Focal compression of the cervical spinal cord alone does not indicate high risk of neurological deterioration in patients with a diagnosis of mild degenerative cervical myelopathy.

Degenerative Cervical Myelopathy (DCM) is the functional derangement of the spinal cord resulting from vertebral column spondylotic degeneration. Typical neurological symptoms of DCM include gait imbalance, hand/arm numbness, and upper extremity dexterity loss. Greater spinal cord compression is believed to lead to a higher rate of neurological deterioration, although clinical experience suggests a more complex mechanism involving spinal canal diameter (SCD). In this study, we utilized machine learning clustering to understand the relationship between SCD and different patterns of cord compression (i.e. compression at one disc level, two disc levels, etc.) to identify patient groups at risk of neurological deterioration. 124 MRI scans from 51 non-operative DCM patients were assessed through manual scoring of cord compression and SCD measurements. Dimensionality reduction techniques and k-means clustering established patient groups that were then defined with their unique risk criteria. We found that the compression pattern is unimportant at SCD extremes (≤14.5 mm or > 15.75 mm). Otherwise, severe spinal cord compression at two disc levels increases deterioration likelihood. Notably, if SCD is normal and cord compression is not severe at multiple levels, deterioration likelihood is relatively reduced, even if the spinal cord is experiencing compression. We elucidated five patient groups with their associated risks of deterioration, according to both SCD range and cord compression pattern. Overall, SCD and focal cord compression alone do not reliably predict an increased risk of neurological deterioration. Instead, the specific combination of narrow SCD with multi-level focal cord compression increases the likelihood of neurological deterioration in mild DCM patients.

Advanced MRI metrics improve the prediction of baseline disease severity for individuals with degenerative cervical myelopathy.

BACKGROUND CONTEXT: Degenerative cervical myelopathy (DCM) is the most common form of atraumatic spinal cord injury globally. Degeneration of spinal discs, bony osteophyte growth and ligament pathology results in physical compression of the spinal cord contributing to damage of white matter tracts and grey matter cellular populations. This results in an insidious neurological and functional decline in patients which can lead to paralysis. Magnetic resonance imaging (MRI) confirms the diagnosis of DCM and is a prerequisite to surgical intervention, the only known treatment for this disorder. Unfortunately, there is a weak correlation between features of current commonly acquired MRI scans ("community MRI, cMRI") and the degree of disability experienced by a patient. PURPOSE: This study examines the predictive ability of current MRI sequences relative to "advanced MRI" (aMRI) metrics designed to detect evidence of spinal cord injury secondary to degenerative myelopathy. We hypothesize that the utilization of higher fidelity aMRI scans will increase the effectiveness of machine learning models predicting DCM severity and may ultimately lead to a more efficient protocol for identifying patients in need of surgical intervention. STUDY DESIGN/SETTING: Single institution analysis of imaging registry of patients with DCM. PATIENT SAMPLE: A total of 296 patients in the cMRI group and 228 patients in the aMRI group. OUTCOME MEASURES: Physiologic measures: accuracy of machine learning algorithms to detect severity of DCM assessed clinically based on the modified Japanese Orthopedic Association (mJOA) scale. METHODS: Patients enrolled in the Canadian Spine Outcomes Research Network registry with DCM were screened and 296 cervical spine MRIs acquired in cMRI were compared with 228 aMRI acquisitions. aMRI acquisitions consisted of diffusion tensor imaging, magnetization transfer, T2-weighted, and T2*-weighted images. The cMRI group consisted of only T2-weighted MRI scans. Various machine learning models were applied to both MRI groups to assess accuracy of prediction of baseline disease severity assessed clinically using the mJOA scale for cervical myelopathy. RESULTS: Through the utilization of Random Forest Classifiers, disease severity was predicted with 41.8% accuracy in cMRI scans and 73.3% in the aMRI scans. Across different predictive model variations tested, the aMRI scans consistently produced higher prediction accuracies compared to the cMRI counterparts. CONCLUSIONS: aMRI metrics perform better in machine learning models at predicting disease severity of patients with DCM. Continued work is needed to refine these models and address DCM severity class imbalance concerns, ultimately improving model confidence for clinical implementation.

Prx1+ MPCs Accumulate in the Dura Mater of Wild-Type and p21-/- Mice Followed by a Specific Reduction in p21-/- Dural MPCs.

