Management of paracondylar process fracture in three horses.

BACKGROUND: Fractures of the paracondylar process of the occipital bone may cause headshaking, neck pain and neurologic deficits. The condition is being recognised more frequently with increasing availability of computed tomography. However, to date only limited information is available as to presentation, treatment, surgical approach and outcome. OBJECTIVES: To describe the clinical signs, imaging findings, treatment, surgical approach and outcome in three horses diagnosed with paracondylar process fracture. STUDY DESIGN: Retrospective case series. METHODS: Clinical records and diagnostic images of affected cases were reviewed. RESULTS: Two cases had ventral nonunion fractures-one of these presented with neck pain, headshaking and behavioural changes, while in the other the fracture was a suspected incidental finding in a case of poor performance. A third case with a more dorsal fracture presented with acute facial nerve paralysis. Diagnosis was by computed tomography in all cases, although imaging of ventral fractures by radiography was found to be feasible. Where clinical signs could be associated confidently with the fracture, conservative management resulted in improvement but not complete resolution. Repeated recurrence of clinical signs after prolonged periods of remission necessitated surgical removal in one case, which was readily accomplished with the aid of ultrasound guidance, and led to rapid resolution of clinical signs without significant post-operative complications. The surgical approach is described. MAIN LIMITATIONS: Limited follow-up was available. CONCLUSIONS: Paracondylar process fracture should be considered as a differential diagnosis for headshaking, neck pain, poor performance and facial paresis, and is a justification for performing computed tomography in such cases. A multi-disciplinary approach is beneficial due to the potential for orthopaedic, neurologic, ophthalmologic and behavioural clinical signs, with additional need for expertise in diagnostic imaging and pain management. Surgical fragment removal should be considered for ventral fractures.

Preliminary study of proton magnetic resonance spectroscopy to assess bone marrow adiposity in the third metacarpus or metatarsus in Thoroughbred racehorses.

BACKGROUND: Magnetic resonance spectroscopy (MRS) has been used to investigate metabolic changes within human bone. It may be possible to use MRS to investigate bone metabolism and fracture risk in the distal third metacarpal/tarsal bone (MC/MTIII) in racehorses. OBJECTIVES: To determine the feasibility of using MRS as a quantitative imaging technique in equine bone by using the 1H spectra for the MC/MTIII to calculate fat content (FC). STUDY DESIGN: Observational cross-sectional study. METHODS: Limbs from Thoroughbred racehorses were collected from horses that died or were subjected to euthanasia on racecourses. Each limb underwent magnetic resonance imaging (MRI) at 3 T followed by single-voxel MRS at three regions of interest (ROI) within MC/MTIII (lateral condyle, medial condyle, proximal bone marrow [PBM]). Percentage FC was calculated at each ROI. Each limb underwent computed tomography (CT) and bone mineral density (BMD) was calculated for the same ROIs. All MR and CT images were graded for sclerosis. Histology slides were graded for sclerosis and proximal marrow space was calculated. Pearson or Spearman correlations were used to assess the relationship between BMD, FC and marrow space. Kruskal-Wallis tests were used to check for differences between sclerosis groups for BMD or FC. RESULTS: Eighteen limbs from 10 horses were included. A negative correlation was identified for mean BMD and FC for the lateral condyle (correlation coefficient = -0.60, p = 0.01) and PBM (correlation coefficient = -0.5, p = 0.04). There was a significant difference between median BMD for different sclerosis grades in the condyles on both MRI and CT. A significant difference in FC was identified between sclerosis groups in the lateral condyle on MRI and CT. MAIN LIMITATIONS: Small sample size. CONCLUSIONS: 1H Proton MRS is feasible in the equine MC/MTIII. Further work is required to evaluate the use of this technique to predict fracture risk in racehorses.

QCT-based computational bone strength assessment updated with MRI-derived 'hidden' microporosity.

Microdamage accumulated through sustained periods of cyclic loading or single overloading events contributes to bone fragility through a reduction in stiffness and strength. Monitoring microdamage in vivo remains unattainable by clinical imaging modalities. As such, there are no established computational methods for clinical fracture risk assessment that account for microdamage that exists in vivo at any specific timepoint. We propose a method that combines multiple clinical imaging modalities to identify an indicative surrogate, which we term 'hidden porosity', that incorporates pre-existing bone microdamage in vivo. To do so, we use the third metacarpal bone of the equine athlete as an exemplary model for fatigue induced microdamage, which coalesces in the subchondral bone. N = 10 metacarpals were scanned by clinical quantitative computed tomography (QCT) and magnetic resonance imaging (MRI). We used a patch-based similarity method to quantify the signal intensity of a fluid sensitive MRI sequence in bone regions where microdamage coalesces. The method generated MRI-derived pseudoCT images which were then used to determine a pre-existing damage (Dpex) variable to quantify the proposed surrogate and which we incorporate into a nonlinear constitutive model for bone tissue. The minimum, median, and maximum detected Dpex of 0.059, 0.209, and 0.353 reduced material stiffness by 5.9%, 20.9%, and 35.3% as well as yield stress by 5.9%, 20.3%, and 35.3%. Limb-specific voxel-based finite element meshes were equipped with the updated material model. Lateral and medial condyles of each metacarpal were loaded to simulate physiological joint loading during gallop. The degree of detected Dpex correlated with a relative reduction in both condylar stiffness (p = 0.001, R2 > 0.74) and strength (p < 0.001, R2 > 0.80). Our results illustrate the complementary value of looking beyond clinical CT, which neglects the inclusion of microdamage due to partial volume effects. As we use clinically available imaging techniques, our results may aid research beyond the equine model on fracture risk assessment in human diseases such as osteoarthritis, bone cancer, or osteoporosis.

