Nerve-specific extracellular matrix hydrogel promotes functional regeneration following nerve gap injury.

Nerve transection requires surgical intervention to restore function. The standard of care involves coaptation when a tension-free repair is achievable, or interposition of a graft or conduit when a gap remains. Despite advances, nerve gap injury is associated with unsatisfactory recovery. This study investigates the use of a decellularized, porcine nerve-derived hydrogel filler (peripheral nerve matrix, PNM) for conduits in an 8 mm rat sciatic nerve gap model. The decellularized tissue maintained multiple nerve-specific matrix components and nerve growth factors. This decellularized tissue was used to formulate hydrogels, which were deployed into conduits for nerve gap repair. Nerve recovery was assessed up to 24 weeks post injury by gait analysis, electrophysiology, and axon counting. Deployment of PNM within conduits was shown to improve electrophysiologic response and axon counts compared with those of empty conduit controls. These results indicate that PNM has potential benefits when used as a filler for conduits in nerve gap injuries.

Characterization of cognition in mild cognitive impairment with and without Parkinson's disease.

•Screening tests can diagnose PD-MCI but do not give detailed cognitive profiles.•Criteria based on a complete neuropsychological battery identify more PD patients with MCI.•The overall cognitive profile is similar in PD-MCI and MCI.•Neuropsychological batteries and definition of impairment cut-offs should be refined.

Ex vivo investigation of the effect of the transverse arytenoid ligament on abduction of the arytenoid cartilage when performing equine laryngoplasty.

Aims: To investigate the effect of the transverse arytenoid ligament (TAL) on abduction of the arytenoid cartilage when performing laryngoplasty. Methods: Modified prosthetic laryngoplasty was performed on right and left sides of 13 cadaver larynges. Increasing force was sequentially applied to the left arytenoid cartilage at 3 N intervals from 0-24 N, when the force on the right arytenoid cartilage was either 0 or 24 N, before and after TAL transection. Digital photographs of the rostral aspect of the larynx were used to determine the left arytenoid abduction angles for these given force combinations and results compared before and after TAL transection. Longitudinal and transverse sections of the TAL from seven other equine larynges were also examined histologically. Results: Increasing force on the left arytenoid cartilage from 0-24 N produced a progressive increase in the angle of the left arytenoid cartilage (p < 0.001) and increasing force on the right arytenoid cartilage from 0-24 N reduced the angle of the left arytenoid cartilage (p < 0.001). Following transection of the TAL the mean angle of the left arytenoid increased from 36.7 (95% CI = 30.5-42.8)° to 38.4 (95% CI = 32.3-44.5)°. Histological examination showed that the TAL was not a discrete ligament between the arytenoid cartilages but was formed by the convergence of the ligament and the left and right arytenoideus transversus muscles. Conclusions: Transection of the TAL in ex vivo equine larynges enabled greater abduction of the left arytenoid cartilage for a given force. These results indicate that TAL transection in conjunction with prosthetic laryngoplasty may have value, but the efficacy and safety of TAL transection under load in vivo, and in horses clinically affected with recurrent laryngeal neuropathy must be evaluated. Abbreviations: Fmax: Force needed to maximally abduct the left or right arytenoid; TAL: Transverse arytenoid ligament.

Meta-analysis evaluating resting laryngeal endoscopy as a diagnostic tool for recurrent laryngeal neuropathy in the equine athlete.

BACKGROUND: Resting endoscopy has commonly been used as a method to predict laryngeal function at exercise. OBJECTIVES: To perform a meta-analysis to determine the sensitivity and specificity of resting laryngeal endoscopy to predict clinical recurrent laryngeal neuropathy at exercise. STUDY DESIGN: Meta-analysis. METHODS: Manuscripts were included if data were available for both resting and exercising airway function on all or a subset of horses. Normal resting endoscopy was defined as laryngeal grades 1 or 2 on a 4-/7-point scale or 1, 2 or 3 on a 5-point scale and normal dynamic endoscopy as a dynamic laryngeal grade A. RESULTS: Twelve studies including 1827 horses were evaluated. A small proportion of horses with grade 1 or grade 2 laryngeal function at rest, 3.5 and 11.9%, respectively, were identified as having abnormal laryngeal function at exercise. Within the horses with grade 3 laryngeal function at rest, 16% were classified as grade A, 26.4% as grade B and 57.6% as grade C at exercise. Worsening subgrades within resting grade 3 demonstrated an increasing proportion of complete or partial paralysis at exercise. The sensitivity and specificity of resting endoscopy was 74.4 and 95.1%, respectively, and the positive and negative predictive values were 85.6 and 90.5% respectively. MAIN LIMITATIONS: Use of two separate grading systems for evaluating resting laryngeal function. Other forms of dynamic airway collapse were not evaluated. CONCLUSIONS: Resting endoscopy is sensitive and highly specific for predicting laryngeal function at exercise. Dynamic endoscopy is important to assess multiple causes of airway collapse.

