Evaluation of poor performance in competition horses: A musculoskeletal perspective. Part 1: Clinical assessment

Lack of willingness to go forward freely, lack of power, shortened steps, stiffness of the cervical or thoracolumbosacral regions are common nonspecific signs of musculoskeletal causes of poor performance in sports horses. Understanding musculoskeletal causes of poor performance requires knowledge of how normal horses move, the requirements of specific work disciplines, the nomenclature used by riders to describe how a horse is performing and the interactions between horses and riders. Determining the underlying causes needs an in‐depth history and clinical assessment, including in hand, on the lunge and ridden. Ridden exercise should include all aspects with which the rider is experiencing problems. Change of the rider can sometimes help to differentiate between horse and rider problems, but most normal horses are compliant and just because a horse goes better for a more skilled rider does not preclude an underlying pain‐related condition. Lungeing and ridden exercise should include not only trot but also transitions and canter which may highlight gait abnormalities not seen at trot. An accurate history combined with thorough clinical examination of the whole horse should permit the establishment of a list of problems requiring further investigation.     

Idiopathic hopping‐like forelimb lameness syndrome in ridden horses: 46 horses (2002–2014)

There has been no analysis of a hopping‐type forelimb lameness syndrome seen in ridden horses. The objectives of this retrospective study were to describe the clinical features of this syndrome, response to diagnostic analgesia and imaging findings and to document post mortem findings. Clinical records from 2002 to 2014 were reviewed and data concerning signalment, history, lame limb(s), lameness characteristics, response to diagnostic analgesia and diagnostic imaging were recorded. There were 46 horses from 4 to 13 years of age, 6 of which had a history of known or suspected trauma immediately before the onset of reduced performance or lameness. Lameness seen when ridden was characterised by an intermittent shortened cranial phase of the step of the lame forelimb at the trot and marked elevation of the head as the affected limb was protracted, with the horse appearing to ‘hop’ (on the contralateral limb) as if trying to break to canter. When lameness was at its worst horses were unwilling to trot. Three horses showed sporadic severe stumbling. Local analgesia of the affected limb did not improve the lameness and in 16 horses lameness deteriorated. Three of 5 horses showed some improvement (≥2/8 grades) in the hopping‐type lameness after intra‐articular analgesia of the articular process joints of the sixth and seventh cervical vertebrae, ipsilateral to the lame forelimb. Radiographic, ultrasonographic and nuclear scintigraphic examinations were inconclusive. Two of 4 horses responded to treatment with gabapentin. In 3 horses post mortem examination revealed mild lymphocytic inflammation within or around the dorsal root ganglia of the fifth and sixth cervical nerve roots, sixth cervical nerve root or second thoracic nerve root ipsilateral to the lame limb. Idiopathic hopping‐type lameness syndrome in ridden horses may be a pain‐related condition ± a neurological component and currently has a guarded prognosis.     

A comparative study of proximal hindlimb flexion in horses: 5 versus 60 seconds

Reasons for performing study: The flexion test is routinely used in lameness and prepurchase examinations. There is no accepted standard for duration of flexion or evidence that interpretation of results would differ with different durations of flexion. Hypothesis: There will be no difference in interpretation of proximal hindlimb flexion for 5 or 60 s. Methods: Video recordings of lameness examinations of 34 client‐owned horses were performed that included: baseline lameness, proximal hindlimb flexion for 60 s, and flexion of the same limb for 5 s. Videos were edited to blind reviewers to the hypothesis being tested. The baseline lameness video from each horse was paired with each flexion to make 2 pairs of videos for each case. Twenty video pairs were repeated to assess intraobserver repeatability. Fifteen experienced equine clinicians were asked to review the baseline lameness video followed by the flexion test and grade the response to flexion as either positive or negative. Potential associations between the duration of flexion and the likelihood of a positive flexion test were evaluated using generalised linear mixed models. A kappa value was calculated to assess the degree of intraobserver agreement on the repeated videos. Significance level was set at P<0.05. Results: Proximal hindlimb flexion of 60 s was more likely to be called positive than flexion of 5 s (P<0.0001), with the likelihood of the same interpretation 74% of the time. The first flexion performed was more likely to be called positive than subsequent flexions (P = 0.029). Intra‐assessor agreement averaged 75% with κ= 0.49. Conclusions: Proximal hindlimb flexion of a limb for 5 s does not yield the same result as flexing a limb for 60 s. Potential relevance: Shorter durations of flexion may be useful for clinicians that have good agreement with flexions of 5 and 60 s.     

