Biomechanical evaluation of suture pullout from canine arytenoid cartilages: effects of hole diameter, suture configuration, suture size, and distraction rate

OBJECTIVE: To evaluate the mechanical properties of canine arytenoid cartilage-suture constructs. STUDY DESIGN: Experimental study. SAMPLE POPULATION: Eighty canine cadaveric larynges. METHODS: Arytenoid cartilage-suture constructs were loaded to failure on a materials testing machine. The effect of hole size, suture configuration, suture size, and rate of distraction on load at failure, displacement at failure, energy to failure, and construct stiffness were evaluated. Polypropylene sutures were used exclusively. Specific variables evaluated were: (1) hole size-SH needle, 22, 20, and 18 ga hypodermic needles; (2) suture configurations-single dorsal and ventral articular sutures, double sutures, horizontal mattress, locking loop, and single non-articular sutures; (3) suture size-1, 0, 2-0, and 3-0; and (4) distraction rate-0.83 and 36.66 mm/s. RESULTS: Hole size had no effect on any biomechanical variable. Double suture and horizontal mattress configurations had the highest median load and energy at failure. Single dorsal suture configurations that did not include the arcuate crest had the lowest median load at failure. Larger suture sizes tended to result in stiffer constructs. Cartilage-suture constructs behaved in a viscoelastic manner where load at failure, energy at failure, and stiffness increased when distraction rate was increased, whereas displacement at failure did not. Most constructs failed by suture pullout regardless of distraction rate, although 50% of horizontal mattress configurations failed by avulsion of the muscular process. CONCLUSION: Suture and hole sizes appear to have few effects on the biomechanical performance of arytenoid-suture constructs. Double-suture and horizontal mattress suture patterns had the best overall mechanical properties for arytenoid lateralization. Single-suture techniques, which do not incorporate the arcuate crest, were biomechanically inferior. CLINICAL RELEVANCE: Cumbersome large-diameter sutures offer no advantage over smaller sutures when performing arytenoid lateralization. The cross-sectional geometry of the muscular process should be taken into account when placing sutures in the arytenoid cartilages. Single-suture techniques that do not incorporate the arcuate crest should be avoided.     

In vitro evaluation of a novel prosthesis for laryngoplasty of horses with recurrent laryngeal neuropathy

A prosthesis, composed of a steel cable and stress-reducing washers, was developed to prevent failure of laryngoplasty, a common treatment for horses affected by recurrent laryngeal neuropathy. Laryngoplasties were performed on 15 cadaveric larynges using a polyester suture on one side and the cable prosthesis on the other. Each prosthesis was distracted at a displacement rate of 20 mm/s using a servohydraulic materials testing machine until laryngoplasty failed. Distraction force and actuator displacement were recorded and analysed. All 15 laryngoplasties performed with a suture failed at the muscular process at a mean +/- s.d. force of 55.8 +/- 13.1 N. Six laryngoplasties performed with the cable prosthesis failed at the muscular process at mean force 219.6 +/- 125.0 N. In the other 9, the arytenoid cartilage was avulsed from the larynx at mean force 206.4 +/- 75.3 N, and the cable then tore through the muscular process at mean force 357.0 +/- 32.0 N. The difference in force required to cause failure of laryngoplasty was significant (P<0.0001). Although the prosthesis resisted substantially higher forces than did the suture, the effects of the prosthesis in vivo must be evaluated.     

Biomechanical Comparison of Six Suture Configurations Using a Large Diameter Polyester Prosthesis in the Muscular Process of the Equine Arytenoid Cartilage

