An ultrasonographic off-set system for examination of equine tendons and ligaments.

In a dorsal plane, an improved ultrasonographic off-set system was used to obtain serial ultrasonographic images with enhanced anatomic and pathologic detail of the tendons, ligaments, and associated structures of the limbs of 100 horses. The off-set provided good acoustic coupling between a linear array ultrasonographic transducer and the horse's skin. A water-soluble gel contained within the off-set had acoustic properties similar to those of mammalian soft tissues.     

Finite element analysis of wall stress in the equine pulmonary artery

Reasons for performing study: Arterial calcification is found frequently in the pulmonary artery of racehorses, but the aetiology is unknown. Calcification might be associated with increased wall stress due to arterial geometry (shape) and exercise‐induced hypertension. Hypothesis: High wall stress levels are found in the regions associated with calcified lesion formation, exacerbated as transluminal pressure increases to levels associated with exercise. Methods: The pulmonary arteries of 5 horses, unaffected by calcification, were dissected and pressurised to resting and exercising physiological transluminal pressures and scanned with MRI. Arterial geometries were reconstructed to form 3D computer models and finite element analyses performed. Wall stress levels were measured in 4 regions of interest: the arterial trunk and bifurcation, the wall ipsilateral and contralateral to the bifurcation. Measurements were made for arterial transluminal pressures of 25, 50 and 100 mmHg. Results: High wall stress levels were consistently found at the pulmonary artery bifurcation and wall ipsilateral to the bifurcation, where calcified lesions typically form. Lower wall stress levels were found along the trunk and the wall contralateral to the bifurcation where lesions are less frequently found. Wall stress levels increased 5‐fold over a 4‐fold increase in pressure. The wall stress levels ranged 10 kPa in the wall of the branch contralateral to the bifurcation at 25 mmHg to 400 kPa in the bifurcation at 100 mmHg. Conclusions: Wall stress from arterial geometry and increased pulmonary artery transluminal pressure are factors that may be associated with calcification of the equine pulmonary artery. Potential relevance: Arterial calcification may increase the risk of arterial wall failure in racing horses.     

Effects of exercise on tenocyte cellularity and tenocyte nuclear morphology in immature and mature equine digital tendons

REASON FOR PERFORMING STUDY: The injury-prone, energy-storing equine superficial digital flexor tendon (SDFT) of the mature performance horse has a limited ability to respond to exercise in contrast with the noninjury-prone, anatomically opposing common digital extensor tendon (CDET). Previous studies have indicated low levels of cellular activity in the mature SDFT, but in foal tendons the tenocytes may still have the ability to adapt positively to increased exercise. OBJECTIVES: To measure tenocyte densities and types in histological sections from the SDFT and CDET of horses from controlled long-term, short-term and foal exercise studies. METHODS: Specimens were collected from mid-metacarpal segments of the CDET and SDFT for each horse and processed for histology; central and peripheral regions of the SDFT cross-section were analysed separately (SDFTc, SDFTp). Tenocyte nuclei were counted in a total area of 1.59 mm(2) for each tendon region in each horse. Each nucleus was classified as type 1 (elongate and thin), type 2 (ovoid and plump) or type 3 (chondrocyte-like); type 1 cells are proposed to be less synthetically active than type 2 cells. RESULTS: No significant differences were noted between exercise and control groups in any of the studies, with the exception of an exercise-related reduction in the proportion of type 1 tenocytes for all tendons combined in the long-term study. There were tendon- and site-specific differences in tenocyte densities and proportions of type 1 and 2 cells in all 3 studies. CONCLUSIONS AND POTENTIAL RELEVANCE: There was no indication that exercise increased tenocyte density or proportions of the (theoretically) more active type 2 cells in immature horses (short-term and foal studies), perhaps because the training regimens did not achieve certain threshold strain levels. In the foal study these findings can still be interpreted positively as evidence that the training regimen did not induce subclinical damage.     

The effect of focused extracorporeal shock wave therapy on collagen matrix and gene expression in normal tendons and ligaments

