The development of posttraumatic arthritis after articular fracture

Palmitate has proapoptotic and proinflammatory effects on articular cartilage and synergizes with interleukin-1

OBJECTIVE

Obesity is a major risk factor for the development of osteoarthritis (OA) that is associated with a state of low-grade inflammation and increased circulating levels of adipokines and free fatty acids (FFAs). The aim of this study was to analyze the effects of saturated (palmitate) and monounsaturated (oleate) FFAs on articular chondrocytes, synoviocytes, and cartilage.

METHODS

Human articular chondrocytes and fibroblast-like synoviocytes obtained from young healthy donors and OA chondrocytes from patients undergoing total knee replacement surgery were treated with palmitate or oleate alone or in combination with interleukin-1β (IL-1β). Cell viability, caspase activation, and gene expression of proinflammatory factors, extracellular matrix (ECM) proteins, and proteases were studied. In addition, chondrocyte viability, IL-6 production, and matrix damage were assessed in bovine and human articular cartilage explants cultured with FFAs in the presence or absence of IL-1β.

RESULTS

Palmitate, but not oleate, induced caspase activation and cell death in IL-1β-stimulated normal chondrocytes, and up-regulated the expression of IL-6 and cyclooxygenase 2 in chondrocytes and fibroblast-like synoviocytes through Toll-like receptor 4 (TLR-4) signaling. In cartilage explants, palmitate induced chondrocyte death, IL-6 release, and ECM degradation. Palmitate synergized with IL-1β in stimulating proapoptotic and proinflammatory cellular responses. Pharmacologic inhibition of caspases or TLR-4 signaling reduced palmitate and IL-1β induced cartilage damage.

CONCLUSION

Palmitate acts as a proinflammatory and catabolic factor that, in synergy with IL-1β, induces chondrocyte apoptosis and articular cartilage breakdown. Collectively, our data suggest that elevated levels of saturated FFAs that are often found in patients who are obese may contribute to the pathogenesis of OA.

Targeting pro-inflammatory cytokines following joint injury: acute intra-articular inhibition of interleukin-1 following knee injury prevents post-traumatic arthritis

Introduction

Post-traumatic arthritis (PTA) is a progressive, degenerative response to joint injury, such as articular fracture. The pro-inflammatory cytokines, interleukin 1(IL-1) and tumor necrosis factor alpha (TNF-α), are acutely elevated following joint injury and remain elevated for prolonged periods post-injury. To investigate the role of local and systemic inflammation in the development of post-traumatic arthritis, we targeted both the initial acute local inflammatory response and a prolonged 4 week systemic inflammatory response by inhibiting IL-1 or TNF-α following articular fracture in the mouse knee.

Methods

Anti-cytokine agents, IL-1 receptor antagonist (IL-1Ra) or soluble TNF receptor II (sTNFRII), were administered either locally via an acute intra-articular injection or systemically for a prolonged 4 week period following articular fracture of the knee in C57BL/6 mice. The severity of arthritis was then assessed at 8 weeks post-injury in joint tissues via histology and micro computed tomography, and systemic and local biomarkers were assessed in serum and synovial fluid.

Results

Intra-articular inhibition of IL-1 significantly reduced cartilage degeneration, synovial inflammation, and did not alter bone morphology following articular fracture. However, systemic inhibition of IL-1, and local or systemic inhibition of TNF provided no benefit or conversely led to increased arthritic changes in the joint tissues.

Conclusion

These results show that intra-articular IL-1, rather than TNF-α, plays a critical role in the acute inflammatory phase of joint injury and can be inhibited locally to reduce post-traumatic arthritis following a closed articular fracture. Targeted local inhibition of IL-1 following joint injury may represent a novel treatment option for PTA.

Soft tissue knee injury with concomitant osteochondral fracture is associated with higher degree of acute joint inflammation

BACKGROUND

Osteochondral fractures are often seen on magnetic resonance imaging (MRI) of acutely injured knees, but their existence has gained little interest because of a lack of knowledge of their relation to treatment options and outcome. It is not clear whether acute phase synovial fluid (SF) concentrations of cartilage and bone markers and proinflammatory cytokines are different between traumatically injured knees with or without osteochondral fracture.

HYPOTHESIS

Acutely injured knees with an osteochondral fracture, particularly fractures with disrupted cortical bone, have higher concentrations of bone markers and cytokines than do knees without an osteochondral fracture.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Synovial fluid (hemarthrosis) was aspirated (median 1 day after injury) and 1.5-T MRI was performed (median 8 days after injury) in the acutely injured knee of 98 individuals (26% women; mean age, 23 years). As visualized on MRI, 39% knees had an osteochondral fracture with disrupted cortical bone, 30% had an osteochondral fracture with intact cortical bone, and 32% did not have an osteochondral fracture. Concentrations of sulfated glycosaminoglycan, ARGS aggrecan, cartilage oligomeric matrix protein, osteocalcin, secreted protein acidic and rich in cysteine (SPARC), osteopontin and proinflammatory cytokines (interleukin [IL]-1β, IL-6, IL-8, and tumor necrosis factor [TNF]-α) were analyzed.

RESULTS

After adjusting for days between injury and SF aspiration, age at injury, and sex, knees with any osteochondral fracture (with or without disrupted cortical bone) had significantly higher SF concentrations of TNF-α (median [interquartile range (IQR)] = 9 [7-12] pg/mL vs. 7 [5-14] pg/mL; P = .013), whereas knees with an osteochondral fracture with disrupted cortical bone had significantly higher SF concentrations (medians [IQRs]) of SPARC (492 [328-754] ng/mL vs. 407 [140-685] ng/mL; P = .030), IL-8 (278 [148-628] pg/mL vs. 138 [67-413] pg/mL; P = .028), and TNF-α (11 [7-15] pg/mL vs. 7 [5-14] pg/mL; P = .004) compared with knees without an osteochondral fracture.

CONCLUSION

In acutely injured knees with hemarthrosis, a concomitant osteochondral fracture with disrupted cortical bone is associated with a higher degree of joint inflammation.

Factors predicting the development of early osteoarthritis following lateral tibial plateau fractures: mid-term clinical and radiographic outcomes of 73 operatively treated patients

Background and Aims:

The indications for operative treatment of lateral tibial plateau fractures are still controversial. The objective of this study was to determine whether residual articular surface depression and valgus malalignment of plated lateral tibial plateau fractures at medium-term follow-up affect the clinical and radiographic outcomes.

Material and Methods:

A chart review of patients with operatively treated (AO type B3.1) tibial plateau fractures that were admitted to our level I trauma center between 2002 and 2008 was performed. Out of 123 patients, 73 were available to participate in a clinical and radiographic follow-up examination. The mean follow-up time was 54 months. Patients were clinically assessed and completed the Lysholm knee score and Western Ontario and McMaster Universities Osteoarthritis Index. Maximal articular surface depression, radiological mechanical axis, and degree of posttraumatic osteoarthritis were evaluated from standing radiographs.

Results:

Patients with valgus malalignment of 5° or greater at follow-up developed more advanced osteoarthritis (Kellgren–Lawrence grade 3–4) than patients with a normal mechanical axis (p = 0.006). Similarly, patients with articular depression greater than 2 mm at follow-up also developed more advanced osteoarthritis compared to patients with a depression of 2 mm or less (p = 0.001). The degree of valgus malalignment or articular depression had no effect on the Western Ontario and McMaster Universities Osteoarthritis Index or Lysholm scores.

Conclusions:

The postoperative articular congruity and normal mechanical axis of the lower leg after plate fixation in lateral tibial plateau fractures seem to have a role in prevention of posttraumatic osteoarthritis but does not appear to predict clinical outcome at medium-term follow-up. The role of initial dislocation and associated cartilage damage in the development of osteoarthritis following these fractures is still unknown.