Objective— To compare biomechanical properties of 6 suture configurations using a large diameter polyester prosthesis in the muscular process (MP) of the arytenoid cartilage and to determine failure mode.
Study Design— Experimental study.
Sample Population— Cadaveric equine larynges (n=121).
Methods— Suture configurations (4 single, 2 double) were inserted, and then constructs were tested in a single-cycle to failure at a 100 mm/min distraction. Load deformation curves were generated to assess the biomechanical properties of each construct. A 1-way ANOVA was used to compare the mean differences in construct failure force, cricoarytenoid joint (CAJ) disarticulation force, and energy stored at failure. A 2-sample t-test was used to compare single versus double suture patterns and a Fisher's exact test was used to compare failure mode.
Results— Both construct and CAJ failure force were significantly greater ( P <.05) for double suture patterns compared with single suture patterns; however, there were no significant differences in energy stored at construct failure. Failure at the MP accounted for ≥50% of construct failures for 3 of the single suture patterns and 1 of the double suture patterns tested. The remaining 2 patterns had an increased frequency of clamp failures as well as failure of the cricoid cartilage.
Conclusions— Sutures that sufficiently engage the spine of the MP alone or in conjunction with a second suture were found to be biomechanically superior.
Clinical Relevance— Engaging the spine of the MP appears to result in the most biomechanically sound laryngeal construct.     

Evaluation of a canine cranial cruciate ligament repair system for use in equine laryngoplasty

OBJECTIVE: To report the use of a nylon suture system (Canine Cranial Cruciate Ligament Repair System; Securos Inc Veterinary Orthopedics) as a prosthesis for equine laryngoplasty. STUDY DESIGN: Experimental and prospective clinical study. ANIMALS: Cadaver specimens (n = 5) and 7 horses with left laryngeal hemiplegia. METHODS: A commercially available monofilament nylon suture system was implanted as a laryngeal prosthesis. Arytenoid cartilage abduction was achieved with a tensioning device applied to the suture prosthesis during transnasal endoscopic observation. Suture fixation was achieved with crimping clamps and a crimping device. RESULTS: The nylon suture system was suitable as a laryngeal prosthesis for arytenoid cartilage abduction. The ratchet mechanism of the tensioning device facilitated abduction of the arytenoid cartilage and suture fixation was achieved by the crimped clamp without any loss of tension. Postoperatively, there was a slight loss of tension in 4 horses and complete loss of tension in 1 horse because of cartilage failure. After convalescence, none of the horses had abnormal respiratory noise, exercise intolerance or cough. CONCLUSIONS: A nylon suture system designed for canine cranial cruciate ligament repair was used successfully as a laryngeal prosthesis and facilitated control of the degree of arytenoid cartilage abduction during laryngoplasty. CLINICAL RELEVANCE: For improved control of the degree of arytenoid cartilage abduction during laryngoplasty, use of a nylon suture system with metal crimps should be considered.     

Effects of age and prosthesis material on in vitro cartilage retention of laryngoplasty prostheses in horses

Cartilage retention strengths of laryngoplasty prostheses were compared in larynges of 2-, 3-, and 4-year-old horses, using doubled polyester and expanded polytetrafluoroethylene prostheses. Bilateral laryngoplasties were performed on each of 15 (seven 2-year-old, two 3-year-old, and six 4-year-old) larynges, which were collected at an abbatoir. Prostheses were secured to a mechanical testing machine, and tension causing arytenoid cartilage abduction was applied, until total failure of the cartilage or prosthesis resulted. Tension caused cricoid cartilage failure in 1 specimen, and muscular process cartilage failure in the remainder. There was no significant effect of age, prosthetic material, or side of prosthesis placement on cartilage retention of the prostheses. Additionally, frequency of multiple load-displacement peaks, indicating partial muscular process failure, was not affected by age or prosthetic material variables.     

An in vitro comparison of cordopexy, cordopexy and laryngoplasty, and laryngoplasty for treatment of equine laryngeal hemiplegia

