There were 3.6 times as many noncatastrophic fractures as catastrophic fractures in Thoroughbreds racing in Hong Kong between 2004 and 2011. Noncatastrophic fractures interfere with race training schedules and may predispose to catastrophic fracture. Future analytical studies on noncatastrophic racing fractures should be a priority for the racing industry.

The current clinical techniques for neuraxial needle placement in dogs are predominantly blind without prior knowledge of the depth required to reach the desired space. This study investigated the correlation and defined the relationship between easily obtainable external landmark variables in the dog; occipital–coccygeal length (OCL) and ilium wings distance (IWD), with the skin to epidural and intrathecal space distances using computed tomography (CT). The CT images of 86 dogs of different breeds were examined in this retrospective observational study. Images of dogs in sternal recumbency were optimized to the sagittal view. The distances between the skin and lumbosacral epidural space (LSE) and skin to sacrococcygeal space (SCE) were measured to the ligamentum flavum surrogate (LFS) line. The distance between the skin and the intrathecal space (ITS) was measured from the skin to the vertebral canal at the interlumbar (L5–L6) space. Measurements of the IWD and OCL were performed on dorsal and scout views, respectively. Linear regression equations and Pearson’s correlation coefficients were calculated between variables. Data were reported as mean (standard deviation). Significance was set as alpha < 0.05. After exclusion of four dogs, 82 CT scans were included. The depths were LSE 45 (15) mm, SCE 23 (10) mm, and ITS 50 (15) mm. There was a moderate correlation between OCL with LSE (=14.2 + OCL * 0.05 (r = 0.59, p < 0.0001)), and a strong correlation with ITS (=11.4 + OCL * 0.07 (r = 0.76, p < 0.0001)), while a very weak correlation was found with SCE (=14.0 + OCL * 0.02 (r = 0.27, p < 0.0584)). Similarly, with IWD, there was a moderate correlation with LSE (=10.8 + IWD * 0.56 (r = 0.61, p < 0.0001)), and strong correlation with ITS (=9.2 + IWD * 0.67 (r = 0.75, p < 0.0001)), while a weak correlation was found with SCE (=11.2 + IWD * 0.2 (r = 0.32, p < 0.0033)). Mathematical formulae derived from the multiple regression showed that the body condition score (BCS) improved the relationship between IWD and OCL and the LSE, SCE and ITS, while the addition of body weight was associated with multicollinearity. Further studies are required to determine the accuracy of the algorithms to demonstrate their ability for prediction in a clinical setting.

The study aimed to compare bupivacaine onset time when administered via epidural anaesthesia injecting both at the lumbosacral and sacrococcygeal spaces, spinal anaesthesia, and DPE in clinical dogs. A total of 41 dogs requiring neuraxial anaesthesia as part of their anaesthetic protocol were recruited. They were randomly allocated to receive an epidural injection in the sacrococcygeal space aided by the nerve stimulator (SCO), an epidural injection in the lumbosacral (LS), a subarachnoid injection (SPI), or a DPE. The onset of anaesthesia was assessed every 30 s after the injection by testing the presence of patellar ligament reflex. The number of attempts and time to perform the technique were also recorded. Data were analysed using a one-way ANOVA for trimmed means with post hoc Lincoln test and a Kaplan–Meier curve. The significance level was set at p < 0.05, and the results are presented in absolute values and median (range). There was no difference in the number of attempts required to complete the techniques between groups (p = 0.97). Epidural injections (LS and SCO) tended to be shorter than SPI and DPE techniques, but there was no statistically significant difference (p = 0.071). The time to the disappearance of patellar ligament reflex (Westphal’s sign) in the SCO group was longer than in any other group. In conclusion, all techniques provided a rapid block of the patellar reflex. The SCO technique was the slowest in onset, while the other groups (SPI, DPE, and LS) were faster and almost indistinguishable.

Resorption within cortices of long bones removes excess mass and damaged tissue, and increases during periods of reduced mechanical loading. Returning to high-intensity exercise may place bones at risk of failure due to increased porosity caused by bone resorption. We used microradiographic images of bone slices from highly-loaded (metacarpal, tibia, humerus) and minimally-loaded (rib) bones from 12 racehorses, 6 in active high-intensity exercise and 6 in a period of rest following intense exercise, and measured intracortical canal cross-sectional area (Ca.Ar) and number (N.Ca) to infer remodelling activity across sites and exercise groups. Large canals representing resorption spaces (Ca.Ar > 0.04 mm2) were 5- to 18-fold greater in number and area in the third metacarpal bone from rested than exercised animals (p = 0.005–0.008), but were similar in number and area in ribs from rested and exercised animals (p = 0.575–0.688). A weaker, intermediate relationship was present in tibia and humerus, and when resorption spaces and partially-infilled canals (Ca.Ar > 0.002 mm2) were considered together. The mechanostat may override targeted remodelling during periods of high mechanical load by enhancing bone formation, reducing resorption and suppressing turnover, but both systems may work synergistically in rest periods to remove excess and damaged tissue.

