Does surgical technique influence the burden of lung metastases in patients with pathologic long bone fractures?

BACKGROUND: The aims of this study are to (1) determine whether fixation of metastatic long bone fractures with an intramedullary nail (IMN) influences the incidence of lung metastasis in comparison to arthroplasty or ORIF (Arthro/ORIF); and (2) assess this relationship in primary tumor types; and (3) to assess survival implications of lung metastasis after surgery. METHODS: Retrospective cohort study investigating 184 patients (107 IMN, and 77 Arthro/ORIF) surgically treated for metastatic long bone fractures. Patients were required to have a single surgically treated impending or established pathologic fracture of a long bone, pre-operative lung imaging (lung radiograph or computed tomography) and post-operative lung imaging within 6 months of surgery. Primary cancer types included were breast (n = 70), lung (n = 43), prostate (n = 34), renal cell (n = 37). Statistical analyses were conducted using two-tailed Fisher's exact tests, and Kaplan-Meier survival analyses. RESULTS: Patients treated with IMN and Arthro/ORIF developed new or progressive lung metastases following surgery at an incidence of 34 and 26%, respectively. Surgical method did not significantly influence lung metastasis (p = 0.33). Furthermore, an analysis of primary cancer subgroups did not yield any differences between IMN vs Arthro/ORIF. Median survival for the entire cohort was 11 months and 1-year overall survival was 42.7% (95% CI: 35.4-49.8). Regardless of fixation method, the presence of new or progressive lung metastatic disease at follow up imaging study was found to have a negative impact on patient survival (p < 0.001). CONCLUSIONS: In this study, development or progression of metastatic lung disease was not affected by long bone stabilization strategy. IM manipulation of metastatic long bone fractures therefore may not result in a clinically relevant increase in metastatic lung burden. The results of this study also suggest that lung metastasis within 6 months of surgery for metastatic long bone lesions is negatively associated with patient survival. LEVEL OF EVIDENCE: III, therapeutic study.

Structural Consequences of a Partial Anterior Cruciate Ligament Injury on Remaining Joint Integrity: Evidence for Ligament and Bone Changes Over Time in an Ovine Model.

BACKGROUND: Severe injury to the knee joint often results in accelerated posttraumatic osteoarthritis (PTOA). In an ovine knee injury model, altered kinematics and degradation of the cartilage have been observed at 20 and 40 weeks after partial anterior cruciate ligament (ACL) transection (p-ACL Tx) surgery. However, changes to the integrity of the remaining intact intra-articular ligaments (posterolateral [PL] band and posterior cruciate ligament [PCL]) as well as the subchondral bone after anteromedial (AM) band Tx remain to be characterized. PURPOSE: (1) To investigate histological alterations to the remaining intact intra-articular ligaments, the synovium, and the infrapatellar fat pad (IPFP) and (2) to quantify subchondral bone changes at the contact surfaces of the proximal tibia at 20 and 40 weeks after AM band Tx. STUDY DESIGN: Descriptive laboratory study. METHODS: Mature female Suffolk cross sheep were allocated into 3 groups: nonoperative controls (n = 6), 20 weeks after partial ACL transection (p-ACL Tx; n = 5), and 40 weeks after p-ACL Tx (n = 6). Ligament, synovium, and IPFP sections were stained and graded. Tibial subchondral bone microarchitecture was assessed using high-resolution peripheral quantitative computed tomography. RESULTS: p-ACL Tx of the AM band led to significant change in histological scores of the PL band and the PCL at 20 weeks after p-ACL Tx (P = .031 and P = .033, respectively) and 40 weeks after p-ACL Tx (P = .011 and P = .029) as compared with nonoperative controls. Alterations in inflammatory cells and collagen fiber orientation contributed to the greatest extent of the combined histological score in the PL band and PCL. p-ACL Tx did not lead to chronic activation of the synovium or IPFP. Trabecular bone mineral density was strongly inversely correlated with combined gross morphological damage in the top and middle layers of the subchondral bone in the lateral tibial plateau for animals at 40 weeks after p-ACL Tx. CONCLUSION: p-ACL Tx influences the integrity (biology and structure) of remaining intact intra-articular ligaments and bone microarchitecture in a partial knee injury ovine model. CLINICAL RELEVANCE: p-ACL Tx leads to alterations in structural integrity of the remaining intact ligaments and degenerative changes in the trabecular bone mineral density, which may be detrimental to the injured athlete's knee joint in the long term.

