LAMENESS ARISING FROM DISEASES OR ABNORMALITIES OF MUSCLES Inflammation of muscular tissue, or myositis in its varying forms, is responsible for many of the cases of lameness encountered in veterinary practice, and it is probable that many of the so-called cases of"obscure lameness"might justly be attributed to disorders of certain muscles or groups of muscles.
Myositis may be more easily discussed under the following headings: (1) traumatic; (2) rheumatic or toxic. Parasitic myositis is of little importance in equine medicine, though sarcosporidiw have frequently been observed living as parasitic colonies, surrounded by a tube, in the striated muscles (Miescher's tubes).
Muscular atrophy usually occurs as a sequel to myositis, particularly traumatic myositis.
Traumatic Myositis.Causes.In brief, these may be external violence or strain.
Bruising of the muscular tissues may occur from kicks, blows, or collision with moving bodies, such as vehicles. Constant or inter mittent pressure, such as may be set up by badly-fitting harness, may produce inflammatory changes as in the so-called"collar lameness,"due to bruising of the mastoido-humeralis.
Strains are very common, particularly in the regions of the shoulder, loins, and quarters. Excessive strain may lead to rupture of a muscle. This may be complete or only partial. Com plete rupture is rare, though it has been fre quently observed in the case of the flexor metatarsi, gastrocnemii, and others.
Over-exertion and bad horsemanship are the most frequent causes of myositis, whilst lack of condition and putting horses to work at too early an age predispose.
General Symptoms. The affected muscles are sometimes swollen, though in many cases this is not apparent. They are usually held whilst at rest in a state of relaxation, but when handled the animal contracts them to a moderate extent in order to avoid the pain induced by manipula tion. The muscles appear firm or even in durated in the early stages, and occasionally the surrounding tissues may be (edematous. Pain is usually evidenced upon palpation or when the limb is forcibly moved in certain directions. In myositis of the lumbar region"crouching"may often be observed when pressure is exerted upon the loins.
Movement of the affected muscles is restricted as far as possible, or the animal may even be unable to move them, even if he so wish.
The acute symptoms gradually subside, though in some cases of traumatic myositis suppuration may occur as a complication.
The usual sequel is atrophy of the affected muscles. This may be moderate, or only slightly noticeable after even severe injury, or it may be very marked, particularly when the nerve supply has been interfered with. The type of lameness is naturally dependent upon the situation and functions of the muscles affected.
Excessive strain resulting in partial rupture is accompanied by marked swelling in most cases, though this is by no means a constant symptom. Heat and pain are usually evident. The function of the muscle is temporarily suspended.
Complete rupture of a muscle is usually the result of over-extension and may be produced by forced movements of the limb, particularly when the foot or some portion of the leg is fixed, or by sudden contraction of one set of muscles without due co-ordination of those opposed to them.
It is probable that pathological degeneration in many cases precedes rupture, particularly when muscles have been the seat of changes arising from hmmoglobinuria, as may occur in the rectus femoris, vasti, and neighbouring muscles, or occasionally in those covering the outer surface of the shoulder region.
General Treatment of Myositis. Treatment may be local only, though in some cases medicinal treatment is beneficial.
The affected muscles should be repeatedly bathed with hot water and subsequently gently rubbed with a mild stimulating liniment, or they may be covered with a dressing soaked in an astringent lotion. Lead and arnica lotion is useful in bruising of muscle. A liniment con taining belladonna and camphor may be em ployed when there are severe pain and swelling. Rest is essential, particularly in myositis of the lumbar region, and in severe cases slinging may be necessary.
Internally sodium salicylate may be given with advantage in many cases. Aperients are useful, particularly in the form of small repeated doses of magnesium or sodium sulphate.
After the acute symptoms have subsided gentle exercise is beneficial and tends to prevent atrophy, which often follows myositis. Atrophy is best treated by exercise and hand-rubbing, followed by repeated blistering when necessary. Subcutaneous injections of oil of turpentine produce good results, but the subsequent swelling and pain are often undesirable. Other forms of counter-irritation produce equally satisfactory results.
Myositis of Special Muscles. Injury to the Trapezius and Rhomboideus Muscles. This is more common in cart horses than in those of lighter breed, though it may occur in saddle horses with narrow sloping withers. The direct cause of the injury is bruising from a badly fitting collar or saddle.
Symptoms. Slight swelling of the muscles and pain on pressure are commonly observable, though the swelling may be covered by the mane and overlooked. There is inability to draw up the dorsal or cervical angles of the scapula, and forced abduction or elevation of the limb causes pain. Lameness is not as a rule marked, though there is usually defective action.
