Lameness of horse

LAMENESS OF HORSE

 

Body conformation of the horse in relation to lameness:

 

Conformation is defined as the form or outline of an animal.It may include the relation of form to function.The conformation of todays horse is a result of natural selection and demands of human like body proportion, colour, heart to race.

 

 

External Anatomy:

·         back: the area where the saddle sits, beginning at the end of the withers, extending to the last thoracic vertebrae (colloquially includes the loin or "coupling," though technically incorrect usage)

·         barrel: the body of the horse enclosing the rib cage and the major internal organs

·         buttock: the part of the hindquarters behind the thighs and below the root of the tail

·         cannon or cannon bone: the area between the knee or hock and the fetlock joint, sometimes called the "shin" of the horse, though technically it is the metacarpal III

·         chestnut: a callosity on the inside of each leg

·         chin groove: the part of the horse's head behind the lower lip and chin, the area that dips down slightly on the lower jaw; area where the curb chain of certain bits is fastened

·         coronet or coronary band: the ring of soft tissue just above the horny hoof that blends into the skin of the leg

·         crest: the upper portion of the neck where the mane grows

·         croup: the topline of the hindquarters, beginning at the hip, extending proximate to the sacral vertebrae and stopping at the dock of the tail (where the coccygeal vertebrae begin); sometimes called "rump"

·         dock: the living part of the tail, consisting of the coccygeal vertebrae, muscles and ligaments. Sometimes used colloquially to refer to the root of the tail, below.

·         elbow: The joint of the front leg at the point where the belly of the horse meets the leg. Homologous to the elbow in humans

·         ergot: a callosity on the back of the fetlock

·         face: the area between the forehead and the tip of the upper lip

·         fetlock: sometimes called the "ankle" of the horse, though it is not the same skeletal structure as an ankle in humans; known to anatomists as the metacarpophalangeal (front) or metatarsophalangeal (hind) joint; homologous to the "ball" of the foot or the metacarpophalangeal joints of the fingers in humans

·         flank: where the hind legs and the barrel meet, specifically the area right behind the rib cage and in front of the stifle joint

·         forearm: the area of the front leg between the knee and elbow, consisting of the fused radius and ulna, and all the tissue around these bones; anatomically, the antebrachium.

·         forehead: the area between the poll, the eyes and the arch of the nose

·         forelock: the continuation of the mane, which hangs from between the ears down onto the forehead of the horse

·         frog: the highly elastic wedge-shaped mass on the underside of the hoof, which normally makes contact with the ground every stride, and supports both the locomotion and circulation of the horse

·         gaskin: the large muscle on the hind leg, just above the hock, below the stifle, homologous to the calf of a human

·         girth or heartgirth: the area right behind the elbow of the horse, where the girth of the saddle would go; this area should be where the barrel is at its greatest diameter in a properly-conditioned horse that is not pregnant or obese

·         hindquarters: the large, muscular area of the hind legs, above the stifle and behind the barrel

·         hock: the tarsus of the horse (hindlimb equivalent to the human ankle and heel), the large joint on the hind leg

·         hoof: the foot of the horse; the hoof wall is the tough outside covering of the hoof that comes into contact with the ground and is, in many respects, a much larger and stronger version of the human fingernail

·         jugular groove: the line of indentation on the lower portion of the neck, can be seen from either side, just above the windpipe; beneath this area run the jugular vein, the carotid artery and part of thesympathetic trunk

·         knee: the carpus of the horse (equivalent to the human wrist), the large joint in the front legs, above the cannon bone

·         loin: the area right behind the saddle, going from the last rib to the croup, anatomically approximate to the lumbar spine

·         mane: long and relatively coarse hair growing from the dorsal ridge of the neck

·         muzzle: the chin, mouth, and nostrils of the face

·         pastern: the connection between the coronet and the fetlock, made up of the middle and proximal phalanx

·         poll: commonly refers to the poll joint at the beginning of the neck, immediately behind the ears, a slight depression at the joint where the atlas (C1) meets the occipital crest; anatomically, the occipital crest itself is the "poll"

·         root of the tail or root of the dock: the point where the tail is "set on" (attached) to the rump;^[3] Sometimes also called the "dock"

·         shoulder: made up of the scapula and associated muscles, runs from the withers to the point of shoulder (the joint at the front of the chest, i.e. the glenoid); the angle of the shoulder has a great effect on the horse's movement and jumping ability, and is an important aspect of equine conformation

·         splints: bones found on each of the legs, on either side of the cannon bone (8 total); partially vestigial, these bones support the corresponding carpal bones in the forelimb, and the corresponding tarsal bones in the hindlimb; anatomically referred to as Metacarpal/Metatarsal II (on the medial aspect (inside)) and IV (on the lateral aspect (outside))

·         stifle: corresponds to the knee of a human, consists of the articulation between femur and tibia, as well as the articulation between patella and femur

·         tail: the long hairs which grow from the dock; may also include the dock

·         throatlatch: the point at which the windpipe meets the head at the underside of the jaw,^[3] corresponding to where the eponymous part of a bridle goes.^[12]

·         withers: the highest point of the thoracic vertebrae, the point just above the tops of the shoulder blades, seen best with horse standing square and head slightly lowered; the height of the horse is measured at the withers.

