Race performance following epiglottic entrapment surgery in Thoroughbred yearlings.

BACKGROUND: Epiglottic entrapment can occur in yearling Thoroughbreds (TB); however, race performance following surgical correction is unknown. OBJECTIVES: To determine the race performance of horses treated surgically for epiglottic entrapment as yearlings as compared to an untreated cohort. A second objective was to identify risk factors for treated horses not racing post-operatively. STUDY DESIGN: Retrospective cohort and case-control studies. METHODS: Medical (1989-2014) and race records of 66 treated TB racehorses were reviewed. Observed abnormalities on pre- and post-operative endoscopic images and surgical method were recorded. Race records (EquineLine) were recorded. Racing performance of treated yearling TBs and two of their maternal half-siblings, which were used as the untreated cohort, was evaluated in a cohort study. A case-control study was used to investigate risk factors for not racing post-operatively among treated horses. Quarterly starts and earnings were compared to an untreated cohort. Survival analysis was used to assess career longevity. Rates of racing and earnings were compared between groups using Poisson and negative binomial regression respectively. Associations between clinical variables and not racing post-surgery were evaluated using logistic regression. RESULTS: Sixty-six treated horses were identified, 65 of which had at least one half-sibling. Proportions of horses that raced were similar for treated and maternal cohorts (70.0 vs. 70.8%, P = 0.9). Treated horses performed similarly to untreated horses. In treated horses, epiglottic entrapment with abnormal right arytenoid movement was associated with never racing (OR 15.40, 95% CI 1.64-144.23, P = 0.02). More females were affected by epiglottic entrapment than males (47/66 vs. 19/66 respectively, P<0.001). MAIN LIMITATIONS: The retrospective design over a prolonged period of time with cases obtained from a single hospital population. Low case numbers likely influenced the outcome of the multivariable analysis. CONCLUSIONS: Thoroughbred racehorses treated in their yearling year for epiglottic entrapment had no differences in performance variables compared to their untreated cohort. Epiglottic entrapment with abnormal right arytenoid movement might decrease odds of racing post-operatively.

Reproductive careers of Thoroughbred broodmares before and after surgical correction of ≥360 degree large colon volvulus.

BACKGROUND: Limited data exist describing broodmare longevity and reproductive efficiency after surgical correction of ≥360 degree large colon volvulus (° LCV). OBJECTIVES: Compare career duration and foals delivered for broodmares before and after ≥360° LCV surgery. STUDY DESIGN: Retrospective case series. METHODS: Broodmares registered with The Jockey Club that had surgical correction of ≥360° LCV and survived to hospital discharge at Rood and Riddle Equine Hospital from 1 January 2000 to 31 December 2015 were included. Information was collected from the hospital's medical data base and The Jockey Club produce records about the mares' reproductive careers. Data were evaluated using parametric and nonparametric tests, P≤0.05. RESULTS: Mares that were bred but never foaled prior to surgery (n = 19) had shorter careers (mean ± standard deviation [s.d.]), 4.4 ± 4.5 years, and fewer foals, 3.1 ± 3.3, compared with mares that delivered ≥1 foal before surgery (n = 565), 10.4 ± 4.5 years and 7.4 ± 3.4 foals, respectively, P<0.001. Broodmares that delivered foals before surgery produced more foals in the years before surgery, 4.8 ± 3.0, than after surgery, 2.6 ± 2.4, P<0.001, and had longer breeding careers, 5.9 ± 3.8 vs. 4.5 ± 3.3 years before compared with after surgery, P<0.001. No significant differences in career length or number of foals delivered were detected for mares with a single compared with multiple LCV surgeries. Mares that were 3-11 years old at the time of surgery had significantly more foals after surgery compared with mares ≥12 years old, P<0.001, as expected. MAIN LIMITATIONS: Retrospective collection of data. CONCLUSIONS: Broodmares had productive careers following surgery for ≥360° LCV that were largely influenced by the mares' age at the time of surgery.

Increased serum nonesterified fatty acid and low ionised calcium concentrations are associated with post partum colic in mares.