OBJECTIVE: To examine the effect of cordopexy, laryngoplasty, and cordopexy combined with a modified laryngoplasty on airway mechanics. STUDY DESIGN: Experimental airway mechanics were determined by subjecting equine cadaveric larynges to airflows similar to inspiratory airflow of exercising horses. ANIMALS OR SAMPLE POPULATION: Twenty equine larynges. METHODS: Using cadaveric larynges, we developed and tested a new technique of arytenoid cartilage abduction. All larynges had the right arytenoid cartilage abducted to mimic the degree of arytenoid abduction that occurs at maximal exertion in live horses. Three surgical techniques were used to stabilize the left arytenoid cartilage of treated larynges; the left arytenoid cartilage was not stabilized in control larynges. Technique 1: Cordopexy--a suture was placed between the vocal ligament and the lamina of the thyroid cartilage. Technique 2: Standard laryngoplasty--a suture was placed between the muscular process of the arytenoid cartilage and the caudomedial aspect of the cricoid cartilage. Technique 3: Cordopexy plus modified laryngoplasty--the cordopexy suture was placed with a second suture between the horizontal ridge rostral to the muscular process of the left arytenoid cartilage and the lamina of the thyroid cartilage. Translaryngeal impedances (TI) were determined for each surgical technique by subjecting the larynges to increasing airflows and measuring the translaryngeal pressure differences. The arytenoid right to left angle quotient (RLQ) and the glottic cross-sectional area (CSA) were also measured. RESULTS: At maximal airflow, the adjusted means for the arytenoid RLQ and the TI for the cordopexy plus modified laryngoplasty (1.48 +/- 0.04, 0.69 +/- 0.05 cm H2O/L/s) and the standard laryngoplasty (1.39 +/- 0.04, 0.78 cm H2O/L/s) were different (P < .05) from values obtained after cordopexy alone (2.74 +/- 0.37, 1.76 +/- 0.48 cm H2O/L/s) or in control larynges (3.66 +/- 0.54, 4.16 +/- 0.96 cm H2O/L/s). Overall, a cordopexy plus modified laryngoplasty (9.69 cm2), a standard laryngoplasty (9.34 cm2), and a cordopexy alone (9 cm2) resulted in an increased glottic CSA greater than that for control larynges (6.94 cm2; P = .0001). CONCLUSIONS: Cordopexy alone did not improve airflow in a left laryngeal hemiplegic model. Cordopexy plus modified laryngoplasty was as efficacious as the standard laryngoplasty in alleviating the effects of left laryngeal hemiplegia on TI, glottic CSA, and arytenoid RLQ. CLINICAL RELEVANCE: Fixation of the vocal cord (cordopexy) in addition to a laryngoplasty procedure may prove useful in the surgical treatment of equine laryngeal hemiplegia.     

Xeroradiographic evaluation of the equine larynx

The normal radiographic anatomy of the equine larynx was determine by use of xeroradiography and dissection. The body and laminae of the thyroid cartilage, the muscular process of the arytenoid cartilages, and the dorsal lamina and arch of the cricoid cartilage had radiographic evidence of mineralization (calcification) and/or ossification in clinically normal horses. There was a significant (P less than 0.01) increase in the degree of mineralization of the thyroid and arytenoid cartilages with advancing age. Horses with diagnosis of arytenoid chondrosis (arytenoid chondral dysplasia, arytenoid chondropathy) by use of endoscopy had radiographic changes that included: enlargement with increased density of the arytenoid cartilage region, abnormal patterns of mineralization (dystrophic mineralization or osseous metaplasia), abnormal contour of the corniculate process(es) and laryngeal masses, sometimes obliterating part or all of the lateral laryngeal ventricles.     

Partial Arytenoidectomy in the Horse

Four horses were examined because of inspiratory dyspnea and noise resulting from an inability to abduct one or both arytenoid cartilages. Two unilateral arytenoidectomies were done following failure of laryngoplasty, and two bilateral arytenoidectomies were done to correct permanent arytenoid adduction caused by laryngeal ossification. The surgical procedure included submucosal dissection of the arytenoid cartilage and removal of the vocal fold, lateral ventricle (when present), and the arytenoid cartilage, excluding the muscular process. Excessive mucous membrane was pulled caudally from the opening of the larynx and carefully sutured to close the mucous membrane and smooth the rima glottis. Postoperative swelling was greatest between the 3rd and 7th days. Long-term results included one horse returned to normal function with no noise, one horse returned to normal function but with respiratory noise, one horse returned to light riding with reduced noise, and one horse salvaged for pasture use.     