Factors associated with self-reported arthritis 7 to 24 years after a traumatic brain injury

The purpose of this study was to profile characteristics of people with traumatic brain injury (TBI) who self-reported arthritis 7 to 24 yr. post-injury. Pre- and post-injury socio-demographic factors, injury-related factors, and postinjury standardized assessments measuring health, activity, and participation outcomes were assessed in a retrospective cohort study of 274 participants. The group self-reporting arthritis had significantly more sleep disturbances, poorer overall health, lower mental health and physical function, and decreased productivity. Also, they were older and reported a shorter length of loss of consciousness from TBI. These resulted suggest that musculoskeletal complaints from long-term survivors of TBI sholud be addressed in post-acute care and could guide future research on arthritis in the TBI population.

Up-regulation of the chemo-attractive receptor ChemR23 and occurrence of apoptosis in human chondrocytes isolated from fractured calcaneal osteochondral fragments

To study the expression level of a panel of pro/anti-apoptotic factors and inflammation-related receptors in chondral fragments from patients undergoing surgical treatment for intra-articular calcaneal fractures, cartilage fragments were retrieved from calcaneal fractures of 20 patients subjected to surgical treatment. Primary cultures were performed using chondral fragments from fractured and control patients. Chondrocyte cultures from each patient of the fractured and control groups were subjected to immunofluorescence staining and quantitatively analyzed under confocal microscopy. Proteins extracted from the cultured chondrocytes taken from the fractured and control groups were processed for Western blot experiments and densitometric analysis. The percentage of apoptotic cells was determined using the cleaved PARP-1 antibody. The proportion of labelled cells was 35% for fractured specimens, compared with 7% for control samples. Quantification of caspase-3 active and Bcl-2 proteins in chondrocyte cultures showed a significant increase of the apoptotic process in fractured specimens compared with control ones. Fractured chondrocytes were positively stained for ChemR23 with statistically significant differences with respect to control samples. Densitometric evaluation of the immunoreactive bands confirmed these observations. Human articular chondrocytes obtained from patients with intra-articular calcaneal fractures express higher levels of pivotal pro-apoptotic factors, and of the chemo-attractive receptor ChemR23, compared with control cultures. On the basis of these observations, the authors hypothesize that consistent prolonged chondrocyte death, associated with the persistence of high levels of pro-inflammatory factors, could enhance the deterioration of cartilage tissue with consequent development of post-traumatic arthritis following intra-articular bone fracture.

The role of cytokines in posttraumatic arthritis

The development of arthritis after joint injury is commonly known as posttraumatic arthritis (PTA). The inciting traumatic event may range from cartilage contusion and bone bruise combined with meniscus or ligament tear, to intra-articular fracture. End-stage PTA is often indistinguishable from primary osteoarthritis. However, knowing the time of the inciting traumatic event in a patient with PTA provides an opportunity to understand the events following joint injury that lead to the progression of arthritis. Joint injury often leads to mechanical alterations in loading of the injured joint, and restoration of joint mechanics through surgical repair remains an important aspect of treatment. However, the accuracy of joint reduction by itself does not account for the variability in outcome following joint injury, as evidenced by the fact that PTA remains a significant clinical problem. Emerging research in animal models and human subjects indicates that several inflammatory cytokines and related inflammatory mediators are elevated following joint injury. Data from animal studies and early clinical trials suggest that early inhibition of the intra-articular inflammatory response may improve clinical outcomes.

Articular Cartilage Repair: Where We Have Been, Where We Are Now, and Where We Are Headed

This review traces the genealogy of the field of articular cartilage repair from its earliest attempts to its present day vast proliferation of research advances. Prior to the 1980s there was only sporadic efforts to regenerate articular cartilage as it was considered to be incapable of regeneration based on historical dogma. The first flurry of reports documented the use of various cell types ultimately leading to the first successful demonstration of autologous chondrocyte transplantation which was later translated to clinical use and has resulted in the revised axiom that cartilage regeneration is possible. The current field of cartilage repair is multifaceted and some of the 1980s' vintage concepts have been revisited with state of the art technology now available. The future of the field is now poised to undertake the repair of whole cartilage surfaces beyond focal defects and an appreciation for integrated whole joint health to restore cartilage homeostasis.

The Roles of Mechanical Stresses in the Pathogenesis of Osteoarthritis: Implications for Treatment of Joint Injuries

Excessive joint surface loadings, either single (acute impact event) or repetitive (cumulative contact stress), can cause the clinical syndrome of osteoarthritis (OA). Despite advances in treatment of injured joints, the risk of OA following joint injuries has not decreased in the last 50 years. Cumulative excessive articular surface contact stress that leads to OA results from post-traumatic joint incongruity and instability, and joint dysplasia, but also may cause OA in patients without known joint abnormalities. In vitro investigations show that excessive articular cartilage loading triggers release of reactive oxygen species (ROS) from mitochondria, and that these ROS cause chondrocyte death and matrix degradation. Preventing release of ROS or inhibiting their effects preserves chondrocytes and their matrix. Fibronectin fragments released from articular cartilage subjected to excessive loads also stimulate matrix degradation; inhibition of molecular pathways initiated by these fragments prevents this effect. Additionally, injured chondrocytes release alarmins that activate chondroprogentior cells in vitro that propogate and migrate to regions of damaged cartilage. These cells also release chemokines and cytokines that may contribute to inflammation that causes progressive cartilage loss. Distraction and motion of osteoarthritic human ankles can promote joint remodeling, decrease pain and improve joint function in patients with end-stage post-traumatic OA. These advances in understanding of how altering mechanical stresses can lead to remodeling of osteoarthritic joints and how excessive stress causes loss of articular cartilage, including identification of mechanically induced mediators of cartilage loss, provide the basis for new biologic and mechanical approaches to the prevention and treatment of OA.

Cryopreservation-Induced Stress on Long-Term Preserved Articular Cartilage

Tissue engineered cartilage constructs have potential clinical applications in human healthcare. Their effective utilization is, however, hampered by the lack of an optimal cryopreservation procedure that ensures their availability as and when required at the patient’s bedside. Cryopreservation-induced stress represents a major barrier towards the cryopreservation of such tissue constructs, and they remain a scientific challenge despite the significant progress in the long-term storage and banking of isolated chondrocytes and thin cartilage tissue slices. These stresses are caused by intra- and extracellular ice crystallization, cryoprotectant (CPA) toxicity, suboptimal rates of cooling and warming, osmotic imbalance, and altered intracellular pH that might cause cellular death and/or a disruption of extracellular matrix (ECM). This paper reviews the cryopreservation-induced stresses on tissue engineered cartilages and discusses how they influence the integrity of the tissue during its long-term preservation. We have also reported how various antioxidants, vitamins, and plant extracts have been used to inhibit and overcome the stress during cryopreservation and provide promising results. Based on the reviewed information, the paper has also proposed some novel ways which might help in increasing the postthawing cell viability of cryopreserved cartilage.

Effects of cartilage impact with and without fracture on chondrocyte viability and the release of inflammatory markers

Post-traumatic arthritis (PTA) frequently develops after intra-articular fracture of weight bearing joints. Loss of cartilage viability and post-injury inflammation have both been implicated as possible contributing factors to PTA progression. To further investigate chondrocyte response to impact and fracture, we developed a blunt impact model applying 70%, 80%, or 90% surface-to-surface compressive strain with or without induction of an articular fracture in a cartilage explant model. Following mechanical loading, chondrocyte viability, and apoptosis were assessed. Culture media were evaluated for the release of double-stranded DNA (dsDNA) and immunostimulatory activity via nuclear factor kappa B (NF-κB) activity in Toll-like receptor (TLR) -expressing Ramos-Blue reporter cells. High compressive strains, with or without articular fracture, resulted in significantly reduced chondrocyte viability. Blunt impact at 70% strain induced a loss in viability over time through a combination of apoptosis and necrosis, whereas blunt impact above 80% strain caused predominantly necrosis. In the fracture model, a high level of primarily necrotic chondrocyte death occurred along the fracture edges. At sites away from the fracture, viability was not significantly different than controls. Interestingly, both dsDNA release and NF-κB activity in Ramos-Blue cells increased with blunt impact, but was only significantly increased in the media from fractured cores. This study indicates that the mechanism of trauma determines the type of chondrocyte death and the potential for post-injury inflammation.