REASONS FOR PERFORMING STUDY: Increased serum nonesterified fatty acids (NEFA) and decreased serum electrolytes are linked to abdomasal displacements in post partum dairy cattle. Post partum colic in mares may be associated with metabolic changes specific to pregnancy and the periparturient period. OBJECTIVES: To determine if fluctuations in serum NEFA, ionised calcium (iCa) and magnesium (iMg) occurred in periparturient mares and if these alterations were associated with post partum colic. STUDY DESIGN: Longitudinal observational study. METHODS: Mares from 3 farms in central Kentucky were enrolled. Blood samples were collected 14 days prior to the estimated foaling date, within 4 days post parturition, and 14 and 28 days after foaling for batch analysis of serum NEFA, iCa and iMg. Health information was provided by farm managers and veterinarians. Data were analysed using Kruskal-Wallis χ(2) statistic for nonparametric data and a matched case/control approach. Repeated measures logistic regression models were developed. RESULTS: Serum NEFAs were higher at 14-1 day before foaling (mean ± s.d., mmol/l), 0.28 ± 0.12, P = 0.04 and from foaling to 4 days after foaling, 0.29 ± 0.20 (P = 0.05) in mares that developed colic compared with those that did not colic, 0.19 ± 0.05 and 0.21 ± 0.14, respectively. Ionised calcium was lower at 15-28 days post foaling in mares that showed colic, 1.50 ± 0.17 compared to mares that did not colic, 1.60 ± 0.12, P = 0.02. Risk of colic in post partum mares increased 38% for each 0.1 mmol/l increase in serum NEFA (odds ratio = 1.38, 95% confidence interval 1.06-1.81, P = 0.02). CONCLUSIONS: Mares with post partum colic had significantly higher serum NEFA and lower iCa prior to the colic episode compared with mares that did not develop colic. Monitoring these metabolic alterations may lead to predictive and preventive colic strategies for post partum mares.

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.

Changes in the faecal microbiota of mares precede the development of post partum colic.

REASONS FOR PERFORMING STUDY: Disruptions in the gastrointestinal microbiota may trigger development of post partum colic. OBJECTIVES: To determine the effects of the periparturient period on the faecal microbiome and identify associations between the faecal microbiota and post partum colic. STUDY DESIGN: Longitudinal case-control study. METHODS: Pre- and post partum faecal samples were collected from mares on 3 farms in central Kentucky. Next generation sequencing of the V4 region of the 16S rRNA gene was performed on samples from 13 mares that developed colic, 13 mares that did not display colic and 5 nonpregnant controls. RESULTS: There were 4,523,727 sequences from 85 samples evaluated (mean ± s.d. 53,220 ± 29,160, range 8442-122,535). Twenty-five phyla were identified, although only Firmicutes, Verrucomicrobia, Actinobacteria and Proteobacteria were present at a relative abundance of 1% or greater. The faecal microbiota of late-term mares differed from nonpregnant mares, with differences in microbial community membership and structure but not the relative abundance of major phyla. There was limited impact of foaling and the post partum period on the faecal microbiome. Faecal samples obtained from mares prior to episodes of colic had significantly higher relative abundance of Proteobacteria (8.2%, P = 0.0006) compared with samples from mares that did not display colic (3.7%). All samples with a relative abundance of Firmicutes of ≤50% preceded colic, as did 6/7 (86%) samples with >4% Proteobacteria. Differences in microbiota membership and structure were also present between mares that developed large colon volvulus and matched controls that did not have colic. Sixty-one indicator operational taxon units were identified for the control (vs. volvulus) samples, and these were dominated by Lachnospiraceae (n = 38) and Ruminococcaceae (n = 8). CONCLUSIONS: Foaling had minimal effects on the mares' faecal microbiota. Numerous differences in the faecal microbiota preceded colic. Associations between Firmicutes (particularly Lachnospiraceae and Ruminococcaceae) and Proteobacteria and development of colic could lead to measures to predict and prevent colic. The Summary is available in Chinese - see Supporting information.