Relationship between CT-Derived Bone Mineral Density and UTE-MR-Derived Porosity Index in Equine Third Metacarpal and Metatarsal Bones.

Fatigue-related subchondral bone injuries of the third metacarpal/metatarsal (McIII/MtIII) bones are common causes of wastage, and they are welfare concerns in racehorses. A better understanding of bone health and strength would improve animal welfare and be of benefit for the racing industry. The porosity index (PI) is an indirect measure of osseous pore size and number in bones, and it is therefore an interesting indicator of bone strength. MRI of compact bone using traditional methods, even with short echo times, fail to generate enough signal to assess bone architecture as water protons are tightly bound. Ultra-short echo time (UTE) sequences aim to increase the amount of signal detected in equine McIII/MtIII condyles. Cadaver specimens were imaged using a novel dual-echo UTE MRI technique, and PI was calculated and validated against quantitative CT-derived bone mineral density (BMD) measures. BMD and PI are inversely correlated in equine distal Mc/MtIII bone, with a weak mean r value of -0.29. There is a statistically significant difference in r values between the forelimbs and hindlimbs. Further work is needed to assess how correlation patterns behave in different areas of bone and to evaluate PI in horses with and without clinically relevant stress injuries.

T2 mapping of cartilage in the equine distal interphalangeal joint with corresponding histology using 0.27 T and 3.0 T magnetic resonance imaging.

BACKGROUND: Low-field magnetic resonance imaging (MRI) is widely available to equine veterinarians yet is insensitive at detecting cartilage damage in the distal interphalangeal joint (DIPJ). T2 mapping is a quantitative imaging technique that can detect cartilage damage before morphological change is apparent. OBJECTIVES: Validation of a T2 mapping sequence on a low-field MR system. Correlation of the mean T2 relaxation time in sections of cartilage with varying levels of pathology using low- and high-field MRI. STUDY DESIGN: Cross-sectional study. METHODS: Eight phantoms with known (nominal) T2 values underwent low-field (0.27 T) MRI and 38 ex vivo DIPJs were imaged. A further 9 ex vivo DIPJs were imaged on both the low- and high-field MR systems. Immediately after imaging, the DIPJs were disarticulated and samples collected for histology. Histological sections were graded using the Osteoarthritis Research Society International (OARSI) scoring system. Fiji ImageJ software with the MRIAnalysisPak plugin was used to calculate T2 maps and draw the regions of interest (ROIs). RESULTS: There was close agreement between the nominal and the measured T2 values in the phantom study. Spearman's rank correlation demonstrated significant positive correlation between low- and high-field T2 measurements, rho 0.644 (p < 0.001). The intrarater agreement for T2 measurements was excellent, intraclass correlation coefficient (ICC) = 0.99 (95% confidence interval [CI] = 0.99-1.00), the inter-rater agreement was excellent, ICC = 0.88 (95% CI = 0.82-0.92) and there was good intrarater agreement for OARSI scores (к = 0.76). MAIN LIMITATIONS: Only a small number of histological samples were analysed. Both articular cartilage surfaces were measured within the ROI. There were no OARSI grade 0 control samples. CONCLUSIONS: A T2 mapping sequence on a low-field 0.27 T MR system was validated. There was a positive correlation between low- and high-field T2 measurements. The findings suggest a higher mean T2 relaxation time in pathological cartilage tissue examined in this study compared to normal equine cartilage tissue.

Kyphosis (humpy back) in growing pigs.

This focus article has been prepared by Jill Thomson of SRUC Veterinary Services and Paul Wood and Carola Daniel of the Royal (Dick) School of Veterinary Studies.

Studies on Age-Related Changes in Equine Cheek Teeth Angulation and Dental Drift.

