Florent David

Effect of Antigenic Exposure on Airway Smooth Muscle Remodeling in an Equine Model of Chronic Asthma

Recent studies suggest that airway smooth muscle remodeling is an early event in asthma, but whether it remains a dynamic process late in the course of the disease is unknown. Moreover, little is known about the effects of an antigenic exposure on chronically established smooth muscle remodeling. We measured the effects of antigenic exposure on airway smooth muscle in the central and peripheral airways of horses with heaves, a naturally occurring airway disease that shares similarities with chronic asthma. Heaves-affected horses (n = 6) and age-matched control horses (n = 5) were kept on pasture before being exposed to indoor antigens for 30 days to induce airway inflammation and bronchoconstriction. Peripheral lung and endobronchial biopsies were collected before and after antigenic exposure by thoracoscopy and bronchoscopy, respectively. Immunohistochemistry and enzymatic labeling were used for morphometric analyses of airway smooth muscle mass and proliferative and apoptotic myocytes. In the peripheral airways, heaves-affected horses had twice as much smooth muscle as control horses. Remodeling was associated with smooth muscle hyperplasia and in situ proliferation, without reduced apoptosis. Further antigenic exposure had no effect on the morphometric data. In central airways, proliferating myocytes were increased compared with control horses only after antigenic exposure. Peripheral airway smooth muscle mass is stable in chronically affected animals subjected to antigenic exposure. This increased mass is maintained in a dynamic equilibrium by an elevated cellular turnover, suggesting that targeting smooth muscle proliferation could be effective at decreasing chronic remodeling.

Evaluation of a thoracoscopic technique using ligating loops to obtain large lung biopsies in standing healthy and heaves-affected horses.

OBJECTIVE To evaluate use of pre-tied ligating loop to perform thoracoscopic, large lung biopsy in normal and heaves-affected horses. STUDY DESIGN Prospective clinical study. ANIMALS Normal (n=5) and heaves-affected (n=6) horses. METHODS Lung biopsies, 1 from each hemithorax, were collected thoracoscopically using a pre-tied ligating loop. Horses were either normal (C) or heaves-affected with the latter being in remission (Ha) for the initial biopsy and in exacerbation (Hs) for the 2nd biopsy. Clinical variables, PaO(2), and PaCO(2) were used to determine the effect of surgical biopsy. Postoperative pneumothorax was monitored by serial thoracic radiographic examinations. RESULTS Thoracoscopic lung biopsy (n=29, 22 procedures) was well tolerated by all horses. Complication rate was 31%, including 8 ligature slippage and 1 pulmonary hemorrhage. Intranasal oxygen was administered intraoperatively to 6 horses (2 C, 1 Ha, 3 Hs) with severe hypoxemia or labored breathing. There was a significant decrease in PaO(2) during surgery in horses not supplemented with oxygen. Postoperative pneumothorax (21/22 procedures) detected radiographically resolved within 3 weeks. CONCLUSION Thoracoscopic lung biopsy using pre-tied ligating loops was minimally invasive, relatively inexpensive, and fairly efficient. Heaves-affected horses tolerated the surgery well, even when in exacerbation; however, the technique was associated with non life-threatening complications in 31% of the biopsies, most of which required correction with additional ligating loops or more sophisticated instrumentation. CLINICAL RELEVANCE Using laparoscopic pre-tied ligating loop for thoracoscopically-assisted lung biopsy can be considered in horses with normal and impaired lung function but alternative instrumentation and access to intranasal oxygen must be available to the surgeon in case of complications.

Enhanced bone healing using collagen-hydroxyapatite scaffold implantation in the treatment of a large multiloculated mandibular aneurysmal bone cyst in a thoroughbred filly.

An unmet need remains for a bone graft substitute material that is biocompatible, biodegradable and capable of promoting osteogenesis safely in vivo. The aim of this study was to investigate the use of a novel collagen–hydroxyapatite (CHA) bone graft substitute in the clinical treatment of a mandibular bone cyst in a young horse and to assess its potential to enhance repair of the affected bone. A 2 year‐old thoroughbred filly, presenting with a multilobulated aneurysmal bone cyst, was treated using the CHA scaffold. Post‐operative clinical follow‐up was carried out at 2 weeks and 3, 6 and 14 months. Cortical thickening in the affected area was observed from computed tomography (CT) examination as early as 3 months post‐surgery. At 14 months, reduced enlargement of the operated mandible was observed, with no fluid‐filled area. The expansile cavity was occupied by moderately dense mineralized tissue and fat and the compact bone was remodelled, with a clearer definition between cortex and medulla observed. This report demonstrates the promotion of enhanced bone repair following application of the CHA scaffold material in this craniomaxillofacial indication, and thus the potential of this material for translation to human applications. Copyright

Congenital branchial apparatus malformation in a Haflinger colt.