Transoesophageal ultrasound and computer tomographic assessment of the equine cricoarytenoid dorsalis muscle: Relationship between muscle geometry and exercising laryngeal function.

REASONS FOR PERFORMING STUDY: Early detection of recurrent laryngeal neuropathy (RLN) is of considerable interest to the equine industry. OBJECTIVES: To describe two imaging modalities, transoesophageal ultrasound (TEU) and computed tomography (CT) with multiplanar reconstruction to assess laryngeal muscle geometry, and determine the relationship between cricoarytenoid dorsalis (CAD) geometry and function. STUDY DESIGN: Two-phase study evaluating CAD geometry in experimental horses and horses with naturally occurring RLN. METHODS: Equine CAD muscle volume was determined from CT scan sets using volumetric reconstruction with LiveWire. The midbody and caudal dorsal-ventral thickness of the CAD muscle was determined using a TEU in the same horses; and in horses with a range of severity of RLN (n = 112). RESULTS: Transoesophageal ultrasound was able to readily image the CAD muscles and lower left:right CAD thickness ratios were observed with increasing disease severity. Computed tomography based muscle volume correlated very closely with ex vivo muscle volume (R2 = 0.77). CONCLUSIONS: Computed tomography reconstruction can accurately determine intrinsic laryngeal muscle geometry. A relationship between TEU measurements of CAD geometry and laryngeal function was established. These imaging techniques could be used to track the response of the CAD muscle to restorative surgical treatments such as nerve muscle pedicle graft, nerve anastomosis and functional electrical stimulation.

Laryngeal advancement surgery improves swallowing function in a reversible equine dysphagia model.

REASONS FOR PERFORMING STUDY: Pharyngeal dysphagia is a debilitating, sometimes fatal condition in horses, with multiple aetiologies. The pathophysiology is complex and not fully understood. Treatment is largely supportive. Laryngeal advancement surgery may diminish symptoms of dysphagia and improve swallowing in affected horses. OBJECTIVES: 1) to induce reversible moderate and marked pharyngeal dysphagia by regional anaesthesia of branches of the glossopharyngeal (IX), vagus (X) and hypoglossal (XII) nerves; 2) to characterise the dysphagia produced by each model; and 3) to determine whether laryngeal advancement surgery improves swallowing in these models. STUDY DESIGN: Experimental design using 6 adult horses. METHODS: Two dysphagia models were produced by blocking IX, the pharyngeal branch of X and XII unilaterally (moderate model) and only the pharyngeal branch of X bilaterally (marked model) within the guttural pouches. Both models were performed on each horse before and after surgery in order to assess the effectiveness of the surgical procedure as a potential treatment for pharyngeal dysphagia. Dysphagia was scored by partly blinded observers on a scale of 0-12 based on observations of eating (nonblinded), endoscopic examinations and fluoroscopic swallowing (blinded), where 0 = normal swallow and 12 = severe dysphagia with tracheal aspiration. Data were analysed by 3-factor ANOVA, with significance taken as P<0.05. RESULTS: Dysphagia models were reversible, and horses swallowed normally within 3 h of model induction. The marked dysphagia model impaired movement of feed from the base of the tongue to the oesophagus and caused severe airway contamination. The average dysphagia score (mean ± s.d.) for the marked dysphagia model was 10.6 ± 1.1 before surgery and 6.1 ± 4.3 after surgery (P = 0.007). Laryngeal advancement surgery did not significantly improve the dysphagia scores in the moderate model (P = 0.5). CONCLUSIONS: Laryngeal advancement surgery may improve swallowing and reduce aspiration in horses affected with diseases that cause pharyngeal dysphagia.