Key Pathways to Prevent Posttraumatic Arthritis for Future Molecule-Based Therapy

Joint injuries are common, especially among young adults aged 18 to 44 years. They are accompanied by a cascade of events that increase the risk of posttraumatic osteoarthritis (PTOA). Therefore, understanding of biological responses that predispose to PTOA should help in determining treatment modalities to delay and/or prevent the onset and progression of the disease. The vast majority of the literature pointed to chondrocyte death and apoptosis, inflammation and matrix damage/fragmentation being the earliest events that follow joint trauma. Together these events lead to the development of osteoarthritis-like focal cartilage lesions that if untreated have a tendency to expand and progress to fully developed disease. Currently, the only treatments available for joint trauma are surgical interventions. Experimental biologic approaches involve engineering of cartilage with the use of cells (stem cells or chondrocytes), juvenile or adult cartilage pieces, scaffolds, and various polymeric matrices. The major challenge for all of them is regeneration of normal functional mature hyaline cartilage that can sustain the load, resist compression, and most important, integrate with the host tissue. If the tissue is spontaneously repaired it fails to reproduce original structure and function and thus, may be more susceptible to re-injury. Thus, there is a critical need to develop novel molecular mechanism-based therapeutic approaches to biologic chondral and/or osteochondral repair. The focus of this review is on the earliest molecular and cellular manifestations of injury that can be grouped based on the following therapeutic options for PTOA: chondroprotection, anti-inflammatory, matrix protection, and matrix remodeling/matrix synthesis.

Clinical outcomes of surgical treatment for talar malunions and nonunions

OBJECTIVE:

To present our experiences of treating talar malunions and nonunions.

METHOD:

Between January 2000 and September 2009, 26 patients with malunions or nonunions after talar fractures underwent surgical treatment according to different types of talar deformities. The treatment outcomes were evaluated using AOFAS ankle-hindfoot scale as well as plain radiographs.

RESULTS:

20 patients were available for follow-up for 30 (range, 24 to 60) months. No wound healing problems or infections occurred and solid unions were achieved in all patients. Radiological unions were achieved at a mean time of 14 (range, 12 to 18) weeks. The mean time to complete weight-bearing was 16 (range, 14 to 20) weeks. The mean AOFAS score increased significantly from 36.2 (range, 27 to 43) to 85.8 (range, 74 to 98).

CONCLUSION:

Surgical interventions for malunions and nonunions after talar fractures can bring about satisfactory outcomes, and the appropriate procedure should be adopted according to different types of posttraumatic deformities. Level of Evidence: IV, Retrospective Study.

Chondrogenic differentiation of human pluripotent stem cells in chondrocyte co-culture

Chondrogenic differentiation of human embryonic (hESCs) or induced pluripotent stem cells (hiPSCs) has been achieved in embryoid bodies (EBs) by adding selected growth factors to the medium. Also chondrocyte-secreted factors have been considered to promote the chondrogenic differentiation. Hence, we studied whether co-culture with primary chondrocytes can induce hESCs or hiPSCs to differentiate into chondrocyte lineage. Co-culture of hESCs or hiPSCs was established in a transwell insert system in feeder-free culture conditions, while hESCs or hiPSCs grown alone in the wells were used as controls. After 3-week co-culture with weekly replenished chondrocytes, the chondrogenically committed cells (hCCCs) were evaluated by morphology, immunocytochemistry, quantitative real-time RT-PCR, and analysis of chondrogenic, osteogenic and adipogenic differentiation markers. The expressions of chondrocyte- and pluripotency-associated genes were frequently measured during the monolayer expansion of hCCCs from passage 1 to 10. Human CCCs displayed morphology similar to chondrocytes, and expressed chondrocyte-associated genes, which were declined following passaging, similarly to passaged chondrocytes. They also formed a chondrogenic cell pellet, and differentiated into chondrocytic cells, which secreted abundant extracellular matrix. Human CCCs also proliferated rapidly. However, they did not show osteogenic or adipogenic differentiation capacity. Our results show that co-culture of hESCs or hiPSCs with primary chondrocytes could induce specific chondrogenic differentiation.

Non-terminal animal model of post-traumatic osteoarthritis induced by acute joint injury

OBJECTIVE

Develop a non-terminal animal model of acute joint injury that demonstrates clinical and morphological evidence of early post-traumatic osteoarthritis (PTOA).

METHODS

An osteochondral (OC) fragment was created arthroscopically in one metacarpophalangeal (MCP) joint of 11 horses and the contralateral joint was sham operated. Eleven additional horses served as unoperated controls. Every 2 weeks, force plate analysis, flexion response, joint circumference, and synovial effusion scores were recorded. At weeks 0 and 16, radiographs (all horses) and arthroscopic videos (OC injured and sham joints) were graded. At week 16, synovium and cartilage biopsies were taken arthroscopically from OC injured and sham joints for histologic evaluation and the OC fragment was removed.

RESULTS

OC fragments were successfully created and horses were free of clinical lameness after fragment removal. Forelimb gait asymmetry was observed at week 2 (P = 0.0012), while joint circumference (P < 0.0001) and effusion scores (P < 0.0001) were increased in injured limbs compared to baseline from weeks 2 to 16. Positive flexion response of injured limbs was noted at multiple time points. Capsular enthesophytes were seen radiographically in injured limbs. Articular cartilage damage was demonstrated arthroscopically as mild wear-lines and histologically as superficial zone chondrocyte death accompanied by mild proliferation. Synovial hyperemia and fibrosis were present at the site of OC injury.

CONCLUSION

Acute OC injury to the MCP joint resulted in clinical, imaging, and histologic changes in cartilage and synovium characteristic of early PTOA. This model will be useful for defining biomarkers of early osteoarthritis and for monitoring response to therapy and surgery.

Genetic and cellular evidence of decreased inflammation associated with reduced incidence of posttraumatic arthritis in MRL/MpJ mice

OBJECTIVE

To examine the relationship between inflammation and posttraumatic arthritis (PTA) in a murine intraarticular fracture model.

METHODS

Male C57BL/6 and MRL/MpJ "superhealer" mice received tibial plateau fractures using a previously established method. Mice were killed on day 0 (within 4 hours of fracture) and days 1, 3, 5, 7, 28, and 56 after fracture. Synovial tissue samples, obtained prior to fracture and on days 0, 1, 3, 5, and 7 after fracture, were examined by reverse transcription-polymerase chain reaction for gene expression of proinflammatory cytokines and chemokines. Synovial fluid and serum samples were collected to measure cytokine concentrations, using enzyme-linked immunosorbent assay. Whole joints were examined histologically for the extent of synovitis and cartilage degradation, and joint tissue samples from all time points were analyzed immunohistochemically to evaluate the distribution of interleukin-1 (IL-1).

RESULTS

Compared to C57BL/6 mice, MRL/MpJ mice had less severe intraarticular and systemic inflammation following joint injury, as evidenced by lower gene expression of tumor necrosis factor α and IL-1β in the synovial tissue and lower protein levels of IL-1α and IL-1β in the synovial fluid, serum, and joint tissues. Furthermore, after joint injury, MRL/MpJ mice had lower gene expression of macrophage inflammatory proteins and macrophage-derived chemokine (CCL22) in the synovial tissue, and also had reduced acute and late-stage infiltration of synovial macrophages.

CONCLUSION

C57BL/6 mice exhibited higher levels of inflammation than MRL/MpJ mice, indicating that MRL/MpJ mice are protected from PTA in this model. These data thus suggest an association between joint tissue inflammation and the development and progression of PTA in mice.