The Effect of Unilateral Arytenoid Lateralization on Rima Glottidis Area in Canine Cadaver Larynges

Five modifications of a cricoarytenoid lateralization and two modifications of a thyroarytenoid lateralization laryngoplasty technique were evaluated for their effect on rima glottidis area. All procedures and evaluations were performed on canine cadaver larynges. Cricoarytenoid lateralization (CAL) techniques provided a greater increase of the size of the glottic opening than did any of the thyroarytenoid lateralization techniques. Cricoarytenoid and interarytenoid disarticulation associated with CAL did not significantly increase glottic size compared with normal. After disarticulation of the cricoarytenoid joint, there was no difference in glottic enlargement whether the suture was placed through the muscular process or through the articular facet of the arytenoid cartilage. Transection of the sesamoid band combined with cricoarytenoid diarticulation distorted the dorsal margin of the rima glottidis.     

Analysis of conformational variations of the cricoid cartilages in Thoroughbred horses using computed tomography

Reasons for performing study: Loss of arytenoid abduction is a common post operative complication of laryngoplasty without a definitive cause. It has been a clinical impression during laryngoplasty surgery that there is great conformational variability along the caudal edge of the Thoroughbred cricoid cartilage that could impact post operative retention of suture position. A change in suture position would probably lead to some loss of abduction. Defining any structural variability of the cricoid would be an initial step in determining whether this variability could impact on the retention of suture position. Hypothesis: Anatomical variations in the larynx of Thoroughbred horses may be detected and measured using objective analysis and computed tomography. Methods: Larynges were harvested from 15 mature Thoroughbred horses. Helical CT scans were performed on each specimen. Three independent observers performed a series of measurements on 2D and 3D reconstruction images using digital software. Measurements included the lateral cricoid angle, the caudal cricoid prominences, the distance to the cricoid slope, the angle of the cricoarytenoid joints (CAJ), the cricoid thickness and the suture angle. Mean, standard deviation, coefficient of variation and linear regression analysis were performed among all observers and all measurements. Results: Notable conformational differences were evident on the 3D reconstructions. The highest degree of variability was found in 3 measurements: the distance to the lateral cricoid slope, the lateral cricoid angle and the cricoid thickness. A larger left CAJ angle directly and significantly correlated with a larger suture angle. Conclusions: There are notable conformational differences among cricoid specimens in the Thoroughbred larynx. Potential relevance: The morphometric differences identified may impact on optimal prosthesis placement and long‐term retention. Since a larger lateral cricoid angle may facilitate abduction loss secondary to a displaced and loosened suture, alternative techniques for suture placement may be of value to prevent arytenoid abduction loss.     

Equine laryngoplasty sutures undergo increased loading during coughing and swallowing

Objectives: To report (1) the force required on a single laryngoplasty suture to achieve optimal abduction of the left arytenoid cartilage, (2) peak forces experienced by the suture during induced swallowing and coughing, and during 24‐hour resting activity in a stall, and (3) peak forces during induced swallowing and coughing after left recurrent laryngeal nerve blockade. Study Design: Experimental study. Animals: Horses (n=8). Methods: Each laryngoplasty suture was instrumented with an E‐type buckle force transducer to measure the force required for optimal intraoperative left arytenoid cartilage abduction. This was correlated with abduction observed postoperatively. Change in suture force from baseline was measured during induced coughing and swallowing, and during normal stall activity. Results: Optimal intraoperative arytenoid abduction was achieved with a mean (±SD) force of 27.6±7.5 N. During saline‐induced swallowing and coughing mean force on the suture increased by 19.0±5.6 N (n=233 measurements; 7 horses) and 12.1±3.6 N (n=31; 4 horses), respectively. Sutures underwent increased loading a mean of 1152 times in 24 hours. No change in suture force was observed with respiratory rhythm. Conclusion: Swallowing increases laryngoplasty suture force to a greater extent than coughing.     