Reasons for performing study: Extracorporeal shock wave therapy (ESWT) is frequently used in equine practice, but little is known about its biological action. Objectives: To study the effects of ESWT on matrix structure and gene expression levels in normal, physiologically loaded tendinous structures in ponies. Methods: Six Shetland ponies, free of lameness and with ultrasonographically normal flexor and extensor tendons and suspensory ligaments (SL), were used. ESWT was applied at the origin of the suspensory ligament and the mid‐metacarpal region of the superficial digital flexor tendon (SDFT) 6 weeks prior to sample taking, and at the mid‐metacarpal region (ET) and the insertion on the extensor process of the distal phalanx (EP) of the common digital extensor tendon 3 h prior to tendon sampling. In all animals one forelimb was treated and the other limb was used as control. After euthanasia, tendon tissue was harvested for real‐time PCR to determine gene expression levels and additional samples were taken for histological evaluation and biochemical analyses Results: Histologically a disorganisation of the normal collagen structure was observed 3 h after ESWT, remnants of which were still visible after 6 weeks. While degraded collagen levels showed an increase at 3 h post treatment (P = 0.012) they were reduced at 6 weeks post ESWT (P = 0.039). Gene expression for both COL1 (P = 0.004) and MMP14 (P = 0.020) was upregulated at 6 weeks after treatment. Conclusions: Exposure of normal tendinous tissue to ESWT is not uneventful; it leads to a disorganisation of matrix structure and changes in degraded collagen levels. The upregulation of COL1 expression 6 weeks after ESWT may be indicative for repair. Potential relevance: The observed disorganisation of the collagen network warrants caution when using ESWT. Exposing noninjured tissue to ESWT should be avoided and it may be advisable to restrict exercise in recently treated patients. However, the induced tissue disorganisation might also be a trigger for repair in chronic tendinopathies.     

Magic angle magnetic resonance imaging of diode laser induced and naturally occurring lesions in equine tendons

Magic angle magnetic resonance (MR) imaging consists of imaging tendons at 55° to the magnetic field. In people, magic angle MR imaging is valuable for detection of chronic tendon lesions and allows calculation of tendon T1 values. Increased T1 values occur in people with chronic tendinopathy. The T1 values of normal equine tendons have been reported but there are no available data for abnormal equine tendons. Twelve limbs were studied. Two limbs had diode laser tendon lesions induced postmortem, four limbs had diode laser tendon lesions induced in vivo and six limbs had naturally occurring tendon lesions. The limbs were imaged at 1.5 T using both conventional MR imaging and magic angle MR imaging. The post-mortem laser induced lesions were identified only with magic angle MR imaging. The in vivo induced lesions and naturally occurring lesions were identified with both techniques but had a different appearance with the two imaging techniques. Magic angle imaging was helpful at identifying lesions that were hypointense on conventional imaging. Increased T1 values were observed in all abnormal tendons and in several tendons with a subjectively normal MR appearance. The increased T1 value may reflect diffuse changes in the biochemical composition of tendons. Magic angle imaging has potential as a useful noninvasive tool to assess the changes of the extracellular tendon matrix using T1 values.     

Clinical and ultrasonographic evaluation of three suture techniques for closure of the equine linea alba

Surgical technique plays an important role in preventing ventral midline incisional complications. The aim of this study was to compare the clinical and ultrasonographic outcome of three suture techniques for closure of the linea alba. In this prospective case series (n = 43), horses operated for acute abdominal intestinal disease through a midline incision were randomised in three groups: closure with a conventional continuous technique (Group 1), a small stitches continuous technique (Group 2) and the UX-technique (shoe-lace configuration, Group 3). Age, sex, body weight, type and duration of surgery were recorded and the suture to wound length ratio was calculated. Clinical evaluation of the wound (wound discharge) was performed daily during hospitalisation. At 7 weeks post-operatively the linea alba was evaluated clinically and ultrasonographically. The linea alba width was measured halfway along the length of the incision. One horse in Group 1 had acute incisional dehiscence, but there were no further significant differences between the groups in the short term. Seven weeks post-operatively two horses had complete herniation in Group 1 and one horse had partial herniation in Group 2. In the UX group no herniation occurred. The incidence of herniation was not significantly different between the groups. On ultrasound at 7 weeks the linea alba width was significantly smaller in Group 2 (P = 0.00029) and Group 3 (P = 0.0018) compared with Group 1, even with exclusion of the acute incisional dehiscence and two herniated horses. Limitations were the small group size and relatively low incidence of incisional complications for statistical analysis. It was concluded that the use of small stitches and the UX-technique resulted in a smaller linea alba width compared with the conventional continuous suture technique and might therefore be preferred for closure of the linea alba in equine colic surgery.     

Standing laparoscopic castration in an equine male pseudohermaphrodite

This report describes the surgical anatomy and successful removal of the internal gonads in a 6-year-old male pseudohermaphrodite Friesian horse by standing laparoscopy. Gonads could not be identified by physical or ultrasonographic examination and bilateral standing flank laparoscopy revealed the presence of intra-abdominal gonads suspended from the dorsal aspect of the abdominal cavity by 10–15 cm long vascular pedicles. No evidence of female internal genitalia such as a uterus was found and bilateral gonadectomy was performed laparoscopically. Histological analysis of the excised gonads confirmed the diagnosis of male pseudohermaphroditism. Minor cosmetic surgery of the external genitalia to correct urinary misdirection was successfully performed 3 months after laparoscopic castration. Standing flank laparoscopic examination was excellent for identification and surgical removal of internal genitalia. Standing flank laparoscopy should be considered for inspection and removal of internal genitalia in intersex horses.     

