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Preventing laminitis in the contralateral limb of horses with nonweight-bearing lameness
Abstract
Laminitis will occur in the contralateral limb in horses with fore or hindlimb unilateral nonweight-bearing lameness. To prevent this the weight-bearing foot should be mechanically supported in a way that preserves laminar perfusion during full loading. This goal is achieved by (1) raising the heels and moving the functional breakover point back so that the horse preferentially stands with a P3 palmar angle of 20°, and (2) providing arch support. The support device should be applied as soon as possible after injury.
... Supporting limb laminitis is believed to be primarily an ischemic event, wherein the constant pull of the DDFT on the distal phalanx is transmitted across the dorsal lamellar bond to the dorsal hoof wall for as long as the limb remains fully loaded. Digital venography performed while the healthy foot is fully loaded shows a reduction or even absence of filling in the dorsal lamellar vasculature and a resumption of normal vascular fill when the foot is unloaded [11]. In some cases of supporting limb laminitis, systemic factors may also be involved, such as the stress associated with severe injury and hospitalization, and a defective gut barrier associated with medications the horse may be receiving for its primary condition. ...
... And now recent research into the developmental or prodromal phase of laminitis suggests that, at least in the carbohydrate-overload [23] and black-walnut models [18], it all starts with up regulation of genes that code for inflammatory cytokines and chemokines. Supporting limb laminitis further suggests that mechanical overload may play a pivotal role in some situations [11]. In addition, in vitro studies have shown that the lamellar bond can fail even in the absence of basement membrane pathology when the glucose supply is inadequate [24]. ...
... All the elements outside the system that have the potential to affect all or part of the system. ü via gut-derived vasoactive amines [17], platelet aggregation [40], and with chronic intake insulin resistance [41] ü via gut-derived bacterial exotoxins [31] and possibly also preformed MMP-2 [6] ü trigger(s) unknown but probably hindgut bacterial elements [16,31] Black walnut heartwood ü toxic principle(s) unknown, may simply be inflammatory cytokines [18] ü MMP-9 upregulated [18] ü inflammatory mediators triggered by toxic principle(s) [18] Supporting limb laminitis ü constant tension in DDFT reduces BF in lamellar dermis [11] ? probable, secondary to ischemia ? ...
Systems theory is a way of describing complex and dynamic relationships. I applied systems theory to the structure and function of the equine foot in an effort to better understand laminitis and, in so doing, reconcile the various theories of its etiopathogenesis and find more universally effective preventive and therapeutic strategies. The foot is described as an open system, and its inherent vulnerabilities are explored. Cascade failure is discussed as a potentially unifying theory of laminitis. The fundamental failure in laminitis is failure of the lamellar dermal-epidermal bond, but that endpoint can be reached via vascular, enzymatic, inflammatory, or mechanical mechanisms, or any combination thereof. Inflammation is discussed as a common denominator, making anti-inflammatory therapy of greater importance than just pain management. Multimodal anti-inflammatory therapy is discussed, including selective COX-2 inhibitors, heparin, nutraceuticals, and inhibitors of MMPs. Multimodal analgesic therapy also is important and may include NSAIDs, opiates, epidural analgesics, physical therapy, relief of weight bearing, diligent nursing care, deep digital flexor tenotomy, and case-appropriate trimming and shoeing. Preventing laminitis still comes down to risk management: knowing the risk factors applicable to an individual horse and adjusting the management accordingly. Examples include weight management and control of carbohydrate intake in overweight horses and ponies, the use of pergolide in patients with PPID, and distal limb cryotherapy in high-risk patients. It is anticipated that application of molecular biological techniques will further advance treatment and prevention of laminitis.
... We've known for some time that, when the foot is fully loaded, vascular filling in the lamellar dermis is substantially decreased or even absent in angiographic studies (Redden 2004;van Eps et al. 2010). But recently, computer-generated models using computed tomography of the distal limb under load have revealed some further, and even surprising, insights into this phenomenon: occlusion of the palmar/plantar digital arteries occurs at various levels, including sites proximal to the coronary band, depending on the intensity of load (van Eps et al. 2010). ...
... It has been proposed that the deep digital flexor tendon (DDFT) causes occlusion of the vessels in the dorsal lamellar dermis via its pull on the distal or third phalanx (P3) and thus on the SADP (Redden 2004). In support of that theory, Redden reported a SLL incidence of only 2.3% (2 of 85 horses) with the pre-emptive use of his 18-degree heel wedge and toe cuff system (Redden 2004). ...
... It has been proposed that the deep digital flexor tendon (DDFT) causes occlusion of the vessels in the dorsal lamellar dermis via its pull on the distal or third phalanx (P3) and thus on the SADP (Redden 2004). In support of that theory, Redden reported a SLL incidence of only 2.3% (2 of 85 horses) with the pre-emptive use of his 18-degree heel wedge and toe cuff system (Redden 2004). However, the aforementioned models of limb loading clearly show that arterial occlusion does indeed involve the DDFT, but it occurs both more proximally and more directly than previously thought. ...
Despite how far we’ve come with laminitis research, there are still some gaps in our understanding of this destructive disease. Supporting limb laminitis (SLL) is a veritable dark corner when it comes to our goal of fully elucidating the pathogenesis and thus the prevention of all forms and presentations of laminitis. We do know that SLL occurs in the foot of the contralateral or supporting limb in horses with a severe, unilateral lameness that persists for more than a couple of weeks. So, clearly mechanical load or overload is a primary factor in its pathogenesis.