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.

Complications after two transphyseal bridging techniques for treatment of angular limb deformities of the distal radius in 568 Thoroughbred yearlings.

REASONS FOR PERFORMING STUDY: Surgical correction of carpal angular limb deformities by growth retardation is commonly undertaken with a screws and tension band wire loop technique (S&W) or a single transphyseal screw (STS). This study compares complications after S&W and STS bridging in the distal radius of Thoroughbred yearlings. OBJECTIVE: To compare the prevalence of complications serious enough to require follow-up radiographs following either S&W or STS surgery for growth manipulation in the distal radius of Thoroughbred yearlings. METHODS: Medical records and radiographs from Thoroughbred yearlings (age range 261-457 days) treated for carpal angular limb deformities at a single hospital over 2 years were reviewed. Each of the techniques was used exclusively during a single year. The complication threshold criterion for inclusion was the need for nonroutine radiographs of the operated site anytime after implant insertion or removal. RESULTS: Of 568 horses, 253 received S&W and 315 received STS. Horses were of similar age at the time of surgery for STS and S&W. Single transphyseal screws were left in place for a significantly shorter amount of time (16 days). Sex, the limb(s) treated and medial vs. lateral placement were not significantly different between techniques. Complications included physitis post implant removal, metaphyseal collapse post implant removal, infection, overcorrection and seroma formation severe enough to require radiography. Physitis and metaphyseal collapse occurred significantly more frequently with STS compared with S&W. Infection, overcorrection and seromas were not significantly different between techniques. CONCLUSION: The STS and S&W techniques are both viable treatment options for correction of carpal angular limb deformities. However, horses treated with the STS technique have a significantly increased risk of developing physitis or metaphyseal collapse. POTENTIAL RELEVANCE: Horses treated with STS bridging have a significantly increased risk of developing the post correction complications of moderate to severe physitis and metaphyseal collapse compared with horses treated with S&W bridging.

Size and geometry of apical sesamoid fracture fragments as a determinant of prognosis in Thoroughbred racehorses.

REASON FOR PERFORMING STUDY: Analysis was performed to examine a method for refining the preoperative prognosis for horses that had surgery to remove apical fractures of the proximal sesamoid bones (PSBs). OBJECTIVES: To determine if: 1) there was a difference in size or configuration of apical fractures between the different anatomical locations of the PSBs, which have been shown to affect the prognosis; and 2) the size or configuration could predict the prognosis for racehorses with these fractures. METHODS: The study included 110 weanlings and yearlings and 56 training racehorses that underwent surgery to remove apical PSB fractures. Radiographs of the fractures were used for measurement of the abaxial and axial proportion and the abaxial to axial ratio, and race records were used to determine average earnings per start (AEPS) and total post operative starts. Analysis of variance and regression statistics were used to compare the fragment sizes between the specific PSBs on each of the limbs and compare size and configuration of the fractures to prognosis. RESULTS: There was a significantly larger abaxial to axial ratio (more transverse fracture) for the forelimb medial sesamoids than for all other sesamoids in untrained racehorses (P = 0.03). There were no other significant differences in size. There was no relationship between fracture size or configuration and AEPS nor total post operative starts. CONCLUSIONS: Apical fractures in weanlings and yearlings tend to be more transverse in the forelimb medial PSBs than the other PSBs. Apical fracture size and geometry does not determine prognosis for apical sesamoid fractures. POTENTIAL RELEVANCE: Horses that undergo surgery to remove larger apical fractures of the PSBs do not have a worse outcome than those horses with smaller fractures.

Association of treadmill upper airway endoscopic evaluation with results of ultrasonography and resting upper airway endoscopic evaluation.