Postoperative fever in the time of COVID-19.

Summary: Postoperative fever is common following orthopedic trauma surgery. As the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection increases in the community, migration into the acute care hospital setting intensifies, creating confusion when fever develops postoperatively. The transmission dynamics of SARS-CoV-2 make it difficult to adequately gauge and pinpoint risk groups with questionnaires at the time of hospital admission. This is particularly problematic when asymptomatic or presymptomatic patients infected with SARS-CoV-2 require urgent surgery and cannot be screened effectively. One approach is to treat every patient as though they were SARS-CoV-2-positive in preparation for surgery, but doing so could exacerbate shortages of personal protective equipment and staffing limitations. Uncertainty regarding the etiology of postoperative fever could be significantly reduced by universal SARS-CoV-2 testing of all surgical patients at the time of hospital admission in addition to routine screening, but testing capacity and a rapid turnaround time would be required.

Molecular Response of Rabbit Menisci to Surgically Induced Hemarthrosis and a Single Intra-Articular Dexamethasone Treatment.

Anterior cruciate ligament reconstructive surgery can restore biomechanical stability, however, such surgery cannot reliably prevent the onset of post-traumatic osteoarthritis. The aim of this study was to elucidate the molecular response that occurs within the menisci following a surgical injury that allows bleeding into the joint space, and then to investigate the effect of dexamethasone (DEX) on this molecular response. Cell viability studies following acute controlled exposure to blood and blood plus DEX were also conducted. Forty-eight New Zealand white rabbits were randomly allocated into control, sham, surgical, and surgical + DEX groups (each group n = 6). Animals were sacrificed at 48 h and 9 weeks, and menisci were harvested. The messenger RNA (mRNA) expression levels for key inflammatory, and degradative proteins, as well as mRNA levels for autophagy pathway molecules were quantified, and statistically significant changes were described. Meniscal cell viability was calculated by incubating groups of medial and lateral menisci in autologous blood, or autologous blood plus DEX for 48 h (each group n = 4; total of eight medial and eight lateral menisci), and then conducting a histological live/dead assay. Results indicated a significant reduction in only medial meniscal cell viability when the tissue was exposed to blood in combination with DEX. A single administration of DEX following surgery significantly suppresses the elevated molecular expression for key inflammatory and degradative markers within menisci at 48 h and 9 weeks post-surgery. In vitro, autologous blood did not affect cell viability, but addition of DEX uniquely impacted the medial menisci. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2043-2052, 2019.

Three-dimensional in vivo kinematics and finite helical axis variables of the ovine stifle joint following partial anterior cruciate ligament transection.

Partial anterior cruciate ligament (p-ACL) rupture is a common injury, but the impact of a p-ACL injury on in vivo joint kinematics has yet to be determined in an animal model. The in vivo kinematics of the ovine stifle joint were assessed during 'normal' gait, and at 20 and 40 weeks after p-ACL transection (Tx). Gross morphological scoring of the knee was conducted. p-ACL Tx creates significant progressive post-traumatic osteoarthritis (PTOA)-like damage by 40 weeks. Statistically significant increases for flexion angles at hoof-strike (HS) and mid-stance (MST) were seen at 20 weeks post p-ACL Tx and the HS and hoof-off (HO) points at 40 weeks post p-ACL-Tx, therefore increased flexion angles occurred during stance phase. Statistically significant increases in posterior tibial shift at the mid-flexion (MF) and mid-extension (ME) points were seen during the swing phase of the gait cycle at 40 weeks post p-ACL Tx. Correlation analysis showed a strong and significant correlation between kinematic changes (instabilities) and gross morphological score in the inferior-superior direction at 40 weeks post p-ACL Tx at MST, HO, and MF. Further, there was a significant correlation between change in gross morphological combined score (ΔGCS) and the change in location of the helical axis in the anterior direction (ΔsAP) after p-ACL Tx for all points analyzed through the gait cycle. This study quantified in vivo joint kinematics before and after p-ACL Tx knee injury during gait, and demonstrated that a p-ACL knee injury leads to both PTOA-like damage and kinematic changes.