Fractures in Thoroughbred racehorses are an omnipresent welfare issue. Previous studies have often failed to adequately address the issue of fractures in racing and training because of the limitations associated with record keeping. Racehorses being rested from intensive exercise are also at greater risk of fracture on re-introduction to high intensity work. This thesis aims to accurately report first event fractures and determine racing and training fracture incidence rates in the highly controlled Thoroughbred racehorse population at the Hong Kong Jockey Club (HKJC) and to identify differences in bone remodelling (as defined in this thesis) between racehorses, which have been rested compared to horses in current high intensity exercise. Hong Kong to date of fracture, retirement, or end of the study period, whichever was first. Incidence rates for racing were expressed as catastrophic or non-catastrophic fracture events per 1000 race starts (Chapter Three). Training incidence rates were expressed as catastrophic or non-catastrophic fracture events per 10,000 horse days at risk (Chapter Four). The incidence rate for catastrophic fractures during racing was 0.6 per 1000 race starts (95% CI 0.4 -0.8) and for non-catastrophic fractures it was 2.2 per 1000 race starts (95% CI 1.8 -2.6). The incidence rate for catastrophic fractures in training was 0.08 per 10,000 horse days at risk (95% CI 0.05 -0.11), and for non-catastrophic fractures was 0.85 per 10,000 horse days at risk (95% CI 0.75 -0.96). The incidence rate of catastrophic racing fractures at the HKJC were lower when compared to the results of studies conducted in the UnitedStates (Estberg, Stover et al. 1996b) and higher than in the United Kingdom (Parkin, Clegg et al. In another study, bones were obtained post-mortem from horses in Exercised (n = 6) and Rested (n = 6) Groups who died for reasons unrelated to fracture or the fracture study. Exercised horses had been euthanized within seven days of high intensity exercise while Rested horses had been retired for one to four months and whose work level was much reduced before retirement. Six bone blocks were cut from each horse at the following locations; right third metacarpal bone (MCIII) where samples were collected from the mid-diaphysis, distal lateral metaphysis and medial condyle; right third metatarsal bone (MTIII) where a sample was collected from the lateral condyle; distal left tibia, and middiaphysis of the left tenth rib. Each bone block was cut to 250 µm thick specimens using a diamond 3 annular saw. Microradiographs were obtained using point projection digital microradiography (Faxitron) and analysed to identify radiolucent spaces indicative of recently formed resorption canals as a proxy for active bone remodelling. This study identified that resorption canals of all sections from MCIII and the tibia were significantly greater in the Rested Group compared with the Exercised Group (P < 0.05). There was no significant difference in the resorption canal density of the rib between the two g...

This study aimed to validate previously published computed tomography (CT) derived mathematical equations with the true skin to lumbosacral epidural distance (SLED) in dog cadavers. Phase 1: The lumbar region of 11 dog cadavers were scanned in sternal recumbency to determine the effect of cranial, neutral, and caudal pelvic limb positioning on the CT derived lumbosacral epidural distance (CLED). Phase 2: The epidural space was determined using contrast epidurography, and the SLED was analysed against the mathematical equations using a body condition score (BCS) and either the cadaveric occipital-coccygeal length (OCL) (Equation (1): = 7.3 + 0.05*OCL + 16.45*BCS) or the ilium wing distance (IWD) (Equation (2): = 3.5 + 0.56*IWD + 16.6*BCS). There were no differences detected between the pelvic limb positions and the CLED. Both equations demonstrated strong correlations (Equation (1): r = 0.7196; Equation (2): r = 0.7590) with the SLED. The level of agreement was greater for Equation (1) than with Equation (2) (concordance coefficient 0.6061 and 0.3752, respectively). Equation (1) also demonstrated a closer fit to the concordance line compared with Equation (2) (bias correction factor 0.8422 and 0.4960, respectively). Further studies in live anaesthetised dogs will help to determine the usefulness of the pre-procedural knowledge when performing lumbosacral epidurals.

PICO question In horses undergoing volatile anaesthesia, is recovery quality superior with the use of sevoflurane compared to isoflurane during the maintenance phase?   Clinical bottom line The category of research question Treatment Number and type of study designs reviewed Seven papers were available for critical appraisal. Of the seven papers, six were prospective, randomised trials and four of these were of crossover design. Of the same seven papers, three were experimental and four were clinical. Strength of evidence Moderate Outcomes reported Five out of seven critically appraised articles found that there was no clinically significant improvement in recovery quality following volatile anaesthesia with sevoflurane compared to isoflurane. Two of the seven articles did find improvement in recovery quality following the use of sevoflurane over isoflurane, but both studies were of crossover design, one of these studies used non-blinded evaluators and the second study used both unblinded and blinded evaluators and a recovery quality scoring scale that did not show interobserver reliability. Conclusion In healthy horses presented for elective surgical and diagnostic imaging procedures in a clinical setting, there is no significant difference in recovery quality following the use of sevoflurane or isoflurane for the maintenance phase.   How to apply this evidence in practice The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources. Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.

Two foals undergoing surgery for angular limb deformities were anaesthetised using ketamine:propofol admixture (ketofol). Ketamine was used at 2 and 1 mg/kg, and propofol at 2 and 1.5 mg/kg in cases 1 and 2, respectively. Induction of general anaesthesia was smooth and occurred within 30 seconds after ketofol administration. No apnoea, nystagmus and paddling were noted. In case 1, anaesthesia was maintained with additional boluses of propofol (0.4 mg/kg) and flow‐by oxygen delivered via face mask, and in case 2 with isoflurane delivered in oxygen. The anaesthetic time was 20 and 55 minutes in cases 1 and 2, respectively. Before recovery, xylazine (0.2 mg/kg) was administered IV in case 2. Both foals stood at the first attempt approximately 10 minutes later with mild ataxia. Ketofol could be an alternative for induction of anaesthesia in foals. Further studies are warranted to understand the effects of ketofol especially in comparison to ketamine‐benzodiazepine combinations.