Is the T-ligament a ligament? A histological study in equine cadaver forelimbs

Foot pain is a frequent cause of lameness in horses and can involve multiple structures within the hoof. The T-ligament (an anatomical structure connecting the synovium of the distal interphalangeal joint, the digital flexor tendon sheath and the navicular bursa) is poorly described. Five pairs of equine cadaver distal forelimbs were collected from a slaughterhouse. Sagittal sections (medial, middle and lateral) were obtained and processed with Haematoxylin Eosin Safran, Unna's Orcein, and Picrosirius red stains. Histological assessment revealed that the T-ligament was covered by the surrounding synovia of the distal interphalangeal joint, the digital flexor tendon sheath and the navicular bursa. Its collagen content was lower (30.01%±10.15) than that of the collateral sesamoidean ligament (89.48%±5.8; P = .0008) and the middle phalanx (85.72%±3.67; P = .0008). Under polarized light microscopy, it showed a slight heterogeneous pattern of birefringence, with angle-related changes. Elastic fibres were more numerous (21.76%±8.72) than in the collateral sesamoidean ligament (0.28%±0.45), or deep digital flexor tendon (0.04%±0.02); and were more densely packed. Mean cell count was higher for the T-ligament than for other tissues (P = .0007). Blood vessels were identified in the T-ligament and were penetrating the deep digital flexor tendon (8/10 limbs, 5/5 horses). In conclusion, the T-ligament looked like a vinculum for the deep digital flexor tendon, with a central elastic core, surrounding loose connective tissue and blood vessels. It is not a ligament. Its clinical relevance still needs to be determined.

Local anaesthetics or their combination with morphine and/or magnesium sulphate are toxic for equine chondrocytes and synoviocytes in vitro

Background

Chondrotoxic effects of local anaesthetics are well reported in humans and some animal species but knowledge on their toxic effects on synoviocytes or equine chondrocytes or the effects on cellular production of inflammatory cytokines is limited. The purpose of this study was to evaluate the in vitro effects of local anaesthetics, morphine, magnesium sulphate (MgSO₄) or their combinations on cell viability and pro-inflammatory cytokine gene expression of equine synoviocytes and chondrocytes.

Equine synoviocytes and cartilage explants harvested from normal joints in a co-culture system were exposed to mepivacaine (4.4 mg/ml), bupivacaine (2.2 mg/ml), morphine (2.85 mg/ml) and MgSO₄ (37 mg/ml) alone or each local anaesthetic plus morphine or MgSO₄ or both together. Chondrocyte and synoviocyte cell viability was assessed by CellTiter-Glo Luminescent Cell Viability Assay. Synoviocyte gene expression of IL-1β, IL-6 or TNF-α was measured and compared using the ∆∆CT method.

Results

Morphine alone, MgSO₄ alone or their combination did not alter cell viability or the expression of IL-1β, IL-6 or TNF-α. However, local anaesthetics alone or in combination with morphine and/or MgSO₄ reduced cell viability and increased the gene expression of IL-1β, IL-6 or TNF-α. Single short exposure to local anaesthetics is toxic to both chondrocytes and synoviocytes and their combination with morphine and/or MgSO₄ enhanced the cytotoxic effects.

Conclusions

This in vitro study gives further evidence of the absence of cytotoxic effects of morphine alone, MgSO₄ alone or their combination on normal articular tissues. However, local anaesthetics alone or in combination with morphine and/or MgSO₄ have cytotoxic effects on equine articular tissues.

Electronic supplementary material

The online version of this article (10.1186/s12917-017-1244-8) contains supplementary material, which is available to authorized users.

Computed Tomography and Magnetic Resonance Anatomy of the Normal Orbit and Eye of the Horse

Traumatic and infectious diseases of the eye and orbit can occur in horses. For diagnosis and monitoring of such diseases, medical imaging is useful including computed tomography (CT) and magnetic resonance imaging (MRI). The aim of the current study was to describe CT and MRI anatomy of the equine orbit and ocular globe. The heads from four adult horses were scanned with a 6-slice Emotion 6 CT (Siemens, Erlangen), and a 3.0 Tesla Siemens Verio 6 MRI using T1 and T2-weighted sequences. To validate CT and MR reference images, these were compared with anatomical models and gross anatomical sections. The bony limits of the orbital cavity, the relationship of the orbit with sinuses and foramina of the skull were well identified by CT. MRI was useful to observe soft tissues and was able to identify adnexae of the ocular globe (eyelids, periorbital fat, extraocular muscles, lacrymal and tarsal glands). Although MRI was able to identify all components of the eye (including the posterior chamber), it could not differentiate sclera from choroid and retina. The only nerve identified was the optic nerve. Vessels were not seen in this series of cadaver heads. This study showed that CT and MRI are useful techniques to image the equine orbit and eye that can have clinical applications.

