DIAGNOSIS OF LAMENESS IN EQUINE
Lameness is an indication of functional and/or structural disorder in one or more limb that is manifested in progression by inability to advance one or more limbs in proper manner, or in standing position, and sometimes it is called claudication.
The limb consists of bones, joints, muscles, tendons, blood supply, and nerve supply. Injury to any of them, as a result of trauma, congenital or acquired anomalies, infection, metabolic disturbance like rickets, or circulatory or nervous disturbance, may predispose to lameness.
The hind limbs act as propelling while the forelegs receive the shock of landing so about 75% of lameness affect the forelegs as they carry 60-65% of the weight and thus subjected to greater concussion, and of these 95 % affect the carpus or below, while the stifle and the hock joints are the most common sites of affection in the hind limbs and constitute 80%.
CLASSIFICATION OF LAMENESS: -
1-Supporting-leg lameness: -
It is evident when the horse supporting weight on foot or when he lands on it, and the main causes of such type of lameness are; injury of bones, joints, collateral ligaments, motor nerves, or foot.
2-Swinging-leg lameness: -
It is evident when the limb is in motion, and it is caused by injury to joint capsule, muscles, or tendons.
3-Mixed lameness: -
It is evident when the leg is moving and when it supporting weight, and it is caused by combination of the previously mentioned causes.
Differentiation between the three types depends up on observing gait of the animal from a distance, and this classification is helpful for diagnosis but one shouldn't rely on it completely.
COMPLEMENTARY LAMENESS: -
Pain in one limb may cause uneven distribution of the weight on another limb or limbs leading to lameness in a previously sound limb, also minor lesion in one limb may cause severe lesion either in the same limb or the corresponding one.
Lameness in one foreleg may lead to lameness in the corresponding foreleg (suspensory ligament, sesamoid bones and flexor tendons seem to be the structures that suffer most) and lameness in one hind leg may lead to lameness of the foreleg in the same side. On the contrary, neither lameness of one hind leg affects the other hind, nor a lameness of foreleg affect the hind leg of the same side.
Also one should keep in mind that minor injury to one limb may predispose to more severe injury in the same limb as navicular disease. In such cases animal lands on the toe first leading to bruised sole or soreness of the toe, but later on the animal land on the heel as the soreness of the toe hurts more than navicular area. Also landing on the toe to protect the heel may cause additional stress on suspensory ligament.
Diagnosis depends on detection of lame limb, and seat and nature of lameness
I-DETECTION OF LAME LIMB: -
A-History (anamnesis): -
1-How long has the horse been lame?
Lameness for more than one month is considered chronic with guarded prognosis, but young horse has better prognosis than old one.
2-Does the owners know the cause of lameness?
The owner may say that he removed nail from the foot, saw the injury occur, or saw the character of lameness at the time first noticed (started acute that indicates fracture of the 3rd phalanx or insidiously that indicates arthritis).
3-Does the animal warm out of lameness?
It indicates involvement of muscular structures or arthritis (bone spavin).
4-Does the animal stumble? It is an indication of
1-Interference with synergistic action of the flexor and extensor muscles.
2-Pain on heel pressure like navicular disease or heel puncture wounds.
3-Interference with enough flexion of the carpus as a result of painful condition of carpus, or rupture of extensor carpi radialis.
5-What treatment has been done? And was it helpful?
Some drugs interfere with the signs of lameness (steroids) and some procedures predispose to infection of joint (exploratory puncture), and if the owner treated the animal in right manner with no response, one shouldn't use the same method of treatment.
6-When was the animal shoed?
The nail may be driven into sensitive tissue and pulled out, remains in it, or it is close to sensitive tissue (nail bound).
B-Inspection at rest: -
Animal should be inspected during rest in order to observe the effort he makes to compensate for pain in supporting-leg lameness.
-If the horse stands with the carpus forward and the heel raised; the carpal, posterior fetlock, and heel areas should be examined.
-If the horse points with the affected foot, navicular disease or fracture of the extensor process of the 3rd phalanx should be expected.
-If the forelimb is held posteriorly with flexed carpus and the toe rests on the ground, the shoulder should be examined.