OBJECTIVE To report the diagnosis and treatment of a branchial apparatus anomaly (BAA) associated with a mandibular malformation in a foal. DESIGN Clinical report. ANIMAL Haflinger foal. METHODS A 6-day-old foal had a fluctuating cystic mass in the pharyngeal (throatlatch) region, which changed in appearance after ingestion of milk. Upper airway endoscopy and diagnostic imaging (ultrasonography, radiography, computed tomography) permitted identification of the anatomic location of a communicating tract between the lumen of the cystic mass and the pharynx. The mass was surgically removed and communication with the pharynx ligated. Histologic appearance of this mass was consistent with a branchial cyst or sinus. The mandibular malformation was managed conservatively. RESULTS Surgical resection of a third branchial sinus resulted in an excellent functional and cosmetic outcome. There was no evidence of any mandibular deformity 2 years later. CONCLUSION BAA may induce secondary mandibular deformation in utero and may cause respiratory compromise postpartum. Careful surgical dissection and removal of BAA resulted in an excellent outcome. CLINICAL RELEVANCE BAAs should be included in the differential diagnosis of a throatlatch region mass in equine neonates. Complete surgical excision is recommended and full recovery of any associated mandibular deformity may be anticipated without additional treatment in very young patients.

Ultrasound-guided coxofemoral arthrocentesis in horses

REASON FOR PERFORMING STUDY Coxofemoral joint pain is probably underestimated due to difficulties in identifying hip pain. The deep location of the joint and proximity of the sciatic nerve make arthrocentesis based on external landmarks a difficult and potentially risky procedure in mature horses. OBJECTIVES To describe an ultrasound-guided injection technique of the coxofemoral joint in standing horses and to evaluate its accuracy and potential difficulties/complications. METHODS Nine mature horses had both pelvic areas prepared for sterile ultrasound examination (3.5 MHz curvilinear probe). Coxofemoral joints were located and penetrated at their craniodorsolateral aspect under ultrasonographic guidance and injected with sterile contrast medium. A standing ventrodorsal radiographic view of each hemipelvis centred on the hip was obtained for each horse to assess the injection site. Horses were evaluated for 10 days following injection for possible complications. RESULTS Intra-articular injection was successful in all 18 joints. The procedure was well tolerated by horses under minimal restraint. Mean +/- s.d. needle repositionings required before accurate placement was 1.5 +/- 1.3 per joint. Once the needle was in the joint, synovial fluid was obtained in 7/18 joints. Minimal periarticular contrast medium was detected in 2/18 joints. Mean +/- s.d. ultrasonographic examination time required for coxofemoral localisation, accurate needle positioning and injection was 4.3 +/- 2.1 min. No complications were observed in the 10 days following injection. CONCLUSION The ultrasound-guided coxofemoral arthrocentesis is an accurate, reliable and safe technique that offers a real time evaluation of needle introduction into the deep and narrow coxofemoral joint space. POTENTIAL RELEVANCE Although this technique remains to be tested on clinical cases, it is a promising tool to facilitate diagnosis of coxofemoral pain, septic arthritis or administration of intra-articular medication.

Thoracoscopic lung biopsies in heaves-affected horses using a bipolar tissue sealing system.