But why? The equine hoof wall has been said to be “overengineered,” given that during normal locomotion the stratum medium experiences only one-tenth of the compressive force required to cause its structural failure. The highly adapted dermal-epidermal connection which anchors the hoof wall to the distal phalanx—now termed the suspensory apparatus of the distal phalanx, or SADP—may be similarly described. The surface area of the SADP in the average-size hoof is calculated to be about 0.8 m sq, which is about 8.6 ft sq. At the gallop, the hoof wall and the SADP withstand compressive and distractive forces of up to 3 times the horse’s body weight without sustaining any apparent damage.
So, why does the mere act of standing around cause the SADP to fail? And why does it fail in only some horses with severe, unilateral lameness (reportedly less than 20% of at-risk horses)? Why does it typically not appear until weeks or months after the injury or infection which caused the primary lameness? And why don’t we see it as commonly in foals and yearlings as in adults? If we can answer just these four questions, then we will have a much better understanding of both the pathogenesis of this devastating complication and its prevention.
... Once initiated, this form of laminitis tends to progress to severe and widespread lamellar failure, resulting in downward displacement of the distal phalanx within the hoof capsule [4], which carries a poor prognosis [5]. In horses with painful unilateral limb injuries, supporting limb laminitis has an estimated incidence of between 10 and 27% [6][7][8], with an estimated mortality rate of greater than 50% [9]. Despite the identification of risk factors such as duration of treatment for the primary condition and body weight [8], the occurrence of supporting limb laminitis remains unpredictable. ...
... Instead, increased periods of uninterrupted weightbearing (decreased load cycling) may disrupt lamellar tissue homeostasis, particularly by interfering with normal blood perfusion and therefore energy supply [9][10][11][12]. It has been proposed that intermittent unloading (limb load cycling) of the foot is required for adequate digital perfusion [6]. Since lamellar tissue appears to consume glucose at a high rate [13] and glucose deprivation in vitro leads to lamellar failure [14], hypoperfusion and local tissue negative energy balance may be important contributors to supporting limb laminitis. ...
... Interestingly, when pedometer counts were significantly lower than baseline and close to zero counts/min, a significant change in energy metabolite concentrations and urea clearance compared with baseline was not observed. This appears to contradict the hypotheses that compromised lamellar blood flow occurs secondary to decreased load cycling [9] and that intermittent unloading (limb load cycling) of the equine foot is required for adequate blood flow through the digit [6,16]. However, detomidine (an α2-adrenergic agonist) has dramatic cardiovascular effects in the horse [24], including the induction of a transient, but severe, systemic hypertension [24,25]. ...
Reasons for performing studyLamellar perfusion is thought to be affected by weightbearing and limb load cycling; this may be critical in the development of supporting limb laminitis. Objectives
To document the effects of unilateral weightbearing and altered limb load cycling on lamellar energy metabolism and perfusion. Study designRandomised, controlled (within subject), experimental trial. Methods
Nine Standardbred horses were instrumented with microdialysis probes in the foot lamellar tissue and skin (over the tail base). Urea (20mmol/l) was added to the perfusate. Samples were collected every 15min for a 1h control period, then during periods of unilateral weightbearing (opposite limb held off the ground for 1h); enhanced static limb load cycling (instrumented limb lifted every 10s for 30min); reduced limb load cycling activity (i.v. detomidine sedation) and continuous walking (30min). Dialysate concentrations of glucose, lactate, pyruvate and urea were measured and lactate:glucose (L:G) and lactate:pyruvate (L:P) ratios were calculated. For each intervention, values were compared with baseline using nonparametric statistical testing. ResultsLamellar dialysate glucose increased and L:G decreased significantly during enhanced static limb load cycling. Glucose and pyruvate increased, and L:G, L:P and urea decreased significantly during walking. Simultaneous skin dialysate values did not change significantly. There were no significant dialysate changes during unilateral weightbearing or after detomidine administration, but only the latter resulted in a significant decrease in limb load cycling frequency. Conclusions
Increases in limb load cycling frequency (particularly walking) caused dialysate changes consistent with increased lamellar perfusion. Unilateral weightbearing (1h) and a sedation-induced reduction in limb load cycling frequency did not have a detectable effect on lamellar perfusion. More research is needed to confirm the role of hypoperfusion in supporting limb laminitis, but strategies to increase limb load cycling may be important for prevention.
... We have known for some time that, when the foot is fully loaded, vascular filling in the lamellar dermis is significantly decreased or even absent using angiographic studies as the basis for this conclusion [2,4]. More importantly, computer-generated models using computed tomography (CT) of the distal limb under load have revealed some further, and even surprising, insights into this phenomenon: occlusion of the palmar/plantar digital arteries occurs at various levels, including sites proximal to the coronary band, depending on the intensity of load [4]. ...
... It has been proposed that the deep digital flexor tendon (DDFT) causes obstruction of the vessels in the dorsal lamellar dermis by its pull on the third phalanx (P3) and therefore on the SADP [2]. In support of this theory, Redden reported a SLL incidence of only 2.3% (2 of 85 horses) with the prophylactic use of an 18°heel wedge and toe cuff system [2]. ...
... It has been proposed that the deep digital flexor tendon (DDFT) causes obstruction of the vessels in the dorsal lamellar dermis by its pull on the third phalanx (P3) and therefore on the SADP [2]. In support of this theory, Redden reported a SLL incidence of only 2.3% (2 of 85 horses) with the prophylactic use of an 18°heel wedge and toe cuff system [2]. However, the aforementioned models of limb loading, clearly shows that arterial occlusion does indeed involve the DDFT, but it occurs more proximally and more directly than previously believed. ...