Alterations in Joint Angular Velocity Following Traumatic Knee Injury in Ovine Models.

Little effort has been directed towards the consequence of an injury on joint angular velocity. We hypothesized that the magnitude of knee joint angular velocity would be decreased after injury. Four injury groups were investigated in an ovine model: (1) anterior cruciate ligament (ACL) and medial collateral ligament (MCL) transection (ACL/MCL Tx) (n = 5), (2) lateral meniscectomy (Mx) (n = 5), (3) partial ACL transection (p-ACL Tx) (n = 5), and (4) partial-ACL and MCL transection (p-ACL/MCL Tx) (n = 5). The magnitude of the angular velocities decreased in the subjects of all groups at multiple points of the gait cycle. The maximum angular velocities during stance and the maximum extension angular velocities during swing were decreased in 15/20 and 17/20 subjects, respectively. There were strong correlations between morphological osteoarthritis scores and the reduction in the maximum extension angular velocities during swing 40 weeks post-p-ACL Tx and 20 weeks post-ACL/MCL Tx. There was no correlation between the decrease of the angular velocity and morphological osteoarthritis scores in the Mx group and the p-ACL/MCL Tx group. The reduction in angular velocity may be a helpful addition as a surrogate measure of OA risk after ACL injury, and could have clinical significance after further investigation in humans.

Are re-injured ligaments equivalent mechanically to injured ligaments: The role of re-injury severity?

The consequences of ligament re-injury have received limited attention. Although the mechanical properties of injured ligaments improve over time, these properties are never fully recaptured, rendering these injured ligaments susceptible to re-injury. Previous injury is a significant risk factor for recurrent injury, and this re-injury can result in longer absence from activity than the initial injury. A rabbit medial collateral ligament model was used to compare mechanically re-injured right medial collateral ligaments to injured left medial collateral ligaments. Two groups of different re-injury severity were investigated: 'minor' re-injury comparing transection re-injured right medial collateral ligaments to transection injured left medial collateral ligaments; 'major' re-injury comparing gap re-injured right medial collateral ligaments to transection injured left medial collateral ligaments. Initial injuries for both groups were right medial collateral ligament transections 1 week before re-injury. After 5-6 weeks of healing, mechanical testing was performed to determine (dimensionally) cross-sectional area; (structurally) medial collateral ligament laxity, failure load, and stiffness; and (materially) cyclic creep strain and failure stress. Because we wanted to evaluate whether the mechanical properties of re-injured ligaments were equivalent or, at least, no worse than injured ligaments, we used equivalence/noninferiority testing. This approach evaluates a research hypothesis of equivalence, rather than difference, and determines whether comparisons are 'statistically equivalent', 'noninferior', or 'potentially inferior'. Transection re-injured and gap re-injured ligaments were 'statistically equivalent' structurally to transection injured ligaments. Transection re-injured ligaments were 'noninferior' both materially and dimensionally to transection injured ligaments. Gap re-injured ligaments were 'potentially inferior' both materially and dimensionally to transection injured ligaments. Two differences between the re-injuries, which affect healing, may explain the mechanical outcomes: the presence or lack of healing products and the proximity of ligament ends at the time of re-injury. Our findings suggest that (in the short term) there is a severity of re-injury below which there is no additional disadvantage to the healing process, mechanical behaviour, and resulting potential for re-injury.