REASONS FOR PERFORMING STUDY: Assessment of arytenoid movement has traditionally been performed using upper airway (UA) endoscopy. However, recent work suggests that laryngeal ultrasonography may provide additional complementary information. OBJECTIVE: To determine the value of laryngeal ultrasonography for the diagnosis of recurrent laryngeal neuropathy in the horse. HYPOTHESES: Horses with abnormal arytenoid movement (AM) during treadmill UA endoscopy would have increased echogenicity of the left cricoarytenoideus lateralis muscle (CALM) and smaller left CALM and vocalis size while horses with normal AM during treadmill UA endoscopy would have normal echogenicity of the left CALM and similar left and right CALM and vocalis muscle size. Laryngeal ultrasonography would be more accurate than resting endoscopy at predicting abnormal AM. METHODS: Medical records were examined to identify Thoroughbred racehorses aged ≥2 years that had undergone resting and treadmill UA endoscopy and laryngeal ultrasonography. Resting and treadmill AM was graded using accepted scales. The treadmill examination was used as the criterion standard for AM. Laryngeal ultrasonography was performed and the relative echogenicity of the left and right CALM and the cross-sectional area (CSA) of the CALM and vocalis muscle determined. Data analysis included Chi-squared tests, paired t tests and one-way ANOVA. RESULTS: The presence of abnormal AM was associated with relative hyperechogenicity of the CALM while normal AM was not. Laryngeal ultrasonography had a sensitivity of 90% and specificity of 98% and resting UA endoscopy had a sensitivity of 80% and specificity of 81% for diagnosis of abnormal AM. CSA of the left CALM and vocalis muscle was not different between groups. CONCLUSIONS: Laryngeal ultrasonography has high accuracy for diagnosing abnormal AM. POTENTIAL RELEVANCE: Ultrasonography is a valuable addition to the diagnostic evaluation of the equine UA.

Management and assessment of prognosis after gastrocnemius disruption in Thoroughbred foals: 28 cases (1993-2007).

REASONS FOR PERFORMING STUDY: Few studies have evaluated the athletic prognosis of foals affected by gastrocnemius disruption. OBJECTIVE: To examine the diagnosis and management of gastrocnemius disruption in Thoroughbred (TB) foals, determine short-term survival rate and assess future racing performance. The hypothesis was that Thoroughbred foals with gastrocnemius disruption are able to perform as racehorses comparably to their age matched maternal siblings. METHODS: The medical records of foals diagnosed with gastrocnemius muscle disruption were reviewed. Information on training and racing was acquired from published works and race records. Paired t tests were utilised to compare performance variables of affected racehorses to their maternal siblings in starts, earnings and earnings/start for their 2- and 3-year-old racing seasons. Fisher's exact tests were employed to determine the association between sex, limb affected, age on admission, degree of caudal reciprocal apparatus dysfunction, concurrent disease, antibiotic therapy, complications, abscess formation and likelihood of entering training or starting a race. RESULTS: Sample size was too small to detect significant differences in performance variables between affected horses and controls. Of 28 foals, 17 (61%) presented with concomitant illness; foals without concurrent disease were more likely to achieve race training or start a race (P = 0.04); 23 (82%) were short-term survivors defined as survival to discharge. Of these 23 survivors, 7 were aged <2 years at the time of the study. Eighty-one percent (13/16) of the survivors that were of racing age were in training or had started a race. CONCLUSIONS: In this population, 82% of TB foals affected with gastrocnemius disruption were able to achieve training or start a race. Foals presenting for gastrocnemius disruption have a high prevalence of concurrent disease processes. POTENTIAL RELEVANCE: The assessment of athletic prognosis and treatment complications provides useful information to clinicians treating gastrocnemius muscle disruption in foals and making recommendations to clientele.

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.

The effect of uterine torsion on mare and foal survival: a retrospective study, 1985--2005.