Alkamides from Echinacea disrupt the fungal cell wall-membrane complex.

We tested the hypothesis that alkamides from Echinacea exert antifungal activity by disrupting the fungal cell wall/membrane complex. Saccharomyces cerevisiae cells were treated separately with each of seven synthetic alkamides found in Echinacea extracts. The resulting cell wall damage and cell viability were assessed by fluorescence microscopy after mild sonication. Membrane disrupting properties of test compounds were studied using liposomes encapsulating carboxyfluorescein. Negative controls included hygromycin and nourseothricin (aminoglycosides that inhibit protein synthesis), and the positive control used was caspofungin (an echinocandin that disrupts fungal cell walls). The results show that yeast cells exposed to sub-inhibitory concentrations of each of the seven alkamides and Echinacea extract exhibit increased frequencies of cell wall damage and death that were comparable to caspofungin and significantly greater than negative controls. Consistent with effects of cell wall damaging agents, the growth inhibition by three representative alkamides tested and caspofungin, but not hygromycin B, were partially reversed in sorbitol protection assays. Membrane disruption assays showed that the Echinacea extract and alkamides have pronounced membrane disruption activity, in contrast to caspofungin and other controls that all had little effect on membrane stability. A Quantitative Structure-Activity Relationship (QSAR) analysis was performed to study the effect of structural substituents on the antifungal activity of the alkamides. Among the set studied, diynoic alkamides showed the greatest antifungal and cell wall disruption activities while an opposite trend was observed in the membrane disruption assay where the dienoic group was more effective. We propose that alkamides found in Echinacea act synergistically to disrupt the fungal cell wall/membrane complex, an excellent target for specific inhibition of fungal pathogens. Structure-function relationships provide opportunities for synthesis of alkamide analogs with improved antifungal activities.

Ultrasound features of arytenoid chondritis in Thoroughbred horses.

REASONS FOR PERFORMING STUDY: Laryngeal ultrasonography can provide valuable information when considering a diagnosis of arytenoid chondritis, but specific ultrasonographic parameters have not been defined. OBJECTIVES: To compare ultrasonographic findings of the arytenoid cartilages in horses with endoscopically diagnosed arytenoid chondritis with ultrasonographic findings of the arytenoid cartilages in normal horses. METHODS: Ultrasound images of the larynx were obtained at the level of the arytenoid cartilages in horses with endoscopically diagnosed arytenoid chondritis and horses with normal arytenoid cartilage structure and function. Information obtained from the ultrasound examination included arytenoid cartilage cross-sectional area, arytenoid cartilage echogenicity and arytenoid cartilage shape. Comparisons were performed between affected and unaffected arytenoid cartilages. For horses with multiple examinations, relationships between time point and arytenoid cartilage cross-sectional area were determined. RESULTS: Chondritic arytenoid cartilages were significantly larger and had abnormal shape and echogenicity when compared with normal arytenoid cartilages (P<0.001). For horses with multiple examinations, no significant changes were identified in arytenoid cartilage size over time. CONCLUSIONS: Chondritic arytenoid cartilages are increased in size and have abnormal echogenicity and contour in comparison with normal arytenoid cartilages when assessed using laryngeal ultrasonography. Once enlarged, the cartilage does not appear to return to normal size after the infection and/or inflammation has resolved. POTENTIAL RELEVANCE: Ultrasonography is a valuable diagnostic modality when investigating cases of possible arytenoid chondritis or abnormal arytenoid cartilage movement. It has additional benefit in determining the extent of disease when medial masses are present on the surface of arytenoid cartilages, aiding in surgical decision making.

Anatomic and neuromuscular characterisation of the equine cricothyroid muscle.