-Lameness of the elbow joint is characterized by extension of the forearm, flexion of the knee, and the foot either in the same level or posterior to the opposite member and the elbow may have dropped appearance.
-If the limb is carried; fracture, nail punctures, severe sprains, or septic phlegmon are considered.
2-Shifting of the weight: -
It is normal in the hind limb, but it is abnormal in the forelegs. When the animal refuses to put weight on one hind limb (rests constantly on one limb) the shifting limb should be inspected.
3-Muscular atrophy: -
Muscular group of shoulder and gluteal regions should be inspected, the affected limb usually has atrophied muscles (disuse atrophy).
4-Anatomical abnormalities: -
Like swelling, mal conformation, wound, tumor, etc...
*Forelimb anterior view A line dropped from the point of the shoulder joint bisects the limb.
a-Base narrow: -
The distance between the center lines of the feet is lesser than the distance of the center lines at their origin and the horse bears most of weight on the outside of the foot. This mal formation is associated with articular windpuffs of the fetlock joint, lateral ringbone, lateral sidebone, and excessive wear of the out side of the foot. These animals may have toe-in or toe out but generally land on the outside of the foot.
b-Base wide: -
The distance between the center lines of the feet is greater than the distance of the center lines at their origin. These animals usually have toe-out with winging and tend to land on the inside of the foot leading to articular windpuffs of the fetlock joint, medial ringbone, medial sidebone, and excessive wear of the inside of the foot.
c-Toe-in or Pigeon-toed: -
The toes point toward one another and it is usually associated with base narrow and rare in base wide horses. These animals tend to break over the outside of the toe, paddle during flight, and landing on the outside of toe.
d-Toe-out or Splay-footed: -
The toes point away from one another and it is usually associated with narrow or wide base. The animal tends to wing on flight and when he has base narrow, interference and plaiting are expected.
e-Base narrow, toe-in conformation: -
It causes paddling and great strain on the lateral collateral ligaments of the fetlock and pastern joints leading to articular windpuffs, lateral ringbone, lateral sidebone, and excessive wearing of the out side of the foot.
f-Base narrow, toe-out conformation: -
It is the worst conformation, the closely placed feet and tendency to wing cause interference (leading to injury of the medial aspect of the 2nd and 3rd metacarpal bones and medial sesamoid bone), wearing of the out side of the foot, and plaiting. This is a side from the injury of the lateral collateral ligament of the fetlock and pastern, articular windpuffs of the fetlock joint, lateral ringbone and sidebone, and excessive wear of the out side of the foot.
g-Base wide, toe-out conformation: -
It causes winging and greater strain on medial collateral ligament of the fetlock and pastern joints leading to medial sidebone, ringbone, wearing of the inside of the foot, medial splints, and injury of the medial aspect of the 2nd, 3rd metacarpal bones, and medial sesamoid bone.
h-Base wide, toe-in conformation: -
It causes paddling and greater strain on medial collateral ligament of the fetlock and pastern joints leading to medial sidebone, medial ringbone, and wearing of the inside of the foot.
Plaiting: - It is a tendency to put one forefoot in front of the other foot during motion leading to interference and stumbling, and it is usually occurs in base narrow, toe-out conformation.
i-Medial deviation of the carpal joint, Knock knees, or Knee narrow conformation: -
It is a medial deviation of the two carpal joints toward each other. Strain is put on inferior check ligament, suspensory apparatus, medial capsule of the carpal joint, medial collateral ligament of the carpus, and lateral aspect of the carpal bones.
j-Lateral deviation of the carpal joint, Bow legs, or Bandy-legged conformation: -
It is an outward deviation of the two carpal joints from each other and may be accompanied with base narrow, toe-in conformation. It causes excessive strain on lateral collateral ligament of the carpus, medial side of the carpal bones, and lateral portion of the carpal joint capsule.
k-Lateral deviation of metacarpal bones, Offset knees, or Bench knees: -
The cannon bone is offset to the lateral side and doesn't follow a straight line of the radius. As a result of the anatomical feature of the medial splint bone (flat articulation while the lateral splint bone has oblique articulation), greater strain placed on the medial splint bone and interosseous ligament leading to medial splints.