Effects of suture tension and surgical approach during unilateral arytenoid lateralization on the rima glottidis in the canine larynx

OBJECTIVES: To evaluate the effect of abduction suture tension and cricothyroid (CT) joint disarticulation on the area, height, and width of the rima glottidis (RG) during unilateral arytenoid lateralization. STUDY DESIGN: Experimental study. ANIMALS: Nine canine cadaver larynges. METHODS: Left arytenoid lateralization was performed with high or low abduction suture tension. RG area, height, and width were measured by computerized planimetric analysis with the epiglottis in an open and closed position. The experiment was performed with the CT joint intact and disarticulated. The effects of suture tension, CT disarticulation, and their interaction on RG area with the epiglottis closed or open were evaluated by repeated measures analysis of variance (ANOVA). RESULTS: RG area increased by 82% and 129% (P <.0001) with low and high suture tension, respectively. The aperture not covered by the epiglottis in a closed position was 467% larger with high suture tension than with low tension (P <.0001). CT disarticulation had no significant effect on RG geometry with either low or high suture tension (P =.4970). CONCLUSIONS: Low suture tension increased RG area when the epiglottis was in an open position without increasing RG aperture when the epiglottis was closed. Suture tension had a significant effect on RG opening when the epiglottis was closed. CT disarticulation did not modify the geometry of the RG. CLINICAL RELEVANCE: Use of a low-suture tension should be considered during arytenoid lateralization because it has the potential to reduce the risk of aspiration pneumonia.     

Ventroaxial luxation of the apex of the corniculate process of the arytenoid cartilage in resting horses during induced swallowing or nasal occlusion

OBJECTIVE: To report ventroaxial luxation of the apex of the left or right corniculate process of the arytenoid cartilage under the contralateral corniculate process during resting endoscopic examination, and morphologic features of the larynx of 1 affected horse. STUDY DESIGN: Retrospective study. ANIMALS: Horses (n=8). METHODS: Horses had endoscopic examination as part of a survey of Clydesdale horses (n=7), or investigation of poor performance in Thoroughbred horses (1). One Clydesdale was euthanatized and the larynx examined; 4 cadaver larynges from normal horses were also examined. RESULTS: Ventroaxial luxation of the apex of the left or right corniculate process of the arytenoid cartilage was not detected during quiet breathing but was induced by swallowing or nasal occlusion. Prevalence in Clydesdales was 5.2% (7/133). A Thoroughbred with identical endoscopic appearance of the larynx at rest had progressive ventroaxial luxation of the apex of the arytenoid cartilage during high-speed treadmill endoscopy, associated with abnormal respiratory noise. Necropsy examination of an affected Clydesdale larynx revealed an excessively wide (10 mm) transverse arytenoid ligament that allowed easy separation of the apices of the corniculate processes. In normal cadaver larynges, the apices could not be separated with abaxial traction. CLINICAL RELEVANCE: The clinical relevance of this laryngeal observation in resting horses is unclear. Ventroaxial luxation of the corniculate process of the arytenoid cartilage during induced swallowing or nasal occlusion in resting horses or during high-speed treadmill exercise may be caused by an abnormally wide transverse arytenoid ligament.     

Effect of Prosthesis Number and Position on Rima Glottidis Area in Equine Laryngeal Specimens

Objective— To assess the effect of 1 or 2 laryngeal prosthetic sutures on rima glottidis areas in equine laryngeal specimens. Study Design— Experimental, randomized design. Animals— Cadaveric equine larynges (n=16). Methods— Larynges were collected from 10 horses; 2 sutures each were preplaced in the right and left sides of each larynx. A dorsal suture (DS) was placed through the caudal rim of the dorsal midline of the cricoid cartilage, under the cricopharyngeus muscle and through the proximal and rostral aspect of the muscular process. A lateral suture (LS) was placed 1.5 cm lateral to the DS and through the muscular process more distal and caudal to the 1st suture. Larynges were positioned in a customized stand and the rima glottidis photographed after each suture (LS or DS) or suture combination (CS) was tied in random sequence. An additional 6 larynxes were used to determine whether the tension applied to the sutures was repeatable. Sutures were preplaced in both the right and left side of each larynx as described above and each suture and CS was tied and released 3 times in each larynx. Photographs were taken of the rima glottidis after each suture or CS was tied generating 3 replicates for each suture configuration on each side of the 6 larynges. Results— Mean rima glottidis area was not different between DS and LS when tied alone (P=.85); however, mean area after CS (DS+LS) was greater than DS (P<.001) and LS (P<.001) alone. The coefficient of variation for the 6 suture patterns were low (1–7%) and the intraclass correlation coefficient estimates were very high (0.997–0.998) demonstrating excellent repeatability between replicates for each of the 3 suture configurations. Conclusion— Our results suggest that laryngoplasty using 2 prostheses; 1 placed dorsally in the cricoid and through the rostral and proximal muscular process and 1 placed 1.5 cm lateral to the 1st and more caudal and distal in the muscular process results in a greater cross sectional area of the rima glottidis than either suture used alone. Clinical Relevance— Seemingly prosthetic sutures contribute independently to each other in determining the contour of the rima glottidis. Use of 2 prosthetic sutures improves crosssectional area of the rima glottidis compared with each suture alone and may improve surgical outcome in laryngoplasty.     