BACKGROUND: Cheek teeth (second through fourth premolars and first through third molars) diastema is a common and painful equine disorder caused by the absence of effective tight interdental contact between these teeth. Limited objective information is available on the angulation of equine cheek teeth that control dental drift or on mesial or distal equine cheek teeth drift that should normally prevent this disorder. OBJECTIVES: To measure the angulation of the mesial and distal cheek teeth in horses of different ages, quantify age-related cheek teeth mesial and distal dental drift, and measure the cheek teeth row length in horses of different ages. STUDY DESIGN: Retrospective review of computed tomographic images of equine heads. METHODS: Case details and CT images from clinical equine cases that had undergone standing CT head examination were collated.Three sets of measurements were acquired from each head. "Head size" calculated as the distance between the caudal aspect of the orbit and the caudal aspect of the naso-incisive notch was used to standardize measurements in different sized heads. The length of the cheek teeth rows measured from the mesial aspect of the Triadan 06 occlusal surface to the distal aspect of the Triadan 11 occlusal surface. The rostro-caudal (antero-posterior) position and angulation of the mandibular and maxillary Triadan 06 and 11 teeth were measured in relation to reference lines drawn on CT images. RESULTS: Significant mesial drift occurred in the maxillary and mandibular Triadan 11s. Despite their distal angulation, the upper and lower Triadan 06s also drifted mesially. The mean angulation of Triadan 06 and 11 mandibular teeth (17.8 and 26.2°, respectively) was almost double that of maxillary teeth (9.2 and 13.3°, respectively) with both Triadan 11s having greater angulation than the 06s. Cheek teeth angulation only significantly decreased in the mandibular 06s. Cheek teeth arcade lengths decreased with age, but these decreases were not significant. MAIN LIMITATIONS: Limitations include the relatively small sample size. CONCLUSIONS: In the population of horses used for this study, age related mesial drift occurred in both Triadan 06 and 11s, and the angulation of these teeth did not decrease with age in most arcades.

Extracorporeal perfusion of isolated organs of large animals - Bridging the gap between in vitro and in vivo studies.

Since the early 20th century, extracorporeal perfusion of large animal organs has been used to investigate a broad variety of research questions, thereby overcoming common drawbacks of in vitro studies without suffering from ethical concerns associated with live animal research. The technique is in accordance with the 3R principles and represents an excellent opportunity to investigate the physiology of organs in detail under standardized conditions. It is also suitable for the translation of basic pre-clinical research into a more relevant arena prior to or avoiding live animal research altogether. Furthermore, organ perfusion has also been an important tool in developing methods of organ preservation for transplantation surgery. Yet, due to the nature of the experiments, only short-term observations can be made and while cells are still exposed to their regional secretome, the whole organ itself is isolated from the body and correlations between organ systems cannot be taken into consideration. This review gives an overview over the history of extracorporeal perfusion of large animal organs and limbs, highlighting major achievements in the field and discussing different experimental set-ups. Advantages and limitations of the technique are presented. Prospective future research perspectives, which may include tracking of specific cell types and study of their distinct behavior towards different stimuli, are given to illustrate the relevance of this method.

Effect of intra-articular administration of superparamagnetic iron oxide nanoparticles (SPIONs) for MRI assessment of the cartilage barrier in a large animal model.

Early diagnosis of cartilage disease at a time when changes are limited to depletion of extracellular matrix components represents an important diagnostic target to reduce patient morbidity. This report is to present proof of concept for nanoparticle dependent cartilage barrier imaging in a large animal model including the use of clinical magnetic resonance imaging (MRI). Conditioned (following matrix depletion) and unconditioned porcine metacarpophalangeal cartilage was evaluated on the basis of fluorophore conjugated 30 nm and 80 nm spherical gold nanoparticle permeation and multiphoton laser scanning and bright field microscopy after autometallographic particle enhancement. Consequently, conditioned and unconditioned joints underwent MRI pre- and post-injection with 12 nm superparamagnetic iron oxide nanoparticles (SPIONs) to evaluate particle permeation in the context of matrix depletion and use of a clinical 1.5 Tesla MRI scanner. To gauge the potential pro-inflammatory effect of intra-articular nanoparticle delivery co-cultures of equine synovium and cartilage tissue were exposed to an escalating dose of SPIONs and IL-6, IL-10, IFN-γ and PGE2 were assessed in culture media. The chemotactic potential of growth media samples was subsequently assessed in transwell migration assays on isolated equine neutrophils. Results demonstrate an increase in MRI signal following conditioning of porcine joints which suggests that nanoparticle dependent compositional cartilage imaging is feasible. Tissue culture and neutrophil migration assays highlight a dose dependent inflammatory response following SPION exposure which at the imaging dose investigated was not different from controls. The preliminary safety and imaging data support the continued investigation of nanoparticle dependent compositional cartilage imaging. To our knowledge, this is the first report in using SPIONs as intra-articular MRI contrast agent for studying cartilage barrier function, which could potentially lead to a new diagnostic technique for early detection of cartilage disease.