REASONS FOR PERFORMING STUDY: As part of investigation into laryngeal stability and reanimation using functional electrical stimulation, the cricothyroid muscle might be utilised to increase laryngeal cross-sectional area in horses with recurrent laryngeal neuropathy. For optimal electrode placement and muscle recruitment, the neuroanatomy and excitability of the equine cricothyroid muscle needs to be defined. OBJECTIVES: To describe the anatomy, innervation and function of the equine cricothyroid muscle and its contribution to laryngeal diameter. METHODS: Seventeen equine larynges were collected at necropsy and 12 were grossly dissected. Seven larynges (five grade 1, two grade 4) were prepared for immunohistochemistry following gross dissection and 5 larynges were prepared for special staining: acetylcholinesterase staining of motor endplates (n = 3) and Sihler's staining (n = 2). Three larynges were stimulated following in situ cadaver dissection and 2 larynges were removed and stimulated ex vivo. RESULTS: Three neuromuscular compartments, each innervated by a primary nerve branch of the external branch of the cranial laryngeal nerve, were identified in all larynges. Stimulation of each neuromuscular compartment resulted in ventral displacement of the thyroid cartilage with respect to the cricoid cartilage, thereby increasing dorsoventral height of the rima glottis. CONCLUSIONS: The equine cricothyroid muscle has 3 distinct neuromuscular compartments with discrete innervation, fibre type distribution and muscle fibre sizes. All neuromuscular compartments tense the vocal cords by increasing dorsoventral height of the rima glottis through ventral displacement of the thyroid cartilage with respect to the cricoid cartilage. POTENTIAL RELEVANCE: Simultaneous functional electrical stimulation of the cricothyroid and dorsal cricoarytenoid muscles may enhance laryngeal cross-sectional area in horses with recurrent laryngeal neuropathy.

Dynamic respiratory endoscopy of Standardbred racehorses during qualifying races.

REASON FOR PERFORMING STUDY: Examination of the equine upper airway during racing has not previously been documented. OBJECTIVE: To describe the feasibility and appearance of the upper airways by overground respiratory endoscopic examination during racing conditions. METHODS: Overground videoendoscopic examinations were performed on 46 Standardbred racehorses during qualifying races. Examined horses' speeds were recorded throughout the race with a portable GPS device. RESULTS: The procedure did not interfere with performance as there were no significant differences in race times between races in which horses were examined with the endoscope in place and prior unexamined races. Airway obstructions during or after the race were documented in 21 horses. Most previously reported causes of upper airway obstruction were observed; surprisingly bilateral ventro-medial arytenoid displacement (VMAD; n = 5) was seen during exercise as frequently as dorsal displacement of the soft palate (DDSP). Although DDSP (n = 10) was the most common diagnosis made, many displacements (n = 5) occurred after the race. Horses that demonstrated DDSP after the race had slower speeds than unaffected horses during the race. CONCLUSIONS: Racing endoscopy permits the diagnosis of upper airway obstructions without affecting performance. The occurrence of DDSP immediately after exercise may be clinically relevant. During racing VMAD may be an important anomaly. POTENTIAL RELEVANCE: Racing endoscopy could be used to correlate the sensitivity of diagnostic endoscopy during race-training or treadmill examination. The pathogenesis and significance of VMAD deserves further investigation.

Visuospatial over verbal demands in predicting Tower of London planning tasks.

The role of verbal and visuospatial information processing in Tower of London (TOL) tasks was investigated. The first part of the investigation examined the verbal and visuospatial abilities and preferred cognitive style (visualizer vs. verbalizer) of 79 participants, in an inter-individual differences approach. Visuospatial abilities significantly predicted TOL performance, but the impact of cognitive style was negligible. The second part applied a dual-task manipulation of concurrent interference of TOL planning tasks on verbal and visuospatial memory, using the same participants. Concurrent processing of the TOL tasks diminished visuospatial memory performance considerably but had no effect on verbal memory, and there was no interaction between cognitive style and memory. These findings clearly underscore the role of visuospatial information processing in TOL tasks and indicate little bearing of verbal or visual cognitive style on TOL problem solving. These results have important implications for TOL and cognitive style in clinical application and cognitive neuroimaging research.

Biomechanical characterisation of equine laryngeal cartilage.