Concurrent proximal suspensory desmopathy and injury of the proximal aspect of the accessory ligament of the deep digital flexor tendon in forelimbs or hindlimbs in 19 horses

Clinical features of proximal suspensory desmopathy (PSD) and concurrent injury of the proximal aspect of the accessory ligament of the deep digital flexor tendon (ALDDFT) have not been documented. The objectives were to describe clinical signs and diagnosis. This was a retrospective study. Patient details, lame limb(s), response to diagnostic analgesia, and radiographic and ultrasonographic findings were recorded. PSD and injury of the proximal aspect of the ALDDFT were identified in 19 horses, 14 with forelimb lameness (unilateral 5, bilateral 9) and 5 with hindlimb lameness (unilateral 2, bilateral 3). Localising clinical signs were seen in 7/31 lame limbs (subtle thickening in the region of the ALDDFT [n = 3], pain on palpation of the body of the suspensory ligament (SL) [n = 6], heat in the proximal metacarpal or metatarsal region [n = 2]). Forelimb lameness was abolished by perineural analgesia of the palmar metacarpal (subcarpal) nerves in 17/23 limbs. In the remaining limbs intra‐articular analgesia of the middle carpal joint (n = 2) or an ulnar nerve block (n = 4) were required to eliminate the lameness. Hindlimb lameness was abolished by perineural analgesia of the deep branch of the lateral plantar nerve (n = 2) or local infiltration of the proximal plantar aspect of the metatarsus (n = 3); a tibial nerve block resolved lameness in the remaining 3 limbs. Lesions of the SL and of the ALDDFT were characterised ultrasonographically by enlargement, heterogeneous echogenicity and loss of long linear echoes in longitudinal images. In 3 horses adhesions between the ALDDFT and the SL were identified post mortem. Close apposition of these structures seen ultrasonographically may indicate adhesion formation. It was concluded that the clinical features of PSD and concurrent injury of the ALDDFT are similar to those for PSD alone, highlighting the need for comprehensive and systematic ultrasonographic assessment.     

High-field magnetic resonance imaging investigation of distal border fragments of the navicular bone in horses with foot pain

Reasons for performing study: Distal border fragments of the navicular bone can be seen in lame and nonlame horses and their clinical significance remains open to debate. Objectives: To describe the magnetic resonance imaging (MRI) appearance of distal border fragments and the adjacent navicular bone. To investigate the relationship between fragments and other abnormalities of the navicular bone and the distal sesamoidean impar ligament (DSIL). Methods: Horses were included if pain causing forelimb lameness was localised to the foot and high‐field MR images were acquired. The size and location of distal border fragments were recorded. Abnormalities in the adjacent navicular bone were graded to obtain a fragment grade. A total navicular bone grade was assigned. The DSIL was also graded. A Chi‐squared test was used to test for associations between the presence of a fragment and specific lesions involving the distal border of the navicular bone, the total grade of the navicular bone, and the grade of the DSIL. Results: 427 horses were included and 111 fragments observed. There was a significant association between the presence of a fragment and the total navicular bone grade, osseous cyst‐like lesions, increased number and size of the synovial invaginations of the distal border, increased signal intensity on fat suppressed images and size of distal border entheseophytes. Conclusions: There is an association between distal border fragments and other pathological MRI abnormalities of the navicular bone. Potential relevance: Distal border fragments are part of navicular disease, but their contribution to pain and lameness remains to be clarified.     

Clinical features and diagnosis of sacroiliac joint region pain in 296 horses: 2004–2014

There has been no large‐scale study of the clinical signs of sacroiliac (SI) joint region pain and its association with lameness and/or thoracolumbar pain. Horses with a positive response to infiltration of local anaesthetic solution around the SI joint regions (SI block) and/or abnormal radiopharmaceutical uptake (RU) in the region of the SI joints were included. History, clinical signs, diagnostic imaging findings, response to SI block, and concurrent lameness and/or thoracolumbar pain were recorded. Horses (n = 296) were divided into 2 groups: SI joint region pain only (Group 1, n = 43) and SI joint region pain and concurrent source(s) of pain (Group 2, n = 253). Clinical signs in Group 1 included increased tension in the longissimus dorsi muscles (40%), restricted flexibility of the thoracolumbar region (44%), trunk stiffness during exercise (61%) and poor hindlimb impulsion (56%). When ridden 65% had a poor contact with the bit, in 81% canter quality was worse than trot, and 35% bucked or kicked out with a hindlimb during canter. In both Groups 1 and 2 clinical signs were seen in a significantly greater proportion of horses during ridden work than lungeing (P<0.0001). Following SI block, 98% of horses showed dramatic improvement in clinical signs, including greater overall movement through the trunk, increased hindlimb impulsion and better quality canter. Abnormal RU in the SI joint regions was seen in 85/180 (47%) horses. Of horses with a positive response to SI block that underwent scintigraphy, only 43% had abnormal RU. Per rectum ultrasonographic examination of the SI joint region revealed abnormalities in 41/129 (32%) horses. Clinical signs of SI joint region pain are worse when horses are ridden. Sacroiliac joint region diagnostic analgesia is a useful, safe but nonspecific block. Ultrasonography and scintigraphy can provide additional information in some horses, but negative results do not preclude SI joint region pain.     

