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Objective: Evaluate a prototype dynamic laryngoplasty system (DLPS) in horses; a feasibility study., Animals: 7 healthy Standardbred adult horses., Methods: This was an in vivo experimental study. Horses had a standing surgical procedure to induce complete laryngeal hemiplegia, which was subsequently treated using the dynamic laryngoplasty system (DLPS). Activation of the DLPS was achieved using an injection port exiting through the skin (n = 2) or a subcutaneous injection port (n = 5). For each horse, endoscopic examinations of the upper respiratory tract were performed preoperatively, intraoperatively, and 7 days postoperatively. Left-to-right quotient ratios calculated during inactivated and activated states were obtained from still images of the rima glottidis acquired during day 7. In 3 horses, the device was intentionally overinflated to evaluate for device failure, and postmortem examinations were performed on day 7. For the remaining 4 horses, upper respiratory tract endoscopy was repeated at 1 month postoperatively, with no subsequent postmortem exam., Results: No perioperative complications occurred, and the DLPS was effectively delivered in all horses under standing sedation. The left-to-right quotient ratio at day 7 postoperatively could be altered from a resting position of 0.76 (± 0.06) to a maximum of 0.97 (± 0.06; P < .05). The degree of arytenoid abduction could not be significantly altered after 1 month of device implantation, suspected to be due to peri-implant fibrosis. No coughing nor tracheal contamination was observed at all time points or during inflation., Clinical Relevance: The ability to alter the degree of abduction at 7 days postoperatively with the DLPS may be beneficial in selective cases.

Objective: To describe left recurrent laryngeal neurectomy (LRLn) performed under standing sedation and evaluate the effect of LRLn on upper respiratory tract function using a high-speed treadmill test (HST). We hypothesized that (1) unilateral LRLn could be performed in standing horses, resulting in ipsilateral arytenoid cartilage collapse (ACC); and (2) HST after LRLn would be associated with alterations in upper respiratory function consistent with dynamic ACC., Animals: 6 Thoroughbred horses., Methods: The horses were trained and underwent a baseline HST up to 14 m/s at 5% incline until fatigue. Evaluation included; airflow, pharyngeal and tracheal pressures, and dynamic upper respiratory tract endoscopy. Trans-laryngeal impedance (TLI) and left-to-right quotient angle ratio (LRQ) were calculated after testing. The following day, standing LRLn was performed in the mid-cervical region. A HST was repeated within 4 days after surgery., Results: Standing LRLn was performed without complication resulting in Havemayer grade 4 ACC at rest (complete paralysis) and Rakestraw grade C or D ACC (collapse up to or beyond rima glottis midline) during exercise. Increasing treadmill speed from 11 to 14 m/s increased TLI (P < .001) and reduced LRQ (P < .001). Neurectomy resulted in an increase in TLI (P = .021) and a reduction in LRQ (P < .001)., Clinical Relevance: Standing LRLn induces laryngeal hemiplegia that can be evaluated using a HST closely after neurectomy. Standing LRLn may be useful for future prospective evaluations of surgical interventions for laryngeal hemiplegia.

Background: Little is known about potential differences in the left recurrent laryngeal nerve (Lrln) and left cricoarytenoideus dorsalis (LCAD) muscle between domestic and feral horse populations. If a difference exists, feral horses may provide a useful control population for research related to recurrent laryngeal neuropathy (RLN) and increase our understanding of potential population pressures influencing the incidence RLN., Objectives: The objective of this study was to compare the Lrln and LCAD of domestic and feral horses using histological and immunohistochemical techniques (IHC)., Methods: Sixteen horses, domestic (n = 8) and feral (n = 8), without clinical or ancillary examinations that were processed at an abattoir had the Lrln and LCAD muscle harvested immediately following death. Carcass weights were recorded. Subjective and morphometric histologic assessment were performed on Lrln sections. The LCAD was assessed for myosin heavy chain (fibre type proportion, diameter and grouping using IHC., Results: Fibre-type grouping consistent with RLN was seen in both groups. Regenerating fibre clusters were more common in domestic compared to feral horses (p = 0.04). No other histologic differences occurred between groups. Muscle fibre typing demonstrated a lower mean percentage of type IIX fibres in the feral group compared to the domestic group (p = 0.03). There was no difference in type I or IIA proportions or mean diameter of any fibre type between the groups., Conclusions: The domestic population showed evidence of nerve regeneration suggesting RLN in this group, yet this was not supported by the higher proportion of type IIX muscle fibres compared to the feral population. Further evaluation to clarify the significance and wider occurrence of the differences is indicated., (© 2023 The Authors. Veterinary Medicine and Science published by John Wiley & Sons Ltd.)