Epidural fat contains a population of mesenchymal progenitor cells (MPCs), and this study explores the behavior of these cells on the adjacent dura mater during growth and in response to injury in a p21 knockout mouse model. p21-/- mice are known to have increased cell proliferation and enhanced tissue regeneration post-injury. Therefore, it is hypothesized that the process by which epidural fat MPCs maintain the dura mater can be accelerated in p21-/- mice. Using a Prx1 lineage tracing mouse model, the epidural fat MPCs are found to increase in the dura mater over time in both C57BL/6 (p21+/+ ) and p21-/- mice; however, by 3 weeks post-tamoxifen induction, few MPCs are observed in p21-/- mice. These endogenous MPCs also localize to dural injuries in both mouse strains, with MPCs in p21-/- mice demonstrating increased proliferation. When epidural fat MPCs derived from p21-/- mice are transplanted into dural injuries in C57BL/6 mice, these MPCs are found in the injury site. It is demonstrated that epidural fat MPCs play a role in dural tissue maintenance and are able to directly contribute to dural injury repair. This suggests that these MPCs have the potential to treat injuries and/or pathologies in tissues surrounding the spinal cord.

Proteoglycan 4 (PRG4) treatment enhances wound closure and tissue regeneration.

The wound healing response is one of most primitive and conserved physiological responses in the animal kingdom, as restoring tissue integrity/homeostasis can be the difference between life and death. Wound healing in mammals is mediated by immune cells and inflammatory signaling molecules that regulate tissue resident cells, including local progenitor cells, to mediate closure of the wound through formation of a scar. Proteoglycan 4 (PRG4), a protein found throughout the animal kingdom from fish to elephants, is best known as a glycoprotein that reduces friction between articulating surfaces (e.g. cartilage). Previously, PRG4 was also shown to regulate the inflammatory and fibrotic response. Based on this, we asked whether PRG4 plays a role in the wound healing response. Using an ear wound model, topical application of exogenous recombinant human (rh)PRG4 hastened wound closure and enhanced tissue regeneration. Our results also suggest that rhPRG4 may impact the fibrotic response, angiogenesis/blood flow to the injury site, macrophage inflammatory dynamics, recruitment of immune and increased proliferation of adult mesenchymal progenitor cells (MPCs) and promoting chondrogenic differentiation of MPCs to form the auricular cartilage scaffold of the injured ear. These results suggest that PRG4 has the potential to suppress scar formation while enhancing connective tissue regeneration post-injury by modulating aspects of each wound healing stage (blood clotting, inflammation, tissue generation and tissue remodeling). Therefore, we propose that rhPRG4 may represent a potential therapy to mitigate scar and improve wound healing.

Proteoglycan 4 is present within the dura mater and produced by mesenchymal progenitor cells.

Mesenchymal progenitor cells (MPCs) have been recently identified in human and murine epidural fat and have been hypothesized to contribute to the maintenance/repair/regeneration of the dura mater. MPCs can secrete proteoglycan 4 (PRG4/lubricin), and this protein can regulate tissue homeostasis through bio-lubrication and immunomodulatory functions. MPC lineage tracing reporter mice (Hic1) and human epidural fat MPCs were used to determine if PRG4 is expressed by these cells in vivo. PRG4 expression co-localized with Hic1+ MPCs in the dura throughout skeletal maturity and was localized adjacent to sites of dural injury. When Hic1+ MPCs were ablated, PRG4 expression was retained in the dura, yet when Prx1+ MPCs were ablated, PRG4 expression was completely lost. A number of cellular processes were impacted in human epidural fat MPCs treated with rhPRG4, and human MPCs contributed to the formation of epidural fat, and dura tissues were xenotransplanted into mouse dural injuries. We have shown that human and mouse MPCs in the epidural/dura microenvironment produce PRG4 and can contribute to dura homeostasis/repair/regeneration. Overall, these results suggest that these MPCs have biological significance within the dural microenvironment and that the role of PRG4 needs to be further elucidated.

Synovial mesenchymal progenitor derived aggrecan regulates cartilage homeostasis and endogenous repair capacity.

