocaudal Joint Capsule Insertion Among Canids

This observational study was conducted to evaluate the anatomic relationship between the proximocaudal femoral joint capsule insertion and the femoral caudolateral curvilinear osteophyte (CCO), across ancient and modern domestic and non-domestic canids. Museum specimens of proximal femora were screened for presence of remnant enthesophytes of the caudal joint capsule insertion (first inclusion criterion) and then for the CCO (second inclusion criterion). The initially screened population included 267 dry bone specimens: Six Canis species, hybrid coyote × domestic dog, and five vulpines (three Vulpes species, one Urocyon, and one Nyctereutes). Proximocaudal joint capsule insertion remnant enthesophytes were limiting at n = 19 specimens: Seven ancient domestic dogs, four modern coyotes, two ancient coyotes, two modern hybrid coyote × dog, two modern red foxes, and two modern raccoon dogs. The joint capsule enthesophytes are associated with inflammation, but are observed far less frequently than the CCO. The CCO is seen radiographically but is visible more frequently by direct inspection. The primary inclusion criterion necessarily was a visible caudal joint capsule insertion; spatial relationships of the CCO can be assigned with confidence only when a capsule insertion line can be recognized clearly. We demonstrate that the anatomic CCO associates with the joint capsule insertion being nonspecific and species-independent. A joint capsule insertion-CCO spatial relationship across species is an important new observation, strongly indicating that both are pathological features. Our data indicate need for new research to characterize the canid coxofemoral joint and its overt and incipient pathology in a phylogenetic context. Anat Rec, 302:2164-2170, 2019. © 2019 American Association for Anatomy.

Osteophyte growth in early thumb carpometacarpal osteoarthritis

OBJECTIVE

Osteophyte formation is a critical part of the degeneration of a joint with osteoarthritis (OA). While often qualitatively described, few studies have succeeded in quantifying osteophyte growth over time. Using computed tomography (CT) image data from a longitudinal, observational study of thumb carpometacarpal (CMC) OA, our aim was to quantify osteophyte growth volume and location over a three-year period in men and women.

METHOD

Ninety patients with early thumb OA were recruited and assessed at baseline, 1.5 years, and 3 years with CT imaging. Osteophyte volume and location on the trapezium and first metacarpal were determined using a library of 46 healthy subjects as a nonarthritic reference database.

RESULTS

There was a significant increase in osteophyte volume for women and men over the three-year follow-up in the trapezium (86.8 mm³-120.5 mm³ and 165.1 mm³-235.3 mm³, means respectively) and in the proximal metacarpal (63 mm³-80.4 mm³, and 115.8 mm³-161.7 mm³, respectively). The location of osteophyte initiation and growth was consistent across subjects and was located in non-opposing regions on the trapezium and first metacarpal. Osteophyte growth occurred about the radial and ulnar margins of the trapezial facet, while on the proximal metacarpal, growth occurred principally about the volar and dorsal margins of the facet.

CONCLUSION

Osteophyte growth occurred in early thumb osteoarthritis over three years. Growth was localized in specific, non-opposing regions on the trapezium and metacarpal, raising intriguing questions about the triggers for their formation, whether the mechanisms are mechanical, biological or a combination of both.

The Biomechanical Effect of the Sagittal Split Ramus Osteotomy on the Temporomandibular Joint: Current Perspectives on the Remodeling Spectrum

The sagittal split ramus osteotomy is a key approach for treating dentofacial deformities. Although it delivers excellent results, the sagittal split ramus osteotomy is believed to induce stress to the temporomandibular joint. Potential stress inducers could be classified as intra- and postoperative factors resulting in an inflammatory response and molecular cascades, which initiate physiological remodeling. Occasionally, this process exceeds its capacity and causes pathological remodeling, through either degenerative joint disease or condylar resorption. Hard evidence on how orthognathic surgery causes inflammation and how this inflammation is linked to the spectrum of remodeling remains scarce. Current concepts on this matter are mainly based on clinical observations and molecular mechanisms are extrapolated from fundamental research in other body parts or joints. This perspective study provides an overview of current knowledge on molecular pathways and biomechanical effects in temporomandibular joint remodeling. It provides research directions that could lead to acquiring fundamental evidence of the relation of orthognathic surgery and inflammation and its role in remodeling. Performing osteotomies in animal models and identifying inflammatory mediators as well as their effect on the joint seem promising. Patients affected by pathological remodeling can also provide samples for histological as well as molecular analysis. Individual susceptibility analysis by linking certain suspect phenotypes to genetic variation could identify the cause and molecular pathway responsible for degenerative joint disease and condylar resorption, ultimately leading to clinically applicable treatment and prevention strategies.

Involvement of ADAM12 in Chondrocyte Differentiation by Regulation of TGF-β1-Induced IGF-1 and RUNX-2 Expressions

A disintegrin and metalloproteinase 12 (ADAM12) is known to be involved in chondrocyte proliferation and maturation; however, the mechanisms are not fully understood. In this study, expression and localization of ADAM12 during chondrocyte differentiation were examined in the mouse growth plate by immunohistochemistry. Adam12 expression during ATDC5 chondrogenic differentiation was examined by real-time PCR and compared with the expression pattern of type X collagen. The clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system was used to generate Adam12-knockout (KO) ATDC5 cells. Adam12-KO and Adam12 overexpressing cells were used for analyses of ADAM12 expression with or without TGF-β1 stimulation. ADAM12 was identified predominantly in chondrocytes of the proliferative zone in mouse growth plates by immunohistochemistry. Adam12 was upregulated prior to Col10a1 during chondrogenic differentiation in wild-type ATDC5 cells. In Adam12-KO ATDC5 cells, following initiation of chondrogenic differentiation, we observed a reduction in Igf-1 expression along with an upregulation of hypertrophy-associated Runx2, Col10a1, and type X collagen protein expressions. In ATDC5 wild-type cells, stimulation with TGF-β1 upregulated the expressions of Adam12 and Igf-1 and downregulated the expression of Runx2. In contrast, in Adam12-KO ATDC5 cells, these TGF-β1-induced changes were suppressed. Adam12 overexpression resulted in an upregulation of Igf-1 and downregulation of Runx2 expression in ATDC5 cells. The findings suggest that ADAM12 has important role in the regulation of chondrocyte differentiation, potentially by regulation of TGF-β1-dependent signaling and that targeting of ADAM12 may have a role in management of abnormal chondrocyte differentiation.