Topical 5-fluorouracil as an adjunct treatment in equine corneolimbal squamous cell carcinoma

An 11-year-old crossbreed mare was presented with a nodular, pink mass at the temporal corneolimbal junction of the right eye. Histopathology confirmed the diagnosis of invasive squamous cell carcinoma. The mare underwent lamellar keratectomy and conjunctivectomy under general anaesthesia, followed by adjunctive topical chemotherapy with 1% 5-fluorouracil solution for 10 days post-operatively. Adverse effects included moderate conjunctival inflammation and exuberant granulation tissue formation at the surgical site, responding to surgical debulking and topical corticosteroid application. No mass regrowth was present at 12 months following discharge. This report describes the successful use of topical 1% 5-FU as an adjunctive treatment for equine ocular squamous cell carcinoma.     

Bilateral oblique facial clefts,rudimentary eyes and hydrocephalus in an aborted equine foetus

Knowledge of congenital malformations and their causes in horses is generally sparse. Such conditions require more scientific attention to improve their diagnostics and inform prevention strategies. Here, a unique syndrome of bilateral oblique facial clefts (meloschisis), rudimentary eyes and hydrocephalus is reported in an equine foetus spontaneously aborted at gestation day 224. The cause of abortion was considered to be intrauterine death caused by umbilical cord torsions and subsequent compromised blood flow, but the aetiology of the malformation could not be determined. A detailed history, which includes exposure to a range of pharmaceutical compounds during the early stages of pregnancy, is provided and emphasizes the need for accurate recording of treatments in pregnant animals.     

Mortality and morbidity in equine anaesthesia

Equine peri-anaesthetic mortality and morbidity are of interest to anaesthetists, practitioners, horse owners and insurance companies. The largest prospective study, ‘The Confidential Enquiry into Perioperative Equine Fatalities’ (CEPEF) was conducted more than 20 years ago. It included over 40,000 horses from multiple centres and reported mortality to be 1.9% that decreased to 0.9% when only elective cases were considered. This is in stark contrast to mortality rates in small animal (dogs: 0.17%, cats: 0.24%) and human anaesthesia (0.04–7/10,000). In spite of developments in understanding the pathophysiology of equine anaesthesia mortality has not decreased in the intervening years. The main contributors to peri-anaesthetic equine mortality are cardiac arrest, fractures and myopathy or neuropathy. Spinal cord myelopathy and cerebral necrosis are less common. Malignant hyperthermia and hyperkalaemic periodic paralysis are diseases associated with genetic mutations that can be triggered during general anaesthesia and may be fatal if not recognised and treated immediately. Morbidities are reported less frequently, presumably because often they do not cause permanent harm and may resolve within a short period of time. Complications in equine anaesthesia are numerous and include injuries at induction and recovery, damage to the airway associated with orotracheal or nasotracheal intubation, post-anaesthetic myopathy or neuropathy, regurgitation and aspiration of stomach contents, ocular injuries and complications associated with intravascular cannulation. Hypotension, hypoventilation, hypoxaemia, hypothermia and dysrhythmias may occur both during the maintenance phase of anaesthesia but also in recovery. Airway obstruction during recovery has repeatedly been reported over the years as causing pulmonary oedema, which is often fatal if the airway is not restored extremely quickly. This review summarises the literature on the risk of mortality and morbidity. Information has been gathered from single case reports as well as larger research studies.     

Hindlimb lameness associated with a focal osseous metaplasia in an 18‐year‐old Welsh Section D mare

This report describes a case of chronic lameness secondary to an extraskeletal osseous mass located in the plantaromedial aspect of the right hind pastern in a mature Welsh Section D mare. The lesion was confirmed to represent metabolically active osseous tissue in close apposition with the adjacent plantar digital neurovascular bundle and digital flexor tendons. Surgical resection of the mass resulted in a complete resolution of lameness and return to previous level of activity. Histopathological examination classified the mass as a focal osseous metaplasia, which was most likely to be the result of previous trauma causing local haemorrhage, which resulted in subsequent dystrophic mineralisation and eventually osseous metaplasia. Similar lesions have been described in man, but have not been previously reported in the horse.