Aggrecan is a critical component of the extracellular matrix of all cartilages. One of the early hallmarks of osteoarthritis (OA) is the loss of aggrecan from articular cartilage followed by degeneration of the tissue. Mesenchymal progenitor cell (MPC) populations in joints, including those in the synovium, have been hypothesized to play a role in the maintenance and/or repair of cartilage, however, the mechanism by which this may occur is unknown. In the current study, we have uncovered that aggrecan is secreted by synovial MPCs from healthy joints yet accumulates inside synovial MPCs within OA joints. Using human synovial biopsies and a rat model of OA, we established that this observation in aggrecan metabolism also occurs in vivo. Moreover, the loss of the "anti-proteinase" molecule alpha-2 macroglobulin (A2M) inhibits aggrecan secretion in OA synovial MPCs, whereas overexpressing A2M rescues the normal secretion of aggrecan. Using mice models of OA and cartilage repair, we have demonstrated that intra-articular injection of aggrecan into OA joints inhibits cartilage degeneration and stimulates cartilage repair respectively. Furthermore, when synovial MPCs overexpressing aggrecan were transplanted into injured joints, increased cartilage regeneration was observed vs. wild-type MPCs or MPCs with diminished aggrecan expression. Overall, these results suggest that aggrecan secreted from joint-associated MPCs may play a role in tissue homeostasis and repair of synovial joints.

Prx1 + and Hic1+ Mesenchymal Progenitors Are Present Within the Epidural Fat and Dura Mater and Participate in Dural Injury Repair.

Epidural fat is commonly discarded during spine surgery to increase the operational field. However, mesenchymal progenitor cells (MPCs) have now been identified in human epidural fat and within the murine dura mater. This led us to believe that epidural fat may regulate homeostasis and regeneration in the vertebral microenvironment. Using two MPC lineage tracing reporter mice (Prx1 and Hic1), not only have we found that epidural fat MPCs become incorporated in the dura mater over the course of normal skeletal maturation, but have also identified these cells as an endogenous source of repair and regeneration post-dural injury. Moreover, our results reveal a partial overlap between Prx1+ and Hic1+ populations, indicating a potential hierarchical relationship between the two MPC populations. This study effectively challenges the notion of epidural fat as an expendable tissue and mandates further research into its biological function and relevance.

The Dose-Response Effect of the Mast Cell Stabilizer Ketotifen Fumarate on Posttraumatic Joint Contracture: An in Vivo Study in a Rabbit Model.

Posttraumatic joint contracture is a debilitating complication following an acute fracture or intra-articular injury that can lead to loss of motion and an inability to complete activities of daily living. In prior studies using an established in vivo model, we found that ketotifen fumarate (KF), a mast cell stabilizer, was associated with a significant reduction in the severity of posttraumatic joint contracture. Our primary research question in the current study was to determine whether a dose-response relationship exists between KF and posttraumatic joint contracture reduction. METHODS: A standardized operative method to create posttraumatic joint contracture in a knee was performed on skeletally mature New Zealand White rabbits. The animals were randomly assigned to 1 of 5 groups (n = 10 per group): a nonoperative control group, an operative control group, or 1 of 3 experimental KF groups (0.01 mg/kg [the KF 0.01 group], 0.1 mg/kg [KF 0.1], or 5.0 mg/kg [KF 5.0]). Flexion contractures were measured following 8 weeks of knee immobilization using a hydraulic material-testing machine. The posterior knee joint capsules were then harvested for quantification of myofibroblast and mast cell numbers with immunohistochemistry analysis. RESULTS: Forty-five rabbits were used in the final analysis. Contracture severity was significantly reduced in the KF 0.1 group (p = 0.016) and the KF 5.0 group (p = 0.001) compared with the operative control group. When converted to a percent response, posttraumatic joint contracture reduction was 13%, 45%, and 63% for the KF 0.01, KF 0.1, and KF 5.0 groups, respectively. A half-maximal effective concentration (EC50) for KF of 0.22 mg/kg was established. There was also a decrease in myofibroblasts, mast cells, and substance P-containing nerve fiber counts with increasing doses of KF. CONCLUSIONS: Using a preclinical, rabbit in vivo model of posttraumatic joint contracture, increasing doses of KF were associated with decreasing biomechanical estimates of knee posttraumatic joint contracture as well as decreasing numbers of myofibroblasts, mast cells, and substance P-containing nerve fibers. CLINICAL RELEVANCE: KF has been used safely in humans for more than 40 years and, to our knowledge, is the first and only agent ready to be potentially translated into an effective treatment for posttraumatic joint contracture.