The condition may be followed by atrophy, but as the muscles in question have no very important function as regards locomotion, this does not usually result in lameness.
Injury to the Causes. Badly-fitting collar, unequal collar pressure, efforts to start a heavy load, unequal length of traces and rough roads, may be responsible for bruising of this muscle.
Symptoms. There is heat, pain, and tender ness of the affected part, and the animal flinches when the muscle is squeezed between the fingers and thumb. Lameness is usually only slight, excepting in neglected cases, and is manifested by shortening of the forward stride. When in harness, an attempt is made to ease the pain by carrying the affected shoulder behind the other as much as possible. This results in a"three cornered"gait.
When the condition is neglected there is a great predisposition to the formation of a shoulder-tumour.
Sprain of the Supraspinatus and Infraspinatus. —This injury in its causation and its symptoms resembles the condition known as and presently to be described under the heading of supra scapular paralysis. It usually occurs in horses working in pairs, and is most often observed in the off-shoulder of the outside horse, according to the direction in which they turn. Animals ploughing in small fields or turning chaffing machines are particularly susceptible.
Strain of the Pectoral Muscles.Causes. Violent abduction, through falling with the fore limbs spread apart, slipping or landing badly from a jump.
Symptoms. There is more or less difficulty in using the fore limbs. Abduction causes pain, and some swelling may be observable.
In one bilateral case recovery occurred in a week without special treatment. Di Nasso observed rupture of the serratus anticus major, subscapularis and pectoral muscles from collision with a tree. The shoulder-joint rotated out wards when weight was placed on the limb. Rigot noted rupture of the lower insertion of the subscapularis in consequence of the limb slipping outwards.
Injury to the Biceps.The cause may be either external violence or strain through at tempting to start an excessive load.
Usually the condition is complicated by injury to the trochlear bursa or shoulder articulation. The symptoms presented are pain on pressure, inability to extend the leg, and dragging of the toe. Lameness becomes most evident when the animal is turned away from the injured limb. Rupture of the biceps, and even of both muscles simultaneously, has been reported, but is exceed ingly rare. Leblanc (Journal de Med. Vet. de Lyon) records the case of a saddle horse which suddenly fell lame on the near fore limb after having the ,off-fore shoe torn off by the toe of the hind foot. The lameness next day was intense. When at rest both fore feet bore equal weight. When made to walk the horse went very lame for a few steps, but if walked in a straight line the lameness diminished as the animal proceeded but became accentuated upon turning. A slight abductory movement of the shoulder was noticed when the foot came to the ground.
The biceps was contracted, hard, and very severepain was manifested upon pressure. The lesion was confined to this muscle alone.
Leblanc considers that at the moment when the horse's progress was arrested the whole weight fell on the near fore limb and that sudden energetic contraction of the biceps caused the strain. Lameness had completely disappeared in three weeks after blistering the course of the muscle.
Sprain of the Triceps.In many respects this resembles true radial paralysis. It is most often caused by getting the leg over the rope of the halter or into the manger, but sometimes occurs during falls and whilst jumping. Sometimes the injury is produced by getting the leg fast in a gate and struggling to get free.
Symptoms. The horse is usually unable to bear weight on the limb unless pressure is put on the front of the forearm. The knee is held in a position of flexion and the animal knuckles over at the fetlock. The leg is brought forward with a rotary movement. In severe cases dropping of the point of the elbow is very noticeable. The condition usually wears off after a few days, without special treatment.
. Rupture of the triceps has been observed as a result of turning suddenly. Marked adduction is usually evident, and in one case reported the lame leg was so much adducted that it crossed the other leg. Recovery is not probable, judging from the results of reported cases.
Bruising of the extensor muscles of the fore arm may produce a condition simulating radial paralysis. Using a rope as a cross-hobble during operations as neurectomy or firing will often cause marked lameness through pressure on the extensors. The knee is flexed, the limb cannot bear weight, and the foot is dragged, with the toe resting upon the ground. There is great difficulty in advancing the limb, but there is no"dropping"of the elbow as in radial paralysis.
Strain of the flexor muscles of the forearm is sometimes seen in hunters and steeplechasers after landing from a jump.
The limb is carried stiffly and pain is exhibited, both on flexion and extension of the knee. The sequel is chronic thickening, and a bent knee often results.
The treatment should include shoeing with raised heels during the acute period, then with out heels, and finally with a toe-prong to avoid contraction. Firing and blistering are usually beneficial.
Strain of the Psoas Muscles.This is produced in heavy horses through overwork, overloading, or slipping when backing. In riding horses, jumping, carrying a heavy weight with the saddle too far back and getting"bogged,"may be responsible. Some cases occur as the result of difficult parturition.