Review of glucocorticoid therapy in horses. Part 2: Clinical use of systemic glucocorticoids in horses

This article is the second in a review series about the use of glucocorticoids to treat medical and musculoskeletal conditions in horses. This segment in the series summarises reported dosages, methods of administration and the efficacy of glucocorticoids for various systemic diseases in equids. The most common use of systemic glucocorticoids reported in the literature for management and treatment of alterations of the respiratory, integumentary, immune and neurological systems are included.     

Diffusion of contrast medium after four different techniques for analgesia of the proximal metacarpal region: an in vivo and in vitro study

Reasons for performing study: There is limited information on potential diffusion of local anaesthetic solution after various diagnostic analgesic techniques of the proximal metacarpal region. Objective: To document potential distribution of local anaesthetic solution following 4 techniques used for diagnostic analgesia of the proximal metacarpal region. Methods: Radiodense contrast medium was injected around the lateral palmar or medial and lateral palmar metacarpal nerves in 8 mature horses, using 4 different techniques. Radiographs were obtained 0, 10 and 20 min after injection and were analysed subjectively. A mixture of radiodense contrast medium and methylene blue was injected into 4 cadaver limbs; the location of the contrast medium and dye was determined by radiography and dissection. Results: Following perineural injection of the palmar metacarpal nerves, most of the contrast medium was distributed in an elongated pattern axial to the second and fourth metacarpal bones. The carpometacarpal joint was inadvertently penetrated in 4/8 limbs after injections of the palmar metacarpal nerves from medial and lateral approaches, and in 1/8 limbs when both injections were performed from the lateral approach. Following perineural injection of the lateral palmar nerve using a lateral approach, the contrast medium was diffusely distributed in all but one limb, in which the carpal sheath was inadvertently penetrated. In 5/8 limbs, following perineural injection of the lateral palmar nerve using a medial approach, the contrast medium diffused proximally to the distal third of the antebrachium. Conclusions and potential relevance: Inadvertent penetration of the carpometacarpal joint is common after perineural injection of the palmar metacarpal nerves, but less so if both palmar metacarpal nerves are injected using a lateral approach. Following injection of the lateral palmar nerve using a medial approach, the entire palmar aspect of the carpus may be desensitised.     

Comparisons of computed tomography, contrast-enhanced computed tomography and standing low-field magnetic resonance imaging in horses with lameness localised to the foot. Part 2: Lesion identification

Reasons for performing study: No previous study compares computed tomography (CT), contrast‐enhanced computed tomography (CECT) and standing low‐field magnetic resonance imaging (LFMRI) to detect lesions in horses with lameness localised to the foot. This study will help clinicians understand the limitations of these techniques. Objectives: To determine if CT, CECT and LFMRI would identify lesions within the distal limb and document discrepancies with lesion distribution and lesion classification. Methods: Lesions in specific structures identified on CT and MR images of feet (31 limbs) from the same horse were reviewed and compared. Distributions of lesions were compared using a Chi‐squared test and techniques analysed using the paired marginal homogeneity test for concordance. Results: Lesions of the deep digital flexor tendon (DDFT) were most common and CT/CECT identified more lesions than LFMRI. Deep digital flexor tendon lesions seen on LFMRI only were frequently distal to the proximal extent of the distal sesamoid and DDFT lesions seen on CT/CECT only were frequently proximal to the distal sesamoid. Lesions identified on LFMRI only were core (23.3%) or splits (43.3%), whereas lesions identified only on CT were abrasions (29.8%), core (15.8%), enlargement (15.8%) or mineralisation (12.3%). Contrast‐enhanced CT improved lesion identification at the DDFT insertion compared to CT and resulted in distal sesamoidean impar ligament and collateral sesamoidean ligament vascular enhancement in 75% of cases. Low‐field MRI and CT/CECT failed to identify soft tissue mineralisation and bone oedema, respectively. Conclusions and potential relevance: Multiple lesions are detected with CT, CECT and LFMRI but there is variability in lesion detection and classification. LFMRI centred only on the podotrochlear apparatus may fail to identify lesions of the pastern or soft tissue mineralisation. Computed tomography may fail to identify DDFT lesions distal to the proximal border of the distal sesamoid.     