Posttraumatic Osteoarthritis Development and Progression in an Ovine Model of Partial Anterior Cruciate Ligament Transection and Effect of Repeated Intra-articular Methylprednisolone Acetate Injections on Early Disease.

BACKGROUND: Partial anterior cruciate ligament (p-ACL) ruptures are a common injury of athletes. However, few preclinical models have investigated the natural history and treatment of p-ACL injuries. PURPOSE: To (1) demonstrate whether a controlled p-ACL injury model (anteromedial band transection) develops progressive gross morphological and histological posttraumatic osteoarthritis (PTOA)-like changes at 20 and 40 weeks after the injury and (2) investigate the efficacy of repeated (0, 5, 10, and 15 weeks) intra-articular injections of methylprednisolone acetate (MPA; 80 mg/mL) in the mitigation of potential PTOA-like changes after p-ACL transection. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-one 3- to 5-year-old female Suffolk-cross sheep were allocated to 4 groups: (1) nonoperative controls (n = 5), (2) 20 weeks after p-ACL transection (n = 5), (3) 40 weeks after p-ACL transection (n = 6), and (4) 20 weeks after p-ACL transection + MPA (n = 5). Gross morphological grading and histological analyses were conducted. mRNA expression levels for inflammatory, degradative, and structural molecules were assessed. RESULTS: p-ACL transection led to significantly more combined gross damage ( P = .008) and significant aggregate histological damage ( P = .009) at 40 weeks after p-ACL transection than the nonoperative controls, and damage was progressive over time. Macroscopically, MPA appeared to slightly mitigate gross damage at 20 weeks after p-ACL transection in some animals. However, microscopic analysis revealed that repeated MPA injections after p-ACL transection led to significant loss in proteoglycan content compared with the nonoperative controls and 20 weeks after p-ACL transection ( P = .008 and P = .008, respectively). CONCLUSION: p-ACL transection led to significant gross and histological damage by 40 weeks, which was progressive over time. Multiple repeated MPA injections were not appropriate to mitigate injury-related damage in a p-ACL transection ovine model as significant proteoglycan loss was observed in MPA-treated knees. CLINICAL RELEVANCE: A p-ACL injury leads to slow and progressive PTOA-like joint damage, and multiple repeated injections of glucocorticoids may be detrimental to the knee joint in the long term.

Diet-induced obesity leads to pro-inflammatory alterations to the vitreous humour of the eye in a rat model.

OBJECTIVE AND DESIGN: The purpose of this study was to investigate if diet-induced obesity (DIO) and subsequent low-level systemic inflammation would result in local increases in pro-inflammatory mediators in the vitreous humour (VH) of the eyes of rats. METHODS: Sixteen male Sprague-Dawley rats were fed a high-fat/high-sucrose (n = 9) or chow control-diet (n = 7) for 12-weeks. RT-qPCR was conducted on RNA from VH cells and a 27-plex Luminex® Assay was conducted on VH fluid and serum. RESULTS: Increased protein levels for IL-1ß, IL-6, and IL-18 in both serum and VH fluid were observed. VH protein levels for IL-13 and IL-17 were also increased. All mediators significantly increased in VH fluid were also positively correlated with percent body fat. Increased mRNA levels in VH cells for an oxidative stress molecule were accompanied by decreased mRNA levels for an antioxidant scavenger, suggesting an antioxidant/oxidant imbalance in the VH with DIO. In addition, decreased mRNA levels for TRAIL, FAS-L and TGF-ß, molecules associated with immune privilege, were also significantly depressed. CONCLUSIONS: DIO-related metabolic disturbances disrupt VH homeostasis in a manner that reflects development of a pro-inflammatory environment. Prolonged exposure to such an environment may lead to overt pathologies with compromised eye function.

Use of pre-clinical surgically induced models to understand biomechanical and biological consequences of PTOA development.