REASONS FOR PERFORMING STUDY: Anecdotal speculation suggests that prognosis for survival of mares and foals following correction of uterine torsion has improved over the past 30 years. OBJECTIVES: To determine statistically the outcome of uterine torsion according to duration of clinical signs, stage of gestation, parity, physical examination findings, method of correction, prognosis for survival and reproductive health of the mare, and prospects for the foal within the neonatal period. METHODS: This retrospective study combined cases from 4 equine referral hospitals. RESULTS: The stage of gestation at which uterine torsion occurred was a risk factor for survival of mare and foal. Overall mare survival was 53/63 (84%); when uterine torsion occurred at < 320 days gestation, 36/37 (97%) of mares survived compared to 17/26 (65%) survival rate when uterine torsion occurred at > or = 320 days gestation. Overall foal survival was 54% (29/54). When uterine torsion occurred at < 320 days gestation, 21/29 (72%) foals survived compared to 8/25 (32%) when uterine torsion occurred at > or = 320 days gestation. Thirty mares were discharged from the hospital carrying a viable fetus following uterine torsion correction and 25/30 (83%) of these mares delivered live foals that survived beyond the neonatal period. CONCLUSIONS: Prognosis for survival for mares and foals following uterine torsion is good and improves if torsion occurs < 320 days compared to > or = 320 days gestation. CLINICAL RELEVANCE: Gestational timing of uterine torsion should be considered when advising clients about the prognosis for survival of the mare and foal. The prognosis for a mare delivering a live foal is good if the mare is discharged from the hospital following uterine torsion correction with a viable fetus.

Racing performance after arthroscopic removal of apical sesamoid fracture fragments in Thoroughbred horses age < 2 years: 151 cases (1989--2002).

REASONS FOR PERFORMING STUDY: Studies on arthroscopic removal of apical proximal sesamoid fracture fragments in Thoroughbred (TB) horses age > or = 2 years have reported a high success rate. However, there are no reports documenting the racing prognosis of TB horses that undergo such surgery as weanlings or yearlings. OBJECTIVES: To describe the incidence of apical proximal sesamoid fractures in immature TB horses, age < 2 years and determine probability and quality of racing performance after arthroscopic removal of such fractures in 151 TB weanlings and yearlings. METHODS: The medical records of TB horses age < 2 years that underwent arthroscopic surgery for removal of apical proximal sesamoid fracture fragments were reviewed. Follow-up information was obtained from race records. Student's t tests were used to compare performance variables of operated racehorses to that of their maternal siblings. RESULTS: Ninety-two percent (139/151) of fractures occurred in the hindlimbs and 8% (11/151) in the forelimbs (fracture of both fore- and hindlimb, n = 1). Horses with forelimb fractures had a greatly reduced probability of racing (55%) compared to those with hindlimb fractures (86%). Overall, 84% of the horses raced post operatively and had performance records similar to that of their maternal siblings, 78% (787/1006) of which raced. CONCLUSIONS: Arthroscopic removal of apical proximal sesamoid fracture fragments in TB weanlings and yearlings carries an excellent prognosis for racing in horses with hindlimb fractures and a reduced prognosis in those with forelimb fractures. Medial fractures of the forelimb carry the worst prognosis. POTENTIAL RELEVANCE: The determination of prognosis increases knowledge on apical sesamoid bone fractures and potential for arthroscopic restoration of the ability to race; and enables the value of yearlings for subsequent sale to be established.

Racing performance after arthroscopic removal of apical sesamoid fracture fragments in Thoroughbred horses age > or = 2 years: 84 cases (1989-2002).

REASONS FOR PERFORMING STUDY: Studies have shown that surgical removal of apical fracture fragments in Standardbred racehorses carries the best prognosis for return to racing performance, but there are no reports involving mature Thoroughbred (TB) racehorses. OBJECTIVES: To describe the incidence of apical proximal sesamoid fractures in TB racehorses and determine probability and quality of racing performance after arthroscopic removal of such fractures in TB racehorses age > or = 2 years. METHODS: Medical records and pre- and post operative race records of TB racehorses age > or = 2 years that underwent arthroscopic surgery for removal of apical proximal sesamoid fracture fragments were reviewed. RESULTS: Sixty-four percent of fractures occurred in the hindlimbs and 36% in the forelimbs. Horses with forelimb fractures had a reduced probability of return to racing (67%) compared to those with hindlimb fractures (83%), but the majority (77%) of treated horses recovered to return to race post operatively. Horses with medial forelimb fractures raced at only a 47% rate; those with suspensory desmitis at 63%. Unlike Standardbreds, there was no difference in probability of racing post operatively between horses that had, and had not, raced preoperatively. CONCLUSIONS: Data show that arthroscopic removal of apical proximal sesamoid fracture fragments is successful at restoring ability to race in skeletally mature TB horses without evidence of severe suspensory ligament damage. Prognosis for return to racing is excellent (83%) in horses with hindlimb fractures and good (67%) in those with forelimb fractures. Medial fractures of the forelimb have the worst prognosis. POTENTIAL RELEVANCE: The determination of prognosis for differing sites in TB racehorses should increase knowledge of apical proximal sesamoid bone fractures and improve communication from veterinarian to owner, and trainer, on the potential for arthroscopic restoration of the ability to race.