*Forelimb side view A line dropped from the tuber spinae of the scapula bisects the limb as far as the fetlock and drops at the heel.
a-Posterior deviation of the carpal joint, Calf knees, or Sheep knees: -
This affection places a strain upon the inferior check ligament, anterior aspect of carpal bones, volar annular ligament of the carpus, and volar aspect of carpal joint capsule, leading to chip fracture of the 3rd, radial and intermediate carpal bones, and radius.
b-Anterior deviation of the carpal joint, Over in the knees, Goat or Bucked knees, or Knee sprung: -
It causes less damage than posterior deviation, and ensues as a result of contraction of carpal flexors (ulnaris lateralis, flexor carpi ulnaris and flexor carpi radials). Extra strain is placed on sesamoid bones, superficial flexor tendon, extensor carpi radialis, and suspensory ligament.
c-Open knees: -
It is an irregular profile of the carpal joint, which gives impression that the joints are not fully closed. It affects young horses as a result of mineral deficiency and epiphysitis.
d-Tied-in knees: -
The flexor tendons appear to be close to the cannon bone just below the carpus.
e-Cut out under the knees: -
It is a cut out appearance of the knee just below the carpus on the anterior surface of the cannon bone.
f-Standing under in front: -
The entire forelimb from the elbow down is placed back of the perpendicular and too far under the body. It may be brought about by disease not by conformation and the base of support is shorter, limbs are over loaded, steps are more frequent, the anterior phase of stride is limited, and the arc of foot in flight is low as the limb of motion comes down to the ground sooner predisposing to stumbling, diminution of speed, and falling. This affection is associated with excessive wear and fatigue of bones, ligaments, and tendons
g-Camped in front: -
The entire forelimb is too far forward, and it can be observed in some pathological conditions like bilateral navicular disease and laminitis.
h-Short upright pastern: -
It is often associate base narrow toe-in especially in short horses, and it increases the concussion on fetlock and pastern joints and navicular bone, with increased predisposition to; osselets (traumatic arthritis of fetlock joint), ring bone of pastern, and navicular disease.
i-Long sloping pastern: -
It is normal or subnormal angulation the forefoot (45 or under) with a too long pastern for the length of the limb. It predisposes to injury of the flexor tendons (tenosynovitis), sesamoid bones (sesamoiditis and fracture), and suspensory ligament (desmitis).
j-Long upright pastern: -
It predisposes to injury of the fetlock (osselets) and navicular bursa as a result of increased concussion to these areas, but affection of the pastern is not so common. Increased pressure on the navicular bone increases by corrective lowering of the heel by the horseshoer leading to break between the pastern and foot axis at the coronary band.
*Hind limb posterior view A line dropped from the tuber ischii bisects the limb.
a-Base narrow: -
The distance between the center lines of the feet is lesser than that of the limbs in the thigh region. It is often accompanied with bow legs or a condition in which the hocks are too far apart, and the feet may be toe-in. It is associated with excessive strain on the lateral aspect of the limbs in the bones, ligaments, and joints, and may predisposes to interference with the forelegs if he has good conformation in the forelegs.
b-Base wide: -
The distance between the center lines of the feet is greater than that of the limbs in the thigh region. It is less frequent in hind limbs than forelimbs and the most common form is cow hock.
c-Medial deviation of the hock joints or Cow hocks: -
It is the worst conformation of the hind limbs, and when viewed from behind, the limbs are base narrow to the hock then base wide from the hock to the feet so the two hocks are too close and point toward each other and the feet are widely separated leading to excessive strain on the medial aspect of the hock joints and predisposes to bone spavin. When viewed laterally, the horse may be sickle-hocked.
d-Base narrow from fetlocks down: -
It places great strain on the lateral aspect of the fetlock, pastern and coffin joints.