Post-traumatic osteoarthritis (PTOA) development is often observed following traumatic knee injuries involving key stabilising structures such as the cruciate ligaments or the menisci. Both biomechanical and biological alterations that follow knee injuries have been implicated in PTOA development, although it has not been possible to differentiate clearly between the two causal factors. This review critically examines the outcomes from pre-clinical lapine and ovine injury models arising in the authors' laboratories and differing in severity of PTOA development and progression. Specifically, we focus on how varying severity of knee injuries influence the subsequent alterations in kinematics, kinetics, and biological outcomes. The immediate impact of injury on the lubrication capacity of the joint is examined in the context of its influence on biomechanical alterations, thus linking the biological changes to abnormal kinematics, leading to a focus on the potential areas for interventions to inhibit or prevent development of the disease. We believe that PTOA results from altered cartilage surface interactions where biological and biomechanical factors intersect, and mitigating acute joint inflammation may be critical to prolonging PTOA development. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:454-465, 2017.

Location and gene-specific effects of methylprednisolone acetate on mitigating IL1ß-induced inflammation in mature ovine explant knee tissue.

OBJECTIVE AND DESIGN: To determine the ability of methylprednisolone acetate (MPA) to influence interleukin 1ß (IL1ß)-induced gene expression in ovine knee joint tissues. MATERIAL OR SUBJECTS: Ovine articular cartilage, synovium, and infrapatellar fat pad (IPFP) explants. TREATMENT: Explants were treated with 10-3 M or 10-4 M MPA. METHODS: Explant treatment groups: (1) control (DMEM); (2) inflammation (IL1ß); (3) IL1ß + 10-3 M MPA; or (4) IL1ß + 10-4 M MPA. Cell viability was assessed pre- and post-treatment. Expression of mRNA levels for inflammatory, degradative, anabolic, innate immunity, and adipose-related molecules was quantified via qPCR, and analyzed via the comparative C T method. RESULTS: Except for IL8 in a subset of cartilage locations, matrix metalloproteinases (MMPs) were the only genes consistently affected by MPA. MPA mitigated IL1ß-induced MMP3 expression levels in all regions of the articular cartilage, and in the synovium and IPFP, while MMP1 mRNA expression levels were significantly decreased with MPA after IL1ß in the tibial plateau and synovium, but paradoxical increases in the IPFP. MMP13 mRNA expression levels exhibited significant decreases with MPA after IL1ß in the femoral condyles, tibial plateau, synovium, and IPFP. CONCLUSIONS: MPA treatment suppressed IL1ß-induced mRNA levels for MMPs in articular cartilage, synovium, and IPFP and was found to be tissue-, location-, and gene-specific.

The infrapatellar fat pad is affected by injury induced inflammation in the rabbit knee: use of dexamethasone to mitigate damage.

OBJECTIVE AND DESIGN: The health of the infrapatellar fat pad (IFP) has been linked to pain, joint inflammation, and the onset of post-traumatic osteoarthritis. Thus, early inflammation effects on the IFP could have long term sequelae on joint integrity. This study was designed to characterize the natural history of the IFP in a model of surgically induced knee injury and inflammation, and to test the efficacy of one intra-articular (IA) administration of dexamethasone (DEX) immediately following surgery. METHODS: An IA bone drill hole injury to the rabbit knee was conducted and immediately treated with DEX (n = 12). Early and late post-surgical time-points were investigated (48 h and 9 weeks) and the outcome measures were analysis of IFP histology, mRNA levels for relevant molecules, and protein levels for a subset of cytokines. Data were analyzed against a surgical control (injury without treatment; n = 12), a surgical sham (capsular incision only; n = 12), and normal control (n = 6). TREATMENT: Single IA injection of DEX (0.5 mg/kg), administered at the completion of surgery. RESULTS: IFPs from injured joints exhibited significantly increased cellularity and early fibrosis at 48 h post surgery. While the histological inflammation from a capsular incision alone resolved, knee injured animals progressed to a significantly more fibrotic IFP by 9 weeks. DEX significantly lowered histological scores at 48 h, but not at the 9 weeks. DEX did not influence mRNA levels for IL-1ß, 6, and 8, however, protein analysis indicated that IL-8 levels were lower in DEX treated joints. DEX resulted in significantly elevated expression of mRNA for MCP-1, leptin, and VEGF. CONCLUSION: One IA administration of a glucocorticoid appears to mitigate the initial inflammation within the joint, but is not sufficient to protect the joint to 9 weeks post-surgery.