Equine placenta – A clinician's perspective. Part 2: Abnormalities

Any insufficiency of the equine placenta has dramatic effects on the developing equine fetus. Placental abnormalities, such as the separation of the chorioallantois from the maternal endometrium or torsion of the umbilical cord, lead to fetal demise, premature labour or abortion. These conditions are each associated with characteristic lesions on the equine placenta, which can be found during a detailed examination. These findings can be very helpful for diagnosing problems and implementing appropriate treatments for mares and affected newborn foals. Furthermore, the retention of the entire placenta or any small fragment thereof can cause metritis, laminitis and sepsis. The prompt diagnosis and aggressive treatment of this condition is necessary to save the mare from becoming seriously ill. Therefore, a thorough evaluation of the equine placenta is a crucial element of the post partum evaluation of every brood mare.     

Patterns of scintigraphic uptake in the fetlock joint of Thoroughbred racehorses and the effect of increased radiopharmaceutical uptake in the distal metacarpal/tarsal condyle on performance

Reasons for performing study: The effect of palmar osteochondral disease lesions on performance of Thoroughbred (TB) racehorses is unclear. There is a need to describe patterns of radiopharmaceutical uptake (IRU) in fetlock joints of TB racehorses and to evaluate post scintigraphy performance. Hypotheses: IRU in the metacarpal (MC) and metatarsal (MT) condyles is more common than IRU in the parasagittal grooves and is associated with poorer post diagnosis performance than controls. Methods: Location of IRU within the fetlock region was identified and graded subjectively in TB racehorses. Performance variables were determined from race records for horses with moderate/marked MC/MT condylar IRU (cases), other horses undergoing scintigraphy (scintigraphy controls) and age/sex matched controls from the last race in which a case participated (controls). Statistical analyses included quantile regression, Fisher's exact test, Kaplan‐Meier survival curves, log‐rank test and Cox regression. Results: Metacarpal/MT condylar IRU was identified in 103/220 horses with only 3/220 having parasagittal IRU. Moderate/marked IRU was identified in the MC and MT condylar regions in 62 and 39 horses, respectively, with palmaromedial and plantarolateral IRU most common. Fore‐ and hindlimb cases had fewer starts, reduced earnings (P<0.001) and reduced earnings/start than controls respectively. Cases were more likely to return to racing later than controls following a rest period. Cases were older than scintigraphy controls. Conclusions: In TB racehorses presenting for lameness MC/MT condylar IRU is the most common abnormality identified within the fetlock joint. Racehorses with moderate/marked condylar IRU have a shortened racing career, are less successful than age/sex matched controls and are older than other racehorses presented for scintigraphy. Potential relevance: Overload of the MC/MT condyles is a common and significant problem in TB racehorses that is readily identified with scintigraphy. Scintigraphy of horses that are lame or performing poorly is less useful for screening for potential condylar fractures.     

Recognition and quantification of pain in horses: A tutorial review

Pain management is dependent on the quality of the pain evaluation. Ideally, pain evaluation is objective, pain‐specific and easily incorporated into a busy equine clinic. This paper reviews the existing knowledge base regarding the identification and quantification of pain in horses. Behavioural indicators of pain in horses in the context of normal equine behaviour, as well as various physiological parameters potentially useful for pain evaluation, are discussed. Areas where knowledge is sparse are identified and a new equine pain scale based on results from all reviewed papers is proposed. Finally, the most important considerations in relation to the implementation of a pain scale in a hospital setting are discussed.     

A cross-sectional study of geriatric horses in the United Kingdom. Part 2: Health care and disease