Prevalence of naturally occurring cartilage defects in the ovine knee

OBJECTIVE

To determine the prevalence, anatomical location and severity of cartilage defects in the stifle (knee) within a population of adult ewes (N = 65).

MATERIALS AND METHODS

Articular cartilage (AC) of the distal femur, proximal tibia and patella was assessed using Osteoarthritis Research Society International (OARSI) recommendations for macroscopic and microscopic scoring of ovine cartilage. Synovial fluid analysis and histology of the synovial membrane were performed. All limbs were examined by computed tomography.

RESULTS

Twenty-eight sheep (n = 28; 43%) presented at least one score 2 or score 3 lesion. Twenty-two (n = 22; 34%) sheep were macroscopically normal. Most frequent localizations of lesions were: axial aspect of the central third of the medial tibial condyle (32.7% of the lesions), middle third of the medial femoral condyle (29.4%), middle third of the articular surface of the patella (9.8%), and axial aspect of the central third of the lateral tibial condyle (9.8%). Grade of macroscopic lesions was significantly (H (3) = 29.31, P 0.000) affected by age. Macroscopic score correlated well with histological changes that can be found in osteoarthritis (OA) (r 0.83; P 0.000). Neither clinical signs of OA, nor cytological and histological signs of inflammation were identified, while imaging abnormalities were very rare.

CONCLUSIONS

Our data seem to indicate that naturally occurring OA exists in ageing sheep, at least subclinically. It might be useful to take into account prevalent cartilage defects at baseline in studies using ovine models.

Magnetic resonance imaging (MRI) anatomy of the ovine lumbar spine

Although the ovine spine is a useful research model for intervertebral disc pathology and vertebral surgery, there is little peer-reviewed information regarding the MRI anatomy of the ovine spine. To describe the lumbar spine MRI anatomy, 10 lumbar segments of cadaver ewes were imaged by 1.5-Tesla MR. Sagittal and transverse sequences were performed in T1 and T2 weighting (T1W, T2W), and the images were compared to gross anatomic sagittal and transverse sections performed through frozen spines. MRI was able to define most anatomic structures of the ovine spine in a similar way as can be imaged in humans. In both T1W and T2W, the signals of ovine IVDs were similar to those observed in humans. Salient anatomic features were identified: (1) a 2- to 3-mm linear zone of hypersignal was noticed on both extremities of the vertebral body parallel to the vertebral plates in sagittal planes; (2) the tendon of the crura of the diaphragm appeared as a hypointense circular structure between hypaxial muscles and the aorta and caudal vena cava; (3) dorsal and ventral longitudinal ligaments and ligamentum flavum were poorly imaged; (4) no ilio-lumbar ligament was present; (5) the spinal cord ended between S1-S2 level, and the peripheral white matter and central grey matter were easily distinguished on T1W and T2W images. This study provides useful reference images to researchers working with ovine models.

Antimicrobial prescribing practice in UK equine veterinary practice

REASONS FOR PERFORMING STUDY

Antimicrobial use is known to select for the emergence of resistant strains of bacteria; therefore prudent use in both human and veterinary medicine is essential to preserve their efficacy.

OBJECTIVES

To characterise antimicrobial prescribing patterns in UK equine practice and evaluate factors associated with prescribing.

METHODS

A postal questionnaire including 4 clinical scenarios was sent to 740 veterinary surgeons that treat horses. Data were collected on the clinician, their practice and sources of information regarding antimicrobials and their use. Multivariable logistic regression analysis was used to ascertain factors associated with 5 outcomes; prescribing off-licence drugs; prescribing at incorrect doses; prescribing 3rd or 4th generation cephalosporins; prescribing fluoroquinolones and prescribing potentiated sulphonamides.