Objectives: To investigate the feasibility and describe the clinical experience of performing laryngeal tie-forward (LTF) in standing horses unaffected (experimental) and affected (clinical) by intermittent dorsal displacement of the soft palate (iDDSP)., Study Design: Experimental study and case series., Animals: Five normal experimental controls and five client owned horses affected by iDDSP., Methods: Standing LTF was performed and evaluated in five experimental horses and five clinical cases diagnosed with iDDSP. Standing LTF was performed under endoscopic guidance with horses sedated and the surgical site desensitized with local anesthetic solution. Short term outcome was assessed using radiography, resting and (in clinical cases) dynamic upper respiratory tract (URT) endoscopy., Results: Standing LTF was well tolerated and completed in all horses. Radiographic assessment demonstrated that compared to preoperatively, the basihyoid bone and thyrohyoid-thyroid articulation were positioned dorsally (9.6 mm, p = .006 and 20.4 mm, p = .007, respectively) at 2 days postoperatively. During repeat dynamic URT endoscopy at 48 hours postoperatively, 3/5 horses showed resolution of iDDSP and 2/5 marked improvement. One horse experienced brief iDDSP associated with neck flexion which corrected after swallowing. The second achieved a greater speed and total distance prior to iDDSP., Conclusions: Standing LTF did not incur any major peri- or postoperative complications. The laryngohyoid apparatus was repositioned dorsally and in a small case series had a similar surgical effect on laryngeal position., Clinical Significance: Standing LTF is feasible, mitigates the risk of general anesthesia related complications and reduces cost., (© 2022 The Authors. Veterinary Surgery published by Wiley Periodicals LLC on behalf of American College of Veterinary Surgeons.)

Objective: To assess the effect of vocal cordectomy on airflow across equine larynges at different Rakestraw grades of arytenoid abduction using a unidirectional airflow model., Study Design: Ex vivo, repeated measures., Sample Population: Twenty cadaveric equine larynges., Methods: The right arytenoid cartilage was maximally abducted in all larynges. Each larynx was assigned a Rakestraw grade A or B, and the left arytenoid was abducted accordingly. Each larynx was tested under 3 conditions: intact, left vocal cordectomy (LVC), and bilateral vocal cordectomy (BVC). Translaryngeal pressure and airflow were measured, and digital video footage was obtained. Translaryngeal impedance (TLI) was calculated, and the arytenoid left-to-right quotient angle (LRQ) and rima glottis cross-sectional area (CSA) were measured from standardized still images., Results: Vocal cordectomy reduced TLI by 14.5% in LVC in comparison with intact larynges at Rakestraw grade B (P = .014). In Rakestraw grade A position, neither unilateral nor bilateral vocal cordectomy had any effect on TLI. Regardless of Rakestraw allocation, both LVC and BVC increased CSA in comparison with intact larynges (P < .005), with BVC larynges experiencing a greater effect than LVC (P < .0001)., Conclusion: Using a unilateral airflow model, LVC improved TLI in larynges where arytenoid position approximated Rakestraw grade B. However, when the arytenoid position approximated Rakestraw grade A, there was no effect on TLI following LVC or BVC., Clinical Significance: Surgeons considering a vocal cordectomy should take into account the degree of arytenoid abduction before performing the procedure, as it may not be warranted from a TLI point of view., (© 2022 The Authors. Veterinary Surgery published by Wiley Periodicals LLC on behalf of American College of Veterinary Surgeons.)