REASONS FOR PERFORMING THE STUDY: Upper airway obstruction is a common problem in the performance horse as the soft tissues of the larynx collapse into the airway, yet there is a paucity of information on biomechanical properties for the structural cartilage components. OBJECTIVE: To measure the geometry and compressive mechanical properties of the hyaline cartilage to improve understanding of laryngeal function and morphology. METHODS: A total of 11 larynges were harvested from Thoroughbred and Standardbred racehorses. During gross dissection, linear dimensions of the cricoid were obtained. From both the cricoid and arytenoid, specimens were cored to obtain 6 mm disc samples from 3 sites within the dorsal cricoid (caudal, middle and rostral) and 2 central sites in the arytenoids (inner, outer). The specimens were mechanically tested using radial confined compression to calculate the aggregate modulus and permeability of the tissue. The biomechanical data were analysed using a nested mixed effects model. RESULTS: Geometrically, the cricoid has relatively straight walls compared to the morphology of human, ovine and canine larynges. There were significant observations of higher modulus with increasing age (0.13 MPa per year; P = 0.007) and stiffer cricoid cartilage (2.29 MPa) than the arytenoid cartilage (0.42 MPa; P<0.001), but no difference was observed between the left and right sides. Linear contrasts showed that the rostral aspect (2.51 MPa) of the cricoid was 20% stiffer than the caudal aspect (2.09 MPa; P = 0.025), with no difference between the arytenoid sites. CONCLUSIONS: The equine larynx is a well supported structure due to both the geometry and material properties of the cricoid cartilage. The hyaline structure is an order of magnitude higher in compressive modulus compared to the arytenoids and other hyaline-composed tissues. POTENTIAL RELEVANCE: These characterisations are important to understand the biomechanics of laryngeal function and the mechanisms involved with surgical interventions.

Incidence of swallowing during exercise in horses with dorsal displacement of the soft palate.

REASONS FOR PERFORMING STUDY: The relationship between dorsal displacement of the soft palate (DDSP) and swallowing is unclear. OBJECTIVE: To quantify the relationship between DDSP and swallowing in horses at exercise. HYPOTHESES: The frequency of swallowing increases immediately prior to DDSP in horses at exercise. METHODS: Videoendoscopic and upper airway pressure data were collated from horses with a definitive diagnosis of DDSP at exercise. Horses with no upper airway abnormalities were matched by age, breed and sex and used as controls. Sixty-nine horses were identified with a definitive diagnosis of DDSP during the study interval. Airway pressure data were available for 42 horses. RESULTS: The majority of horses displaced at high exercising speeds while accelerating; a smaller number displaced during deceleration after peak speed had been reached. Horses swallowed significantly more frequently in the 1 min immediately preceding DDSP than in the control horses at equivalent speeds. DDSP at exercise results in a significant increase in tracheal expiratory pressure, a significant decrease in pharyngeal expiratory pressure and a significantly less negative pharyngeal inspiratory pressure compared to matched controls and compared to the pressures during the 1 min interval prior to DDSP. There was no significant difference between any measure of airway pressure before or after a swallow when examined at each time interval in the DDSP population. CONCLUSIONS: The frequency of swallowing decreases with increasing speed in normal horses. In contrast, the frequency of swallowing increases immediately prior to onset of DDSP. This is not a result of pharyngeal and tracheal pressure changes. POTENTIAL RELEVANCE: The increased frequency of swallowing observed prior to DDSP may be related to the aetiology of the disease.

Considerations for pacing of the cricoarytenoid dorsalis muscle by neuroprosthesis in horses.

REASONS FOR PERFORMING STUDY: The success rate of prosthetic laryngoplasty is limited and may be associated with significant sequelae. Nerve muscle pedicle transplantation has been attempted but requires a year before function is restored. OBJECTIVE: To determine the optimal parameters for functional electrical stimulation of the recurrent laryngeal nerve in horses. METHODS: An experimental in vivo study was performed on 7 mature horses (2-21 years). A nerve cuff was placed on the distal end of the common trunk of the recurrent laryngeal nerve (RLN). In 6 horses the ipsilateral adductor branch of RLN was also transected. The electrodes were connected to programmable internal stimulator. Stimulation was performed using cathodic phase and then biphasic pulses at 24 Hz with a 0.427 ms pulse duration. Stimulation-response experiments were performed at monthly intervals, from one week following implantation. The study continued until unit failure or the end of project (12 months). Two of the horses were stimulated continuously for 60 min to assess onset of fatigue. RESULTS: Excellent arytenoid cartilage abduction (mean arytenoid angle of 52.7 degrees, range 48.5-56.2 degrees) was obtained in 6 horses (laryngeal grades I or II (n = 3) and III (n = 2). Poor abduction was obtained in grade IV horses (n = 2). Arytenoid abduction was maintained for up to a year in one horse. Technical implant failure resulted in loss of abduction in 6 horses at one week to 11 months post operatively. Mean tissue impedance was 1.06 kOhm (range 0.64-1.67 kOhm) at one week, twice this value at 2 months (mean 2.32, range 1.11-3.75 kOhm) and was stable thereafter. Maximal abduction was achieved at a stimulation range of 0.65-7.2 mA. No electrical leakage was observed. Constant stimulation of the recurrent laryngeal nerve for 60 min led to full abduction without evidence of muscle fatigue. CONCLUSIONS: Functional electrical stimulation of the recurrent laryngeal nerve leading to full arytenoid abduction can be achieved. The minimal stimulation amplitude for maximal abduction angle is slightly higher than those for man and dogs. CLINICAL RELEVANCE: This treatment modality could eventually be applicable to horses with recurrent laryngeal neuropathy.