... Painful conditions such as complete fractures, osteoarthritis, severe wounds or sepsis of synovial structures are most often clinically associated with developing support limb laminitis, but it may also occur with any condition that causes prolonged unilateral weightbearing, including neurological deficits or mechanical lameness (Baxter and Morrison 2009). In the authors' experience, support limb laminitis occurs more frequently than previously reported (Peloso et al. 1996;Redden 2004;Richardson 2008) and is a substantial risk when managing surgical cases that develop severe unilateral lameness. ...
... Given the degree of drastic lamellar separation typically observed with support limb laminitis and weightbearing capacity of the suspensory apparatus of the distal phalanx (reportedly up to 3 times the horse's weight), some authors consider a direct mechanical overload to be an unlikely aetiology (Van Eps et al. 2010). The cyclic loading and unloading of the foot is thought to be integral in maintaining adequate perfusion to the digital lamellae and it has been proposed that the reduction in the frequency of this cyclic loading predisposes and potentially initiates, support limb laminitis (Redden 2004;Van Eps et al. 2010). ...
... J. ( -3306.2011 laminitis (Redden 2004;Baxter and Morrison 2009;Van Eps et al. 2010). Peloso et al. (1996) confirmed in a case-control study of 20 horses that the duration of unilateral lameness was positively associated with the risk of developing laminitis but other factors including bodyweight, age, breed, limb affected, heart rate and temperature at admission, clinicopathological tests or casting were not significantly associated with a greater risk of support limb laminitis (Peloso et al. 1996). ...
To determine the incidence of support limb laminitis among horses treated with half limb, full limb or transfixation pin casts and determine potential risk factors.
Medical records of 113 horses treated with half limb, full limb or transfixation pin casts at an equine referral hospital from 2000 to 2009 were reviewed. Associations between potential risk factors and development of support limb laminitis were evaluated by bivariable and multivariable logistic regression analyses.
Of the 113 horses that received casts, 14 (12%) developed confirmed support limb laminitis. The bodyweight of the horse and duration of casting in weeks were significantly associated with support limb laminitis. Horses requiring full limb casts or transfixation pin casts were more likely to develop this complication than horses requiring half limb casts. There were no significant associations between developing support limb laminitis and weightbearing capacity on presentation to the hospital, the limb affected (fore- or hind), whether there was a fracture present or breed of horse.
Support limb laminitis is a relatively common complication among horses treated with half limb, full limb and transfixation pin casts. Greater durations of casting and higher bodyweights increase the likelihood of developing this complication.
Support limb laminitis may occur secondary to any painful unilateral lameness and is not necessarily more likely to develop in horses with severe orthopaedic conditions such as fractures. However, heavier horses, those requiring casts for longer periods of time and those that require a full limb or transfixation pin cast as opposed to a half limb cast should be considered to have an increased risk for developing support limb laminitis post operatively.
... A tool to support this redistributed weight is much needed to prevent complications such as SLL and muscle wasting. SLL may be more painful than the initial injury (van Eps et al. 2010;Virgin et al. 2011), causing the horse to transfer weight back to the injured limb; due to a poor prognosis after the development of SLL, euthanasia may become necessary (Redden 2004;van Eps et al. 2010). The mortality rate following the onset of SLL is reported to be between 50% and 75% (Gardner et al. 2017). ...
... Current SLL preventative techniques are focused on increasing blood flow, encouraging movement and the periodic cyclic loading and unloading of the supporting limbs (Belknap and Durham 2017). Redden (2004) suggested that even slight weightbearing and movement around the stall may significantly reduce the development of SLL. Similarly, shifting of weight may be sufficient to reduce the risk of SLL; healthy horses have been shown to shift weight between the forelegs one to five times per minute, aiding in blood flow to the foot (Baxter and Morrison 2009;van Eps et al. 2010). ...
Equine musculoskeletal injuries, or other causes of reduced movement, can have a poor prognosis partially due to the secondary complications that may develop during recovery or rehabilitation. These can include supporting limb laminitis due to excessive weightbearing on healthy limbs and also problems associated with ventilation or perfusion due to prolonged recumbency. The risk of these complications is reported to increase with increasing body weight. While many methods have been attempted to reduce load and prevent complications, there is no current standard practice when managing horses with ambulatory difficulties. One critical consideration with load reduction devices is maintaining sufficient mobility to allow for blood flow and the prevention of muscle wasting. One of the most challenging obstacles with any weight reduction method or device is preventing pressure sores/ulcers or other tissue trauma because load is redistributed away from the limbs and onto regions of the body unaccustomed to weightbearing. Reported methods to aid in recovery and rehabilitation include rescue slings, forced recumbency, flotation tanks, water treadmills and aquatic therapy. While these methods have been successful in some horses, significant complications have also been reported. If too much weight is removed, muscle wasting or osteopenia occurs; conversely, if insufficient weight is lifted blood flow is hindered. The optimal load reduction is not known because each individual horse will have different requirements depending on the severity of the injury. The goal would be to restore normal weight distribution on the noninjured limbs, while supporting the weight that would normally be placed on the injured limb.
... The authors also believe that the horse's behavior of self-protection, which was observed since the beginning of treatment, helped to minimize its chances of developing SLL. Horses that are able to relieve weight from the contralateral limb have a lower risk of developing SLL [2,16]. Jackson [11] reported a mare with complete hoof avulsion that was maintained in a sling during 10 h/day to relieve weight from the contralateral limb with no development of SLL. ...