Human serum mast cell tryptase levels in elbow fractures or dislocations and its association with injury severity.

Mast cells contain an abundance of tryptase, and preclinical models have shown elevated serum mast cell tryptase (SMCT) in the setting of posttraumatic joint contractures. Therefore, SMCT emerged as a potential biomarker to help recognize patients with more severe injuries and a higher likelihood of developing contractures. The objective of this study is to assess SMCT levels in participants with varying severity of elbow fractures and/or dislocations. A prospective cohort including 13 participants with more severe injuries that required an operation and 28 participants with less severe injuries managed nonoperatively were evaluated. A control group of eight individuals without elbow injuries was also evaluated. The SMCT levels were measured using an enzyme-linked immunosorbent assay kit specific for human mast cell tryptase. A one-way analysis of variance and Tukey's Honest Significance test was used to assess for statistical significance among and between the three groups. The average time from injury to the collection of the blood samples was 4 ± 2 days. Highly significant differences were identified between the operative, nonoperative, and control groups (P = .0005). In the operative group, SMCT levels were significantly higher than the nonoperative group (P = .0005) and the control group (P = .009), suggesting a correlation between SMCT levels and injury severity. There was no statistically significant difference in SMCT levels between the nonoperative and control groups. The SMCT levels were elevated in participants with acute elbow injuries requiring operative intervention, suggesting that SMCT levels were higher in injuries regarded as more severe.

Serum Mast Cell Tryptase as a Marker of Posttraumatic Joint Contracture in a Rabbit Model.

OBJECTIVES: Mast cells have been identified as key mediators of posttraumatic joint contracture, and stabilizing medications (ketotifen) have been shown to decrease contracture severity. Serum mast cell tryptase (SMCT) levels are used clinically to monitor mast cell-mediated conditions. The goals of this study were to determine if SMCT levels are elevated in the setting of joint contracture, if they can be decreased in association with ketotifen therapy, and if they correlate with contracture severity. METHODS: This study used a previously developed rabbit model in which 39 animals were divided into 4 groups: operatively created joint contracture (ORC, n = 13), operatively created contracture treated with ketotifen at 2 doses (KF0.5, n = 9; KF1.0, n = 9), and healthy rabbits (NC, n = 8). Range of motion measures were performed at 8 weeks after the surgery. Serum samples were collected on postoperative days 1, 3, 5, 7, 21, 35, and 49. SMCT levels were measured using a rabbit-specific enzyme-linked immunosorbent assay. RESULTS: Levels of SMCT were highest in the operatively created joint contracture group and were significantly greater compared with both ketotifen groups (P < 0.001). Levels were highest at postoperative day 1 with a trend to decrease over time. A positive correlation between SMCT levels and contracture severity was observed in all operative groups (P < 0.05). CONCLUSIONS: Levels of SMCT are elevated in the setting of joint contracture, decreased in association with ketotifen therapy, and positively correlated with contracture severity. This is the first study to establish a relationship between SMCT and joint injury. Measurement of SMCT may be valuable in identifying those at risk of posttraumatic joint contracture.

Compromised Neurotrophic and Angiogenic Regenerative Capability during Tendon Healing in a Rat Model of Type-II Diabetes.

