Dr Fabrice Rossignol

Objective: To describe the anatomy of the entry to the equine esophagus (vestibulum esophagi) and to assess the risk of penetrating its adventitia and/or lumen during laryngoplasty.

Study design: Ex vivo cadaveric study.

Sample population: Five isolated equine larynges and 39 equine head and neck specimens.

Methods: The anatomy of the vestibulum esophagi was studied by dissection of 5 cadaver specimens. Then, a bilateral laryngoplasty was performed, including 5 suture placements through the muscular processes, caudal, rostral, and sagittal, with straight and curved needles. Two of the 3 surgeons performing the implantations were unaware of the goals of the study. Suture positions and iatrogenic trauma to the lumen and/or adventitia of the vestibulum esophagi were identified during dissection of the specimens. Risk factors for penetrating the adventitia were evaluated with a multivariate regression model.

Results: The vestibulum esophagi spans between both wings of the thyroid cartilage over the entire width of the larynx, covering the rostral spine (arcuate crest) of the arytenoid cartilages. It is covered by the thyropharyngeus and cricopharyngeus muscles. Masked surgeons were associated with a significantly higher number of adventitia penetrations (72%) compared to the nonmasked surgeon (9%). The lumen of the vestibulum esophagi was penetrated in 4.6% of suture placements and only by the 2 masked surgeons.

Conclusion: Penetration of the adventitia was more common when surgeons were unaware of the anatomical extent of the vestibulum esophagi.

Clinical significance: Anatomical knowledge of the extent of the vestibulum esophagi reduces the risk of penetrating its lumen or adventitia during suture placement on the muscular process of the arytenoid cartilage.

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Objective: To report the outcome of horses after pancarpal or partial carpal arthrodesis with 3 locking compression plates (LCP).

Study design: Case series.

Animals: Six horses ranging in age from 8 months to 16 years and weighing 227-580 kg with severe carpal pathology including acute fractures, chronic osteoarthritis, and chronic angular limb deformity.

Methods: Pancarpal or partial carpal arthrodesis was performed with 3 LCP. Autologous cancellous bone grafts were used in 5 of 6 cases to facilitate joint arthrodesis.

Results: External coaptation was maintained for 4 to 6 weeks after surgery. Radiographic follow-up was available in all 6 cases, all of which reached arthrodesis and pasture soundness by 4-5 months postoperatively. One case required implant removal at 6 months because of implant exposure through the skin but returned to pasture soundness after removal.

Conclusion: Carpal instability due to acute fractures or chronic disease was successfully stabilized with 3 short LCP, leading to pasture soundness in all 6 horses.

Clinical significance: The use of 3 short LCP should be considered as a strategy to facilitate pancarpal or partial carpal arthrodesis by providing superior stability without placement of implants in the diaphysis of the radius and third metacarpus.

Objective: To determine the biomechanical properties of 5 suture constructs in the equine cricoid under cyclic loading and load to failure testing.

Study design: Ex vivo study.

Samples: Seventy-five equine cadaver larynges.

Methods: Each larynx was implanted with 1 of 5 cricoid-suture constructs. The standard laryngoplasty, where a suture is passed once through the cricoid, including its caudal edge, was used in 2 constructs: 1 with 5 USP Ethibond (ES) and 1 with 2 mm Fibertape (FS). In the third construct, the 2 mm Fibertape was passed twice through the cricoid including its caudal edge (Double Loop-DL). Constructs 4 and 5 used 2 mm Fibertape in a U-shaped loop passed through the cricoid but excluding its caudal edge. One construct was supported with a metallic button (MB) on the caudo-ventral aspect of the cricoid while the other included only the U-shaped loop (U). Constructs were subjected to cyclic loading and to single cycle to failure. Reduction of the left-to-right arytenoid angle quotient (LRQ), suture migration, and load at failure were compared.

Results: LRQ reduction after cyclic loading was lower in MB and U than ES constructs. During cyclic loading, suture migration was reduced in MB, U, and DL compared to ES constructs. Mean load at failure was lower in FS and U than in ES constructs.

Conclusion: Loss of abduction after equine laryngoplasty may be reduced and pullout forces increased by applying a MB construct in the cricoid cartilage. In vivo testing is required to verify these results.

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Objective: To describe the surgical treatment outcome of cervical fractures in 3 horses.

Study design: Case report.

Animals: Three client-owned horses with cervical vertebral fractures.