Ligament and meniscus loading in the ovine stifle joint during normal gait.

BACKGROUND: The ovine stifle joint is an ideal preclinical model to study knee joint biomechanics. Knowledge of the ovine ligamentous and meniscal loading during normal gait is currently limited. METHODS: The in vivo kinematics of the ovine stifle joint (N=4) were measured during "normal" gait using a highly accurate instrumented spatial linkage (ISL, 0.3±0.2mm). These motions were reproduced in vitro using a unique robotic testing platform and the loads carried by the anterior/posterior cruciate ligaments (ACL/PCL), medial/lateral collateral ligaments (MCL/LCL), and medial/lateral menisci (MM/LM) during gait were determined. RESULTS: Considerable inter-subject variability in tissue loads was observed. The load in the ACL was near zero at hoof-strike (0% gait) and reached a peak (100 to 300N) during early-stance (~10% gait). The PCL reached a peak load (200 to 500N) just after hoof-strike (~5% gait) and was mostly unloaded throughout the remainder of stance. Load in the MCL was substantially lower than the cruciate ligaments, reaching a maximum of 50 to 100N near the beginning of stance. The LCL carried a negligible amount of load through the entire gait cycle. There was also a major contribution of the MM and LM to load transfer from the femur to the tibia during normal gait. The total meniscal load reached a maximum average between 350 and 550N during gait. CONCLUSION: Knowledge of joint function during normal motion is essential for understanding normal and pathologic joint states. The considerable variability in the magnitudes and patterns of tissue loads among animals simulates clinical variability in humans. LEVEL OF EVIDENCE: III.

Relationship between increased in vivo meniscal loads and abnormal tibiofemoral surface alignment in ACL deficient sheep is varied.

The aim of this study was to quantify how abnormal dynamic tibiofemoral surface alignment affects the load bearing function of menisci in vivo. Using a sheep model of ACL deficiency, we tested the hypothesis that increased in vivo meniscal loads correlate with greater tibiofemoral surface alignment abnormality. Stifle kinematics were recorded using a bone-mounted instrumented spatial linkage in four sheep before, and at four and twenty weeks (w) after ACL transection. A parallel robotic manipulator was used to quantify stifle kinetics by reproducing each animal׳s in vivo kinematics and measuring tissue loads during gait. Meniscal resultant loads were estimated from the change in joint reaction force after sequentially removing load-bearing tissues. Tibiofemoral subchondral surfaces were then traced and modeled using thin plate splines. Proximity disturbance is a surface interaction measure used to quantify dynamic tibiofemoral surface alignment abnormality. ACL transection increased meniscal loads by 30-145% at 20w post-ACL transection, whereas the degree of dynamic tibiofemoral subchondral surface alignment varied between sheep. Positive and significant correlations between increased meniscal loads and proximity disturbance values >10mm were observed (R2=0.04-0.57; p≤0.05). Our results suggest that the proximity disturbance measure reflects abnormal meniscal loads following ACL injury; however given the range of R2 values, perturbations in dynamic tibiofemoral subchondral surface alignment do not explain abnormal joint kinetics entirely, and point to the presence of other dynamic compensatory mechanisms that may have a significant bearing on in vivo joint function and long-term joint health.

Single intra-articular dexamethasone injection immediately post-surgery in a rabbit model mitigates early inflammatory responses and post-traumatic osteoarthritis-like alterations.