Subject-specific analysis of joint contact mechanics: application to the study of osteoarthritis and surgical planning

Advances in computational mechanics, constitutive modeling, and techniques for subject-specific modeling have opened the door to patient-specific simulation of the relationships between joint mechanics and osteoarthritis (OA), as well as patient-specific preoperative planning. This article reviews the application of computational biomechanics to the simulation of joint contact mechanics as relevant to the study of OA. This review begins with background regarding OA and the mechanical causes of OA in the context of simulations of joint mechanics. The broad range of technical considerations in creating validated subject-specific whole joint models is discussed. The types of computational models available for the study of joint mechanics are reviewed. The types of constitutive models that are available for articular cartilage are reviewed, with special attention to choosing an appropriate constitutive model for the application at hand. Issues related to model generation are discussed, including acquisition of model geometry from volumetric image data and specific considerations for acquisition of computed tomography and magnetic resonance imaging data. Approaches to model validation are reviewed. The areas of parametric analysis, factorial design, and probabilistic analysis are reviewed in the context of simulations of joint contact mechanics. Following the review of technical considerations, the article details insights that have been obtained from computational models of joint mechanics for normal joints; patient populations; the study of specific aspects of joint mechanics relevant to OA, such as congruency and instability; and preoperative planning. Finally, future directions for research and application are summarized.

Diet-induced obesity significantly increases the severity of posttraumatic arthritis in mice

OBJECTIVE

Obesity and joint injury are primary risk factors for osteoarthritis (OA) that involve potential alterations in the biomechanical and inflammatory environments of the joint. Posttraumatic arthritis is a frequent long-term complication of intraarticular fractures. Obesity has been linked to primary OA and may potentially contribute to the development of posttraumatic arthritis by a variety of mechanisms. The objectives of this study were to determine whether diet-induced obesity influences the severity of posttraumatic arthritis in mice and to examine the interrelationships between joint degeneration and serum levels of the inflammatory cytokines and adipokines that are involved in this response.

METHODS

C57BL/6 mice were fed either normal chow (13% fat) or a high-fat diet (60% fat) starting at 4 weeks of age. At 16 weeks of age, half of the mice in each group were subjected to a closed intraarticular fracture of the left knee. At 8 weeks postfracture, knee OA was assessed by cartilage and synovium histology in addition to bone morphology. Serum cytokine concentrations were determined with multiplex assays.

RESULTS

Fractured knee joints of mice receiving a high-fat diet showed significantly increased OA degeneration compared with nonfractured contralateral control knees, while fractured knee joints of mice receiving a low-fat diet did not demonstrate significant differences from nonfractured contralateral control knees. A high-fat diet increased serum concentrations of interleukin-12p70 (IL-12p70), IL-6, and keratinocyte-derived chemokine while decreasing adiponectin concentrations. Joint injury also increased IL-12p70 concentrations in mice receiving a high-fat diet. Systemic levels of adiponectin were inversely correlated with synovial inflammation in control limbs.

CONCLUSION

Diet-induced obesity significantly increased the severity of OA following intraarticular fracture. Obesity and joint injury together can alter systemic levels of inflammatory cytokines such as IL-12p70.

A novel impaction technique to create experimental articular fractures in large animal joints

OBJECTIVE

A novel impaction fracture insult technique, developed for modeling post-traumatic osteoarthritis in porcine hocks in vivo, was tested to determine the extent to which it could replicate the cell-level cartilage pathology in human clinical intra-articular fractures.

DESIGN

Eight fresh porcine hocks (whole-joint specimens with fully viable chondrocytes) were subjected to fracture insult. From the fractured distal tibial surfaces, osteoarticular fragments were immediately sampled and cultured in vitro for 48 h. These samples were analyzed for the distribution and progression of chondrocyte death, using the Live/Dead assay. Five control joints, in which "fractures" were simulated by means of surgical osteotomy, were also similarly analyzed.

RESULTS

In the impaction-fractured joints, chondrocyte death was concentrated in regions adjacent to fracture lines (near-fracture regions), as evidenced by fractional cell death significantly higher (P < 0.0001) than in central non-fracture (control) regions. Although nominally similar spatial distribution patterns were identified in the osteotomized joints, fractional cell death in the near-osteotomy regions was nine-fold lower (P < 0.0001) than in the near-fracture regions. Cell death in the near-fracture regions increased monotonically during 48 h after impaction, dominantly within 1 mm from the fracture lines.

CONCLUSION

The impaction-fractured joints exhibited chondrocyte death characteristics reasonably consistent with those in human intra-articular fractures, but were strikingly different from those in "fractures" simulated by surgical osteotomy. These observations support promise of this new impaction fracture technique as a mechanical insult modality to replicate the pathophysiology of human intra-articular fractures in large animal joints in vivo.

Increased susceptibility of Trpv4-deficient mice to obesity and obesity-induced osteoarthritis with very high-fat diet

OBJECTIVE

To test the hypotheses that: (1) the transient receptor potential vanilloid 4 (TRPV4) ion channel is protective in the obesity model of osteoarthritis (OA), resulting in more severe obesity-induced OA in Trpv4 knockout (Trpv4(-/-)) mice; and (2) loss of TRPV4 alters mesodermal stem cell differentiation.

METHODS

Male Trpv4(-/-) and wild-type (Trpv4(+/+)) mice were fed a control or high-fat diet (10% kcal and 60% kcal from fat, respectively) for 22 weeks, at which time spontaneous cage activity and severity of knee OA were evaluated. In addition, the adipogenic, osteogenic and chondrogenic potential of bone marrow-derived (MSC) and adipose-derived (ASC) stem cells from Trpv4(-/-) and Trpv4(+/+) mice were compared.

RESULTS

A high-fat diet significantly increased knee OA scores and reduced spontaneous cage activity in Trpv4(-/-) mice, while also increasing weight gain and adiposity. MSCs from Trpv4(-/-) mice had decreased adipogenic and osteogenic differentiation potential versus Trpv4(+/+) MSCs. ASCs from Trpv4(-/-) mice had increased adipogenic and osteogenic and reduced chondrogenic differentiation potential versus Trpv4(+/+) ASCs.

CONCLUSIONS

Pan-Trpv4(-/-) mice develop more severe OA with high-fat feeding, potentially due to more severe diet-induced obesity. The altered differentiation potential of Trpv4(-/-) progenitor cells may reflect the importance of this ion channel in the maintenance and turnover of mesodermally-derived tissues.

Ankle arthrodiastasis and interpositional ankle exostectomy

Arthrosis of the ankle joint, typically posttraumatic in nature, can affect younger and older populations alike. A multitude of procedures exist for treatment, such as arthrodesis, total joint replacement, arthrodiastasis, and articular repair. Current literature has demonstrated success in articular surface repair and arthrodiastasis as separate procedures. This article reviews the technique of ankle arthrodiastasis and interpositional ankle exostectomy, consisting of background, mechanism of action, indications, patient selection criteria, complications, and advantages in the current literature.

Intra-articular delivery of purified mesenchymal stem cells from C57BL/6 or MRL/MpJ superhealer mice prevents posttraumatic arthritis

Joint injury dramatically enhances the onset of osteoarthritis (OA) and is responsible for an estimated 12% of OA. Posttraumatic arthritis (PTA) is especially common after intra-articular fracture, and no disease-modifying therapies are currently available. We hypothesized that the delivery of mesenchymal stem cells (MSCs) would prevent PTA by altering the balance of inflammation and regeneration after fracture of the mouse knee. Additionally, we examined the hypothesis that MSCs from the MRL/MpJ (MRL) "superhealer" mouse strain would show increased multilineage and therapeutic potentials as compared to those from C57BL/6 (B6) mice, as MRL mice have shown exceptional in vivo regenerative abilities. A highly purified population of MSCs was prospectively isolated from bone marrow using cell surface markers (CD45-/TER119-/PDGFRα+/Sca-1+). B6 MSCs expanded greater than 100,000-fold in 3 weeks when cultured at 2% oxygen and displayed greater adipogenic, osteogenic, and chondrogenic differentiation as compared to MRL MSCs. Mice receiving only a control saline injection after fracture demonstrated PTA after 8 weeks, but the delivery of 10,000 B6 or MRL MSCs to the joint prevented the development of PTA. Cytokine levels in serum and synovial fluid were affected by treatment with stem cells, including elevated systemic interleukin-10 at several time points. The delivery of MSCs did not reduce the degree of synovial inflammation but did show increased bone volume during repair. This study provides evidence that intra-articular stem cell therapy can prevent the development of PTA after fracture and has implications for possible clinical interventions after joint injury before evidence of significant OA.