Methods: Three horses were refered for neck stiffness, pain, and ataxia after a cervical trauma because of a fall. Radiographic examination showed an oblique displaced fracture of the caudal aspect of the body of the second cervical vertebra (C2) in horse 1, an oblique displaced fracture of the caudal aspect of C4 involving the disc between C4 and C5 in horse 2, and a displaced transverse fracture of the body of the axis (C2) extending to the lateral arches and involving the vertebral canal in horse 3. In horse 1, the fracture was reduced and stabilized using a 14-hole narrow DCP plate, applied ventrally, and fixed with cancellous screws. A cervical fusion was performed. In horses 2 and 3, fracture fixation was performed using a 5-hole narrow LCP and 5 mm locking screws.

Results: All horses showed improvement and returned to full activity. The fracture healed in all horses.

Conclusion: Internal fixation of cervical fracture in these horses was associated with minimal complications, and was associated with healing and a highly functional outcome in all horses. The LCP was preferred and would be recommended for ventral stabilization of selected cases of vertebral fractures.

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Objective: To describe the clinical experience with standing laryngoplasty in a series of horses mostly nonracing.

Study design: Case series.

Animals: Seventy-one client-owned horses.

Methods: Medical records (April 2008-February 2014) of horses treated by standing laryngoplasty for abnormal respiratory noise and or poor performance were reviewed. Horses were included if they had a diagnosis of idiopathic right or left recurrent laryngeal neuropathy confirmed by videoendoscopy. All horses underwent a unilateral laryngoplasty with a unilateral or bilateral ventriculectomy or ventriculocordectomy. Follow-up endoscopy was performed in all horses within 24 hours postoperative, in 24 horses at 2-weeks, and in 65 horses at 6 weeks. Late follow-up was obtained from the trainer, owner, or referring veterinarian by telephone.

Results: Laryngoplasty was performed under endoscopic guidance with the horses sedated, and the surgical site was desensitized with local anesthetic solution. Laryngoplasty was completed in all horses and was well tolerated. No hyperabduction was observed. Two horses developed incisional swelling that resolved with drainage only. Late follow-up reported satisfactory improvement in respiration in all but 3 horses.

Conclusions: Laryngoplasty performed with the horse standing avoids risks associated with general anesthesia and recovery and yields comparable results in nonracing horses, to laryngoplasty performed with the horse anesthetized. This technique reduces cost and allows accurate intraoperative adjustment of the degree of arytenoid abduction.

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Objective: To compare mechanical properties of 2 techniques with a conventional technique for anchoring the muscular process in a laryngoplasty procedure.

Study design: Experimental ex vivo study.

Sample population: Equine larynges (n = 60).

Methods: A single loop (SL), a screw (SC), and a double loop technique (DL) were compared. Constructs were subjected to cyclic loading, oscillating from 5 to 50 N for 3000 cycles, followed by a single cycle to failure test. Mean distraction, load at failure, stiffness, and failure mode were compared between groups.

Results: Mean ± SD distraction in cyclic loading was greater for DL (2.1 ± 0.7 mm) than for SL (1.9 ± 1.3 mm) and SC (1.539 ± 0.9 mm); however, there was no significant difference between SL and SC or between SL and DL. Mean ultimate failure load was greater for DL (240 ± 44.56 N) than for SC (189.59 ± 46.16 N) and SL (150.93 ± 44.43 N) and greater for SC compared with SL. Failure occurred by cartilage tearing for DL and SL, and by screw pull out (n = 13) or knot slippage (4) for SC.

Conclusion: In cyclic loading, SC is more stable than DL and at least as stable as SL. In single cycle to failure, DL is the strongest construct and SC is stronger than SL.

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Objectives: To (1) report a modified transfixation pin cast technique, using dorsal recumbency for fracture reduction, distal positioning of the pins in the epiphysis and distal metaphysis, and a hybrid cast, combining plaster of Paris (POP) and fiberglass casting, and (2) report outcome in 11 adult horses.

Study design: Case series.

Animals: Adult horses (n = 11) with comminuted phalangeal fractures.

Methods: Horses were anesthetized and positioned in dorsal recumbency. The phalangeal fracture was reduced by limb traction using a cable attached to the hoof. Screw fixation in lag fashion of fracture fragments was performed when possible. Transfixation casting was performed using two 6.3 mm positive profile centrally threaded pins with the 1st pin placed in the epiphysis of the metacarpus/tarsus at the center of, or slightly proximal to, the condylar fossa and the 2nd one 3-4 cm proximal. A hybrid cast was applied.

