Assessment Of The Thoroughbred Horse Visimotion Biology Essay

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Born in the USA. Arrived to the UK as a yearling. Raced (Flat) as a two, three, and four year old after which he was retired from racing

Participated in the British Show Jumping Association (BSJA) and British Eventing competitions as a six, seven and eight year old

Privately owned until 1998

INJURIES/ AILMENTS:

History of poor feet with no growth in addition to cracks from the coronary band

To limit the widening of these cracks Bar shoes were used

In August 2000 Visimotion was diagnosed with Laminitis. He was box rested on soft bedding for two weeks with the administration of painkillers. Recovered within two weeks and has restricted access to rich grass

During October 2002 large cracks appeared down both front feet from coronary band and as a result became very lame. He was box rested and staples applied for three months

Recently diagnosed with an injury to the superficial digital flexor (SFDT) on his left hind above the hock

Visi

Table 1 General information and history

Skeletal measurements

Table 2 Skeletal measurements in centimetres and inches

Measured structure

Length (cm)

Length (inches)

Head (A-B)

63.5

25

Back (C-D)

63.5

25

Depth (E-F)

71

28

Stifle - Hock (M-K)

52

20.5

Shoulder (H-G)

52

20.5

Elbow - Fetlock (I-J)

73.5

29

Hock - Ground (K - L)

63.5

25

Height (G - L)

162.5

64

Length (N - O)

163

64.2

Croup Height (P - L)

62

24.4

Thickness of head (Q - U)

29.5

11.6

Attachment of head (U- W)

36.8

14.5

Front of withers - Bottom of Neck (X - Y)

57.2

22.5

Bottom of neck - Throat (Y - U)

50.8

20

Haunch - Point of buttock (D - O)

54.6

21.5

Point of buttock - Stifle (O - M)

58.4

2

Assessment

At rest

C:\Users\qazamel\Desktop\IMGA002601.jpg

Figure Side view of the horse

This horse displays a calm and confident temperament. From the yellow lines in figure1 it can be seen that this horse has a good balance overall with his body being in almost equal proportion. This horse has a broad, full and flat head that is well formed and in proportion with the rest of the body. His ears are medium sized and pointy and are carried alertly. He has big, bright and well placed intelligent eyes. His nostrils are large symmetrical and his teeth meet correctly and are in a relatively reasonable condition. His neck is well carried with a good length being neither too short nor too long. The shoulder is of reasonable length slightly sloping at an angle of 60.1° (ideally would be around 45-50°). The humerus is at a more ideal angle of 114°. His back is broad and symmetrical with a straight spine and a good length which is in proportion to the rest of the horse (Figure 2). The horses' hindquarters seem to be less muscular than his front end. The length between the haunch and point of buttock should be the same as the length between the point of buttock - stifle however, the length between the haunch and point of buttock ends up being a bit on the short flat side meaning that there is not much room for optimal muscle attachment. The length between the stifle joint to the point of hock has a much better length to it allowing for more muscle attachment in that area. The hocks are at a slightly higher level than the knee (purple lines). His front limbs are placed behind the ideal making him very slightly camped under (figure 3). The hind limbs are also camped under making him post legged due to insufficient angle to the hock.

Figure View of the horses' back

Figure Side view of the horseC:\Users\qazamel\Desktop\IMGA002f01.jpg

From behind this horse is base narrow with toe-out conformation (cow hocked) (Figure 4). There is also obvious swelling and heat on palpation of the left hind around and above the hock (Figure 5).C:\Users\qazamel\Desktop\IMGA02406.jpg

Figure Rear view of the horse

Figure Rear view showing swelling

Figure Toe angle of front limb (56°) The Ideal toe angle in the front ranges from 45°-55° (Dyson et al. 2010)

Figure Heel angle of front limb (28°) Heel angle is believed to play an important role in providing palmar support to the foot (Dyson et al. 2010)

C:\Users\qazamel\Desktop\IMGA5544400201.jpgC:\Users\qazamel\Desktop\IMGA00240143.jpg

C:\Users\qazamel\Desktop\IMGA0024014334.jpgC:\Users\qazamel\Desktop\IMGA545500201.jpg