Symptoms. — There is an appearance of general stiffness of both hind limbs, which are advanced with difficulty. The horse usually travels"wide"behind, and frequently groans when turning or backing. Rectal examination and pressure on the affected muscles causes severe pain, and the animal may be unable to rise from the ground. Anal swelling may be sometimes observed.
Atrophy may result, with permanent lame ness as a sequel.
The longissimus dorsi is sometimes strained in a similar manner, with marked atrophy as a result.
Strain of the Gluteal Muscles.This may be caused by slipping during rearing or copulation, or through straining at a load. There is in flammatory swelling, followed by atrophy.
Rupture of the Rectus Femoris.This condi tion has been reported on several occasions. The symptoms closely resemble those seen in crural paralysis, viz. dropping of the stifle, flexion of the limb, and dragging the toe.
Rupture of the vastus externus produces similar symptoms.
Injury to muscles in the region of the hip is accompanied by difficulty in advancing the limb, dragging the toe, and difficulty in backing. Very little weight is placed on the limb, and the condition may be confused with stifle lameness.
Rupture of the Flexor Metatarsi.The rupture usually occurs in the tendinous portion of the muscle, either close to its origin at the lower end of the femur, or near the middle of the tibial region.
The division may be complete or partial; the latter occurs more frequently when the rupture is situated in the tibial region. The cause is usually severe strain, such as may be produced by falling with one hind foot carried backwards, over-extension during shoeing or operations on the foot, slipping on stone or paved floors, or through getting the leg over a bail. Rupture has also been observed as the result of the animal struggling whilst lying hobbled.
Symptoms. The flexor metatarsi arises from the lower end of the femur and is inserted into the hock and upper end of the metatarsus. The tendinous portion is an inextensible cord, and so flexion of the stifle-joint must necessarily be accompanied by flexion of the hock also. Opposed to this muscle are the gastrocnemius and the flexor perforatus, the former being in serted into the tuber calcis and the latter giving off a slip to either side of this point. The gastroc nemius tendon, or, as it is sometimes called, the tondo Achillis, is quite conspicuous, .and in the normal limb appears as a firm, tightly stretched cord.
When rupture of the flexor metatarsi occurs, the tension is withdrawn and the action of the gastrocnemius muscle is unopposed. The hind limb is therefore drawn back behind the body, the hock is extended, and indeed cannot be properly flexed. The tendo Achillis then appears lengthened and falls into one or more folds, and upon moving the animal the limb may be jerked violently backwards. Occasion ally swelling and pain may be observed over the site of the rupture, but more frequently there is no indication that anything is wrong at the part.
Prognosis is in the majority of cases favour able, particularly in partial rupture occurring in the tibial region. When the upper insertion is torn away from the bone, recovery is by no means so certain, and frequently a consider able exostosis develops on the lower end of the femur. As it is usually a difficult matter to decide exactly where the rupture has occurred and its extent, a guarded prognosis should be given. In favourable cases union is complete in from four to eight weeks, though when the upper insertion is torn it may require several months.
Treatment. — The first consideration is to ensure complete rest of the limb, and it is well to secure it in a position of flexion if this can be effected without unduly exciting the patient. Slinging is beneficial in quiet horses. The limb may be secured by means of a rope fastened to the animal's collar at the one end and to the metatarsus at the other, with the limb advanced a few inches in front of its fellow, but not sufficiently to prevent the foot resting on the ground. Blistering or other treatment is un
necessary, and may do harm through increasing movement by causing pain. Swelling of the part may be treated by hot fomentation if excessive and very painful.
Excessive extension of the hock-joint may persist for some weeks, but disappears upon ultimate contraction of the scar tissue. It is inadvisable to work the animal for several weeks after the disappearance of lameness.
Rupture of the Gastrocnemius Muscle or its Tendon. This condition is distinctly rare among horses, but has frequently been observed in cattle. In many cases, however, the muscle and tendon are not affected, but the bony cap of the tuber calcis is torn off, especially in young animals in which ossification is not complete.
Complete rupture of the gastrocnemius muscle itself has been reported on several occasions, though in some of these cases the ruptured muscle, whether external or internal gastroc nemius, is not clearly indicated.
Causes. In horses the injury may arise from suddenly being pulled up whilst at the gallop, from falling with the hind legs doubled under neath the animal, or in efforts to avoid slipping on paved or asphalt roads. Jumping has apparently accounted for several cases. In cattle, attempts to rise from unfavourable situa tions or riding on other cows may be responsible. In the smaller animals external violence may cause rupture of the muscle or its tendon.