Metabolic diseases such as diabetes mellitus type-II (DM-II) may increase the risk of suffering painful connective tissue disorders and tendon ruptures. The pathomechanisms, however, by which diabetes adversely affects connective tissue matrix metabolism and regeneration, still need better definition. Our aim was to study the effect of DM-II on expressional changes of neuro- and angiotrophic mediators and receptors in intact and healing Achilles tendon. The right Achilles tendon was transected in 5 male DM-II Goto-Kakizaki (GK) and 4 age-matched Wistar control rats. The left Achilles tendons were left intact. At week 2 post-injury, NGF, BDNF, TSP, and receptors TrkA, TrkB and Nk1 gene expression was studied by quantitative RT-PCR (qRT-PCR) and their protein distribution by immunohistochemistry in intact and injured tendons. The expression of tendon-related markers, Scleraxis (SCX) and Tenomodulin (TNMD), was evaluated by qRT-PCR in intact and injured tendons. Injured tendons of diabetic GK rats exhibited significantly down-regulated Ngf and Tsp1 mRNA and corresponding protein levels, and down-regulated Trka gene expression compared to injured Wistar controls. Intact tendons of DM-II GK rats displayed reduced mRNA levels for Ngf, Tsp1 and Trkb compared to corresponding intact non-diabetic tendons. Up-regulated Scx and Tnmd gene expression was observed in injured tendons of normal and diabetic GK rats compared to intact Wistar controls. However, these molecules were not up-regulated in injured DM-II GK rats compared to their corresponding controls. Our results suggest that DM-II has detrimental effects on neuro- and angiotrophic pathways, and such effects may reflect the compromised repair seen in diabetic Achilles tendon. Thus, novel approaches for regeneration of injured, including tendinopathic, and surgically repaired diabetic tendons may include therapeutic molecular modulation of neurotrophic pathways such as NGF and its receptors.

Allogeneic Bone Marrow Transplant from MRL/MpJ Super-Healer Mice Does Not Improve Articular Cartilage Repair in the C57Bl/6 Strain.

BACKGROUND: Articular cartilage has been the focus of multiple strategies to improve its regenerative/ repair capacity. The Murphy Roths Large (MRL/MpJ) "super-healer" mouse demonstrates an unusual enhanced regenerative capacity in many tissues and provides an opportunity to further study endogenous cartilage repair. The objective of this study was to test whether the super-healer phenotype could be transferred from MRL/MpJ to non-healer C57Bl/6 mice by allogeneic bone marrow transplant. METHODOLOGY: The healing of 2mm ear punches and full thickness cartilage defects was measured 4 and 8 weeks after injury in control C57Bl/6 and MRL/MpJ "super-healer" mice, and in radiation chimeras reconstituted with bone marrow from the other mouse strain. Healing was assessed using ear hole diameter measurement, a 14 point histological scoring scale for the cartilage defect and an adapted version of the Osteoarthritis Research Society International scale for assessment of osteoarthritis in mouse knee joints. PRINCIPAL FINDINGS: Normal and chimeric MRL mice showed significantly better healing of articular cartilage and ear wounds along with less severe signs of osteoarthritis after cartilage injury than the control strain. Contrary to our hypothesis, however, bone marrow transplant from MRL mice did not confer improved healing on the C57Bl/6 chimeras, either in regards to ear wound healing or cartilage repair. CONCLUSION AND SIGNIFICANCE: The elusive cellular basis for the MRL regenerative phenotype still requires additional study and may possibly be dependent on additional cell types external to the bone marrow.

Neuroinflammatory Mechanisms of Connective Tissue Fibrosis: Targeting Neurogenic and Mast Cell Contributions.

Significance: The pathogenesis of fibrogenic wound and connective tissue healing is complex and incompletely understood. Common observations across a vast array of human and animal models of fibroproliferative conditions suggest neuroinflammatory mechanisms are important upstream fibrogenic events. Recent Advances: As detailed in this review, mast cell hyperplasia is a common observation in fibrotic tissue. Recent investigations in human and preclinical models of hypertrophic wound healing and post-traumatic joint fibrosis provides evidence that fibrogenesis is governed by a maladaptive neuropeptide-mast cell-myofibroblast signaling pathway. Critical Issues: The blockade and manipulation of these factors is providing promising evidence that if timed correctly, the fibrogenic process can be appropriately regulated. Clinically, abnormal fibrogenic healing responses are not ubiquitous to all patients and the identification of those at-risk remains an area of priority. Future Directions: Ultimately, an integrated appreciation of the common pathobiology shared by many fibrogenic connective tissue conditions may provide a scientific framework to facilitate the development of novel antifibrotic prevention and treatment strategies.

A myofibroblast-mast cell-neuropeptide axis of fibrosis in post-traumatic joint contractures: an in vitro analysis of mechanistic components.