Laryngeal paralysis in dogs: An evaluation of the bilateral arytenoid lateralisation procedure

Within the past decade, the number of reported cases of laryngeal paralysis in dogs has increased markedly. The disease is characterised by laryngeal obstruction caused by the inadequate abduction and instability of the arytenoid cartilages, aryepiglottic folds and vocal cords. Therefore, surgery performed to alleviate the clinical signs should ideally aim to reduce the airway obstruction and to prevent dynamic collapse. This paper presents the effectiveness of bilateral arytenoid lateralisation in 19 dogs with bilateral laryngeal paralysis. The procedure was effective in alleviating the clinical signs of laryngeal obstruction in all 19 dogs, with most surviving for several years. Postoperative laryngoscopic observations showed that the arytenoid cartilages were held in a satisfactory abducted position. A comparison of PaO₂ values before and after surgery demonstrated a significant (P 0·001) fall in the PaO₂ measurement between the pre- and postoperative blood samples. Postoperative complications included suture prosthesis failure in two dogs and a single non-fatal incident of aspiration pneumonia in two dogs.     

Upper airway dysfunction associated with collapse of the apex of the corniculate process of the left arytenoid cartilage during exercise in 15 horses

OBJECTIVE: To report dynamic collapse of the apex of the left corniculate process under the right corniculate process into the airway at the dorsal apposition of the paired arytenoid cartilages during exercise as a cause of upper airway dysfunction in horses. DESIGN: Retrospective study. ANIMALS: Fifteen horses with a history of poor performance and/or upper respiratory tract noise during exercise. METHODS: Video recordings of all horses referred for upper airway evaluation using high-speed treadmill videoendoscopy (HSTV) between January 1998 and December 2003 were reviewed. Records of horses that developed dynamic collapse of the apex of the left corniculate process into the airway were included. Clinical history, age, gender, breed, and use of the horse were retrieved. RESULTS: Of 309 horses referred for examination for poor performance and/or upper respiratory tract noise during exercise, 15 (4.9%) had collapse of the apex of the left corniculate process under the right and into the airway at the dorsal apposition between the paired arytenoid cartilages during HSTV. There were 3 females and 13 males, aged from 2 to 5 years. Five horses had previous surgery for left recurrent laryngeal neuropathy (RLN): 2 had nerve muscle pedicle graft and 3 had laryngeal prosthesis. During HSTV, all 15 horses had progressive collapse of the apex of the left corniculate process under the right at the dorsal apposition of the 2 arytenoid cartilages, and into the dorsal aspect of the rima glottidis. Review of video recordings revealed that collapse of the apex of the corniculate process was followed by progressive collapse of the left aryepiglottic fold and left vocal fold. The ventral aspect of the left corniculate cartilage maintained abduction in all horses. Two horses also had progressive collapse of the right vocal fold, 1 had rostral displacement of the palatopharyngeal arch, and another had dorsal displacement of the soft palate. CONCLUSIONS: Dynamic collapse of the apex of the left corniculate process of the arytenoid cartilage under the right is an uncommon cause of upper airway dysfunction in horses and the pathogenesis is unclear. We speculate that the left arytenoideus transversus muscle is unable to support the dorsal apposition between the arytenoid cartilages. This loss of support allows the elastic cartilage of the left corniculate process to collapse under the right and into the airway, as inspiratory pressure increases during exercise. This condition may be associated with an unusually advanced neuropathy of the adductor components of the left recurrent laryngeal nerve and may be an unusual manifestation of RLN; however, this is speculative and further investigation is required to determine its cause. CLINICAL RELEVANCE: Dynamic collapse of the apex of the left corniculate process and into the airway at the dorsal apposition between the paired arytenoid cartilages can only be diagnosed during HSTV. It is an uncommon cause of upper airway dysfunction but may affect the athletic potential of racing Thoroughbreds and Standardbreds.     

