Evaluation of equine articular cartilage degeneration after mechanical impact injury using cationic contrast-enhanced computed tomography.

OBJECTIVE: Cationic agent contrast-enhanced computed tomography (cationic CECT) characterizes articular cartilage ex vivo, however, its capacity to detect post-traumatic injury is unknown. The study objectives were to correlate cationic CECT attenuation with biochemical, mechanical and histological properties of cartilage and morphologic computed tomography (CT) measures of bone, and to determine the ability of cationic CECT to distinguish subtly damaged from normal cartilage in an in vivo equine model. DESIGN: Mechanical impact injury was initiated in equine femoropatellar joints in vivo to establish subtle cartilage degeneration with site-matched controls. Cationic CECT was performed in vivo (clinical) and postmortem (microCT). Articular cartilage was characterized by glycosaminoglycan (GAG) content, biochemical moduli and histological scores. Bone was characterized by volume density (BV/TV) and trabecular number (Tb.N.), thickness (Tb.Th.) and spacing (Tb.Sp.). RESULTS: Cationic CECT attenuation (microCT) of cartilage correlated with GAG (r = 0.74, P < 0.0001), compressive modulus (Eeq) (r = 0.79, P < 0.0001) and safranin-O histological score (r = -0.66, P < 0.0001) of cartilage, and correlated with BV/TV (r = 0.37, P = 0.0005), Tb.N. (r = 0.39, P = 0.0003), Tb.Th. (r = 0.28, P = 0.0095) and Tb.Sp. (r = -0.44, P < 0.0001) of bone. Mean [95% CI] cationic CECT attenuation at the impact site (2215 [1987, 2443] Hounsfield Units [HUs]) was lower than site-matched controls (2836 [2490, 3182] HUs, P = 0.036). Clinical cationic CECT attenuation correlated with GAG (r = 0.23, P = 0.049), Eeq (r = 0.26, P = 0.025) and safranin-O histology score (r = -0.32, P = 0.0046). CONCLUSIONS: Cationic CECT (microCT) reflects articular cartilage properties enabling segregation of subtly degenerated from healthy tissue and also reflects bone morphometric properties on CT. Cationic CECT is capable of characterizing articular cartilage in clinical scanners.

Recent advances in articular cartilage evaluation using computed tomography and magnetic resonance imaging.

Articular cartilage is a critical joint tissue and its evaluation remains a diagnostic challenge in horses. Coupled with a poor capacity for healing, early degenerative changes in articular cartilage are difficult to characterise using routine diagnostic imaging evaluations. Both computed tomography (CT) and magnetic resonance imaging (MRI) provide volumetric joint assessment and highlight morphological and quantitative properties of articular cartilage, improving assessment of this essential tissue. While the use of CT and MRI for joint evaluation is not new, there still remains a shortage of literature and scientific studies on the ability of these methods to evaluate articular cartilage in the horse. This review article summarises current CT and MRI techniques capable of characterising equine articular cartilage, highlights recent advances in these techniques and discusses the numerous methods studied in human subjects that have been minimally investigated in horses. Imaging techniques are presented in terms of their capabilities of offering morphological and quantitative evaluation along with a discussion of their benefits and limitations. Finally, it summarises the current state-of-the-art approaches and identifies unmet clinical imaging needs to propel the advancement of articular cartilage and joint imaging in the horse.

Assessment of a novel equine tarsocrural experimental joint disease model using recombinant interleukin-1ß and arthroscopic articular sampling of the medial malleolus of the tibia on the standing sedated horse.

Joint disease and osteoarthritis are common problems in the horse and numerous experimental studies have been developed to determine the safety and efficacy of new therapies. Synovitis, a critical component of joint disease, has been experimentally induced using recombinant interleukin-1 beta (reIL-1ß) to investigate new joint therapies in a controlled environment, although the use of reIL-1ß has not been reported in the equine tarsocrural joint. A common consequence of performing controlled experiments is that articular tissue collection typically requires general anesthesia or euthanasia. This report describes a minimally invasive surgical biopsy technique to harvest joint tissues from the tarsocrural joint in standing horses. The aims of the study were to assess subjective and objective pain parameters following reIL-1ß induced synovitis in the tarsocrural joint and to describe the surgical technique including the location and quantity of tissues obtained with this method. Experimental synovitis was induced using reIL-1ß in one equine tarsocrural joint of each horse using a randomised controlled design. The minimally invasive surgical technique provided sufficient amounts of articular cartilage from the medial malleolus of the tibia and synovium to perform viability, biochemical and histological assessments without necessitating general anesthesia. The minimally invasive technique also allowed for lameness assessment that could have been influenced by more invasive methods of tissue collection. No incisional or lameness complications were detected after use. The synovitis model and surgical technique provided ample tissue for laboratory evaluation and avoided general anesthesia or sacrifice of the horse.

Use of contrast media in computed tomography and magnetic resonance imaging in horses: Techniques, adverse events and opportunities.

The use of contrast media in computed tomography (CT) and magnetic resonance imaging (MRI) is increasing in horses. These contrast-enhanced imaging techniques provide improved tissue delineation and evaluation, thereby expanding diagnostic capabilities. While generally considered safe, not all contrast media exhibit the same safety profiles. The safety of contrast media use and descriptions of adverse events occurring in horses are sparsely reported. This review summarises the reported evidence of contrast media use and adverse events that occur in horses, with added contribution from other veterinary species and studies in man for comparison. This comprehensive data set empowers equine clinicians to develop use and monitoring strategies when working with contrast media. Finally, it summarises the current state-of-the-art and highlights the potential applications of contrast-enhanced CT and MRI for assessment of diseased or injured equine tissues, as well as (patho)physiological processes.

Plasma, subcutaneous tissue and bone concentrations of ceftiofur sodium after regional limb perfusion in horses.