Effect of tibial plateau fracture on lubrication function and composition of synovial fluid

BACKGROUND

Intra-articular fractures may hasten posttraumatic arthritis in patients who are typically too active and too young for joint replacement. Current orthopaedic treatment principles, including recreating anatomic alignment and establishing articular congruity, have not eliminated posttraumatic arthritis. Additional biomechanical and biological factors may contribute to the development of arthritis. The objective of the present study was to evaluate human synovial fluid for friction-lowering function and the concentrations of putative lubricant molecules following tibial plateau fractures.

METHODS

Synovial fluid specimens were obtained from the knees of eight patients (twenty-five to fifty-seven years old) with a tibial plateau fracture, with five specimens from the injured knee as plateau fracture synovial fluid and six specimens from the contralateral knee as control synovial fluid. Each specimen was centrifuged to obtain a fluid sample, separated from a cell pellet, for further analysis. For each fluid sample, the start-up (static) and steady-state (kinetic) friction coefficients in the boundary mode of lubrication were determined from a cartilage-on-cartilage biomechanical test of friction. Also, concentrations of the putative lubricants, hyaluronan and proteoglycan-4, as well as total protein, were determined for fluid samples.

RESULTS

The group of experimental samples were obtained at a mean (and standard deviation) of 11 ± 9 days after injury from patients with a mean age of 45 ± 13 years. Start-up and kinetic friction coefficients demonstrated similar trends and dependencies. The kinetic friction coefficients for human plateau fracture synovial fluid were approximately 100% higher than those for control human synovial fluid. Hyaluronan concentrations were ninefold lower for plateau fracture synovial fluid compared with the control synovial fluid, whereas proteoglycan-4 concentrations were more than twofold higher in plateau fracture synovial fluid compared with the control synovial fluid. Univariate and multivariate regression analysis indicated that kinetic friction coefficient increased as hyaluronan concentration decreased.

CONCLUSIONS

Knees afflicted with a tibial plateau fracture have synovial fluid with decreased lubrication properties in association with a decreased concentration of hyaluronan.

Development of a new biomechanically defined single impact rabbit cartilage trauma model for in vivo-studies

BACKGROUND

Clinically oriented and easy to handle animal models are urgently needed to test pharmacologic treatment of cartilage trauma to reduce the resulting tissue damage by chondrocyte apoptosis and induction of matrix-degrading enzymes.

AIM

To develop a biomechanically defined cartilage trauma model.

MATERIAL AND METHODS

We constructed a novel trauma device that allows biomechanically defined force application to the load-bearing region of the medial and lateral femoral condyles in adult rabbits. The fixation to the femur was specially designed to avoid uncontrolled influx of blood into the joint. The device was tested on the articular femoral surface of cadaveric rabbits.

RESULTS

At a lower energy (1.0 J), the tests showed that superficial and partially deep fissuring, partial necrosis of the chondrocytes, and early proteoglycan loss occurred at the region of impact. Subchondral fractures could be excluded by micro CT. At higher energy (≥ 1.4 J), we observed more pronounced deep fissuring and in some cases complete shearing of the articular cartilage from the subchondral bone.

CONCLUSION

Our model represents an easy to use method to create a biomechanically defined cartilage trauma and offers some advantages with respect to handling under aseptic surgical conditions and prevention of uncontrolled intra-articular bleeding from the bone marrow compartment for pharmacologic studies.

Biological aspects of early osteoarthritis

PURPOSE

Early OA primarily affects articular cartilage and involves the entire joint, including the subchondral bone, synovial membrane, menisci and periarticular structures. The aim of this review is to highlight the molecular basis and histopathological features of early OA.

METHODS

Selective review of literature.

RESULTS

Risk factors for developing early OA include, but are not limited to, a genetic predisposition, mechanical factors such as axial malalignment, and aging. In early OA, the articular cartilage surface is progressively becoming discontinuous, showing fibrillation and vertical fissures that extend not deeper than into the mid-zone of the articular cartilage, reflective of OARSI grades 1.0-3.0. Early changes in the subchondral bone comprise a progressive increase in subchondral plate and subarticular spongiosa thickness. Early OA affects not only the articular cartilage and the subchondral bone but also other structures of the joint, such as the menisci, the synovial membrane, the joint capsule, ligaments, muscles and the infrapatellar fat pad. Genetic markers or marker combinations may become useful in the future to identify early OA and patients at risk.

CONCLUSION

The high socioeconomic impact of OA suggests that a better insight into the mechanisms of early OA may be a key to develop more targeted reconstructive therapies at this first stage of the disease.

LEVEL OF EVIDENCE

Systematic review, Level II.

Management of posttraumatic osteoarthritis with an integrated orthotic and rehabilitation initiative

Posttraumatic osteoarthritis affects approximately 5.6 million Americans annually. Those affected are typically younger and more active than persons with primary osteoarthritis. Arthrodesis is the typical management option for persons with end-stage ankle and subtalar posttraumatic arthritis. Arthroplasty is typically reserved for elderly persons. The functional limitations resulting from any of these strategies make treatment of this young population challenging. Combat wounds frequently lead to severe lower extremity injuries. We present a series of patients with severe posttraumatic osteoarthritis of the ankle and subtalar joint after combat trauma. They were treated at our institution with an integrated orthotic and rehabilitation initiative called the Return To Run clinical pathway. This clinical pathway may serve as an alternative or adjunct to arthrodesis and arthroplasty for young patients with severe posttraumatic osteoarthritis of the ankle and subtalar joint.

A systems biology approach to synovial joint lubrication in health, injury, and disease

The synovial joint contains synovial fluid (SF) within a cavity bounded by articular cartilage and synovium. SF is a viscous fluid that has lubrication, metabolic, and regulatory functions within synovial joints. SF contains lubricant molecules, including proteoglycan-4 and hyaluronan. SF is an ultrafiltrate of plasma with secreted contributions from cell populations lining and within the synovial joint space, including chondrocytes and synoviocytes. Maintenance of normal SF lubricant composition and function are important for joint homeostasis. In osteoarthritis, rheumatoid arthritis, and joint injury, changes in lubricant composition and function accompany alterations in the cytokine and growth factor environment and increased fluid and molecular transport through joint tissues. Thus, understanding the synovial joint lubrication system requires a multifaceted study of the various parts of the synovial joint and their interactions. Systems biology approaches at multiple scales are being used to describe the molecular, cellular, and tissue components and their interactions that comprise the functioning synovial joint. Analyses of the transcriptome and proteome of SF, cartilage, and synovium suggest that particular molecules and pathways play important roles in joint homeostasis and disease. Such information may be integrated with physicochemical tissue descriptions to construct integrative models of the synovial joint that ultimately may explain maintenance of health, recovery from injury, or development and progression of arthritis.

Acute joint pathology and synovial inflammation is associated with increased intra-articular fracture severity in the mouse knee

OBJECTIVE

Post-traumatic arthritis is a frequent cause of disability and occurs most commonly and predictably after articular fracture. The objective of this investigation was to examine the effect of fracture severity on acute joint pathology in a novel murine model of intra-articular fracture.

DESIGN

Low and high energy articular fractures (n=25 per group) of the tibial plateau were created in adult male C57BL/6 mice. The acute effect of articular fracture severity on synovial inflammation, bone morphology, liberated fracture area, cartilage pathology, chondrocyte viability, and systemic cytokines and biomarkers levels was assessed at 0, 1, 3, 5, and 7 days post-fracture.