Objective: To validate the use of the LigaSure™ Vessel Sealing System (LVSS) to perform thoracoscopic lung tissue biopsies in heaves-affected horses. Study design: Prospective clinical study. Animals: Heaves-affected horses (n=12). Methods: Lung biopsies (n=34) were collected with the LVSS (2–4 biopsies/horse) in horses with and without clinical signs of heaves. Thoracoscope (13th intercostal space [ICS]) and 2 instruments (between the 12–15th ICS) portals were used. Selected clinical and arterial blood gas variables were monitored. Postoperative pneumothorax was evaluated. Depth of thermal injury to the surrounding tissue and representativeness of the biopsies were determined. Results: Mean surgical time was 22.9±8.0 minutes. The complication rate was 5.6%, and primarily related to a focal inadequate sealing of the biopsy margin. Five horses in exacerbation required intraoperative intranasal O2. Mean PaO2 was significantly lower in heaves-affected horses with clinical signs compared with those without clinical signs. Postoperative pneumothorax was detected radiographically after 20 of the 34 procedures. One horse with clinical signs of heaves developed a fatal tension pneumothorax 5 days postoperatively despite close radiographic monitoring. Conclusion: Thoracoscopic lung biopsy using LVSS is a rapid and effective technique to harvest peripheral lung tissues from heaves-affected horses. Although the complication rate was tolerable, tension pneumothorax was a potential life-threatening complication because of incomplete lung sealing. Clinical Relevance: LVSS can be used with relative safety to perform thoracoscopic lung biopsy, but close postoperative monitoring is necessary to avoid tension pneumothorax.OBJECTIVE To validate the use of the LigaSure™ Vessel Sealing System (LVSS) to perform thoracoscopic lung tissue biopsies in heaves-affected horses. STUDY DESIGN Prospective clinical study. ANIMALS Heaves-affected horses (n=12). METHODS Lung biopsies (n=34) were collected with the LVSS (2-4 biopsies/horse) in horses with and without clinical signs of heaves. Thoracoscope (13th intercostal space [ICS]) and 2 instruments (between the 12-15th ICS) portals were used. Selected clinical and arterial blood gas variables were monitored. Postoperative pneumothorax was evaluated. Depth of thermal injury to the surrounding tissue and representativeness of the biopsies were determined. RESULTS Mean surgical time was 22.9±8.0 minutes. The complication rate was 5.6%, and primarily related to a focal inadequate sealing of the biopsy margin. Five horses in exacerbation required intraoperative intranasal O(2) . Mean PaO(2) was significantly lower in heaves-affected horses with clinical signs compared with those without clinical signs. Postoperative pneumothorax was detected radiographically after 20 of the 34 procedures. One horse with clinical signs of heaves developed a fatal tension pneumothorax 5 days postoperatively despite close radiographic monitoring. CONCLUSION Thoracoscopic lung biopsy using LVSS is a rapid and effective technique to harvest peripheral lung tissues from heaves-affected horses. Although the complication rate was tolerable, tension pneumothorax was a potential life-threatening complication because of incomplete lung sealing. CLINICAL RELEVANCE LVSS can be used with relative safety to perform thoracoscopic lung biopsy, but close postoperative monitoring is necessary to avoid tension pneumothorax.

Further characterisation of an experimental model of tendinopathy in the horse

REASONS FOR PERFORMING STUDY Injuries in energy-storing tendons are common in both horses and man. The high prevalence of reinjury and the relatively poor prognosis for returning to preinjury performance levels warrant further research, for which well characterised models would be very helpful. OBJECTIVES Given the clinical similarities in tendinopathy of energy-storing tendons, we hypothesised that a recently developed experimental model of equine tendon injury would display many of the characteristics of clinical tendinopathy and could therefore be of use for both species, thus providing comparative insight to the human condition and offering direct potential impact to equine medicine. STUDY DESIGN In vivo experimental study. METHODS Surgical lesions were created in the superficial digital flexor tendon (SDFT) of 6 horses. Clinical examination, as well as biochemistry, histology and immunohistochemistry were performed on the harvested samples at 6 weeks post surgery. RESULTS Disrupted collagen fibres, increased glycosaminoglycan content, increased presence of tenocytes with plump nuclei, the scarcity of inflammatory cells, increased matrix metalloproteinase (MMP) activity and neovascularisation were observed and found to be consistent with clinical tendinopathy. CONCLUSION AND RELEVANCE This model displays the key features of the most common human and equine degenerative tendon disorders and is therefore an appropriate, if still imperfect, model of tendinopathy.

