Duration of disease influences survival to discharge of Thoroughbred mares with surgically treated large colon volvulus.

REASONS FOR PERFORMING STUDY: Large colon volvulus results in strangulating obstruction requiring surgical treatment. Duration of this disease prior to surgical treatment is likely to influence survival directly. OBJECTIVES: The primary objective of this study was to evaluate the influence of duration of large colon volvulus on patient survival to discharge. Relationships between other factors and survival following large colon volvulus were also examined. STUDY DESIGN: Retrospective case analysis. METHODS: Medical records of Thoroughbred mares aged ≥2 years undergoing surgical treatment for large colon volvulus between 1 March 1986 and 28 February 2011 were reviewed. Multivariable logistic regression was used to identify influence of duration and other factors on survival to discharge. RESULTS: Within the study period, 1039 surgeries were performed to correct large colon volvulus in 896 Thoroughbred mares. Median duration of colic signs prior to admission was 2 h (interquartile range [IQR] 1-4 h). Median time from admission to anaesthetic induction was 25 min (IQR 15-45 min). Median surgical time was 70 min (IQR 55-85 min). Primary surgical treatment was simple correction of the large colon volvulus followed by replacement of the colon. The overall survival to discharge was 88%. The final model identified risk factors significantly associated with survival and included colic duration prior to admission, packed cell volume at admission, surgery length, duration of hypotension while under anaesthesia, heart rate 48 h post operatively, post operative manure consistency and days hospitalised. CONCLUSIONS: Duration of colic prior to admission was statistically associated with patient survival to discharge. Other factors significantly associated with survival in mares with large colon volvulus were related to disease severity and degree of colonic compromise. Mares with large colon volvulus have a good prognosis for recovery with early referral and prompt surgical treatment.

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.

Factors influencing foaling rate following colic surgery in pregnant Thoroughbred mares in Central Kentucky.

REASONS FOR PERFORMING STUDY: Clinical experience has suggested that foaling rates following colic surgery in the pregnant mare are influenced by days of gestation. This premise has not been supported in previous studies. We also aimed to determine the effects of other potential influencing factors. OBJECTIVE: To determine the influence of age of gestation on foaling rates in pregnant mares following colic surgery and evaluate the relationships between other factors and foaling rates. METHODS: Medical records of Thoroughbred mares, which had colic surgery performed from 1993 to 2007 at the Rood and Riddle Equine Hospital, were reviewed. Mares identified in the record as pregnant or bred within the previous 15 days were included in this study. Age of the mare, date of surgery, gestational age, duration of colic at admission, packed cell volume at admission, surgical diagnosis, duration of general anaesthesia, intraoperative hypotension, intraoperative hypoxaemia and post operative signs of endotoxaemia were recorded. A mare was considered to have a live foal if that foal was registered with the North American Jockey Club. RESULTS: Of the 228 mares, where pregnancy had been confirmed, 152 (66.7%) had a live foal registered after surgery. Mares bred <40 days before surgery had a lower foaling rate compared with mares undergoing surgery ≥40 days after breeding: 48.7% vs. 69.8% (odds ratio [OR] = 0.41 [95% confidence interval (CI) 0.20-0.83], P = 0.012). Foaling rate was also influenced by mare's age (P = 0.008) and duration of colic signs before surgery (P = 0.03). CONCLUSIONS: The prognosis for a live foal after colic surgery in the pregnant Thoroughbred mare is significantly better if the mare is ≤15 years of age and ≥40 days of gestation. POTENTIAL RELEVANCE: The results of this study are useful for clinicians offering a prognosis for a live foal following colic surgery in pregnant mares.

Diagnosis of laryngeal dysplasia in five horses using magnetic resonance imaging and ultrasonography.

REASONS FOR PERFORMING STUDY: Laryngeal dysplasia due to suspected maldevelopment of the fourth branchial arch has been reported previously in the horse and has been associated with rostral displacement of the palatopharyngeal arch and/or right laryngeal dysfunction. These studies all described the endoscopic and/or anatomical post mortem identification of the disease, but ultrasonography or magnetic resonance imaging (MRI) of this disease have not been described. HYPOTHESIS: MRI and ultrasound findings accurately reflect the anatomical features of presumptive fourth branchial arch abnormality and allow accurate ante mortem diagnosis of this condition and, therefore, appropriate management. METHODS: Between February 2008 and January 2009, all horses examined at Rood and Riddle Equine Hospital diagnosed with rostral displacement of the palatopharyngeal arch and/or right laryngeal dysfunction using upper airway endoscopy (n=5) underwent ultrasonography and MRI of the laryngeal region. RESULTS: All 5 horses that met the inclusion criteria were identified and all underwent laryngeal MRI and ultrasound examinations. Features consistent with laryngeal dysplasia, including lack of the cricothyroid articulation, dorsal extension of the thyroid cartilage lamina, and absence or hypoplasia of the cricopharyngeus muscle, were seen in all cases using both types of imaging. CONCLUSIONS AND POTENTIAL RELEVANCE: MRI and ultrasonography permit definitive premortem diagnosis of laryngeal dysplasia. Upper airway abnormalities identified using endoscopy can be more fully characterised using MRI and ultrasonography allowing more appropriate recommendations to be made. Preoperative imaging may also prevent inappropriate surgical intervention.