Dystocia in a referral hospital setting: approach and results.

REASONS FOR PERFORMING STUDY: Dystocia in the mare is an emergency in which duration has a profound effect on survival of the foal. Specific examination of the effects of dystocia duration on foal survival provides information to enable horse care personnel and veterinarians to manage these cases more effectively and maximise the chances of obtaining a live foal. HYPOTHESIS: Dystocia duration would have a negative impact on foal survival while method of dystocia resolution would not have an effect on foal survival. Additionally, we were interested in determining the effects of dystocia on subsequent fertility. METHODS AND RESULTS: In the years 1986-1999, 247 dystocias were admitted. Of these, 91 % resulted in survival and discharge of the mare, 42% in delivery of a live foal, and 29% of foals survived to discharge. Period from hospital arrival to delivery for foals alive at discharge (23.0 +/- 14.1 mins) was not significantly different than for foals not surviving (24.8 +/- 10.6 mins) (P > 0.05); and from chorioallantoic rupture to delivery for foals alive at discharge (71.7 +/- 343 mins) was significantly less than for foals not surviving (853 +/- 37.4 mins) (P < 0.05). Average predystocia live foaling rates for all mares with available records was 84%. Overall post dystocia live foaling rates over the entire period of this study were 67%. Of mares bred in the year of the dystocia, 59% had a live foal in the year following. CONCLUSIONS: Based on these results, dystocia duration has a significant effect on foal survival and resolution methods should be chosen to minimise this time, as the difference between mean dystocia duration for foals that lived and those that did not in this study was 13.6 mins. Post dystocia foaling rates reported here are higher than previously reported for both same-season and overall breedings, indicating same-season breeding may be rewarding for select dystocia cases. POTENTIAL RELEVANCE: Dystocia resolution methods that minimise delivery time may maximise foal survival. Post dystoicia breeding may be rewarding in select cases.

Proximal interphalangeal arthrodesis in 22 horses.

The purpose of this study was to evaluate a new method of internal fixation technique for pastern arthrodesis. Pastern arthrodeses are performed commonly in horses with chronic osteoarthritis of the pastern joint or, in cases of acute traumatic injury to the pastern, in which the weightbearing bony column must be restored. Chronic osteoarthritis of the pastern is a frequent cause of lameness in the equine athlete and is evidenced by chronic lameness localised to the pastern joint, and supported radiographically by periosteal proliferation and loss of joint space. Nonsurgical and surgical treatments have both been described in the literature. Complications following pastern arthrodesis have been reported on several occasions and appear to focus on excessive periarticular exostoses and increased time in a cast due to prolonged time to bony fusion. The hospital records of horses presenting for pastern arthrodesis to the Rood and Riddle Equine Hospital in Lexington, Kentucky, were reviewed and 22 met criteria for inclusion in the study. Horses with chronic osteoarthritis of the proximal interphalangeal joint or horses with an acute traumatic injury to the pastern undergoing pastern arthrodesis with one of the following techniques were included in the study. Horses with severe comminution of the middle phalanx were excluded. Three 5.5 mm cortical bone screws placed in lag fashion alone or in combination with a 4 or 3 hole dynamic compression plate affixed with 4.5 mm cortical bone screws were compared. A lower limb fibreglass cast was applied in all cases. Period in cast, time to return to intended use, complications encountered and outcome were evaluated. Seven of the 8 hindlimbs treated with the combination technique became sound. Three out of 6 of the front limbs treated with the combination technique became sound. Four of the 5 horses with hindlimbs, and one of the 2 with front limbs, treated with screws only returned to their intended use. The type of internal fixation did not appear to influence the overall number of horses returning to the intended level of performance. The period spent in cast and the time to return to soundness were decreased in horses operated on using the combination technique. We concluded that, in the immediate postoperative period, the combination of the parallel screw technique with a dorsally-applied dynamic compression plate provides the most stable and secure fixation, minimising motion, expediting bone remodelling and therefore favouring rapid fusion of that joint.