Figure 8 Toe angle of hind limb (65°) The ideal toe angle in the hind limb ranges from 50°-60° (Dyson et al. 2010) high hoof angle are associated with increased strain on the SDFT (Karle et al. 2010; O'Grady and Poupard 2001)

Figure 9 Heel angle of hind limb (23°) low heel angle has been positively associated with musculoskeletal injury (Dyson et al. 2010)

C:\Users\qazamel\Desktop\IMGA0024014.jpgC:\Users\qazamel\Desktop\IMGA54555500201.jpg

Figure The hind foot has a slightly broken forward hoof-pastern axis. This place extra strain on the tendons and ligaments (Myers, 2009)

Figure 10 The front foot has an ideal unbroken hoof-pastern axis

Walk

The horse moves in a straight line with some degree of over tracking. Very slightly lame on the left hind.

Trot

From the front the horse moves in a true straight line with over tracking (causing brushing) and toe first stride landings. From behind the horse move a bit close at the hock due to his toe out conformation. The lameness to the left hind is more pronounced at the trot.

Tendon injury

Injuries to the SDFT are most commonly reported in Thoroughbred racehorses and National Hunt horses but have also been known to afflict Dressage horses as well as Show Jumpers (Ely et al. 2009; Lam et al. 2007; Pinchbeck et al. 2004; Smith and Schramme, 2003; Yamasaki et al. 2001). Injuries to the SDFT therefore are a common cause of high morbidity and wastage in sports horses (Thorpe et al. 2010; Patterson-Kane and Firth 2009; Dowling et al. 2000) and the treatment of such injuries is clinically challenging and with a high risk of re-injury (Crovace et al. 2007; O'Sullivan, 2007).

Through connecting muscle to bone, tendons permit the transmission of forces that are generated by muscle contraction to bone thus making joint movement possible (Sharma and Maffulli, 2005b; Lin et al. 2004; Magnusson et al. 2003; Yamasaki et al. 2001). They also play an important role in limiting muscle damage by absorbing external forces (Sharma and Maffulli, 2005a) and by storing and releasing energy to reduce the energetic cost of locomotion thus making locomotion more efficient (Thorpe et al. 2010; Patterson-Kane and Firth 2009; Dahlgren, 2007; Dudhia et al. 2007; Kasashima et al. 2004; Smith and Schramme, 2003; Yamasaki et al. 2001; Smith et al. 1999). An injury to such a structure would naturally have a long term dramatic effect on the horse. The ability of an injured tendon to store and release energy is greatly reduced and as a result the efficiency of locomotion diminishes forcing the horse to compensate for that injury by working harder on the other side of the body. This places a tremendous amount of stress on the rest of the horses' apparatus thus increasing the risk of further injury.

When tendons are injured, the body goes through a process of healing that is divided into three overlapping phases: acute inflammation, proliferation, and remodelling (Lin et al. 2004; Sharma and Maffulli, 2005b). This process may last anywhere from 10 to 18 months and the healed tendon never regains its original shape and strength leaving the horse prone to re-injury.

Because tendons are known for their slow and fragile healing process, knowledge about the cellular and biochemical events that take place during each of the healing phases is of utmost importance when designing a rehabilitation programme that should be tailored to match the various stages of healing.

The acute inflammatory phase (0-7 days) represents the first phase in process of healing. This period which starts immediately following injury manifests clinically as pain on palpation, oedematous swelling and heat (Spurlock et al. 1999; Dahlgren, 2007; Smith and Schramme, 2003; Kannus 2000 ). Lameness may or may not be present and is not thought to be an indicator of the degree of damage to the tendon but rather the degree of inflammation (Smith and Schramme, 2003).

Inflammation forms an important process in the initial defence against an injury and is mediated by vascular and chemical factors that initiate angiogenesis and promote the migration of phagocytes, leukocytes, defensive molecules and stimulation of tenocyte proliferation to the site of injury through the bloodstream thus promoting the synthesis of type III collagen and regeneration of normal tissue. (McKenzie and Furr, 2001; Lin et al. 2004; Dahlgren, 2007; Sharma and Maffulli, 2005b).

The principle aim for managing this first stage should be quelling the inflammation and limiting the action of proteolytic enzymes that are released inside the tendon by inflammatory cells (neutrophils, macrophages and monocytes) causing further damage to the injured tendon (Smith and Schramme, 2003).