Surgical advancement of the larynx (laryngeal tie-forward) as a treatment for dorsal displacement of the soft palate in horses: a prospective study 2001-2004.

REASONS FOR PERFORMING STUDY: Correct placement of sutures ('laryngeal tie-forward') in experimentally created dorsal displacement of the soft palate (DDSP) has been observed to replace the function of the thyrohyoideus muscles and prevent DDSP. HYPOTHESIS: The 'laryngeal tie-forward' procedure would prevent or delay the occurrence of DDSP during exercise in horses with naturally occurring DDSP and therefore improve performance. METHODS: A clinical population (n = 116), mainly of racehorses was presented for treatment of naturally occurring exercise-induced DDSP. All horses underwent the 'laryngeal tie-forward' procedure. The relative position of the thyroid and cricoid cartilage in relation to the caudal aspect of the basihyoid bone was recorded; follow-up was obtained by telephone communication with trainers, owners and/or referring veterinarians. In addition, a performance index and earnings were determined using race records. RESULTS: Preoperatively, the median distance between the caudal aspect of the basihyoid bone and rostral aspect of the thyroid cartilage was 3.5 cm. Post operatively, the thyroid cartilage was moved a median distance of 4 cm rostrally and the larynx was shown to be in a position more rostral and dorsal than in preoperative radiographs. Of 98 horses for which follow-up was available, the performance of 87% was classified as improved, 12% as unchanged and 2% as worse. In 20 horses in which the diagnosis had been confirmed by treadmill videoendoscopy, 80% had a significantly increased performance index and earnings (P = 0.007). For the entire population, there was a significant improvement in performance index and earnings after surgery (82%) (P = 0.0001). CONCLUSIONS: Placing the larynx in a more rostral and dorsal position may have improved the performance in 80-82% of the horses affected with naturally-occurring DDSP. POTENTIAL RELEVANCE: 'Laryngeal tie-forward' is a surgical technique that has a measurable effect on the position of the larynx and offers an alternative therapy for treating horses affected with DDSP. More experience may be needed with this technique prior to its widespread use in horses with a clinical diagnosis of DDSP.

In vitro biomechanical properties of 2 compression fixation methods for midbody proximal sesamoid bone fractures in horses.

OBJECTIVE: To evaluate 2 methods of midbody proximal sesamoid bone repair--fixation by a screw placed in lag fashion and circumferential wire fixation--by comparing yield load and the adjacent soft-tissue strain during monotonic loading. STUDY DESIGN: Experimental study. SAMPLE POPULATION: 10 paired equine cadaver forelimbs from race-trained horses. METHODS: A transverse midbody osteotomy of the medial proximal sesamoid bone (PSB) was created. The osteotomy was repaired with a 4.5-mm cortex bone screw placed in lag fashion or a 1.25-mm circumferential wire. The limbs were instrumented with differential variable reluctance transducers placed in the suspensory apparatus and distal sesamoidean ligaments. The limbs were tested in axial compression in a single cycle until failure. RESULTS: The cortex bone screw repairs had a mean yield load of 2,908.2 N; 1 limb did not fail when tested to 5,000 N. All circumferential wire repairs failed with a mean yield load of 3,406.3 N. There was no statistical difference in mean yield load between the 2 repair methods. The maximum strain generated in the soft tissues attached to the proximal sesamoid bones was not significantly different between repair groups. CONCLUSIONS: All repaired limbs were able to withstand loads equal to those reportedly applied to the suspensory apparatus in vivo during walking. CLINICAL RELEVANCE: Each repair technique should have adequate yield strength for repair of midbody fractures of the PSB immediately after surgery.

Apical fracture of the proximal sesamoid bone in standardbred horses: 43 cases (1990-1996).

OBJECTIVE: To determine whether fracture fragment dimensions, suspensory ligament damage, and racing status at the time of injury were associated with outcome in Standardbred horses with apical fracture of the proximal sesamoid bone. DESIGN: Retrospective study. ANIMALS: 43 Standardbred racehorses. PROCEDURE: Medical records, racing records, and radiographs were reviewed, and ultrasonographic findings were scored. Measurements of the fractured portion of the proximal sesamoid bone were made. RESULTS: Seventy-four percent (32/43) of horses were pacers, and 26% (11/43) were trotters. Statistical differences between trotters and pacers regarding ability to start, number of starts, or amount of money earned after injury were not detected. Females earned significantly more money per start after injury than males. Eighty-six percent (37/43) of fractures involved hind limbs and 14% (6/43) involved forelimbs. Horses with forelimb injuries earned less money per start. Severity of suspensory ligament damage did not affect postinjury racing performance. A higher proportion of horses that had raced before injury returned to racing after surgery than horses that had not raced before injury, although a significant difference between these groups was not detected. Eighty-eight percent of horses that raced before injury raced after injury. Fifty-six percent of horses that did not race before injury raced after injury. Fracture fragment dimensions did not affect outcome. CLINICAL IMPLICATIONS: Dimensions of the apical fracture fragment of the proximal sesamoid bone in Standardbred horses and degree of suspensory ligament damage did not affect outcome. Prognosis for return to racing soundness is good in horses that had raced before injury and fair in horses that had not raced before injury.