*Hind limb side view A line dropped from the tuber ischii hits the point of the hock, follows the metatarsus, and strike 3-4 inches behind the heel, and a line dropped from the hip strikes halfway between heel and toe.
a-Excessive angulation of the hock joints, Sickle hocks, or Curby conformation: -
The angle of the hock joint decreases so that the horse is standing under from the hock and down so the planter aspect of the hock and the planter ligament become under greater strain predisposing the horse to curb. The line dropped from the tuber ischii strike the hock then land far behind the heel (more than 4 inches).
b-Excessive straight legs or Straight behind: -
The hock and pastern joint look straight, predisposing the horse to upward patellar fixation and bog spavin (as a result of increased strain on the anterior aspect of the joint capsule of the hock causing chronic distension of the joint capsule with synovia).
c-Standing under behind: -
The entire limb is placed too far forward or sickle hock is present. A dropped line from the tuber ischii hits far behind the hock and the heel, and a dropped line from the hip hits behind the heel.
d-Camped behind: -
The entire limb is placed too far posteriorly. A line dropped from the hip hits the toe or anterior to it, and a line dropped from the tuber ischii passes through the hock and hits the toe.
C-Inspection at motion: -
Walking has four beats gait, near-hind, near-fore, off-hind, and off-fore.
Trotting is two beats gait, near-hind with off-fore and off-hind with near-fore.
Pacing is two beats, near-hind with near-fore and off-hind with off-fore.
Running or galloping is a four beats gait, near-hind, off-hind, near-fore, and off-fore.
Normally, the heel lifted first when the leg advanced, and lands first when the leg lands. If there is pain on concussion to the heel (navicular disease or nail puncture), the horse tends to land on the toe first. If there is diffuse pain in the foot (laminitis) or there is pain in the toe, the horse will make exaggerating effort to land on the heel to avoid bottom of the foot or toe.
In general, forelimb lameness is best observed from the front and side views, while hind limb is best observed from rear and side views. If it is difficult to observe lameness in motion, it will be helpful to examine the animal either in trotting gait, as there will be only one supporting leg on the ground, or using hard surface. On using hard surface, the feet can be seen and heard, and the unsound limb produces less noise on landing. One shouldn't confuse left hind lameness with right fore in trotting gait, as the animal will land more solidly on the right hind and left foreleg, leading to incrimination of the right foreleg, but observing the horse from behind will reveal movement of the hip. Regarding the foreleg, the head will rise when the unsound limb lands but no head movement is present in case of bilateral involvement of the limbs or in mild lameness. With respect to the hind limb, when the unsound limb lands, the hip rises and the head drops.
Characteristics of the stride: -1-Phases of the stride: -
The anterior and posterior phases of stride should be equal. During lameness, and if the horse moves in straight line, the anterior or posterior phases increase on the expense of each other as the stride still have the same length of the corresponding legs, but if there is no compensation, it means that the horse travel sideways with the body at an angle. Affection of the toe causes shortening of the posterior phase with compensatory lengthening of the anterior phase. Affection of heel or interference with normal flexion of shoulder or carpal joints lengthens the posterior phase on expense of the anterior phase.
2-Arc of foot flight: -
In normal horse, and in lateral view, the horse should break squarely over the toe, the arc of foot flight should be normal, the heels lift first and land first, the center of weight should placed at the point of the frog, and the hoof reaches the peak of the flight arc as it passes the opposite supporting limb.
If the heels are too low, the toes are too long, and the angle of the hoof lesser than 45º in forefoot or 50º in the hind hoof, the center of the weight will be anterior to the frog and the added effort (required to force the foot to break over the long toe) causes the horse to have long sweeping stride. This will cause the foot to delay break over, since the toe acts as long leverage point, causing the foot to reach the peak of flight arc before it pass the opposite supporting limb. All of the aforementioned increase strain on flexor tendons, suspensory ligament, and proximal sesamoid bones. If the horse has short toe and high heel, the center of weight will be posterior to the point of the frog, the foot breaks over quickly and reaches the peak of flight arc after passing the opposite supporting foot, shorter stride, and the foot lands steeply. All of the aforementioned increase concussion leading to ring bone, navicular disease, and osselets.
The arc of foot in flight changes when there is pain in the limb that interferes with normal flexion of joints. Detection of it depends on comparing the two opposite legs, but some times the affection is bilateral and it is difficult to be detected. Interference of flexion of shoulder or carpal joints causes low arc. In case of the forelegs, bilateral navicular disease or laminitis change it in both legs, the same can be observed in bilateral spavin in the hind limbs, and some times it is low enough that the animal drag the toe when advanced as in case of bone spavin or gonitis. In case of navicular disease, laminitis, or nail puncture, the arc becomes low as a result of effort to pain when the foot lands, while in case of painful condition of the carpus, the arc becomes low as a result of improper flexion of the knee joint.