Despite surgical reconstruction of the anterior cruciate ligament, a significant number of patients will still develop post-traumatic osteoarthritis (PTOA). Our objective was to determine if mitigating aspects of the acute phase of inflammation following a defined knee surgery with a single administration of a glucocorticoid could prevent the development of PTOA-like changes within an established rabbit model of surgically induced PTOA. An early and late post-surgical time-point was investigated in this study (48 h and 9 weeks post-surgery) in which the following groups were repeated (each n=6, for a total of 24 rabbits per time-point, and 48 rabbits used in the study): control (age/sex matched), sham (arthrotomy), drill injury (arthrotomy+two drill holes to a non-cartilaginous area of the femoral notch), and drill injury+single intra-articular (IA) injection of dexamethasone (DEX). At 48 h post-surgery, DEX treatment significantly lowered the mRNA levels for a subset of pro-inflammatory mediators, and significantly lowered the histological grade. Nine weeks post surgery, DEX treatment significantly lowered the histological scores (presented as effect size) for synovium (3.8), lateral femoral condyle (3.9), and lateral tibial cartilage (5.1) samples. Thus, DEX likely acts to prevent injury induced inflammation that could contribute to subsequent joint damage.

Alterations in Hoffa's fat pad induced by an inflammatory response following idealized anterior cruciate ligament surgery.

OBJECTIVE: To determine whether inflammation following anterior cruciate ligament (ACL) reconstruction leads to long-term pathological changes in the infrapatellar fat pad (IPFP or Hoffa's fat pad) which could compromise the integrity of the knee joint. MATERIALS AND METHODS: Sixteen mature sheep underwent anatomic idealized ACL reconstruction surgery (ACL-R) and were sacrificed at 2 weeks (n = 9) and 20 weeks (n = 7) post-ACL-R. Five additional animals served as unoperated controls. A histological grading protocol was developed to quantify the changes in the IPFP post-injury. mRNA expression levels for key markers of inflammation, angiogenesis and tissue regeneration were assessed by qPCR. RESULTS: The IPFP exhibited altered cellularity and fibrosis at 2 and 20 weeks post-ACL-R. Immunohistochemistry detected macrophage-like cells in the IPFP which were increased at 20 weeks. Specific pro-inflammatory cytokines and IPFP specific adipokines exhibited changes indicating early inflammation mediated alterations. Elevations in CD105 mRNA levels at 2 weeks corroborated the increases in neovascularization observed in the IPFP following injury. CONCLUSIONS: Sustained long-term pathological changes stemming from inflammation are present in IPFP tissue after ACL-R surgery and may compromise the long-term integrity of the knee joint.

Metabolic profiling of synovial fluid in a unilateral ovine model of anterior cruciate ligament reconstruction of the knee suggests biomarkers for early osteoarthritis.

Joint injuries and subsequent osteoarthritis (OA) are the leading causes of chronic joint disease. In this work, we explore the possibility of applying magnetic resonance spectroscopy-based metabolomics to detect host responses to an anterior cruciate ligament (ACL) reconstruction injury in synovial fluid in an ovine model. Using multivariate statistical analysis, we were able to distinguish post-injury joint samples (ACL and sham surgery) from the uninjured control samples, and as well the ACL surgical samples from sham surgery. In all samples there were 65 metabolites quantified, of which six could be suggested as biomarkers for early post-injury degenerative changes in the knee joints: isobutyrate, glucose, hydroxyproline, asparagine, serine, and uridine. Our results raise a cautionary note indicating that surgical interventions into the knee can result in metabolic alterations that need to be distinguished from those caused by the early onset of OA. Our findings illustrate the potential application of metabolomics as a diagnostic and prognostic tool for detection of injuries to the knee joint. The ability to detect a unique pattern of metabolic changes in the synovial fluid of sheep offers the possibility of extending the approach to precision medicine protocols in patient populations in the future.

A new measure of tibiofemoral subchondral bone interactions that correlates with early cartilage damage in injured sheep.