Background: Complete avulsion of the hoof in horses, also known as exungulation, is not a commonly reported injury and usually leads to euthanasia due to the great amount of tissue loss, intense pain, secondary complications, expensive and lengthy treatment. It can involve deep structures and cause different complications leading to chronic lameness. In stallions affected by such injury, the reproductive tract and performance may also be affected. The aim of this study was to report a case of complete avulsion of the right front hoof in a Criollo stallion and subsequent bilateral testicular degeneration. Case: A 10-year-old Criollo stallion was referred to the Veterinary Clinical Hospital of the Federal University of Pelotas (HCV-UFPel) with a complete avulsion of the left front hoof. At admission, the stallion had clinical parameters compatible with intense pain and blood loss. Evaluation of the wound demonstrated that the distal end of the third phalanx (P3) was exposed but no fracture was detected on radiological evaluation. No other structure was apparently affected. Initially, anti-inflammatory (phenylbutazone) and opioid (morphine) was given for pain control and supportive fluid therapy was started to restore hydration. Antibiotic (Sulfamethoxazole with trimethoprim) was administered for 10 days. Continued therapy with phenylbutazone, pentoxifylline, omeprazole and supplementation with methionine, biotin and zinc was also given. Local treatment was carried out by cleaning the wound, applying an antimicrobial ointment and dressing it with a bandage. Wound management was adapted according to the evolution and healing process. The stallion was kept in stall rest during its hospitalization time. In the second month after the injury, accumulation of liquid in the scrotum was observed. Clinical and ultrasound evaluation lead to a presumptive diagnosis of testicular degeneration. The stallion was discharged after three months when the wound was almost healed and the hoof had started to grow. Six month later, a follow up by the referring vet showed that the hoof was almost completely grown and the x-ray assessment demonstrated a dorsal rotation and resorption of the distal end of the third phalanx. Discussion: The stallion of this report had a complete avulsion of the hoof capsule caused by trauma. Conservative treatment was established including wound cleaning and dressing to avoid contamination, control of pain and inflammation, antimicrobial care and supplementation to support hoof growth. Time period for wound healing and hoof growth was in agreement with other cases described previously. Bone sequestrum of the distal end of the third phalanx, and detachment of a fragment were observed in this case, followed by bone resorption. The stallion was closely monitored to prevent laminitis in the contralateral limb and no alterations were detected during the treatment period. Testicular degeneration was observed, probably caused as a consequence of hoof avulsion and due to a long period of stall rest. Degenerative alterations in testicles interfere with thermoregulation and spermatogenesis, affecting semen quality and reproductive performance. Rotation of the third phalanx was also observed six months later caused by the hoof loss. In conclusion, the patient of this report had a complete regrowth of the hoof capsule although a long intensive treatment was necessary to achieve this result. As a consequence, testicles degeneration may happen impairing its function as a stallion.
... Mediolateral imbalance was noticed in donkeys only (2.2% of total hoof affected animals). Moyer and Anderson (1975-a and b) and Redden (2004) attributed that to the inferior care to this breed, faulty trimming and shoeing of the hoof, toe-in, or sheared heel. ...
This study was conducted on 1178 lamed animals of equine species. Cases were classified according to the species, affected part of the foot, and nature of the affection. Hoof affections represented in about 722 animals with 61.3 % of total lame animals. The percentages of hoof affections were higher in forefeet than hind feet. The present study revealed that sandy cracks, toe-in and long toe were the predominant hoof wall affections. The corn was the highest sole affections followed by white line disease and the lowest percentages were flat foot and bruised sole. The highest affection percentage in frog was thrush followed by picked up nail and the lowest was in under run heel.
... In humans, alterations in blood flow resulting in stasis have been shown to lead to venous inflammation and platelet activation [151]. In horses, cyclical loading and unloading plays a role in promoting blood flow through the digit [152], so if there is prolonged weightbearing on one digit with inadequate periods of unloading, then based on what has been demonstrated in humans it has been hypothesised that congestion and slowing of blood flow may occur, with subsequent platelet activation and microthrombi formation, resulting in inadequate perfusion and ischaemia of lamellar tissue [1,149,153,154]. Although largely unrelated to other forms of the disease, this situation does suggest that inadequate vascular perfusion of the lamellar tissues may cause laminitis in the absence of other factors. ...
With the increasing number of studies being published on the different experimental models used to induce and study acute laminitis, the pathophysiological events associated with these various models (i.e. starch overload, oligofructose overload, black walnut extract and hyperinsulinaemia) can be compared more realistically. Within this review, the mechanisms for metabolic vs. inflammatory laminitis are discussed, and the question of how pasture laminitis may fit into any of the proposed mechanisms is addressed.
... According to Peloso et al (34), clinical manifestations of laminitis in the weight-bearing limb may not become apparent until 3 to 6 wk after the onset of severe unilateral lameness, even though lamellar damage in the weight-bearing foot likely begins within hours of constant loading (35). Certainly, prompt resolution of the primary lameness is an essential component of preventing and managing contralateral limb laminitis. ...