Crypotherapy and Bandaging

The first step in the rehabilitation programme that is recommended is the application of crypotherapy as soon as possible after injury is first noticed. In addition to it being relatively cost effective, non invasive and safe, crypotherapy is also believed to reduce the inflammatory reaction, swelling, and leukocyte-mediated tissue damage (Capps, 2009; Hamilton and Purdam, 2004; Sutton, 2003; Kaneps, 2000) as well as the reduction of the hemorrhage and edema through local vasoconstriction (Sutton, 2003; Ramey, 1999). Hunt (2001) found that the use of crypotherapy resulted in the successful return of 25 out 27 horses to racing. Van Eps et al. (2004) also found crypotherapy to be beneficial in treatment of acute laminitis

There is also some evidence that suggests crypotherapy applied within the first 24-48 hours of injury has an analgesic effect resulting from decreased nerve conduction (Buchner and Schildboeck 2006; Rees et al. 2006; Geytenbeek, 2002; Ramey, 1999).

Petrov et al. (2003) found that the application of crypotherapy for one hour reduced the SDFT core temperature by 21 degrees C to a minimum of around 10 degrees C with no apparent detrimental effect on the variability of tendon cells .

In a study by Pollitt and van Eps (2004), the authors concluded that the continuous application of cold therapy (for 48 hours) resulted in a marked cooling of the treated foot with no significant variation in clinical parameters. However, these studies had these studies had a very low number of horses (n=9) and there are currently no other studies that have been carried out to investigate the application of crypotherapy for long periods in horses. The average recommendation for the use of crypotherapy in human studies is between 30-45 minutes four to six times per day. For those reasons, and in addition to the practicality, it is recommended that crypotherapy be applied for 30 minutes every four to six hours per day.

Crypotherapy should also be used in combination with compression in the form of pressure bandaging which helps to disperse the fluids involved in swelling (Sutton, 2003).

A recent human study investigated the effects of combining cryotherapy with compression on tendon microcirculation and found that crypotherapy in comination with compression significantly decreased capillary blood flow within 20 seconds of application (Knobloch et al. 2006).

Mobilization

Although complete immobilization used to be commonly advocated in rehabilitation programmes, new research has suggested that this may have a detrimental effect on the healing process by increasing the crosslinking of collagen fiber as well as random fiber orientation which in turn increases the time the tendon takes to heal and the strength of the healed tendon (Paulekas and Haussler, 2009; Sharma and Mafulli, 2008; Sharma and Maffulli, 2006; Kannus et al. 2003; Kannus, 2000). Immobilization is also believed to cause tendon atrophy (Scott and Swenson, 2009; Sharma and Maffulli, 2005a; Number 1 pp. 85 book). On the other hand, controlled mobilisation in the form of light physical exercise (walking) is believed to promote the restoration of function and early passive movement of the injured tissues which is believed to help in reducing the inflammation and reduce adhesion formation (Torrie et al. 2010; Haussler, 2009; Sharma and Maffulli, 2008; Mansmann and Long, 2004; Smith and Schramme, 2003) as well as improving fiber alignment which results in higher tensile strength (Sharma and Maffulli, 2005a; Dahlgren, 2007). Gillis et al. (1997) found rehabilitation programmes that kept horses in pasture throughout were much less successful than those keeping horses in a controlled exercise regime in terms of re-injury. Therefore, as well as a controlled exercise programme (table 3) it is recommended that the horse be confined to a stable for at least 150 days after which he can be turned out into a small nursery paddock for one hour a day.

One crucial factor to the successful healing and increasing resistance of the tendon is thought to be the way in which collagen fibrils are aligned along lines of tension. Histological examination of injured tendons shows a random clustering of collagen fibrils during the proliferation phase (Sharma and Maffulli, 2005a) and that these become more organised and align in a parallel fashion during the remodelling phase (Dahlgren, 2007). Another important aspect of the proliferation phase is that collagen DNA concentrations and the production of type III collagen reach their peak during this stage (Sharma and Maffulli, 2005b; Lin et al. 2004). A controlled study on human tendons by Almekinders et al. (1995) found that repetitive motion significantly increased the content of DNA in tenocytes.