REASONS FOR PERFORMING STUDY: Regional limb perfusion (RLP) is an effective treatment option for injuries and infections of the distal limb in horses. Using ceftiofur sodium in RLP has been studied due to its superior spectrum of Gram-positive organisms compared to aminoglycosides, but it is not known if this antimicrobial drug adequately penetrates subcutaneous tissue and bone. OBJECTIVE: To determine the concentration of ceftiofur in plasma, subcutaneous tissue and bone in horses after RLP. STUDY DESIGN: Experimental prospective study. METHODS: Six healthy horses were used in this study. Under standing sedation, an Esmarch tourniquet was applied to both proximal metacarpi and RLP was performed in each forelimb by injecting either ceftiofur sodium (experimental limb) or saline (control limb) i.v. in the lateral palmar digital vein. The experimental limb was injected with 2 g ceftiofur diluted to 60 mL with sterile saline. The control limb was injected with 60 mL of sterile saline. The tourniquet was left in place for 30 min post injection. Plasma, subcutaneous tissue and cortical bone samples were collected immediately after tourniquet removal (0.5 h), 12 and 24 h post injection. Ceftiofur concentrations and its active metabolite desfuroylceftiofur were analysed using high performance liquid chromatography-tandem mass spectrometry and the results were compared between control and experimental limbs using a Wilcoxon signed rank test. RESULTS: The median plasma concentrations were greater than the minimum inhibitory concentration (MIC) for common pathogens (1 µg/mL) at 0 and 12 h post RLP. The median subcutaneous tissue concentrations were greater than MIC (1 µg/g) at all 3 time points in the experimental limb. The median bone concentration was above MIC (1 µg/g) at time 0 in the experimental limb but was below MIC at 12 and 24 h in the experimental limb. CONCLUSIONS: Ceftiofur administration via RLP maintained plasma concentrations above MIC for 12 h. Subcutaneous tissue concentrations above MIC were maintained for 24 h. Bone concentrations were only above MIC immediately after tourniquet removal. Further research is needed to evaluate ceftiofur administration via RLP and its implications in disease states.

Risk factors associated with gastrointestinal dysfunction in horses undergoing elective procedures under general anaesthesia.

REASONS FOR PERFORMING STUDY: Gastrointestinal dysfunction occurs commonly following elective anaesthesia. Identification of risk factors may allow implementation of preventative measures to reduce the prevalence of colic following elective anaesthetic procedures. OBJECTIVES: To examine risk factors associated with gastrointestinal dysfunction or post anaesthetic colic for horses undergoing elective surgical or diagnostic procedures under general anaesthesia. STUDY DESIGN: Retrospective case series. METHODS: Medical records were collected from adult horses undergoing general anaesthesia from 1 January 2008 to 31 December 2010 using a retrospective cohort design. Potential risk factors were examined using univariable logistic regression with a limit of a P<0.25. Through backward elimination, the final multivariate model was created to identify variables significantly associated with gastrointestinal dysfunction. RESULTS: Colic or delayed faecal output was reported in 36 out of 416 (8.7%) horses undergoing general anaesthesia in the study period. In the final multivariable model, horse breed (P = 0.05), intraoperative peripheral blood lactate (P = 0.02), right lateral recumbency during general anaesthesia (P = 0.04), post anaesthetic rectal temperature (P = 0.03) and hours to first passage of faeces (P<0.01) were statistically significant between horses that exhibited colic compared with those that did not. Arabians were more likely to develop colic compared with other horse breeds (4/13, 30.8%). Horses that exhibited gastrointestinal dysfunction passed faeces later than those that did not (7.2 ± 0.8 h and 5.4 ± 0.2 h, respectively). As blood lactate increased at the end of anaesthesia, the odds of colic occurring also increased (odds ratio:1.4, 95% confidence interval: 1.04-1.83, P = 0.02). CONCLUSIONS: This study demonstrated the prevalence of colic in horses undergoing elective general anaesthetic procedures in our hospital population. Arabian horses, increasing blood lactate and delayed passage of faeces were significantly associated with an increased risk of gastrointestinal dysfunction.

Organotypic arrangement of mouse embryonic lung cells on a basement membrane extract: involvement of laminin.

The behavior of embryonic murine lung cells on a basement membrane extract (Matrigel) was investigated. Single cell suspensions generated by trypsinization of lungs removed from day 12 embryos were plated on Matrigel and cultured for up to one week. The basement membrane extract was used as a gel, and as a wet or dried film. In all of these instances, organotypic arrangement of the embryonic lung cells was observed. This process consisted of cell aggregation, sorting, polarization and formation of a tridimensional organization resembling embryonic lung. The maximal degree of organotypic development was obtained by using a thick gel; minimal reorganization was observed using a dried film. A rabbit polyclonal serum to laminin inhibited organotypic pattern formation while normal rabbit serum did not. Culture of lung cells on laminin gels promoted epithelial cyst formation but poor mesenchymal organization. By studying the behavior of epithelial and/or mesenchymal enriched cell populations on Matrigel, it was concluded that organotypic pattern formation on Matrigel required the presence of both cell populations. Cultivation of dissociated lung cells on a gel consisting of a mixture of collagens type I and III (Vitrogen-100) produced only cell aggregation. Cultivation of lung cells on a thin film of Vitrogen-100 or on uncoated tissue culture plastic produced monolayers of mesenchymal cells alone. Cultivation of lung cells in suspension also failed to induce organotypic arrangement even at maximal cell densities. The present study strongly supports a role for the basement membrane in the organotypic rearrangement of embryonic lung cells and subsequent in vitro cyst formation and budding of the reestablished epithelium. This, in turn, reinforces the concept of the basement membrane as a major regulator of organogenesis.