We retrospectively reviewed the cases of 15 foals and adult horses in which vancomycin was used, alone or in combination with an aminoglycoside, to treat methicillin-resistant staphylococcal and enterococcal infections. Signalment, presenting complaint, history (including history of treatment for the current complaint), results of bacterial culture and antimicrobial susceptibility testing, treatment, and outcome were reviewed. The average vancomycin dosage was 7.5 mg/kg q8h, administered by intravenous infusion over 30 min. The infection resolved in all 7 horses with soft tissue infections and in 6 of the 8 horses with infections involving a bone or a joint, or both. No adverse effects of vancomycin therapy were noted. Although the number of cases is small, our findings suggest that vancomycin, alone or in combination with an aminoglycoside, is safe and effective for the treatment of resistant staphylococcal and enterococcal infections in horses and foals. However, owing to the importance of staphylococci and enterococci in human medicine and the problems with emerging resistance, we recommend that the use of vancomycin in horses be limited to cases in which culture and susceptibility results clearly indicate that this agent is likely to be effective and in which there is no reasonable alternative.
Laminitis is a medical emergency. It encompasses three distinct forms: sepsis-related laminitis, supporting limb laminitis and endocrinopathic laminitis. The latter is most commonly encountered in equine practice and is associated with hyperinsulinaemia. Regardless of the underlying cause, management of acute laminitis involves treatment of the underlying cause, and providision of analgesia and biomechanical support of the foot.
The chapter provides a comprehensive review of the often overlooked issue of complications that are addressed from recognition, management and avoidance perspectives. The two commonest and most significant outcome limiting issues of infection and supporting limb laminitis are given the most attention. Causes, predisposing factors and risk of surgical site infections precede diagnosis. Antimicrobial use, access and delivery are considered in detail. The pathophysiology of supporting limb laminitis is outlined, and a highly practical approach to identification detailed. Methods of prevention and treatment are considered side by side, and drug doses are provided.
Supporting limb laminitis (SLL) is a relatively frequent complication of painful limb conditions that alter normal weight-bearing patterns in horses. New evidence suggests that a lack of limb load cycling activity (normally associated with ambulation) interferes with normal perfusion of the lamellae in these cases, resulting in ischemia and dysfunction/death of cells critical to the mechanical function of the lamellae. Excessive weight-bearing load drives the progression to overt acute laminitis in the supporting limb. Monitoring and enhancement of limb load cycling activity are key strategies that may lead to successful prevention of SLL by ensuring adequate lamellar perfusion.
Complications are inevitable in any type of surgical intervention. Complications of orthopedic surgery can only be minimized by limiting errors during preparation/planning, intraoperative technique and postoperative management. This chapter presents the definition, risk factors, pathogenesis, prevention, diagnosis, treatment, and expected outcome for the complications associated with equine orthopedic surgery. The complications covered are complications of lag screw fixation, common complications in specific anatomic sites, recovery and postoperative complications, complications secondary to cast immobilization, and complications secondary to cast removal. Proper planning is key to minimizing risk and complications in equine orthopedic surgery. Regardless of the injury, time should be given to accurately assess the patient through a careful physical examination, administration of preoperative medications, and to meticulous surgical planning.
Supporting limb laminitis is the most devastating complication of prolonged unilateral weight bearing. Laminitis in the supporting limb is believed to be caused by mechanical overload, decreased perfusion, and subsequent failure at the lamellar interface. The risk of laminitis in these cases appears to be related to the duration and severity of the lameness in the opposite limb. Frequent examination of the foot at risk is necessary to detect subtle signs of structural failure. Weekly radiographs, and daily palpation of the coronary band and digital pulses, are recommended. To develop an understanding of how to prevent supporting limb laminitis, this chapter first discusses foot perfusion and loading patterns of the foot. In the author's opinion, foot conformation and type should be taken into account when selecting a foot support system to help prevent a supporting limb laminitis. Preventing and managing support limb laminitis requires close monitoring and a proactive, ever‐changing foot support strategy.
Management of severely injured or neurologic horses is challenging, with ambulatory support limited to static lifts and rescue slings. The aim of this study was initial testing and adjustment of a novel computer-integrated dynamic lift system, including measuring effects of increasing weight compensation (i.e. load reduction) and time attached to the lift. This automated system was developed to improve outcomes and reduce complications in horses with ambulatory difficulties, allowing for controlled mobility and varying load carried by the horse with independent front and hind limb support. Two healthy Thoroughbred horses were studied using the Anderson rescue sling. The lift was programmed to respond to weight and movement of horses. Weight compensation (% bodyweight) was incrementally increased, for front and hind limbs, to maximum percent tolerated, based on heart/respiratory rates and behavioural scoring. The time attached to the lift was then incrementally increased at maximum tolerated weight compensation previously determined. Measures included heart/respiratory rates, behavioural scoring, muscle enzyme activity and blood flow to distal limbs. Results were analysed descriptively. Avoidance behaviour was observed at front and hind end weight compensation of 18 and 4%, respectively. Average maximum time attached to the lift was 2.25 hours. After 60 minutes, respiratory rate increased >20 breaths (b)/minute, reaching 60 b/minute in one horse and 36 b/minute in the other, with shallow breathing. Other measures remained normal. In conclusion, lift programming was successful for weight compensation and mobility during lift support. Complications included avoidance behaviour and respiratory distress at >20% weight compensation, likely caused by the Anderson rescue sling. To address these limitations, a new rehabilitation harness better suited for long-term use is under development.