RESULTS

Questionnaires were completed by 38% of veterinary surgeons who were sent questionnaires. Less than 1% of practices had antimicrobial use guidelines. Trimethoprim-sulphonamides were most commonly prescribed in each clinical scenario. Eleven percent of prescriptions were for antimicrobial drugs not licensed for use in horses in the UK. Five percent of prescriptions for licensed antimicrobials were under the recommended dose rate and 56% over the recommended dose rate. Fluoroquinolones and 3rd and 4th generation cephalosporins accounted for 1 and 3% of prescriptions, respectively. Veterinary surgeons working at referral practices were more likely to prescribe 3rd and 4th generation cephalosporins and fluoroquinolones and off-licence antimicrobials whereas those working in first-opinion practices were more likely to prescribe potentiated sulphonamides. Sources of information regarding antimicrobials also had an effect on prescribing.

CONCLUSIONS AND POTENTIAL RELEVANCE

Prescription of antimicrobials at inappropriate doses was common even when provided with the weight of the animal. It is uncommon for UK equine veterinary practices to have guidelines for antimicrobial use. The introduction of such guidelines could lead to more prudent use of antimicrobials.

Innervation and nerve injections of the lumbar spine of the horse: a cadaveric study

REASONS FOR PERFORMING STUDY

The distal limb innervation of the horse has been studied extensively to allow use of local anaesthetic techniques to detect the origin of pain in lameness. However, the innervation of the lumbar spine has so far been poorly described and a more precise description may assist clinicians to localise back pain in the horse.

OBJECTIVES

To gain better knowledge of the innervation of the lumbar spine and identify salient anatomical features that might be used for diagnostic and therapeutic ultrasound guided injections.

METHODS

The spines of 8 mature horses were dissected. Branches of the dorsal rami were followed and their anatomical relationship, with articular facets, interspinous structures and muscles, noted. The spines of 3 other horses were sectioned transversely and dissected to identify ultrasonographic landmarks of the nerves. Six other spines were used to assess the accuracy of ultrasound guided injections of the nerves with blue dye.

RESULTS

Gross dissections confirmed the dual segmental innervation of the articular facets. Each lumbar articular facet of 2 lumbar vertebrae was innervated by the medial branch of the dorsal ramus exiting from the intervertebral foramen between those vertebrae, but also by the branch originating of the dorsal ramus cranial to it. The medial branch divided into 2 nerves before exiting the intertransverse space and has salient anatomical landmarks which could be identified ultrasonographically. The ultrasound guided injection technique appeared to be of an accuracy that would be clinically useful.

CONCLUSION

The results identified that the salient anatomical features of the medial branch of the dorsal ramus, as described in the present study, can be used as landmarks for reliable ultrasound-guided injection.

POTENTIAL RELEVANCE

This study has a clear clinical relevance for development of diagnostic and therapeutic injection techniques of the lumbar spine in the horse.

Polymorphisms of the equine major histocompatibility complex class II DRA locus

The full extent of the polymorphism of ELA-DRA in Equidae is not yet known. Given the apparent differences in DRA polymorphisms between Equidae and other species, the aims of this study were to more fully characterize ELA-DRA, determine the extent of gene polymorphism and establish the allele-frequency distribution. An allele reference panel for the second exon of ELA-DRA was established by sequence-based typing of 69 equine DNA samples consisting of various breeds of domestic horse (Equus caballus), together with donkeys (Equus asinus), Grant's zebras (Equus boehmi) and one onager (Equus hemionus). Five of the six previously reported alleles detected using single-strand conformation polymorphism were found: ELA-DRA*0101, ELA-DRA*0201, ELA-DRA*0301, ELA-DRA*0501 (Albright-Fraser DG et al. Polymorphism of DRA among equids. Immunogenetics 1996: 43: 315-7) and ELA-DRA*0601 (GenBank accession number AF5419361). In addition to the previously reported alleles, five novel ELA-DRA alleles were detected within the ELA-DRA allele reference panel. One of these was identified in E. caballus (ELA-DRA*JBH11), one in E. boehmi and E. hemionus (ELA-DRA*JBZ185) and three in E. asinus (ELA-DRA*JBD3, ELA-DRA*JBD17 and ELA-DRA*JBH45). A total of 565 equine DNA samples were screened using reference-strand-mediated conformation analysis, a double-stranded conformation-based mutation detection system that can be used to type existing ELA-DRA alleles and identify new variants. Based on our findings, at least 11 ELA-DRA alleles are now known to exist, and this level of polymorphism at the DRA locus appears to be unique to the genus Equus. Both the previously reported alleles and the new alleles displayed a species-specific distribution.