Reasons for performing study: Geriatric horses (aged ≥15 years) represent a substantial proportion of the equine population, yet very few studies have investigated the prevalence of diseases within the UK equine geriatric population. Objectives: To describe the provision of routine preventive health care measures, prevalence of clinical signs of disease and the prevalence of owner reported diseases. Additionally, the effect of increasing age on the provision of preventive health care and the presence or absence of clinical signs and disease was assessed. Methods: A cross‐sectional study was conducted, surveying a randomly selected sample of veterinary registered owners with horses aged ≥15 years, using a self‐administered postal questionnaire. Results: As geriatric horses increased in age, there was a reduction in the provision of preventive health care measures, such as vaccination, farrier care and routine veterinary checks. Only 68.7% of horses had received a routine veterinary visit within the previous 12 months. Owners frequently observed clinical signs in their animals, with 77% reporting at least one clinical sign of disease. Increasing age was associated with increased reporting of many clinical signs of disease. Over half (58%) of horses had at least one episode of disease within the previous 12 months, yet only 31% of owners reported that their animal currently suffered from a known disease or disorder. Conclusions and potential relevance: Although owners frequently observed clinical signs in their aged horse, there may be incorrect or under recognition of many diseases and health problems. Reduced frequency of routine preventive health care measures, along with suboptimal owner recognition of health and welfare problems may lead to compromised welfare in the geriatric population.     

Retrospective study of palmar/plantar annular ligament injury in 71 horses: 2001-2006

REASON FOR PERFORMING STUDY: Constriction of the digital flexor tendon sheath (DFTS) and its contents by the palmar/plantar annular ligament (PAL) is well recognised. However, primary injury of the PAL has not been well documented. OBJECTIVES: To describe the clinical features of PAL injury, determine its prevalence with or without subcutaneous fibrosis and/or concurrent injury within the DFTS, and assess response to treatment. METHODS: Horses were selected for inclusion based upon clinical features consistent with PAL injury and the presence of a thickened PAL (> or =2 mm) verified ultrasonographically. A retrospective analysis of case records from 3 clinics was performed. Details of breed, age and use, and results of clinical and ultrasonographic assessments and response to treatment were recorded. Horses were treated conservatively or surgically by desmotomy of the PAL, with or without tenoscopic evaluation of the DFTS. A telephone questionnaire was performed to assess response to treatment. RESULTS: Seventy-one horses were included in the study and middle aged or older general purpose riding horses predominated. PAL desmopathy occurred more frequently in hind- than in forelimbs. The method of treatment, thickness of the PAL or presence of subcutaneous fibrosis did not significantly affect prognosis; however, <50% of horses were able to return to athletic function. There was a trend for horses with PAL desmopathy alone to have the best outcome. Bilateral thickening of the PAL or concurrent fore- and hindlimb injuries had a negative effect on prognosis, as did the simultaneous presence of subcutaneous fibrosis and lesions within the DFTS. CONCLUSIONS AND CLINICAL RELEVANCE: PAL injury is characterised by a convex contour of the palmar/plantar aspect of the fetlock, associated with thickening of the ligament with or without subcutaneous fibrosis. Bilateral PAL thickening is common in older horses, ponies and cobs; however, bilateral PAL enlargement is often present with only unilateral lameness. Treatment methods used in this study did not appear to influence outcome significantly.     

Undesired behaviour in horses: A review of their development,prevention, management and association with welfare

Undesired behaviours are a common problem amongst leisure and sporting horses in the UK and have a significant impact on the work of equine practitioners. In most cases, behaviours considered aberrant by owners are normal responses for their horses. Behaviours perceived as ‘naughtiness’ may in fact signify direct actions to avoid pain‐ or fear‐inducing stimuli. Examples that practitioners might deal with include trailer loading problems, avoidance of having saddlery equipment applied or reluctance to leave the yard. Even where no evidence of physical problems or pain can be detected, avoidance behaviours may reflect learnt responses that previously led to success in evading unpleasant consequences. Because owners often misunderstand the reason for such behaviours to develop in their horses, attempts at resolution often involve suppression or punishment based approaches. Although repeated subjugation of undesirable responses may ultimately appear to resolve the overt behavioural problem in some cases, in many others it can lead to a worsening of the problem, the development of alternative avoidance strategies or the horse learning that escaping the source of its pain or anxiety is impossible and ceasing to respond. Some horses develop abnormal or repetitive behaviours, which are not in the ‘normal’ behavioural repertoire. These stereotypic behaviours, sometimes termed ‘vices’, can indicate strategies to cope with a suboptimal environment. Indeed, their performance may serve to improve the situation for the animal. Attempts to suppress or prevent horses showing stereotypies, therefore, will generally exacerbate the underlying welfare problem. When dealing with either stereotypies or avoidance behaviours, it is important to recognise the role of learning in their development and maintenance. Resolution involves both understanding the underlying motivation for showing the behaviour and how it has become reinforced and established over time, for each individual case. The use of environmental change and/or behavioural modification techniques that are both successful and welfare compatible, are important in dealing with undesired behaviour in horses and selection of suitable professionals for referral an important responsibility for the equine practitioner.