Supporting limb laminitis (SLL) is usually a sequela to the treatment of a primary condition affecting a forelimb or hind limb that results in excessive unilateral weight-bearing. This chapter discusses the clinical presentation, clinical risk factors, clinical signs, and radiographic diagnosis of SLL. The primary factors believed to play a role in the development of SLL are duration and severity of lameness on the contralateral limb. Shifting weight frequently between the injured limb and support limb, or attempts to reduce pressure and pain from the toe by rocking back on the heel of the laminitic foot may be the first clinical signs noted. Radiography is best used to monitor the progression of SLL. Baseline lateral and dorsopalmar/plantar views of the contralateral foot should be obtained early in the treatment period for the primary condition in the opposite limb (prior to SLL).
Most of the preventive measures for supporting limb laminitis (SLL) in horses are based on the following five objectives: provide musculoskeletal and neuropathic analgesia; maintain adequate vascular perfusion of the at-risk digit; provide axial and external support to the at-risk digit; minimize the moment arm around the distal interphalangeal (DIP) joint; and reduce effective bodyweight. The prevention of SLL primarily revolves around two principles: decreasing the forces sustained by the digital lamellae on the supporting limb; and maintaining adequate digital/lamellar perfusion to the overburdened digit when the animal is standing. Techniques used to decrease the forces on the digital lamellae include analgesia, therapeutic shoeing and trimming, management of the environment (e.g., bedding material for foot support and to encourage recumbency), and intermittent slinging to assist the animal to unload the supporting limb.
The digital venogram documents both venous compression and dermal changes resulting from lamellar instability. This chapter presents the procedure to perform the venogram, and discusses the technique errors while performing the evaluation, and the interpretation of results. The venogram should first be performed early during the course of the disease. Prior to removing the horse from its stall, all radiographic, farrier, and medical equipment are gathered and organized. Every attempt is made to reduce trauma to the laminitic patient by quickly and accurately completing the procedure. An inadequate volume of contrast reaching the foot secondary to tourniquet failure is perhaps the most common technique error. A laminitis case that is recognized within hours of onset of clinical signs and treated appropriately may return to use without radiographically recognizable changes of a previous disease. The venogram is key to: diagnosing laminitis within 24 h of the development of clinical signs; and guiding treatment.
With endocrinopathic laminitis, there is no evidence suggesting that platelet activation or microthrombus formation occurs in insulin dysregulation related to either equine metabolic syndrome (EMS) or pituitary pars intermedia dysfunction (PPID). This chapter reviews the normal physiologic processes involved in thrombosis and coagulation (with emphasis on platelets). It discusses the possible involvement of these mechanisms in the pathophysiology of laminitis. Although attention is focused primarily on SRL, endocrinopathic and supporting limb laminitis is also discussed. The role of thrombosis and platelet activation in the pathogenesis of this condition is not clear, but some possible mechanisms will be discussed below. Systemic inflammation and/or sepsis in carbohydrate overload (CHO) models would appear to be the cause of the observed platelet activation, coagulation abnormalities, and microthrombus formation.
Laminitis, a potential problem in all hoofed animals, is the result of a metabolic disturbance that affects the entire animal and is expressed most noticeably in the hoof. Laminitis results when the delicate laminae, which attach the coffin bone to the hoof capsule, become inflamed. This condition can cause severe pain and debilitating lameness in affected animals. Laminitis can be prevented in some cases; therefore, knowledgeable technicians can help educate horse owners about measures that can be taken to protect their animals. Because laminitis is a potential problem in all hoofed animals, technicians who work with equine patients should have an understanding of this condition. "Technicians who are knowledgeable about laminitis can play a key role in identifying this potentially life-threatening condition in their patients," says Debra. Debra, a stay-at-home mom, finds time to teach and volunteer on the Veterinary Support Personnel Network and to write. She lives in Calgary, Alberta, Canada, with her partner, Wayne, and their son, Christopher. The family shares its home with a rosella parakeet, two cats, and, of course, a horse.
The electronic patient records of all equine patients of Rossdales Equine Practice between January 1, 2005 and November 1, 2013 were reviewed to determine the number of cases of supporting limb laminitis (SLL) in a large equine practice and referral hospital setting in the UK and to discuss the implications for future epidemiological studies. The clinical notes were searched electronically for a combination of 'laminitis AND (contralateral OR supporting OR overload OR weight bearing)'. The prevalence of SLL within each identified denominator population and the corresponding 95% CI were calculated. SLL developed in nine horses, one donkey and one pony. Thoroughbreds were the most commonly affected breed (72.7 per cent, CI 46.4 to 99.1 per cent), aged 2-14 years (median six years), and only mares (n=9) and stallions (n=2) were represented. SLL was not restricted to horses that were non-weightbearing lame, it developed within 4-100 days after injury (median 14.5 days) and occurred most commonly in a forelimb (54.6 per cent, CI 25.1 to 84.0 per cent). During the same time frame, a total of 65,327 horses were registered with Rossdales Equine Practice, resulting in an overall practice prevalence of SLL of 0.02 per cent (CI 0.01 to 0.03 per cent). Future epidemiological studies to investigate risk factors for SLL prevention will, therefore, be a logistical challenge.
Failure of lamellar energy metabolism may contribute to the pathophysiology of equine laminitis. Tissue microdialysis has the potential to dynamically monitor lamellar energy balance over time. The objectives of this study were to develop a minimally invasive lamellar microdialysis technique and use it to measure normal lamellar energy metabolite concentrations over 24 h. Microdialysis probes were placed (through the white line) into either the lamellar dermis (LAM) (n = 6) or the sublamellar dermis (SUBLAM) (n = 6) and perfused continuously over a 24 h study period. Probes were placed in the skin dermis (SKIN) for simultaneous comparison to LAM (n = 6). Samples were collected every 2 h and analysed for glucose, lactate, pyruvate, urea and glycerol concentrations. LAM was further compared with SUBLAM by simultaneous placement and sampling in four feet from two horses over 4 h. Horses were monitored for lameness, and either clinically evaluated for 1 month after probe removal (n = 4) or subjected to histological evaluation of the probe site (n = 10).