We have demonstrated previously that chondral damage is associated with increased knee surface velocities following ligament and meniscus injuries in sheep. We tested the hypothesis that cartilage damage scores would correlate with a new bone surface interaction measure that captures complex changes in tibiofemoral alignment, "proximity disturbance" (PD). Six sheep underwent combined anterior cruciate and medial collateral ligament transection (ACL/MCLx), five complete lateral meniscectomy (Mx), and four sham arthrotomy (Sham). Tibiofemoral subchondral bone surfaces were modeled, and the post-operative changes in relative separation of the surfaces (i.e., "proximity") were derived from subject-specific in vivo 3D stifle kinematics. Surface areas of regions of near contact were determined, and PD was calculated as the range of change in tibiofemoral proximity, divided by normalized overlapping proximity surface areas between baseline and post-operative time points. Cartilage morphology was graded at dissection. ACL/MCLx PD was significantly elevated relative to Mx and Shams, and correlated with cartilage damage (r(2) = 0.88-0.98). Although not statistically significant, Mx PD values tended to be higher than those of Shams, and correlated with cartilage damage. Results from both injury models suggest that increasing change in tibiofemoral surface alignment may be increasingly deleterious to long-term cartilage health in sheep.

A computational method to differentiate normal individuals, osteoarthritis and rheumatoid arthritis patients using serum biomarkers.

The objective of this study was to develop a method for categorizing normal individuals (normal, n = 100) as well as patients with osteoarthritis (OA, n = 100), and rheumatoid arthritis (RA, n = 100) based on a panel of inflammatory cytokines expressed in serum samples. Two panels of inflammatory proteins were used as training sets in the construction of two separate artificial neural networks (ANNs). The first training set consisted of all proteins (38 in total) and the second consisted of only the significantly different proteins expressed (12 in total) between at least two patient groups. Both ANNs obtained high levels of sensitivity and specificity, with the first and second ANN each diagnosing 100% of test set patients correctly. These results were then verified by re-investigating the entire dataset using a decision tree algorithm. We show that ANNs can be used for the accurate differentiation between serum samples of patients with OA, a diagnosed RA patient comparator cohort and normal/control cohort. Using neural network and systems biology approaches to manage large datasets derived from high-throughput proteomics should be further explored and considered for diagnosing diseases with complex pathologies.

Monocyte chemotactic protein-1 inhibits chondrogenesis of synovial mesenchymal progenitor cells: an in vitro study.

Osteoarthritis (OA) is a multifactorial, often progressive, painful disease. OA often progresses with an apparent irreversible loss of articular cartilage, exposing underlying bone, resulting in pain and loss of mobility. This cartilage loss is thought to be permanent due to ineffective repair and apparent lack of stem/progenitor cells in that tissue. However, the adjacent synovial lining and synovial fluid are abundant with mesenchymal progenitor/stem cells (synovial mesenchymal progenitor cells [sMPCs]) capable of differentiating into cartilage both in vitro and in vivo. Previous studies have demonstrated that MPCs can home to factors such as monocyte chemotactic protein 1 (MCP-1/CCL2) expressed after injury. While MCP-1 (and its corresponding receptors) appears to play a role in recruiting stem cells to the site of injury, in this study, we have demonstrated that MCP-1 is upregulated in OA synovial fluid and that exposure to MCP-1 activates sMPCs, while concurrently inhibiting these cells from undergoing chondrogenesis in vitro. Furthermore, exposure to physiological (OA knee joint synovial fluid) levels of MCP-1 triggers changes in the transcriptome of sMPCs and prolonged exposure to the chemokine induces the expression of MCP-1 in sMPCs, resulting in a positive feedback loop from which sMPCs cannot apparently escape. Therefore, we propose a model where MCP-1 (normally expressed after joint injury) recruits sMPCs to the area of injury, but concurrently triggers changes in sMPC transcriptional regulation, leading to a blockage in the chondrogenic program. These results may open up new avenues of research into the lack of endogenous repair observed after articular cartilage injury and/or arthritis.