Symptoms. These are in direct contrast to those exhibited in cases of ruptured flexor metatarsi.
No weight can be placed upon the limb, whilst at each step the hock and phalanges are excessively flexed; the hock may even touch the ground when an effort is made to advance the leg. This is particularly noticeable in cattle. At the same time the ordinary taut appearance of the tendo Achillis disappears, and in all posi tions of the limb the tendon is relaxed. Owing to lack of support of the tuber calcis and the tendency of the unopposed flexor metatarsi to extend the stifle-joint, the hock always appears lower than its fellow.
When the rupture occurs in the tendon the separation can usually be plainly felt or even seen through the skin.
Partial rupture is indicated by lameness on attempting to place weight on the limb, and more or less pronounced flexion of the hock and fetlock joints.
Course. — In simple rupture prognosis is always more favourable than when the cap of the tuber calcis is torn off. In large animals there is difficulty in maintaining them sufficiently long in the standing position to secure union, though horses may be slung, but this does not always prevent the occurrence of laminitis in the foot of the other hind limb.
Cattle do not take kindly to slinging and usually remain in the recumbent position, which necessitates flexion of the hock-joint and is very detrimental to satisfactory union. It may be advisable to slaughter cattle according to their fitness for the butcher in other respects.
In small animals prognosis is generally favourable.
Treatment. Horses must at once be placed in slings. Bandaging or the application of splints is a matter which must be left to the judgment of the practitioner, as horses of a quiet disposition may be benefited by their use, whilst in excitable animals interference may result in more harm than benefit. When it is decided to attempt support of the limb a plaster or pitch bandage should first be applied to the fetlock-joint, as this will materially assist in extending the hock.
The latter may be encased in a similar bandage or supported by splints, but care must be taken not to exert undue pressure on the situation of the rupture. A length of planed wood, hollowed out at the lower end to encase the flexor tendons and bearing at its upper extremity two straps of wide webbing with buckles attached, is the best form of splint. The lower end is firmly bandaged into position and the webbing is strapped around the tibia, and may be adjusted to secure the best position. Failing this, a curved splint of wood or metal may be placed in front of the limb, being first well padded and secured in position by straps or bandages.
Satisfactory cases usually require six weeks to effect union, though many cases take several months to recover.
As a last resort, operation has in some cases proved successful when the tendo Achillis has been divided. The skin is divided from above downwards, and the ends of the tendon are first pared with a scalpel and then sutured with silver wire. Deep sutures of wire may also be employed after the extremities have been joined by strong silk thread (see"Sutures,"p. 570). The limb must be fixed in a position of moderate extension by splints. Excessive granulation and suppuration are the chief complications. The former may be removed with the scalpel, or rubbed with nitrate of silver occasionally. To avoid suppuration and its complications continuous irrigation with normal saline solu tion or very weak solution of permanganate of potash or eusol gives the best results. In dogs the limb may easily be fixed by splints and bandages in a position of moderate extension. Treatment is usually satisfactory in this animal.
Displacement or rupture of the biceps femoris muscle may occur in cattle. It is more common in working oxen, especially when in low condition.
The biceps femoris arises from the sacrum and iscbium and has two insertions, one into the tibia and the other throughout almost the whole length of the muscle by means of a fibrous aponeurosis into the fascia lata of the thigh. The muscle covers the trochanter of the femur, and in thin animals this exerts doubt lessly a degree of pressure upon the aponeurosis, particularly during movement of the limb.
Slipping, falling, or heavy draught work may produce laceration or stretching of the musculo aponeurotic layer, with the result that the trochanter becomes caught. In the case of stretching this is merely a temporary matter, and a change of position, as in travelling down hill, will usually effect release.
When, however, the aponeurosis is torn so that the trochanter protrudes through the open ing the latter will be observed to be especially prominent and the former will appear as a rigid cord running parallel with the front edge of the muscle. Flexion of the femur is then im possible, and the limb is kept extended in a position similar to that seen during dislocation of the patella. In attempting to advance the limb it is carried as a whole without flexion, so that the limb appears too long and the toe is dragged along the ground. The"mowing"movement described by many authors is apparently not constant.
Treatment consists in effecting reduction of the displacement under anzesthesia; failing this, incision of the fascia in order to release the trochanter.
Rheumatic Myositis.Causes.Exposure to cold, particularly in damp weather, is one of the commonest causes. Draughts have a similar effect. Turning sweating horses to pasture, or turning them out in bad weather too soon after clipping, may give rise to the condition. Some fodders, such as heated grain, and in some cases excess of barley or maize and damaged hay, occasionally produce symp toms indistinguishable from rheumatism.