Qualitative and quantitative documentation of the racing performance of 461 Thoroughbred racehorses after arthroscopic removal of dorsoproximal first phalanx osteochondral fractures (1986-1995).

The purpose of this study was to examine the longevity of postoperative careers and quality of performance of 461 Thoroughbred racehorses after arthroscopic removal of dorsoproximal first phalanx (P1) osteochondral fractures. Six hundred and 59 dorsoproximal P1 chip fractures were removed arthroscopically from 574 joints in 461 horses presented for lameness or decreased performance attributed to the chip fractures. Radiological and arthroscopic examination revealed an average of 1.43 fragment sites/horse, 1.15 fragment sites/joint and 1.25 affected joints/horse. Eighty-nine percent of the horses (411/461) raced after surgery and 82% (377/461) did so at the same or higher class. Fifty horses did not race after surgery. Sixty-eight percent of the horses raced in a Stake or Allowance race postoperatively. Data, previously undocumented, establishes that the quantity and quality of performance is not diminished after arthroscopic treatment of dorsoproximal P1 fragmentation. Surgical removal of chip fractures is a means of preserving the economic value of an injured Thoroughbred, allowing a rapid and successful return to racing at the previous level of racing performance.

Uroperitoneum in the hospitalised equine neonate: retrospective study of 31 cases, 1988-1997.

Historical, physical and diagnostic data were reviewed retrospectively in 31 equine neonates with uroperitoneum. Gender predilection was not observed, and classic electrolyte abnormalities were seen in less than 50% of the cases. Aetiologies for uroperitoneum have been well described, but this review found that septicaemia/severe illness played a crucial role the outcome of uroperitoneum. Approximately half the individuals with uroperitoneum had positive sepsis scores. Foals receiving fluid therapy were more likely to be septic and to have normal electrolyte concentrations. Ultrasonographic findings, serum creatinine and serum:peritoneal creatinine ratios were not affected by previous fluid therapy and were invaluable aids in the diagnosis of uroperitoneum, even with multisystemic disease such as sepsis.

Colic surgery in 206 juvenile thoroughbreds: survival and racing results.

The purpose of our study was to determine the types of lesions that cause colic in juvenile Thoroughbreds, factors associated with these lesions and the subsequent survival and athletic performance of the juveniles. The age of juvenile Thoroughbreds requiring surgical exploration for abdominal pain has an influence on the type of lesion causing colic. The short-term survival rate (discharge from the hospital) after colic surgery for foals was 85% and was strongly influenced by the lesion causing colic. Thirteen percent of juveniles recovered from the first surgery experienced another severe colic episode requiring additional surgery or euthanasia. Eight percent of foals recovered from the first celiotomy developed adhesions. Adhesion formation was related to the initial lesion causing colic and the foals' age at the first surgery. Foals being suckled (15 days to 6 months) were at greatest risk for adhesions and more frequently required multiple surgeries. Juvenile Thoroughbreds that had a celiotomy were significantly less able to race (63%) than their unaffected siblings (82%), and age at the initial surgery was associated with the percentage of horses that raced. However, affected foals able to race won as much money, raced as often, and made as many starts as their siblings. Colic and surgical treatment have a negative impact on athletic performance, but the majority of foals discharged from the hospital after colic surgery will perform athletically as adults.