Results: Forelimbs were involved in 9 horses and the hind limb in 2. Pins were maintained for a minimum of 6 weeks. No pin loosening was observed at the time of removal (6-8 weeks). A pony fractured the distal aspect of the metacarpus at the proximal pin. Nine horses survived (82%); none of the horses developed septic arthritis despite the distal location of the distal pin, close to the fetlock joint.

Conclusion: This modified transfixation pin casting technique was associated with good pin longevity and could reduce the risk of secondary pin hole fractures and pin loosening.

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Objective: To describe a modified laryngeal tie-forward procedure (LTFP) using metallic implants.

Study design: Retrospective case series.

Population: Twenty-seven horses (including 24 race horses) with dorsal displacement of the soft palate (DDSP) or palatal instability (PI) diagnosed using high-speed treadmill endoscopy (n = 15), history and resting examination (n = 8), or dynamic endoscopy over ground (n = 4).

Methods: All horses underwent the modified LTFP. Modifications of the surgical procedure consisted in the use of 3 metallic stents called Suture Button(TM) through which the sutures are threaded and in a tying technique that involved a single knot connecting left and right suture loops (versus tying each separately). Lateral radiographs were taken 24 hours after surgery. Follow-up was obtained by telephone communication with trainers or owners.

Results: Surgery was performed without complications on all horses. The 3 metallic buttons were clearly visible on the postoperative radiographic examination. No evidence of suture breakage was observed 24 hours postoperatively based on radiographs.

Conclusion: In other aspects, this technique is not very different from that originally described by Ducharme et al; it is an innovation that could offer some advantages to the surgeons and increase suture resistance to pullout from the thyroid cartilage. Our technique was used without complication in a small group of horses and return to performance may be similar to the original technique.

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Objective: To evaluate the efficacy of a laparoscopic peritoneal flap hernioplasty (PFH) to close anatomically the vaginal ring and to evaluate its protective effect in horses with a history of strangulated inguinal hernia (SIH) against future herniation.

Study design: Prospective study.

Animals: A first group of 5 ponies, 3 horses and 1 donkey with no history of SIH and a second group of 4 horses ‘clinical cases’ with a history of SIH.

Methods: A laparoscopic PFH was effected on all horses under general anaesthesia. Peritoneum ventro-lateral to the vaginal ring was elevated and cut on 3 sides, separated from the underlying muscle, then inverted and attached dorso-medially and laterally to the parietal wall using intra-corporeal stitches (6 cases) or laparoscopic staples (7 cases). Animals of the first group (n=9) underwent a standing laparoscopy 7 days post-operatively to visualize the vaginal rings. Horses of the second group were followed to confirm the absence of re-herniation.

Results: The laparoscopic check-up showed that the vaginal ring had been effectively and completely covered in all cases except the first one. No adhesions was observed. In the four clinical cases, none of the horses have had a reccurence of SIH at the time of writing (6 months to 4 years).

Conclusion: Laparoscopic hernioplasty on a recumbent horse is feasible by closing the vaginal ring with a peritoneal flap. This technique was efficient in our cases to prevent recurrence of SIH but more cases are needed. This technique may reduce inflammation and irritation of the spermatic cord, which could otherwise jeopardise the animal’s breeding career.

Clinical relevance: Laparoscopic PFH coud be used in horses with a history of SIH.

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Objective: To compare in vitro the load necessary for a partial and complete rupture of the muscular process arytenoid cartilage when a suture prosthesis is positioned by a bone trocar versus a trocar point needle and to compare failure mode.

Study design: Experimental using cadaver specimens.

Sample population: Larynges from 18 Thoroughbred race horses, aged 2-20 years.

Methods: Arytenoid cartilages were separated randomly into 2 groups: group 1-suture prosthesis inserted directly through the muscular process using a curved trocar point needle and group 2-suture passed through a hole predrilled with a 3 mm bone trocar. Distracting force (constant rate, 1 mm/s) was applied to the suture until failure of the muscular process. Partial failure load, maximum load at complete failure, and force-time curve were recorded. Each arytenoid cartilage was examined, radiographed, and classified as having a linear or curved failure plane.

Results: No significant differences in mechanical test variables were detected. Failure mode followed the fissures occurring at the beginning of failure and then followed the tension axis. Significantly more linear failures occurred in group 2 (trocar) and more curved failures occurred in group 1 (needle).

Conclusion: Use of a bone trocar for tunneling through the muscular process may reduce fissure formation.

Clinical relevance: Use of bone trocar to create a hole in the muscular process of the arytenoid cartilage for suture passage in laryngoplasty may reduce fissure formation and decrease the risk of cartilage failure from suture pullout.

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