RESULTS

Increasing intra-articular fracture severity was associated with greater acute pathology in the synovium and bone compared to control limbs, including increased global synovitis and reduced periarticular bone density and thickness. Applied fracture energy was significantly correlated with degree of liberated cortical bone surface area, indicating greater comminution. Serum concentrations of hyaluronic acid (HA) were significantly increased 1 day post-fracture. While articular fracture significantly reduced chondrocyte viability, there was no relationship between fracture severity and chondrocyte viability, cartilage degeneration, or systemic levels of cytokines and biomarkers.

CONCLUSIONS

This study demonstrates that articular fracture is associated with a loss of chondrocyte viability and increased levels of systemic biomarkers, and that increased intra-articular fracture severity is associated with increased acute joint pathology in a variety of joint tissues, including synovial inflammation, cortical comminution, and bone morphology. Further characterization of the early events following articular fracture could aid in the treatment of post-traumatic arthritis.

Post-traumatic osteoarthritis: improved understanding and opportunities for early intervention

Even with current treatments of acute joint injuries, more than 40% of people who suffer significant ligament or meniscus tears, or articular surface injuries, will develop osteoarthritis (OA). Correspondingly, 12% or more of all patients with lower extremity OA have a history of joint injury. Recent research suggests that acute joint damage that occurs at the time of an injury initiates a sequence of events that can lead to progressive articular surface damage. New molecular interventions, combined with evolving surgical methods, aim to minimize or prevent progressive tissue damage triggered by joint injury. Seizing the potential for progress in the treatment of joint injuries to forestall OA will depend on advances in (1) quantitative methods of assessing the injury severity, including both structural damage and biologic responses, (2) understanding of the pathogenesis of post-traumatic OA, taking into account potential interactions among the different tissues and the role of post-traumatic incongruity and instability, and (3) application of engineering and molecular research to develop new methods of treating injured joints. This paper highlights recent advances in understanding of the structural damage and the acute biological response following joint injury, and it identifies important directions for future research.

Cartilage viability and catabolism in the intact porcine knee following transarticular impact loading with and without articular fracture

Posttraumatic arthritis commonly develops following articular fracture. The objective of this study was to develop a closed joint model of transarticular impact with and without creation of an articular fracture that maintains the physiologic environment during loading. Fresh intact porcine knees were preloaded and impacted at 294 J via a drop track. Osteochondral cores were obtained from the medial and lateral aspects of the femoral condyles and tibial plateau. Chondrocyte viability was assessed at days 0, 3, and 5 postimpact in sham, impacted nonfractured, and impacted fractured joints. Total matrix metalloproteinase (MMP) activity, aggrecanase (ADAMTS-4) activity, and sulfated glycosaminoglycan (S-GAG) release were measured in culture media from days 3 and 5 posttrauma. No differences were observed in chondrocyte viability of impacted nonfractured joints (95.9 ± 6.9%) when compared to sham joints (93.8 ± 7.7%). In impacted fractured joints, viability of the fractured edge was 40.5 ± 27.6% and significantly lower than all other sites, including cartilage adjacent to the fractured edge (p < 0.001). MMP and aggrecanase activity and S-GAG release were significantly increased in specimens from the fractured edge. This study showed that joint impact resulting in articular fracture significantly decreased chondrocyte viability, increased production of MMPs and aggrecanases, and enhanced S-GAG release, whereas the same level of impact without fracture did not cause such changes.

Distribution and progression of chondrocyte damage in a whole-organ model of human ankle intra-articular fracture

BACKGROUND

Despite the best current treatments, intra-articular fractures commonly cause posttraumatic osteoarthritis. In this disorder, death and dysfunction of chondrocytes associated with acute cartilage injury presumably plays an important role in triggering the pathomechanical cascade that eventually leads to whole-joint degeneration. Information regarding this cell-level cartilage injury, particularly at the whole-organ level in actual human joints, has been lacking. In this study, the distribution and progression of fracture-associated cell-level cartilage damage were assessed using a novel whole-organ model of human ankle intra-articular fracture.

METHODS

Seven normal human ankles harvested immediately following amputation were subjected to a transarticular compressive impaction insult that mimicked an injury mechanism typical of tibial plafond fractures. For each ankle, site-specific, time-dependent changes in chondrocyte viability in the fractured tibial surface were studied by means of live-dead assay, using a confocal laser-scanning microscope. Fractional chondrocyte death was measured at several time points, in the superficial zone of the cartilage in "fracture-edge" regions within 1 mm of the fracture lines, as well as in "non-fracture" regions more than 3 mm centrally away from the fracture lines.

RESULTS

All seven experimental fractures morphologically replicated tibial plafond fractures. Immediately post-fracture, superficial-zone chondrocyte death was significantly greater (p = 0.001) in fracture-edge regions (fractional cell death = 7.6%) than in non-fracture regions (1.6%). Progression of cell death over the next forty-eight hours was significantly faster in fracture-edge regions (p = 0.007), with the fractional cell death reaching 25.9%, which was again significantly higher (p < 0.001) than in non-fracture regions (8.6%).

CONCLUSIONS

Cell-level cartilage damage in human intra-articular fractures was characterized by acute chondrocyte death that predominated along fracture lines and that spontaneously progressed in the forty-eight hours following injury.

CLINICAL RELEVANCE

Progressive chondrocyte damage along fracture lines appears to be a reasonable target of therapeutic treatment to preserve the whole-joint cartilage metabolism in intra-articular fractures, eventually to mitigate the risk of posttraumatic osteoarthritis.

Is elevated contact stress predictive of post-traumatic osteoarthritis for imprecisely reduced tibial plafond fractures?

Despite the widely held belief that residual incongruities from intra-articular fractures subject the joint to contact stresses that predispose to post-traumatic osteoarthritis (PTOA), objective evidence has been lacking. This study tested the hypothesis that a metric of elevated contact stress exposure would predict the onset of PTOA. The ankles of 10 tibial plafond fracture patients were treated initially using a spanning fixator, with subsequent screw fixation of the articular surface. Following up on an earlier report of finite element computed post-operative contact stress distributions in these patients' ankles, Kellgren-Lawrence (KL) scores were assessed from minimum 2-year follow-up radiographs to characterize the presence/severity of PTOA. At that time point, seven patients had developed PTOA (KL ≥ 2). Five different metrics of contact stress exposure were calculated, all of which exhibited excellent concordance with KL scores, ranging from 88% to 95%. When time of stress exposure was included, one metric was able to predict PTOA development (KL ≥ 2) with 100% reliability, and all metrics exhibited >94% prediction reliability. These findings, albeit in a small population, support the existence of a contact stress exposure threshold above which incongruously reduced tibial plafond fractures are highly likely to develop PTOA.

Articular step-off and risk of post-traumatic osteoarthritis. Evidence today

The goal of treatment in intra-articular fractures is to obtain anatomical restoration of the articular surface and stable internal fixation. Studies have attempted to specify how accurately an articular fracture needs to be reduced to minimise the chances of a poor clinical outcome. In this study, the current evidence with regard to articular step-offs and risk of post-traumatic osteoarthritis (POA) is evaluated. A literature review based on pre-specified criteria, revealed 36 articles for critical analysis related to intra-articular injuries of distal radius, acetabulum, distal femur and tibial plateau.In the distal radius, step-offs and gaps detected with precise measurement techniques have been correlated with a higher incidence of radiographic POA, but in the second 5 years after injury, a negative clinical impact of these radiographic changes has not been convincingly demonstrated. Restoring the superior weight-bearing dome of the acetabulum to its pre-injury morphology decreases POA and improves patient outcomes. Involvement of the posterior wall, however, seems to bean adverse prognostic sign. This effect may be independent of articular reduction. In the tibial plateau, articular incongruities appear to be well tolerated, and factors only partially related to articular reduction are more important in determining outcome than articular step-off alone;these include joint stability, retention of the meniscus, and coronal alignment. Based on observational approach and evaluation of the studies, factors other than just the extent of articular displacement affect the management of articular fractures. Different joints and even different areas of the same joint appear to have different tolerances for post-traumatic articular step-offs.