Idiopathic mucosal lesions of the arytenoid cartilages of 21 Thoroughbred yearlings: 1997-2001

REASONS FOR PERFORMING STUDY: Mucosal ulcers and, occasionally, small granulomas on the axial surface of one or both arytenoid cartilages have been found in TB yearlings presented for post sale endoscopic examination. OBJECTIVES: To determine the incidence, endoscopic characteristics and outcome of a group of Thoroughbred yearlings affected with mucosal ulcers and granulomas of the arytenoid cartilage. HYPOTHESIS: The incidence of mucosal ulceration of the arytenoid cartilages of yearling Thoroughbreds is relatively high compared to other upper airway abnormalities; and that the majority of mucosal ulcers heal uneventfully, although a small percentage may progress to a granuloma and, less commonly, to arytenoid chondropathy. METHODS: The findings of post sale, upper airway endoscopic examinations of 3312 Thoroughbred yearlings, during a 5 year period, were reviewed, including those abnormalities listed in the conditions of sale and others not listed but considered likely to cause airway obstruction. Information obtained from the medical record of horses that had mucosal ulceration or granuloma of the arytenoid cartilage included the location and size of the lesion(s), sex of the affected horse and the presence and nature of other concurrent abnormalities of the upper portion of the respiratory tract. Additional information included treatment and results of follow-up, endoscopic examination by the authors or attending veterinarian. RESULTS: Mucosal lesions were seen in 0.63% of yearlings evaluated, which represented the most common, documented condition of the upper portion of the respiratory tract. The mucosal ulcers of 15 of 19 horses were considered to have healed without complication during follow-up examination; one of the 19 horses was lost to follow-up. Two horses affected with bilateral, arytenoid mucosal ulceration developed a granuloma at each site of ulceration. One horse developed a granuloma at a site of ulceration and, subsequently, arytenoid chondropathy. CONCLUSIONS: Arytenoid mucosal ulceration in sales yearlings was a relatively commonly encountered abnormality and a small percentage progressed to granuloma or chondropathy. POTENTIAL RELEVANCE: The mucosa of the arytenoid cartilage, particularly at the rostral margin of the vocal process, should be examined carefully during endoscopic examination of the upper portion of the respiratory tract of Thoroughbred yearlings presented for sale. Because a small percentage of mucosal ulcers may progress to granuloma or, less commonly, chondropathy, identification of mucosal ulcers of the arytenoid cartilage seen during post sale, endoscopic examination warrants notification to the purchaser and sales company. Medical therapy of affected horses should be considered and follow-up endoscopic examination performed to determine if the lesion has healed.     

Exercising videoendoscopic evaluation of 45 horses with respiratory noise and/or poor performance after laryngoplasty

Objective: To (1) assess upper airway function by videoendoscopy in horses performing poorly after laryngoplasty and (2) establish whether dynamic collapse of the left arytenoid can be predicted by the degree of resting postsurgical abduction. Study Design: Case series. Animals: Horses that had left laryngoplasty (n=45). Methods: Medical records (June 1993–December 2007) of horses evaluated for abnormal respiratory noise and/or poor performance after laryngoplasty were reviewed. Horses with video recordings of resting and exercising upper airway endoscopy were included and postsurgical abduction categorized. Horses with immediate postoperative endoscopy recordings were also evaluated and postsurgical abduction categorized. Relationships between resting postsurgical abduction and historical information with exercising endoscopic findings were examined. Results: Dynamic collapse of the left arytenoid cartilage was probable in horses with no postsurgical abduction and could not be predicted in horses with grade 3 or 4 postsurgical abduction. Respiratory noise was associated with upper airway obstruction but was not specific for arytenoid collapse. Most horses with a left vocal fold had billowing of the fold during exercise. Other forms of dynamic collapse involved the right vocal fold, aryepiglottic folds, corniculate process of left arytenoid cartilage, dorsal displacement of soft palate, and pharyngeal collapse. Complex obstructions were observed in most examinations and in all horses with exercising collapse of the left arytenoid cartilage. Conclusions: There was no relationship between exercising collapse of the left arytenoid cartilage and grade 3 or 4 postsurgical abduction but was likely in horses with no abduction.     