There were no deleterious clinical effects of probe placement and the histological response was mild. Sample fluid recovery and metabolite concentrations were stable for 24 h. Glucose was lower (and lactate:glucose ratio higher) in LAM compared with SUBLAM and SKIN (P < 0.05). Pyruvate was lower in SUBLAM than SKIN and urea was lower in LAM than SKIN (P < 0.05). These differences suggest lower perfusion and increased glucose consumption in LAM compared with SUBLAM and SKIN. In conclusion, lamellar tissue microdialysis was well tolerated and may be useful for determining the contribution of energy failure in laminitis pathogenesis.
Radiographic studies are an essential component in evaluation of horses with laminitis. The standard radiographs that should be obtained to aid assessment of horses with laminitis are the lateromedial, horizontal dorsopalmar and dorsal 45° proximal palmarodistal oblique views. This article will summarise the assessment of these 3 projections in the laminitic horse as well as discuss the prognostic significance of common radiological abnormalities in horses with laminitis.
A five-week-old American Quarter Horse colt was presented for evaluation of a left hindlimb deformity and lameness. Radiographs of the left hindlimb revealed a varus deformity with recurvatum originating in the mid-diaphysis of the third metatarsal bone. Surgical correction was undertaken by performing an osteotomy through the centre of rotation of angulation located within the mid-diaphysis of the third metatarsal bone, and a four-ring hinged circular external fixator construct was applied. Distraction of the osteotomy site was performed over an 11 day period. Notable complications included failure of a fixation pin, infection of the surgical site, and temporary laxity of the supporting tendons and ligaments of the contralateral metatarsophalangeal joint. The fixator was maintained until there was sufficient bone formation to allow frame removal, 152 days after the initial surgery. Use of a hinged circular construct allowed for partial correction of the deformity with resultant lengthening and resolution of the lameness in this colt.
Systems theory is a way of describing complex and dynamic relationships. We applied systems theory to the structure and function of the equine foot in an effort to better understand laminitis and, in so doing, reconcile the various theories of its etiopathogenesis and find more universally effective preventive and therapeutic strategies. The foot is described as an open system, and its inherent vulnerabilities are explored. Cascade failure is discussed as a potentially unifying theory of laminitis. The fundamental failure in laminitis is failure of the lamellar dermal−epidermal bond, but that endpoint can be reached via vascular, enzymatic, inflammatory, or mechanical mechanisms, or any combination thereof. Inflammation is discussed as a common denominator, making anti-inflammatory therapy of greater importance than just pain management. Multimodal anti-inflammatory therapy is discussed, including selective COX-2 inhibitors, heparin, nutraceuticals, and inhibitors of matrix metalloproteinases (MMPs). Multimodal analgesic therapy also is important and may include nonsteroidal anti-inflammatory drugs (NSAIDs), opiates, epidural analgesics, physical therapy, relief of weight bearing, diligent nursing care, deep digital flexor tenotomy, and case-appropriate trimming and shoeing. Preventing laminitis still comes down to risk management: knowing the risk factors applicable to an individual horse and adjusting the management accordingly. Examples include weight management and control of carbohydrate intake in overweight horses and ponies, the use of pergolide in patients with pituitary pars intermedia dysfunction (PPID), and distal limb cryotherapy in high-risk patients. It is anticipated that application of molecular biologic techniques will further advance treatment and prevention of laminitis.
Transection of the deep digital flexor tendon is a controversial treatment for chronic laminitis largely because of the variation in personal experience with the procedure and the varying success rates reported in the previously published data. Differences in reported success rates are more likely because of the dissimilarities in foot pathology and the foot management associated with the procedure. This report presents 245 tenotomy cases, in which all cases received the same shoeing protocol (realignment shoeing). Outcomes were determined for the following categories: degree of bone disease, solar penetration, sinking, number of limbs involved, and front or hind feet affected. The success rates by different categories of disease may assist the clinician in formulating a prognosis for similar cases.
Laminitis is a disease of the suspensory apparatus of the distal phalanx, which can advance to the chronic stage with varying degrees of structural failure. Because the disease may ultimately lead to mechanical failure of the digit, a foot management plan is required to effectively and mechanically treat these cases. Many laminitis cases can be successfully rehabilitated back to athletic soundness, light use, breeding, or pasture soundness, whereas others suffer from permanent instability and never enjoy an acceptable level of comfort. To understand how to minimize damage in the acute laminitic foot or rehabilitate the chronic laminitic foot, the veterinarian should have an understanding of the normal supporting structures of the digit, the biomechanical forces acting on the foot, and the structural failure that results when these otherwise normal forces act on a diseased, damaged foot.
Clinical diagnostic venography allows in vivo visualization of the digital venous system and the effects of venocompression related to foot load and laminitis pathology. Venography has predictive potential and helps the clinician anticipate and treat laminitis tissue damage before it is detectable by plain radiography. The authors describe the podiatry radiographic technique to correctly perform digital venography and the modifications they have developed. The authors provide guidelines for the interpretation of laminitis venograms in the context of laminitis chronology. Frequent venographic monitoring of laminitis helps clinicians understand the sometimes puzzling chronology of the disease process and improves therapeutic outcome.