Cell transplantation for articular cartilage defects: principles of past, present, and future practice

As articular cartilage has very limited self-repair capability, the repair and regeneration of damaged cartilage is a major challenge. This review aims to outline the past, present, and future of cell therapies for articular cartilage defect repair. Autologous chondrocyte implantation (ACI) has been used clinically for more than 20 years, and the short, medium, and long-term clinical outcomes of three generation of ACI are extensively overviewed. Also, strategies of clinical outcome evaluation, ACI limitations, and the comparison of ACI clinical outcomes with those of other surgical techniques are discussed. Moreover, mesenchymal stem cells and pluripotent stem cells for cartilage regeneration in vitro, in vivo, and in a few clinical studies are reviewed. This review not only comprehensively analyzes the ACI clinical data but also considers the findings from state-of-the-art stem cell research on cartilage repair from bench and bedside. The conclusion provides clues for the future development of strategies for cartilage regeneration.

Evaluation of chondrocyte death in canine osteochondral explants exposed to a 0.5% solution of bupivacaine

OBJECTIVE

To evaluate chondrocyte death in canine articular cartilage exposed in vitro to bupivacaine with and without methylparaben and to compare viability for cartilage with intact or mechanically debrided surfaces.

SAMPLE POPULATION

Both glenohumeral joints from 10 adult canine cadavers.

PROCEDURES

10 osteochondral cores were harvested from each of the 20 humeral heads; synovium and 1 core from each joint were examined to verify joint health, and the other 9 cores were exposed to canine chondrocyte culture medium (CCCM), a 0.5% solution of bupivacaine, or 0.5% solution of bupivacaine with methylparaben for 5, 15, or 30 minutes.

RESULTS

For the superficial zone of surface-intact chondrocytes, bupivacaine with methylparaben caused a significantly higher percentage of chondrocyte death at 5 minutes (47.7%) than did bupivacaine (23.6%) or CCCM (25.4%). Bupivacaine (53.8%) and bupivacaine with methylparaben (62.5%) caused a significantly higher percentage of chondrocyte death at 30 minutes than did CCCM (20.0%). For the superficial zone of chondrocytes with debrided surfaces, bupivacaine with methylparaben caused a significantly higher percentage of chondrocyte death at 30 minutes (59%) than it did at 5 minutes (37.7%). Bupivacaine with methylparaben caused a significantly higher percentage of chondrocyte death at 30 minutes (59.0%) than did CCCM (28.9%). For middle and deep zones of chondrocytes, treatment solution and surface debridement had minimal effects on percentage of chondrocyte death.

CONCLUSIONS AND CLINICAL RELEVANCE

Bupivacaine and bupivacaine with methylparaben were cytotoxic to canine articular chondrocytes in vitro. Intra-articular administration of bupivacaine is not recommended for clinical use until additional studies are conducted.

Optical coherence tomography detection of subclinical traumatic cartilage injury

OBJECTIVES

Posttraumatic arthritis is a major cause of disability. Current clinical imaging modalities are unable to reliably evaluate articular cartilage damage before surface breakdown, when potentially reversible changes are occurring. Optical coherence tomography (OCT) is a nondestructive imaging technology that can detect degenerative changes in articular cartilage with an intact surface. This study tests the hypothesis that OCT detects acute articular cartilage injury after impact at energy levels resulting in chondrocyte death and microstructural changes, but insufficient to produce macroscopic surface damage.

METHODS

Bovine osteochondral cores underwent OCT imaging and were divided into a control with no impact or were subjected to low (0.175 J) or moderate (0.35 J) energy impact. Cores were reimaged with OCT after impact and the OCT signal intensity quantified. A ratio of the superficial to deep layer intensities was calculated and compared before and after impact. Chondrocyte viability was determined 1 day after impact followed by histology and polarized microscopy.

RESULTS

Macroscopic changes to the articular surface were not observed after low and moderate impact. The OCT signal intensity ratio demonstrated a 27% increase (P = 0.006) after low impact and a 38% increase (P = 0.001) after moderate impact. Cell death increased by 150% (P < 0.001) and 200% (P < 0.001) after low and moderate energy impacts, respectively. When compared with unimpacted controls, both Mankin histology and David-Vaudey polarized microscopy scores increased (P = 0.036 and P = 0.002, respectively) after moderate energy impact.

CONCLUSIONS

This study shows that OCT detects acute cartilage changes after impact injury at levels insufficient to cause visible damage to the articular surface but sufficient to cause chondrocyte death and microscopic matrix damage. This finding supports the use of OCT to detect microstructural subsurface cartilage damage that is poorly visualized with conventional imaging.

New developments in osteoarthritis. Posttraumatic osteoarthritis: pathogenesis and pharmacological treatment options

Joint trauma can lead to a spectrum of acute lesions, including osteochondral fractures, ligament or meniscus tears and damage to the articular cartilage. This is often associated with intraarticular bleeding and causes posttraumatic joint inflammation. Although the acute symptoms resolve and some of the lesions can be surgically repaired, joint injury triggers a chronic remodeling process in cartilage and other joint tissues that ultimately manifests as osteoarthritis in a majority of cases. The objective of the present review is to summarize information on pathogenetic mechanisms involved in the acute and chronic consequences of joint trauma and discuss potential pharmacological interventions. The focus of the review is on the early events that follow joint trauma since therapies for posttraumatic joint inflammation are not available and this represents a unique window of opportunity to limit chronic consequences.

Biomechanical study of posterior wall acetabular fracture fixation using acetabular tridimensional memory alloy-fixation system

BACKGROUND

We developed the acetabular tridimensional memory alloy-fixation system (ATMFS), which is made of NiTi shape memory alloy, according to the specific mechanical properties of biological memory material, nitinol alloy and measured distribution of contact area and pressure between the acetabulum and the femoral head of cadaveric pelvis.

METHODS

Six formalin-preserved cadaveric pelvis were used for this investigation. Pressure-sensitive film was used to measure contact area and pressure within the anterior, superior, and posterior regions of the acetabulum. The pelvis were loaded under the following four conditions: (1) intact; (2) following a creation posterior wall fracture defect; (3) following reduction and standard internal fixation with reconstruction plate; (4) following reduction and internal fixation with a new shape memory alloy device named ATMFS. A posterior wall fracture was created along an arc of 40-90 degrees about the acetabular rim.

FINDINGS

Creation of a posterior wall defect resulted in increased load in the superior acetabulum (1422N) as compared to the intact condition (762N, P=0.007). Following reduction and internal fixation, the load distributed to the superior acetabulum (1486N) was not statistically different from the defect condition. Following the fixation with ATMFS, the load seen at the superior region of the actabulum (936N) was less than fixation with reconstruction plate and was not different from intact state (P=0.4).

INTERPRETATION

These data indicate that the use of ATMFS as a fracture internal fixation device resulted a partial restoration of joint loading parameters toward the intact state. ATMFS fixation may result in a clinical benefit.

Effect of exogenous IGF-1 on chondrocyte apoptosis in a rabbit intraarticular osteotomy model

Insulin-like growth factor-1 (IGF-1) has been shown to protect chondrocytes from apoptosis in vitro. IGF-1 expression may also assist in maintaining a fully differentiated chondrocyte phenotype. Theoretically, posttraumatic administration of IGF-1 may inhibit chondrocyte apoptosis. This study is to determine if administration of IGF-1 after fracture inhibits apoptosis in vivo. Twenty-four mature female New Zealand white rabbits were randomized to control and IGF-1 groups. All subjects underwent standardized medial femoral condyle fracture and repair. Fibrin clot was administered in all subjects, with 25 mcg/ml IGF-1 in the clot in half the subjects. Half of the animals in each group were sacrificed at 2 weeks and half at 4 weeks, specimens were fixed and underwent TUNEL staining. Two-week controls showed significantly higher rate of apoptosis than 2-week IGF-1 subjects (21 +/- 6 vs. 12 +/- 6, p = 0.04). Likewise, 4-week controls showed significantly higher rate of apoptosis than 2-week IGF-1 subjects (23 +/- 7 vs. 10 +/- 2, p = 0.01). There was no significant administration difference between 2-week control and 4-week control subjects, or between 2-week IGF-1 and 4-week IGF-1 subjects. Intraarticular IGF-1 at the time of fracture repair appears to inhibit chondrocyte apoptosis in vivo, as judged by TUNEL staining, in this animal model. If administration of IGF-1 inhibits human chondrocyte apoptosis in vivo, this may lead to interventions that may reduce posttraumatic arthritis after fracture.