Effects of Arytenoid Abduction and Modified Castellated Laryngofissure on the Rima Glottidis in Canine Cadavers

The percentages of change in cross-sectional area and dorsoventral height of the rima glottidis were measured after seven types of laryngoplasty in 30 postmortem canine specimens. The mean increases in area after each procedure were, in decreasing order, bilateral cricoarytenoid disarticulation with interarytenoid sesamoid band transection before placement of arytenoid abduction sutures 350% +/- 42%, bilateral placement of arytenoid abduction sutures 318% +/- 40%, bilateral cricothyroid disarticulation before placement of arytenoid abduction sutures 255% +/- 51%, modified castellated laryngofissure 244% +/- 30%, unilateral cricoarytenoid disarticulation with interarytenoid sesamoid band transection before placement of an arytenoid abduction suture 161% +/- 25%, unilateral placement of an arytenoid abduction suture 151% +/- 24% and unilateral cricothyroid disarticulation before placement of an arytenoid abduction suture 108% +/- 25%. Bilateral cricoarytenoid disarticulation with interarytenoid sesamoid band transection before placement of arytenoid abduction sutures resulted in a significantly greater increase in rima glottidis area than modified castellated laryngofissure and all unilateral arytenoid abduction techniques. Modified castellated laryngofissure resulted in a significantly greater increase than unilateral placement of an arytenoid abduction suture and cricothyroid disarticulation before placement of an arytenoid abduction suture. Bilateral disarticulation of the cricothyroid joint before placement of arytenoid abduction sutures resulted in significant collapse of the dorsoventral height of the rima glottidis.     

In vitro evaluation of screws and suture anchors in metaphyseal bone of the canine tibia

OBJECTIVE: To compare ease of insertion, load to failure, and mode of failure of cortical and cancellous screws, BoneBiter, IMEX, and TwinFix suture anchors in canine metaphyseal tibial bone. STUDY DESIGN: Experimental biomechanical study. ANIMALS: Canine cadaveric tibias. METHODS: One investigator inserted all anchors and subjectively evaluated ease of placement. Anchor systems were loaded to failure along axis of insertion with audio-video recording to determine failure mode. RESULTS: BoneBiter was the most difficult anchor to insert successfully. Mean+/-SD loads to failure were cancellous screw (711+/-193 N), IMEX 4.7 mm 18 g wire (661+/-163 N), IMEX 4.0 mm 18 g wire (661+/-165 N), cortical screw (635+/-184 N), BoneBiter #5 Kevlar suture (393+/- 109 N), and TwinFix 5.0 mm #2 polyester (267+/-73 N). No significant differences were noted among the cortical screw, cancellous screw, IMEX 4.7 and 4.0 mm, all of which were significantly (P<.001) greater than BoneBiter and TwinFix . Failure modes were pullout of bone, suture-wire breakage, eyelet breakage, or no failure to 1000 N: screws (18,0,0,2), IMEX (18,1,1,0), BoneBiter (2,8,0,0), and TwinFix (0,10,0,0). CONCLUSIONS: Fixation devices were user friendly, with the exception of BoneBiter. Mode of failure is dependent on suture material and anchor design. Cortical and cancellous screws, and IMEX anchors with 18 g wire have significantly greater load to failure compared with BoneBiter and TwinFix suture anchors. CLINICAL RELEVANCE: Based on load to failure, ease of use, design characteristics, and cost, IMEX anchors may have advantages over other comparable soft tissue fixation devices.