3-The path of the foot in flight: -
If the foot travels inward (winging) it may injury the splint or the carpus of the opposite leg but when it travels in outward path (paddling) it cause no specific injury.
4-How the foot lands: -
In case of navicular disease, the horse lands on toe to avoid pain at the heel and when the animal suffers from nail puncture at the toe, he will land on the heel etc....
5-Interferences or limb contact: -
a-Brushing: -It is a general term for light striking as in forging or interfering.
b-Cross-firing: -The inside of hind foot hits the inside quarter of the diagonal fore foot.
c-Elbow hitting: -The sole of the limb hits the elbow of the same limb.
d-Forging: -The toe of the hind foot hits the sole of the forefoot on the same side.
e-Interfering: -It occurs either in fore or hind feet as a result of hitting the opposite leg anywhere between the coronary band and cannon during motion (winging or toe out).
f-Overreaching: -The toe of the hind foot moves faster than forging and hits the heel of the foot at the same side leading to shoe pulling.
g-Scalping: -The toe of the forefoot hits the hind limb between the coronary band and cannon.
II-DETECTION OF SEAT OF LAMENESS: -
The affected limb is examined visually from top to bottom or from bottom to top, and from every angle. It may reveal presence of lesion like swelling or wound.
B-Palpation and compression: -
For detection of hotness, swelling and tenderness, pain, and anatomical abnormalities.
C-Passive movement of the joints: -
The joint is moved in its physiologic aspects (extension, flexion, abduction, and adduction). Painful reaction from the animal indicates injury of the joint or its vicinity, otherwise, mechanical hinderness of normal movement indicate chronic arthritis. Some chronic inflammations of joints give rise to exaggerated lameness after flexion of the joint for few minutes followed by moving the animal (spavin).
D-Special examination of the foot: -
The pastern axis (as viewed from front, behind and side) is an imaginary line passing through the center of the pastern and divides the 1st and 2nd phalanges into equal parts from both views.
The foot axis as viewed from the front is an imaginary line passing through the center of the toe of the hoof wall from the coronary band to the ground surface of the toe and blends above with the pastern axis. The foot axis as viewed from the side should be continuous with the pastern axis too, and follows the same angle, and the angle formed between the dorsal surface of the toe and the ground surface of the hoof wall will be the same angle of the foot axis.
The normal foot axis in forefoot when viewed from the side should be 45º-50º, while in the hind foot it should be 50º-55º.
If the foot and pastern axes are too slope or too steep, pathological conditions ensue, but one shouldn't trim the hoof if the foot and pastern axes are too slope or too steep and the angles of the foot and pastern axes are identical as continuous line to avoid strain on navicular bone.
Foot level indicates that the lateral and medial walls are of the same length and wear identically, and this can be achieved by lifting the limb so that the ground surface can be seen along the longitudinal axis, then an imaginary line dividing the cannon, fetlock, and pastern is crossed by a transverse line touching the ground surface of the heels, resulting in two 90º angles at the junction of these lines. If the too angles are not 90º, the foot is called off level.
Ideally it is round with wide heels and will-developed bars, the wall is thickest at toe and thin gradually toward heels, the inside wall straighter than the outer one, the sole is concave (but the excessive concavity indicates chronic foot disease) and has no contact with the ground as t is not a weight bearing structure. The foot should show that the animal breaks squarely over the center of the toe and the frog should be large, well developed with good cleft, has normal elasticity, and it should divide the sole into two equal parts with the apex of the frog pointing to the center of the toe, since unequal halves of the sole indicating base narrow or base wide conformation.
It should has more pointed appearance than the forefoot with evidence of straight breaking over the toe, the frog divides the sole into two equal parts, and the sole is more concave than that of forefoot.