Biglycan and fibromodulin have essential roles in regulating chondrogenesis and extracellular matrix turnover in temporomandibular joint osteoarthritis

The temporomandibular joint is critical for jaw movements and allows for mastication, digestion of food, and speech. Temporomandibular joint osteoarthritis is a degenerative disease that is marked by permanent cartilage destruction and loss of extracellular matrix (ECM). To understand how the ECM regulates mandibular condylar chondrocyte (MCC) differentiation and function, we used a genetic mouse model of temporomandibular joint osteoarthritis that is deficient in two ECM proteins, biglycan and fibromodulin (Bgn(-/0)Fmod(-/-)). Given the unavailability of cell lines, we first isolated primary MCCs and found that they were phenotypically unique from hyaline articular chondrocytes isolated from the knee joint. Using Bgn(-/0) Fmod(-/-) MCCs, we discovered the early basis for temporomandibular joint osteoarthritis arises from abnormal and accelerated chondrogenesis. Transforming growth factor (TGF)-beta1 is a growth factor that is critical for chondrogenesis and binds to both biglycan and fibromodulin. Our studies revealed the sequestration of TGF-beta1 was decreased within the ECM of Bgn(-/0) Fmod(-/-) MCCs, leading to overactive TGF-beta1 signal transduction. Using an explant culture system, we found that overactive TGF-beta1 signals induced chondrogenesis and ECM turnover in this model. We demonstrated for the first time a comprehensive study revealing the importance of the ECM in maintaining the mandibular condylar cartilage integrity and identified biglycan and fibromodulin as novel key players in regulating chondrogenesis and ECM turnover during temoporomandibular joint osteoarthritis pathology.

Ankle arthrodiastasis

Ankle joint distraction, or arthrodiastasis, has emerged as a viable treatment alternative for recalcitrant ankle arthritis. This joint salvage procedure avoids the potential complications associated with joint arthrodesis or joint arthroplasty in the young patient population typically affected by posttraumatic ankle arthritis. The treatment is predicated on the knowledge that osteoarthritic ankle cartilage is capable of repair. The reparative capacity of the ankle chondrocyte is enhanced through the mechanical offloading of the joint and maintenance of intra-articular fluid pressure changes. Scientific data demonstrate positive biochemical and biomechanical intra-articular changes associated with joint distraction, facilitating an environment for cartilage repair. Clinical studies, although limited, have resulted in significant patient benefit in the short-term and long-term treatment of arthritis. Further studies are needed to evaluate this technique and its ideal indication. Current literature does support its use in the treatment of ankle arthritis, however.

Derivation of chondrogenically-committed cells from human embryonic cells for cartilage tissue regeneration

Background

Heterogeneous and uncontrolled differentiation of human embryonic stem cells (hESCs) in embryoid bodies (EBs) limits the potential use of hESCs for cell-based therapies. More efficient strategies are needed for the commitment and differentiation of hESCs to produce a homogeneous population of specific cell types for tissue regeneration applications.

Methodology/Principal Findings

We report here that significant chondrocytic commitment of feeder-free cultured human embryonic stem cells (FF-hESCs), as determined by gene expression and immunostaining analysis, was induced by co-culture with primary chondrocytes. Furthermore, a dynamic expression profile of chondrocyte-specific genes was observed during monolayer expansion of the chondrogenically-committed cells. Chondrogenically-committed cells synergistically responded to transforming growth factor-β1 (TGF-β1) and β1-integrin activating antibody by increasing tissue mass in pellet culture. In addition, when encapsulated in hydrogels, these cells formed cartilage tissue both in vitro and in vivo. In contrast, the absence of chondrocyte co-culture did not result in an expandable cell population from FF-hESCs.

Conclusions/Significance

The direct chondrocytic commitment of FF-hESCs can be induced by morphogenetic factors from chondrocytes without EB formation and homogenous cartilage tissue can be formed in vitro and in vivo.

Absence of posttraumatic arthritis following intraarticular fracture in the MRL/MpJ mouse

OBJECTIVE

Posttraumatic arthritis is a frequent long-term complication of intraarticular fractures. A model of a closed intraarticular fracture in C57BL/6 mice that progresses to posttraumatic arthritis has been developed. The MRL/MpJ mouse has shown unique regenerative abilities in response to injury. The objective of this study was to determine if the MRL/MpJ mouse is protected from posttraumatic arthritis after intraarticular fractures.

METHODS

Intraarticular fractures were created in MRL/MpJ mice and C57BL/6 control mice (n = 16 each). Limbs were analyzed for posttraumatic arthritis 4 and 8 weeks after fracture using microfocal computed tomography bone morphology, subchondral bone thickness evaluation, and histologic evaluation of cartilage degeneration. Serum cytokines and biomarkers were measured after the mice were killed.

RESULTS

Intraarticular fractures were successfully created in all 32 mice. In the experimental fractured limbs, C57BL/6 mice had a decrease in bone density, increased subchondral bone thickness, and increased cartilage degeneration compared with normal contralateral control limbs. In the MRL/MpJ mice, no differences in bone density, subchondral bone thickness, or histologic grading of cartilage degeneration were seen between fractured and contralateral control limbs. Cytokine analysis showed lower systemic levels of the proinflammatory cytokine interleukin-1alpha (IL-1alpha) and higher levels of the antiinflammatory cytokines IL-4 and IL-10 in the MRL/MpJ mice.

CONCLUSION

This study shows that the MRL/MpJ mouse is relatively protected from posttraumatic arthritis after intraarticular fracture. Further investigation into the mechanism involved in this response will hopefully provide new insight into the pathogenesis, prevention, and treatment of posttraumatic arthritis after intraarticular fracture.

Forced mobilization accelerates pathogenesis: characterization of a preclinical surgical model of osteoarthritis

Preclinical osteoarthritis (OA) models are often employed in studies investigating disease-modifying OA drugs (DMOADs). In this study we present a comprehensive, longitudinal evaluation of OA pathogenesis in a rat model of OA, including histologic and biochemical analyses of articular cartilage degradation and assessment of subchondral bone sclerosis. Male Sprague-Dawley rats underwent joint destabilization surgery by anterior cruciate ligament transection and partial medial meniscectomy. The contralateral joint was evaluated as a secondary treatment, and sham surgery was performed in a separate group of animals (controls). Furthermore, the effects of walking on a rotating cylinder (to force mobilization of the joint) on OA pathogenesis were assessed. Destabilization-induced OA was investigated at several time points up to 20 weeks after surgery using Osteoarthritis Research Society International histopathology scores, in vivo micro-computed tomography (CT) volumetric bone mineral density analysis, and biochemical analysis of type II collagen breakdown using the CTX II biomarker. Expression of hypertrophic chondrocyte markers was also assessed in articular cartilage. Cartilage degradation, subchondral changes, and subchondral bone loss were observed as early as 2 weeks after surgery, with considerable correlation to that seen in human OA. We found excellent correlation between histologic changes and micro-CT analysis of underlying bone, which reflected properties of human OA, and identified additional molecular changes that enhance our understanding of OA pathogenesis. Interestingly, forced mobilization exercise accelerated OA progression. Minor OA activity was also observed in the contralateral joint, including proteoglycan loss. Finally, we observed increased chondrocyte hypertrophy during pathogenesis. We conclude that forced mobilization accelerates OA damage in the destabilized joint. This surgical model of OA with forced mobilization is suitable for longitudinal preclinical studies, and it is well adapted for investigation of both early and late stages of OA. The time course of OA progression can be modulated through the use of forced mobilization.