Background: Laser salpingopharyngostomy has been used as an adjunct to primary medical therapy allowing for topical debridement, topical treatment or to potentially alter the guttural pouch environment in horses with guttural pouch disease., Objectives: To evaluate the effect of a laser salpingopharyngostomy on the guttural pouch environment in healthy horses., Study Design: Experimental study., Methods: In six adult Standardbred female horses, under standing sedation a stab incision was made ventral to the sternocephalicus tendon and a customised trocar inserted into the medial guttural pouch compartment. Baseline (day 0) temperature, humidity, oxygen (O 2 ) and carbon dioxide (CO 2 ) levels were recorded. A laser salpingopharyngostomy was subsequently made into the right guttural pouch. The guttural pouch environment was re-sampled as above on days 7 and 14 to detect differences in the local environment of the guttural pouch caused by the laser salpingopharyngostomy., Results: The guttural pouch environment was altered by the laser salpingopharyngostomy. Baseline recorded values within the guttural pouch were highly constant within each horse. Post laser salpingopharyngostomy there was considerable variation within the guttural pouch between horse and during the period of sampling. Specifically, CO 2 levels post laser salpingopharyngostomy appeared to be linked directly to the horse's respiratory pattern with peaks and troughs recorded post laser salpingopharyngostomy. The variation in CO 2 was significantly different at days 7 and 14 post laser salpingopharyngostomy compared with baseline levels (day 7 = 6 mm Hg, day 14 = 8.83 mm Hg). Oxygen levels were also more varied during sampling compared with baseline (day 7 = 3.4%, day 14 = 1.83%). There was no change in humidity or temperature during the study., Main Limitations: This study was conducted on horses with no evidence of guttural pouch abnormalities or disease., Conclusions: Laser salpingopharyngostomy alters the guttural pouch environment and this may be useful in the treatment of guttural pouch disease where this alteration is desirable., (© 2019 EVJ Ltd.)

Objective: To evaluate equids with enostosis-like lesions (ELLs) and document the clinical and epidemiological features of this disease., Design: Retrospective case series., Animals: 79 equids with a scintigraphic diagnosis of at least 1 ELL on ≥ 1 occasion., Procedures: Medical records of 4,992 equids that underwent bone scintigraphy between March 1997 and March 2009 were reviewed; 78 horses and 1 pony had a scintigraphic diagnosis of an ELL. For those equids, signalment; physical, scintigraphic, radiographic, and lameness examination results; and outcome were reviewed., Results: Of the 79 equids, 4 (5.1%) had anatomically distinct ELLs on 2 (n = 3) or 4 (1) separate occasions that caused lameness in different limbs. Thus, there were 85 ELL-related admissions to the hospital. Overall, 157 ELLs were detected. Among all equids undergoing scintigraphic examination, Thoroughbreds were more commonly and Standardbreds were less commonly affected. Older animals were more likely to have ELLs. Lameness was directly attributed to scintigraphically evident ELLs in 42 of the 85 (49.4%) admissions. The tibia (62/157 [39.5%]) and the radius (46/157 [29.3%]) were most commonly affected. The ELLs located in the humerus caused more severe lameness than did ELLs in other anatomic locations. Lameness severity was associated with radiopharmaceutical uptake intensity. Among racehorses, those with 1 ELL were more likely to return to racing than were those with multiple ELLs detected in 1 scintigraphic examination; mean interval from diagnosis to first start was 184 days., Conclusions and Clinical Relevance: Results of this retrospective evaluation of a large group of equids with ELLs have provided a better understanding of this disease process.

Objective: To determine the rate of postoperative infection (POI) for internal fixation repaired equine long bone fractures and arthrodeses and identify associated risk factors., Study Design: Case series., Animals: Horses (n=192) with fracture repair of the third metacarpal and metatarsal bones, radius, ulna, humerus, tibia, and femur, or arthrodesis with internal fixation., Methods: Medical records (1990-2006) were reviewed for signalment, anatomic location, fracture classification and method of repair, technique and surgical duration, bacterial species isolated, postoperative care, onset of POI, and outcome., Results: Of 192 horses (171 [89%] closed, 21 [11%] open fractures), 157 (82%) were discharged from the hospital. Infection occurred in 53 (28% horses), of which 31 (59%) were discharged. Repairs without POI were 7.25 times more likely to be discharged from the hospital. Closed fractures were 4.23 times more likely to remain uninfected and 4.59 times more likely to be discharged from the hospital compared with open fractures. Closed reduction and internal fixation was associated with a 2.5-fold reduction in rate of POI and a 5.9 times greater chance for discharge from the hospital compared with open reduction and internal fixation. Females had a strong trend for increased POI when compared with colts and stallion but not geldings., Conclusions: Overall rate of POI was 28%. Fracture classification, method of repair, gender, and surgical duration were significant risk factors.

Upper respiratory abnormalities are common performance-limiting problems in horses. The complications of various treatment methods, including laryngoplasty surgery, sinus surgery, intermittent dorsal displacement of the soft palate, laser surgery, and tracheal disorders, are discussed.