It is performed by visual examination of the affected foot after removal of the shoe, picking up of the sole, and washing the wall, and by this method we can observe cracks, sinus at the coronary band, abnormal shape of the hoof, or any of the following abnormalities.
a-Flat foot: -
It is a state of lacking concavity of the sole and it is a common affection of the forefoot than hind foot. The horse tends to land on the heel to avoid sole pressure and sole bruising is a common affection of such foot.
b-Dropped sole or Pumiced foot: -
The sole dropped beyond the bearing surface of the hoof wall and it is either flat or convex. This affection usually associates chronic laminitis and is accompanied with heavy rings on the hoof wall. The sole is very thick and composed of heavy flakes that usually bring a pink-colored sole when removed, or even it may harbor infection similar to thrush that may penetrate to sensitive laminae. The affection usually associated with rotation of the 3rd phalanx that can be viewed after removal of the heavy flakes, so trimming of a sole with protrusion below the wall at the toe, should be performed carefully to avoid exposure of the 3rd phalanx.
c-Contracted foot or Contracted heels: -
It is a much more condition of the forefoot in which the foot is narrow than normal especially at the posterior half, due to lack of frog pressure and prevention of contact of the frog with ground, and usually associated with dished sole (increased sole concavity) and the frog is recessed, and in severe cases the bars may touch each other, while the 3rd phalanx may become deformed and lose its circular shape.
This may occur hereditary or as a result of improper shoeing or lameness (that prevent the animal from pressing the foot firmly to the ground like navicular disease). If the hoof wall is contracted sufficiently at heels, it may press firmly against the 3rd phalanx leading to hoof-bound lameness. Treatment of contracted foot or heels, which have resulted from one month of disuse, may last more than year. The primary cause should be detected and removed and the frog pressure should be re-established.
d-Brittle foot: -
It is a more common affection of un-pigmented foot as a result dryness of atmosphere and lack of soil moisture. It predisposes to cracks and fracture of the wall as a result of brittleness. Using nondrying agents, shoeing to prevent fracture of hoof wall, and feeding of gelatine, can treat such affection.
e-Bull nose foot: -
It is a condition ensues when the toe is rasped to fit the shoe.
f-Buttress foot: -
It is an exostosis on the extensor process of the 3rd phalanx (low ring bone or fracture of extensor process) leading to formation of swelling at the anterior surface of the hoof wall at the coronary band.
g-Rings of the wall of the foot: -
It is thick rings on the heels or quarters as a result of chronic foot disease or ring bones and the affection can't be treated.
h-Thin wall and sole: -
The wall wears away too rapidly or doesn't grow fast enough to avoid sole pressure. The affected animal has broken foot axis, too low heel, sole bruising and lameness (after hoof trimming), and very thin easily compressible sole on using hoof tester. Treatment directed towards;
1-stimulation of growth of the wall by using tincture iodine at the coronet, feeding gelatine, or turning the horse unshod for six months on rough ground
2-protection of the sole with rising of the heel by using leather pads
i-Club foot: -
The foot axis is more than 60º with contraction of superficial digital flexor tendon, deep flexor tendon, and suspensory ligament.
It is a state of broken angle between hoof and pastern axes at the coronary band and it is characterized by a slope pastern axis, leading to much strain on flexor tendons, sesamoid bones, and distal sesamoid ligaments. Treatment directed toward trimming of the heel to create continuity of the two axes but the angle of the foot axis shouldn't be trimmed lesser than 45º.
By placing the back of the hand over the affected foot and comparing its temperature with the other foot for detection of hotness associating inflammation (acute laminitis).
Making gentle taps by wooden hammer over the wall of the foot that may indicate seedy toe (sound) or acute laminitis (pain reaction).
By using hoof tester and squeezing the wall against the sole for detection of any hidden lesion in the hoof.
It means removal of the horny tissue by hoof knife for exposure of any hidden lesion in the sole like nail puncture.
E-Block anesthesia: -
It is performed in systemic manner from bottom to top. At the beginning, block of the low volar should be performed followed by; ring block at the pastern region; high volar; ring block at the level of the high volar; carpal desensitization; and median, ulnar and musculocutaneous nerves. When arthritis is suspected, desensitization of the joint is indicated.
After using nerve block, the suspected area examined radio-graphically for presence of ringbone, fracture, chronic inflammation with new bone growths etc....
III-DETECTION OF NATURE OF LESION: -