Supporting limb laminitis poses a threat to all horses suffering from severe unilateral lameness. Despite its devastating effects, relatively little is known about the precise pathologic processes that lead to its development. This article reviews the potential mechanisms of supporting limb laminitis, and the authors present some preliminary data based on advanced imaging and computer-based modeling techniques aimed at further elucidating the etiology of this unique form of laminitis. Gaining a better understanding of the pathologic processes that lead to supporting limb laminitis is essential to enable the development of appropriate countermeasures to safeguard horses at risk of the disease.
The most common and significant complication of excessive unilateral weight bearing in adult horses is support limb laminitis. Young horses with unilateral lameness problems develop support limb laminitis infrequently compared with adult horses.
The effect of varying the toe angle on strain characteris tics of the deep digital flexor tendon, superficial digital flexor tendon, suspensory ligament, and hoof wall were investi gated. This study was conducted in vitro using limbs recov ered at necropsy and transected 15 cm above the carpus. Hall effect strain sensors and uniaxial strain gages were used to measure tissue strain. Data were averaged by treatment, and means compared using analysis of variance procedures and Tukeys studentized range test. Deep digital flexor tendon strain decreased (P<.05) as toe angle increased from 55° to 78°. Decreases in strain were linear at both sites on the deep digital flexor tendon with increasing toe angle. Strain of the superficial digital flexor tendon and the suspensory ligament were not changed (P>.05) by toe angle. Strain of the extensor branch of the suspensory ligament increased (P<.05) rapidly when toe angle increased. Strain of the hoof wall did not change (P.>05) on the dorsal and lateral sides with increasing toe angle. Medial hoof wall strain increased (P<.05) with the addition of the 23° heel wedge. The data show that strain of the deep digital flexor tendon and extensor branches of the suspensory ligament are affected by toe angle.
The vast majority of equine oral procedures are dental-related and, unless great care is taken, almost all such procedures have the potential to cause marked short- or long-term damage to other oral structures. This review of the more common complications of oral surgery begins at the rostral oral cavity with procedures of the incisors, and then moves caudally to deal with complications related to procedures of wolf teeth and cheek teeth, including salivary duct disruption and dental sinusitis. Finally, complications associated with maxillary and mandibular fractures are discussed.
Case records of 202 horses treated for laminitis were reviewed with the intent of determining the long-term outcome and correlating this with digital radiographic findings and with the degree of pain associated with the laminitis. At long-term follow-up 57 horses had returned to athletic soundness (Group 1), 20 horses were intermittently lame (Group 2), 19 horses had permanent severe lameness (Group 3), 97 were dead (Group 4), and 9 were lost to follow up. Using simple regression analysis, functional outcome did not correlate with the degree of rotation (R2 = 0.004) or the presence of distal displacement (R2 = 0.139). Functional outcome did correlate with the clinical grade of laminitis (R2 = 0.504). Horses in Group 1 had significantly less distal phalangeal rotation (5.89 +/- 6.48 degrees) than did horses in Group 2 (11.10 +/- 8.19) and Group 3 (14.50 +/- 10.80), but were not significantly different from Group 4 horses (7.49 +/- 6.57). Of 96 surviving horses, 23 had evidence of distal displacement compared with 54 of 97 non-survivors. Based on these results, horses that develop distal displacement of the distal phalanx are more likely to die than are horses without distal displacement; however, the presence or absence of distal phalangeal displacement and the degree of distal phalangeal rotation cannot be used to predict the outcome of a horse with laminitis. Clinical assessment is a more reliable means of determining the final outcome and should be given precedence over radiographic findings.
To identify risk factors associated with development of laminitis of the supporting limb in Equidae with unilateral laminitis and to determine the radiographic appearance of this type of laminitis.
Retrospective analysis of medical records.
20 Equidae with unilateral lameness that developed laminitis of the contralateral limb.
Case animals were compared with matched and unmatched populations of control animals that did not develop contralateral limb laminitis. Lateromedial radiographic projections of affected feet were evaluated for evidence of laminitis.
Body weight of case animals was not significantly different from that of control animals, but number of days that control animals were lame prior to recovery was significantly less than number of days that case animals were lame prior to the onset of laminitis. Lateromedial radiographic projections of the foot of the support limb were available for 16 of the 20 case animals. For all 16, thickness of the soft tissue dorsal to the distal phalanx was > 29% of the palmar cortical length of the distal phalanx, but only 1 had evidence of rotation of the distal phalanx. The proportion of case animals that were euthanatized was significantly greater than the proportion of control animals that were euthanatized.
Duration of lameness, but not body weight, was a risk factor for development of laminitis in the contralateral limb in Equidae with unilateral lameness, and animals that developed this complication were more likely to be euthanatized than were animals that did not.
Complications of equine surgery McIlwraith and Turner's Equine Sur-gery—Advanced Techniques
- Mcilwraith Cw
- Robertson
McIlwraith CW, Robertson JT: Complications of equine surgery. In: McIlwraith CW, Turner S, editors: McIlwraith and Turner's Equine Sur-gery—Advanced Techniques. Second ed. Baltimore, MD: Williams and Wilkins, 36-40, 1998
Radiography of the Equine Foot—Techniques for Enhancing the Quality of your Films
- Redden
Redden RF: Radiography of the Equine Foot—Techniques for Enhancing the Quality of your Films. Versailles: Nanric Inc., 1-24,