Short-term cast immobilisation is effective in reducing lesion propagation in a surgical model of equine superficial digital flexor tendon injury

REASONS FOR PERFORMING THE STUDY Larger superficial digital flexor tendon (SDFT) injuries have a poorer prognosis than smaller lesions. During the inflammatory phase enlargement of the initial lesion is frequently noted, with biomechanical loading being recently proposed to play an important role. OBJECTIVES To evaluate the effect of lower limb cast immobilisation on tendon lesion propagation in an equine model of surgically induced SDFT injury. METHODS Core lesions were surgically induced in both front SDFTs of 6 young mature horses. At the end of surgery, one leg was randomly placed in a lower limb cast and the other leg (control) was bandaged for 10 days. Computerised ultrasonographic tissue characterisation performed at Days 10, 15, 21, 28, 35 and 42 allowed measurement of lesion length (cm) and width (expressed as a percentage of whole tendon cross-section). On Day 42 horses were subjected to euthanasia and both SDFTs were sectioned every centimetre to assess the lesion length macroscopically. Statistics were performed to compare cast vs. control legs with significance set at P<0.05. RESULTS When all time points were combined, lesion length was 19% shorter (P<0.0001) and lesion width 57% smaller (P = 0.0002) in the cast legs (6.13 ± 0.12 cm; 6.90 ± 0.64%) than in the control legs (7.30 ± 0.21 cm; 10.85 ± 1.22%). On Day 42 the lesion length on macroscopic evaluation was 19% shorter (P = 0.04) in the cast (7.00 ± 0.36 cm) than in the control legs (8.33 ± 0.33 cm). CONCLUSIONS Cast immobilisation for 10 days effectively reduced lesion propagation (length and width) compared to bandaging in an in vivo model of artificially-induced tendon lesions. POTENTIAL RELEVANCE A short period of cast immobilisation during the early phase of tendon healing may be an easy and cost-effective way to reduce the initial enlargement of lesion size and hence to improve prognosis.

Comparison of medial and lateral ultrasound-guided approaches for periarticular injection of the thoracolumbar intervertebral facet joints in horses.

OBJECTIVE To compare ultrasound-guided lateral and medial approaches for periarticular injections of the thoracolumbar intervertebral facet joints (IFJ). STUDY DESIGN Experimental cadaveric study. SAMPLE POPULATION Adult equine cadavers (n=4). METHODS IFJ (T12-T13 to L5-L6) were identified by ultrasound (transducer perpendicular to the spine axis) and insertion of a 13 cm, 18 g spinal needle monitored until bone contact using medial (right side) and lateral (left side) approaches. Number of needle insertions at each site, needle repositioning, and insertion depth were recorded. On bone contact 2 mL latex was injected. Intraarticular deposition, distance of latex from the closest articular margin, and presence of latex in the multifidus muscle were established by dissection. RESULTS Of 96 attempts, only 1 site require reinsertion of the needle; however, 46% of the injections required needle repositioning. Mean ± SD insertion depth was 8.5 ± 1.1 cm. Most injections (86%) were intraarticular and 96% were at or within 0.5 cm of the closest articular margin. Needle insertion relative to the transducer (lateral, medial) had no effect on the distance from the latex to the closest articular margin and all injections were performed into the multifidus muscle. CONCLUSIONS Ultrasound-guidance facilitated accurate periarticular injection of thoracolumbar IFJ irrespective of using a medial or lateral approach.

Branchial remnant cysts of mature and juvenile horses

This clinical report describes 8 cases of branchial remnant cysts (BRC) in the horse. The horses presented with bimodal age distribution, with 5 cases in mature horses (age 8-21 years) and 3 in foals (age 1, 6 and 10 months). Mature cases presented for dysphagia or intermittent oesophageal obstruction (2/5), and retropharyngeal swelling (3/5), whereas respiratory stridor and visible mass were presenting complaints in the foals. Presence of a right-sided (5/8) or dorsally located (2/8) palpable retropharyngeal mass of 3-35 cm diameter was noted clinically; one left-sided mass was identified as an incidental finding at necropsy. Ultrasonography typically revealed a thick-walled cyst containing hypoechoic fluid with dependent hyperechoic masses consistent with blood clots. Radiographs and upper airway endoscopy were also consistent with a retropharyngeal mass. Fluid cytology revealed chronic haemorrhage in 6/8 cases, and squamous epithelial cells in one case. Histopathology in all cases demonstrated an epithelium-lined cyst with no smooth muscle or thyroid tissue. Two cases was subjected to euthanasia; one due to concurrent laryngeal anomalies and one due to financial constraints. The remaining 5 cases were treated via surgical excision. Post operatively, right laryngeal hemiplegia was observed in 4/5 cases. All previous reports of BRC in the horse have described juvenile individuals. Brachial remnant cyst should be considered a differential diagnosis for mature horses with masses of the throatlatch area and can be definitively diagnosed by the presence of squamous epithelium in aspirated fluid or by histopathology of the excised mass. Right recurrent laryngeal nerve damage is a common complication of surgery.