 

Definition of lameness:

 

Percival has given most accepted definition as the lameness is the manifestation in the act of progression by one or more limbs of pain, disease, weakness, deformity or impediment. It is sometimes called claudication.

 

Lameness is an indication of a structural or functional disorder in one or more limbs that is manifested during progression or in the standing position.

Difficulty in locomotion which causes abnormal gait is called lameness. Lameness is not a disease but only a symptom of structural or functional disorder. It may affect one or more limbs.

 

Lameness can be caused by trauma, congenital or acquired anamolies , infection, metabolic disorders, circulatory and nervous disorders or any combination of these.

The diagnosis of lameness requires a detailed knowledge of anatomy, the physiology of the limb movements and an appreciation of geometric design and resultant forces.

To arrive at diagnosis in a case of lameness it is necessary to ascertain 1. which limb is affected 2.the seat of lameness 3. the nature of the lesion.

 

Depending on the severity of the lameness in the scale of 1 to 5 , 1 will indicate minor gait deficit to 5 as broken bone indicating non weight bearing condition.

 

 

 

 

Causes of lamness:

 

 

1	Overwork
2	Back injury
3	Bone,Muscle,tendon,ligament injury from sprain to fracture
4	Nervous disorders Like wobblers syndrome
5	Cellulitis or Thrush (swelling linked to infection)
6	Hoof Problems
7	Connesctive tissue disease ( Equine exertional Rhabdomyolysis)
8	Laminitis
9	Conformation defects leading to stress like cow-hocked or sickle hocked

 

 

Assement of lameness by

 

1. Visual ckeck for cuts and swelling
2. Different gait observation (walk and trot)
3. Flexion tests
4. Hoofs checked for injury.

 

 

After assement to locate pain

1. Regional limb anaesthesia (nerve blocks ) to pin point the affected area.
2. 2.Radiograph or ultrasound to determine involovement of particular structures.
3. Advanced imaging like scintigraphy, CT,Veterinary thermal imaging and MRI.

 

Classification of lameness:(As given by Dollar)

 

1.Supporting limb lamness:

            Injury to bones, joints, ligaments or nerves and to foot itself causes lameness when the horse is supporting weight on the foot or when horse lands on it.

2.Swinging limb lameness;

            When limb in motion, pathological changes involving joint capsule, muscles, tendons,tendon sheaths,or bursae will cause lameness in motion.

3.Mixed lameness:

            Involves 1 and 2 above.

4.Complementary lameness:

            Pain in a limb will cause uneven distribution of weight on another limb or limbs which can produce lameness in a previously sound limb.

 

 

 

 

 

 

Types of lameness:

These are generally encountered:

 

1	Bog Spavin	Inflammation of tibio-tarsal joint
2	Bone Spavin	Infl. Of bone os hock joint
3	Bowed tendon	Rupture of tendon sheaths from knee to fetlock
4	Capped Joint	Hock swelling by hit
5	Curb	Infl. Of upper rear of the cannon bone below hock
6	Laminitis	Infl.of lamina propria
7	Navicular disease	Infl. And degeneration of navicular bone and surrounding tissue.
8	Osselets	Infl. of joint capsule in front of fetlock.
9	Ring Bone	Exostosis in the pastern or coffin joint.
10	Sesamoiditis	Infl. Of sesamoid bone above and back of the fetlock joint.
11	Side bone	Ossification of collateral cartilages of coffin bone .
12	Speedy cut	Inner lower side of knee is cut with hoof of the opposite leg.
13	Splints	Bony enlargements inside front leg by the knee.
14	Sprain	Ankle sprain affects ligaments that support fetlock, and sprain of the suspensory ligament causes inflammation and strain of the ligament.
15	Stocking up	Hind limbs swelling by rest after heavy work.
16	String halt	Spasmodic contraction of lateral extensor tendon.
17	Through pin	Infl. Of the deep digital flexor tendon sheath.
18	Wind puffs	Spongy swelling around back, front and  side of the fetlock

 

 

 

Examination for lameness;

1.      Observation at rest:

           Deformity of a part or whole of a limb, abnormal positioning of a limb like abduction, adduction ets are observed to detect fracture, dislocation, tendon rupture or paralysis.

Eg; Dropped elbow in radial nerve paralysis.