Relationships between race earnings and horse age, sex, gait, track surface and number of race starts for Thoroughbred and Standardbred racehorses in North America.

REASONS FOR PERFORMING STUDY: There is no consensus on objective outcome measures that can be used to determine if a medical or surgical treatment affects race performance. OBJECTIVE: To determine the association between 2 commonly used outcome measures (total starts and total earnings) and age, sex, gait and race surface. METHODS: A cross-sectional study was performed using the race performance data for all Thoroughbred horses age 2, 3, 4 and 5 years racing in the United States, and Standardbred horses of the same ages racing in the United States and Canada during the year 2006. Median earnings and starts were determined for each combination of age, sex and track surface (for Thoroughbred) or gait (for Standardbred). The effect these variables had on starts on race earnings ($) was determined using linear regression. RESULTS: Race records for 68,649 Thoroughbreds and 25,830 Standardbreds were obtained. All independent variables (age, breed, sex, gait, track surface and total number of starts) had a significant impact on total earnings (P<0.0001). CONCLUSIONS: The data show considerable variation across age groups and track surfaces for Thoroughbreds and across age groups for Standardbreds. They also show that the decision to use earnings or starts as outcome measures could have a marked effect on reported success for a particular treatment. POTENTIAL RELEVANCE: Both earning and start data should be reported in studies evaluating outcome following surgery or other intervention. Considerations of age, breed, sex, track surface and gait should be included in the design of these studies.

Successful treatment of persistent dorsal displacement of the soft palate and evaluation of laryngohyoid position in 15 racehorses.

REASONS FOR PERFORMING STUDY: Caudal descent of the larynx has been proposed to be associated with intermittent dorsal displacement of the soft palate (DDSP) as it leads to a loss of the seal between the epiglottis and soft palate but further investigation of this theory is required. OBJECTIVES: To evaluate laryngohyoid position of horses with persistent DDSP in comparison to horses with intermittent DDSP and evaluate the outcome of treatment. HYPOTHESES: Horses with persistent DDSP have a different laryngohyoid position compared to those with intermittent DDSP. Horses with persistent DDSP can be returned successfully to racing with a laryngeal tie-forward procedure. METHODS: Medical records of 15 racehorses presented for persistent DDSP between 2002 and 2007 were reviewed. Age, sex and breed matched horses diagnosed with intermittent DDSP were used as a comparison group. Treatment of all horses was performed by laryngeal tie-forward, 8/15 horses with persistent DDSP had a subsequent laser staphylectomy. Preoperative laryngohyoid position was compared between the 2 groups using a radiographic reference system. Surgical effect on position was assessed by comparing pre- and post operative radiographic measurements. Outcome was assessed by return to racing and comparison of pre- and post operative race earnings ($). RESULTS: Thirteen of 15 horses with persistent DDSP returned to racing. Seven of 15 horses were treated with laryngeal tie-forward alone while 8/15 horses were also treated with a laser staphylectomy. Horses with persistent DDSP had a more caudal larynx (ossification of the thyroid cartilage) (13 mm, P = 0.014), a more caudal (10 mm, P = 0.044) and dorsal (7 mm, P = 0.01) basihyoid bone, and a more dorsal thyrohyoid-thyroid articulation (10 mm, P = 0.002) than horses with intermittent DDSP. CONCLUSIONS AND POTENTIAL RELEVANCE: Racehorses with persistent DDSP can be treated successfully by laryngeal tie-forward or by laryngeal tie-forward followed by laser staphylectomy. Horses with persistent DDSP have a more caudal larynx and more caudal and dorsal basihyoid bone than horses with intermittent DDSP.