Cranial stereotactic multiple arc radiotherapy; treatment planning using angiographic images

Stereotactic multiple arc radiotherapy (SMART) is an irradiation technique developed to treat small intracranial lesions. Calculation of absorbed-dose patterns for this treatment has traditionally involved complex computer programs incorporating algorithms designed to reconstruct the shape of the patient's head from computerized tomography (CT) images. A large proportion of the patients treated with SMART, however, have arteriovenous malformations for which angiography provides a better idea of lesion size and position than CT. This paper describes a computer program developed at St Bartholomew's Hospital which enables calculation of absorbed dose for a SMART treatment directly from angiographic radiographs, avoiding the need for CT. The program is compared with the existing CT-based treatment planning program.

Pressure distribution in the wrist joint

We performed a study to determine pressure distribution properties of the normal radio-carpal joint. A system was developed for measurement of the contact pressure within the wrist joint surfaces. The transducer was based on Fuji pressure-sensitive paper, which was inserted into the joint space through a dorsal capsular incision. The hand was then positioned using a jig that permitted free axial loading of the joint. Each of five specimens was tested in 36 positions combining flexion/extension with radio/ulnar deviation and supination/pronation. The transducers were analyzed for contact area, scapho-lunate contact area ratio, pressure, and centroid locations using a microcomputer-based video-imaging system. The scaphoid and lunate contact areas on the radius and triangular fibrocartilage were separate and distinct in all wrist positions. Together these contact areas accounted for a relatively small fraction of the total joint surface area (average contact area/total joint area = 0.206, SD = 0.0495). For an applied 103 Newton compressive load, the high pressure averaged 3.17 MPa (SD = 0.83 MPa). Overall, the scaphoid contact area was 1.47 times that of the lunate, although variations occurred with position, as in flexion, in which the scaphoid/lunate area ratio was 0.83. The high-pressure centroids of both scaphoid and lunate contact areas shifted palmarly from 20 degrees of flexion to 20 degrees of extension and then dorsally with further extension. The scaphoid-lunate intercentroid distance averaged 14.91 mm with a range of 10-20 mm.

Load transfer characteristics of the wrist. Part II. Perilunate instability

An experimental model with a static positioning frame, pressure-sensitive film (Fuji), and a microcomputer-based video digitizing system, previously developed by the two senior authors, was used in this study to examine the effects of increasing perilunate instability on the load transfer characteristics of the wrist. These effects included a significant dorsal ulnar shift of the scaphoid centroid with increasing perilunate instability together with a less dramatic palmar ulnar shift of the lunate centroid. Overall, the scaphoid contact area was found to decrease as the stage of perilunate instability increased, even in ulnar deviation and/or extension, which in the normal wrist was found to be the positions that had the greatest scaphoid contact area. Average pressures in the high pressure zones were found to significantly increase in wrists with a stage III instability compared with normal wrists. An increase in the intercentroid (scaphoid/lunate) distance was most evident with the wrist in 20 degrees extension, neutral radioulnar deviation, and 90 degrees supination.

Load transfer characteristics of the wrist. Part I. The normal joint

A static positioning frame allows the positioning of unembalmed human upper extremities in any combination of wrist flexion/extension, radio/ulnar deviation, and pronation/supination. Pressure-sensitive film (Fuji) was used to study the contact areas, scaphoid-lunate area ratios, average high pressures, centroid positions, and intercentroid distances of five wrist joints under a uniform load of 103 Newtons (N) in 36 different positions. The contact areas accounted for only 20.6% of the available joint surface. They shift from a primarily palmar location to a primarily dorsal location when the wrist changes from flexion to extension. Overall the scaphoid contact area was 1.47 times that of the lunate and was generally greatest with the wrist in ulnar deviation. The scapho-lunate contact area ratio increased as wrist position changed from radial to ulnar deviation and/or from flexion to extension. For the constant load of 103 Newtons the high pressure averaged 3.17 megapascals (MPa). The scaphoid and lunate high pressure centroids shifted palmar when wrist position changed from 20 degrees of flexion to 20 degrees of extension and then shifted dorsal with further extension of the wrist. The intercentroid distance averaged 14.91 mm and ranged from 10 to 20 mm.