 

2.      Observation during progression:

           Horse trotted by an assistant with lead rope. The horse i first led in a straight track away from observer for 30 yards and turned back. Observe for adducted,abducted , circumaducted limbs during progression, deviation in the long axis of the body. Observe from sides variation in the length of the stride and deminised flexion of joints.

 

           Head and hind quarter movement:

In forelimb lameness animal raises its head when lame limb bears weight, but when good limb bears weight head is down.

           In Hind limb lameness that quarter is raised when it bears weight. If both hind limbs are lame there will be stiff croup movement and backing of horse is difficult.

           Cross lameness: when one hind limb is painful , forelimb of other side appers lame, it is called cross lameness and diagonal lameness in which one fore leg and opposite hind limb are lame.

 

3.Detailed examination of the lame limb;

 

           Palpation of various bones, joints,tendons and tendon sheaths.

           Flexion and extension to see swelling warmth and evidence of pain in various joints and foot.

           In foot shoe is removed and wall, sole, frog are examined. A hoof tester or hammer to know painful place.

 

 

 

 

 

 4.To confirm seat of lameness:

           A) Nerve Block

           B) Radiograph

           C)Cinematograph

           D)Electogoniometric analysis of lameness

           E)Dynamography

           F)Bone scintigraphy

           G)Thermometry

           H)Angiography

           I)Telemetry measurement of bone and hoof capsule strain and joint movement.

 

General Symptoms

1.General symptoms of shoulder lameness:
           Head raising reflex

           Restricted scapula

           Short steps

           Insufficient raising of limb raising from ground

           Circumduction of limb

           Dragging toe

           Lameness increased by trotting uphill

           Disuse atrophy of suprascapular muscles.

3.      General symptoms of elbow lameness:

           Uncommon, heading raising is seen.

4.      General symptoms of knee lameness      

           Limb carried forward with slight circumduction because of knee joint incomplete flexion

           Downhill lameness.

5.      General symptoms of fetlock lameness

           Limited flexon and extension of fetlock joint.A sinking or dropping of fetlock by rupture of flexon tendon or suspensory ligaments.

           Contraction will cause upright pastern.

6.      General symptoms of hip lameness

           Affected quarter carried higher.

           Difficulty in advancing thelimb

           Carries limb in stiff maner

           Short stride

           Circumduction

           Dragging of the toe.(swinging leg lameness.

           Coxitis symptom is diagonal movement during progression and keeping the affected toe turned outwards

7.      General symptoms of stifle lameness

           Same as hip lameness but croup raising not pronounced

8.      General symptoms of hock lameness

           Most common lameness with imperfect flexon of hock, dragging toe and short stride.Dragging causes extensive wear of the hoof.

           Methods of examination of lameness:

1.Thermometry:

           To visualize and quantify changes in the skin surface temperature. An infrared scanner device is used to convert infrared radiation emitted from the skin surface into electrical impulses that are visualized in black and white or colour one. The video screen is called thermogram. White indicates an increase in IR radiation whereas other colours used to quantify the amount of IR being emitted from body surface.

Eg: Navicular Disease,Subsolar abscesses,Arthritis. 

2. Angiography:

           Radio-opaque material injected into an artery or vein to evaluate the blood flow pattern to the musculo-skeletal or other organ systems.

Eg: Laminitis, Carpel tunnel syndrome.

3.Telemetry:

            To measure bone and hoof capsule strain and joint movement. TM measurements of bone strain can be made by surgically implanting an electrical resistance strain gauge on the surface of the bone, from this bone strain measurements are recorded using a wireless telemetric system. By this better understanding of the pathogenesis of equine fractures is possible.

 

4.Cinematography:

            By using high speed camera to record the horse movements at various gaits to evaluate motion. The development of computerized film analysis has permitted rapid complete analysis of locomotor patterns in the horse.

 

5.Electrogoniometric analysis of lameness:

            Electrogoniometer (Elgon) to measure the variation in joint angles during locomotion and a permanent record (goniogram) is obtained. It allows unrestricted movement of horse while recording. This with cinematography to evaluate subtle lameness.

 

6.Dynamography:

            It involves the use of force transducers that measure the amount and direction of force exerted by the foot as it is placed on the ground. The advantage of this technique is that strain forces are recorded during locomotion.

 

7.Bone Scintigraphy:

            It provides an early sensitive means of detecting increased bone tumor and new bone formation. Bone injuries identified 12-24 hrs after injury.It is objective and predictable means to evaluate bone fracture healing. Technetium 99 is the radioisotope most frequently used to bond pyrophosphate or methylene diphospahte. After IV administration, they will attach to bone within 30 minutes and released from soft tissue within 2 hours. Bone imaging is conducted with a gamma camera is conducted 2-5 hrs after the injection of this agent.

8.Radiography:

            Suspected pathological areas are diagnosed, new bone growth and fracture of carpels can be identified.