Previous studies have implicated a myofibroblast-mast cell-neuropeptide axis of fibrosis in pathologic joint capsules from post-traumatic contractures. The hypothesis to be tested is that joint capsule cells (JC) from human elbows with post-traumatic contractures and their interactions with mast cells (MC) and neuropeptides in the microenvironment underlie the pathogenesis of contractures. The hypothesis was tested using an in vitro collagen gel contraction model. The JC were isolated from human elbow capsules and mixed with neutralized PureCol collagen I. The gels were treated in various ways, including addition of MC (HMC-1), the neuropeptide substance P (SP), an NK1 receptor (SP receptor) antagonist RP67580 and the mast cell stabilizer ketotifen fumarate (KF). The collagen gels were released from the wells and gel size (contraction) was measured optically at multiple time points. The JC contracted collagen gels in a dose-dependent manner. This was enhanced in the presence of MC and increased further with SP. Increasing concentrations of the SP receptor antagonist, RP67580 or the mast cell stabilizer, KF decreased the magnitude of contraction. These observations identify putative mechanistic components of a myofibroblast-mast cell-neuropeptide axis of fibrosis in the joint capsules in post-traumatic contractures and potential prophylactic or therapeutic interventions.

Neuronal pathways in tendon healing and tendinopathy--update.

The regulatory mechanisms involved in tendon homeostasis and repair are not fully understood. Accumulating data, however, demonstrate that the nervous system, in addition to afferent (sensory) functions, through efferent pathways plays an active role in regulating pain, inflammation, and tissue repair. In normal-, healing- and tendinopathic tendons three neurosignalling pathways consisting of autonomic, sensory and glutamatergic neuromediators have been established. In healthy tendons, neuromediators are found in the paratenon, whereas the proper tendon is practically devoid of nerves, reflecting that normal tendon homeostasis is regulated by pro- and anti-inflammatory mediators from the tendon surroundings. During tendon repair, however, there is extensive nerve ingrowth into the tendon proper and subsequent time-dependent appearance of sensory, autonomic and glutamatergic mediators, which amplify and fine-tune inflammation and tendon regeneration. In tendinopathy, excessive and protracted sensory and glutamatergic signalling may be involved in inflammatory, painful and hypertrophic tissue reactions. As our understanding of these processes improves, neuronal mediators may prove to be useful in the development of targeted pharmacotherapy and tissue engineering approaches to painful, degenerative and traumatic tendon disorders.

Posttraumatic elbow contractures: targeting neuroinflammatory fibrogenic mechanisms.

Posttraumatic elbow stiffness remains a common and challenging clinical problem. In the setting of a congruent articular surface, the joint capsule is regarded as the major motion-limiting anatomic structure. The affected joint capsule is characterized by irreversible biomechanical and biochemical fibrogenic changes strikingly similar to those observed in many other fibroproliferative human conditions. Studies in humans and preclinical animal models are providing emergent evidence that neuroinflammatory mechanisms are critical upstream events in the pathogenesis of posttraumatic connective tissue fibrogenesis. Maladaptive recruitment and activation of mast cell infiltrates coupled with the aberrant expression of growth factors such as transforming growth factor-beta, nerve growth factor, and neuropeptides such as substance P are common observations in posttraumatic joint contractures and many other fibroproliferative disorders. Blockade of these factors is providing promising evidence that if treatment is timed correctly, the fibrogenic process can be interrupted or impeded. This review serves to highlight opportunities derived from these recent discoveries across many aberrant fibrogenic disorders as we strive to develop novel, targeted antifibrotic prevention and treatment strategies for posttraumatic elbow stiffness.

The mast cell stabilizer ketotifen reduces joint capsule fibrosis in a rabbit model of post-traumatic joint contractures.

OBJECTIVES: Using a rabbit model of post-traumatic joint contractures, we investigated whether treatment with a mast cell stabilizer after joint injury would lessen the molecular manifestations of joint capsule fibrosis. METHODS: Surgical joint injury was used to create stable post-traumatic contractures of the knee in skeletally mature New Zealand white rabbits. Four groups of animals were studied: a non-operated control group (n = 8), an operated contracture group (n = 13) and two operated groups treated with the mast cell stabilizer, ketotifen, at doses of 0.5 mg/kg (n = 9) and 1.0 mg/kg (n = 9) twice daily. Joint capsule fibrosis was assessed by quantifying the mRNA and protein levels of α-SMA, tryptase, TGF-ß1, collagen I and collagen III. Significance was tested using an ANOVA analysis of variance. RESULTS: The protein and mRNA levels of α-SMA, TGF-ß1, tryptase and collagen I and III were significantly elevated in the operated contracture group compared to control (p < 0.01). In both ketotifen-treated groups, protein and mRNA levels of α-SMA, TGF-ß1 and collagen I were significantly reduced compared to the operated contracture group (p < 0.01). CONCLUSIONS: These data suggest an inflammatory pathway mediated by mast cell activation is involved in joint capsule fibrosis after traumatic injury.