Racing performance following the laryngeal tie-forward procedure: a case-controlled study.

REASONS FOR PERFORMING STUDY: The laryngeal tie-forward procedure (LTFP) is becoming widely used for correction of dorsal displacement of the soft palate (DDSP) despite the absence of an evidence-based assessment of its efficacy. HYPOTHESES: The LTFP returns racing performance to preoperative baseline levels and to that of matched controls; and post operative laryngohyoid position is associated with post operative performance. DESIGN AND POPULATION: Case-controlled study of racehorses undergoing a LTFP for dorsal displacement of the soft palate at Cornell University between October 2002 and June 2007. METHODS: The presence of at least one post operative start and race earnings ($) were used as outcome variables. Controls were matched by age, breed and sex from the third race prior to surgery. A novel radiographic reference system was used to determine laryngohyoid position pre- and post operatively. Data for definitively and presumptively diagnosed cases were analysed separately. RESULTS: During the study interval, 263 racehorses presented, of which 106 were included in the study; 36 had a definitive diagnosis of DDSP and 70 a presumptive diagnosis. Treated horses were equally likely to race post operatively as controls in the equivalent race. Treated horses had significantly lower earnings in the race before surgery than matched controls. The procedure moved the basihyoid bone dorsally and caudally and the larynx dorsally and rostrally. A more dorsal post operative basihyoid position and more dorsal and less rostral laryngeal position were associated with an increased probability of racing post operatively. CONCLUSIONS: Horses undergoing a LTFP are as likely to race post operatively as matched controls. The procedure restores race earnings to preoperative baseline levels and to those of matched controls. POTENTIAL RELEVANCE: This study provides strong evidence supporting the use of the LTFP in racehorses. Further work is needed to determine the relationship between laryngohyoid conformation and nasopharyngeal stability in horses.

Intra-articular stabilisation of the equine cricoarytenoid joint.

REASONS FOR PERFORMING STUDY: The success of laryngoplasty is limited by abduction loss in the early post operative period. OBJECTIVE: To determine the efficacy of polymethylmethacrylate (PMMA) in stabilising the cricoarytenoid joint (CAJ) and reducing the force on the laryngoplasty suture. HYPOTHESIS: Injection into the cricoarytenoid joint resists the forces produced by physiological laryngeal air flows and pressures thereby reducing the force experienced by the laryngoplasty suture. METHODS: Ten cadaver larynges were collected at necropsy and PMMA was injected into one CAJ at selected random. Each larynx was subjected to physiological conditions with with constant (static) or cycling (dynamic) flow. The specimens were tested sequentially in each of 4 conditions: 1) bilateral full abduction (Control 1); 2) transection of the suture on the side without PMMA; 3) bilateral abduction achieved by replacing the suture (Control 2); and 4) cutting the suture on the PMMA side. Tracheal pressure and flow and pressure in the flow chamber were recorded using pressure and flow transducers. The strain experienced by each suture during bilateral abduction (Controls 1 and 2) was measured. Statistical comparison of the 4 conditions was performed using a mixed effect model with Tukey's post hoc test for multiple comparisons. The strain gauge data were analysed by paired comparison of the regression slopes. RESULTS: In the static and dynamic states, tracheal pressure increased and tracheal flow decreased when the suture on the non-cement side was cut (P < 0.05). There was no significant difference in any outcome measure between PMMA injected into the CAJ and bilaterally abducted specimens (Controls 1 and 2) for either condition. The rate of increase in strain with increasing translaryngeal pressure was significantly less on the suture with PMMA placed in the CAJ (P = 0.03). CONCLUSIONS: These data provide strong evidence that injecting PMMA into the CAJ resists the collapsing effect of physiological airflows and pressures in vitro and reduces the force experienced by the laryngoplasty suture during maximal abduction. POTENTIAL RELEVANCE: Augmentation of prosthetic laryngoplasty with this technique may reduce arytenoid abduction loss in the early post operative period.