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

Even though it is common practice for veterinarians to prescribe NSAIDs such as Phenylbutazone (PBZ) for almost any injury that afflicts the horse in order to reduce inflammation and to provide pain relief, their use is not advised in this case. This recommendation is based on a number of reasons. Firstly, there seems to be an obvious lack of quality research design methods such as randomized, placebo-controlled and double-blinded studies that are needed to provide good scientific evidence for the efficacy of NSAIDs in horses. Secondly, recent studies have found that the use of NSAIDs may compromise the long-term healing of the injured tissue through suppressing proliferation and arresting cell cycle (Mueller et al. 2010; Hertel, 1997) . Almekinders et al. (1995) found that the presence of NSAIDs (Indomethacin) resulted in a reduction in DNA synthesis. Finally, results of many studies found that PBZ is strongly associated with serious adverse effects in humans which eventually lead to a ban of PBZ for human use in the USA (Dodman et al. 2010). In horses, other studies have strongly connected the use of NSAIDs to adverse systemic effects in horses such as gastrointestinal bleeding, and ulcers both in the long term use and short term use (Radi, 2009; Dezfouli et al. 2009; Radi and Khan, 2006; Hertel, 1997).

Ultrasound

The use of ultrasound as a diagnostic tool throughout the rehabilitation programme should not be underestimated. The initial ultrasound test taken after the injury is first recognised help in determining the severity and location of the tendon lesion. Follow up ultrasound exams allow for the accurate assessment of the progress of the injury upon which an informed decision can be made in terms of increasing or reducing workload.

Prognosis

Although most reported rehabilitation programmes are unsatisfactory (mainly due to high percentage of recurrence), this is mainly seen in horses that are involved in high intensity sports such as flat racing or National Hunt horses and to a lesser extent show jumpers and dressage horses

Table Recommended rehabilitation programme (modified from Gillis et al. 1997)

Days

Ultrasound

Crypotherapy

Pressure Bandage

Confinement

Exercise Protocol

0-30

Initial ultrasound exam to be taken when the injury is noticed to assess severity of injury

To be initiated as soon as possible after injury is first noticed. Use Bubble Boots for 30 minutes every four to Six hours

Bandage both hind limbs between Crypotherapy sessions

Stall rest

Hand walk 15 minutes twice daily

30-60

Use Bubble Boots for 20 minutes three times daily

Bandage both hind limbs between Crypotherapy sessions

Stall rest

Hand walk 40 minutes once daily

60-90

Use Bubble Boots for 20 minutes three times daily

Bandage both hind limbs between Crypotherapy sessions

Stall rest

Hand walk one hour daily

90-120

First recheck exam to assess progress

Bandage both hind limbs

Stall rest

If progress from first exam is good or fair: ride at walk for 30 minutes daily

If progress is poor: hand walk for one hour daily

120-150

Bandage both hind limbs

Stall rest

If progress from first exam is good or fair: ride at walk 45-60 minutes daily

If progress is poor: ride at walk 20-30 minutes daily

150-180

Bandage both hind limbs

Stall rest

Turn out in nursery paddock for one hour daily

If progress from first exam is good or fair: ride at walk for 45-60 minutes and add five minutes of trotting every two weeks

If progress is poor: ride at walk one hour

180-210

Second recheck exam to assess progress

Stall rest

Turn out in nursery paddock for one hour daily

If progress from second exam is good or fair: ride at walk for 45-60 minutes and add five minutes of canter every two weeks

If progress is poor: ride at walk one hour

210-240

Stall rest

Turn out in nursery paddock for one hour twice daily

If progress from second exam is good or fair: ride at walk for 45-60 minutes and add five minutes of canter every two weeks

If progress is poor: ride at walk one hour

240-270

Stall rest

Turn out in nursery paddock for one hour twice daily

If progress from second exam is good or fair: ride at walk for 45-60 minutes and add five minutes of canter every two weeks

If progress is poor: ride at walk one hour

270-300

Third exam to assess progress

If progress from third exam is good or fair: begin normal work

If progress is poor re-evaluate case and discuss further treatment options

Although levels of hydroxylation and the HP cross-link tend to diminish as healing proceeds, incomplete remodelling commonly results in persistently high levels in scar tissue (Rheumatology 2004;43:131-142

The pathogenesis of tendinopathy.

A molecular perspective

G. Riley)

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