The mast cell stabilizer ketotifen fumarate lessens contracture severity and myofibroblast hyperplasia: a study of a rabbit model of posttraumatic joint contractures.

BACKGROUND: The propensity of joints to become stiff after trauma is widely appreciated, and the joint capsule is commonly recognized as the major motion-limiting anatomical structure. Affected joint capsules become fibrotic, characterized by myofibroblast and collagen hyperplasia. Mast cell hyperplasia is common within fibrotic tissue, and mast cells are known to synthesize many profibrotic mediators. We hypothesized that mast cell inhibition after skeletal injury would lessen contracture severity and reduce myofibroblast hyperplasia within the joint capsule. METHODS: Posttraumatic contractures of the knee were created with use of a combination of intra-articular injury and internal immobilization in skeletally mature New Zealand White rabbits. Four groups of animals were studied: a nonoperative control group, a group with the operatively created contracture and no pharmacological treatment (the operative contracture group), and two groups with the operatively created contracture that were treated with a mast cell stabilizer, ketotifen fumarate, at a dose of either 0.5 or 1.0 mg/kg twice daily (the 0.5-mg/kg and 1.0-mg/kg ketotifen groups). After eight weeks of immobilization, flexion contractures were measured and the posterior aspect of the joint capsule was harvested for quantification of myofibroblast and mast cell numbers. RESULTS: Flexion contractures developed in the operative contracture group (mean and standard deviation, 58 degrees +/- 14 degrees ), and the severity of the contractures was reduced in both the group treated with 0.5 mg/kg of ketotifen (42 degrees +/- 17 degrees ) and the group treated with 1.0 mg/kg of ketotifen (45 degrees +/- 10 degrees ) (p < 0.02). The joint capsule myofibroblast and mast cell numbers in the operative contracture group were significantly increased compared with the values in the control group (p < 0.001), and the myofibroblast and mast cell numbers in both ketotifen groups were significantly reduced compared with the values in the operative contracture group (p < 0.001). CONCLUSIONS: The use of a mast cell stabilizer, ketotifen, was effective in reducing the biomechanical and cellular manifestations of joint capsule fibrosis in a rabbit model of posttraumatic joint contracture. This finding suggests that an inflammatory pathway, mediated by mast cell activation, is involved in the induction of joint capsule fibrosis after traumatic injury.

Airway compromise secondary to upper cervical spine injury.

BACKGROUND: Airway compromise secondary to isolated injury at the atlas (C1) and axis (C2) without an associated spinal cord injury is a rare, but recognized phenomenon that results in significant morbidity and mortality. No previous study in the literature has reported the incidence of this potentially lethal complication of these relatively common fractures. METHODS: The medical records for 625 consecutive patients who presented to a Level I trauma center with C1 and C2 fractures during the years from 1996 to 2005 were reviewed retrospectively. Strict inclusion and exclusion criteria were applied to identify adult patients with isolated fractures and no other injuries. All patients that developed significant airway compromise were identified and correlations were made with the patient's demographic features, clinical presentation, and radiologic findings, to determine potential risk factors. RESULTS: During the 10 years studied, 343 patients with isolated C1 and C2 fractures were identified. Of these, 17 patients developed significant airway compromise. This represents a 4.9% incidence of this potentially life-threatening complication. Older age and male gender were found to be risk factors with a statistically significant association (p value <0.05). The majority of patients also exhibited prevertebral swelling, the presence of significant degenerative changes, and significant fracture displacement. Twelve patients required intubation and admission to Intensive Care Unit (ICU). There were four deaths. CONCLUSIONS: Approximately 5% of patients with isolated C1 and C2 fractures developed airway compromise. All patients with these injuries should be assessed for the risk of developing this complication and some will require close monitoring to detect this problem at an early stage.