Dogs are the animals most frequently affected, pigs probably come next in order, then horses and cattle.
Certain animals seem to have a particular susceptibility to rheumatism, which they develop upon the least provocation, whilst others kept under the same conditions remain free from it.
Symptoms. In horses the muscles of the limbs, back, and quarters are most commonly the seat of rheumatic myositis. Usually only one set is affected at a time, but the lameness usually changes from one part of the body to another. It is not at all uncommon to see a horse lame from rheumatism in one limb go sound in that particular member in the course of one or two days and suddenly develop lame ness in another limb. Frequently all four are affected in turn, and usually the symptoms are confined to one at a time.
The type of lameness will depend upon the situation of the affected muscles. The attack comes on suddenly, and the animal shows great stiffness and disinclination to move. These symptoms may disappear quite as suddenly as they made their appearance, or the condition may persist for weeks or months, with frequent changes in the situation of the lameness. Lum bago is characterized by wide action, dragging gait, and a general appearance of stiffness in the hind quarters. The animal usually has difficulty in rising, and may in fact refuse or be unable to assume the standing position. Occasionally articular rheumatism accompanies rheumatic myositis.
In cattle articular and muscular rheumatism are more often associated, and the attack more frequently becomes general instead of being confined to groups of muscles. The appearance may be suggestive of laminitis.
In dogs the whole body may be affected at one time, but more commonly the muscles of one side of the neck or of the shoulder, thigh, or back are the seat of the trouble. The parts are painful on palpation, and the animal usually gives evidence of this by howling when it is handled. Sometimes the masseter and pterygoid muscles alone are affected, and the animal shrieks suddenly whilst eating.
The affected limb is usually carried when the pain is acute, but very often the attacks appear to be intermittent, so that the animal may run for some distance apparently well and will suddenly stop, hold up one foot and howl with pain.
Rheumatism of the back and loins causes the dog to carry himself stiffly, and pain is exhibited, especially whilst climbing a flight of stairs or mounting a hill.
In pigs general stiffness is the rule, particu larly of the hind limbs, and the animal may exhibit symptoms resembling paraplegia arising from spinal tuberculosis.
Lesions. In mild cases no evident change occurs in the muscles. In acute cases the muscle substance is reddened, the fibres softened and disintegrated, and lymph may flow into the interstitial spaces. In chronic cases the inter stitial spaces become filled by connective tissue and the muscle fibres undergo fatty degenera tion, terminating in atrophy of the muscle.
Treatment. Local treatment must be con fined to rubbing the affected parts with a mild liniment. Applications containing methyl sali cylate give the best results. In horses local injection of veratrin gr. i. in alcohol TR xxx. daily has been recommended, but as the opera tion is followed by pain, the animal should be led about.
Exercise usually benefits mild cases of rheu matism, but in acute attacks the animal should be rested.
Aperients are always indicated. In horses a dose of aloes may be given, or magnesium or sodium sulphate in one or two ounce doses daily may be beneficial. Salicylate of soda or salicylic acid has for long been the sheet-anchor in the treatment of rheumatism, and it may be with advantage combined with alkalies and iodide of potash which in chronic cases is especially useful.
In dogs capsules containing methyl sali cylate and colchicine give good results, or sali cylate of soda may be employed. In chronic cases gum guaiacum is useful.
Pigs should receive a dose of calomel, followed by sodium salicylate in powder mixed with the food.
Cattle may receive a liberal dose of magnesium sulphate, followed by sodium salicylate and alkalies.
Myositis of Fatigue. This condition is by no means uncommonly met with amongst equine patients. The exciting cause is overwork of a muscle or of one or more groups of muscles.
Overloading or prolonged exertion, especially when the horse is in low condition or has been put to work at too early an age, may be respon sible, whilst in horses in training for racing, polo, etc., it may be due to heavy demands made upon certain groups of muscles before they have become sufficiently developed to perform the work.
The symptoms vary somewhat according to the nature of the work performed and the degree of fatigue resulting. Horses which have been, in horsemen's parlance,"overdone"show symptoms of general stiffness. The feet are hardly raised from the ground but are dragged or shuffled forward. The animal appears depressed and is often feverish (103°-104° F.). Frequently the bowels are costive, particularly when the horse has sweated profusely whilst at work.
When moved from side to side or turned in short circles the stiffness becomes much more apparent, and in severe cases the animal may groan during these movements. In other cases, particularly after overloading, the symptoms may somewhat resemble those produced by laminitis, although it is quite usual for true laminitis to result from over-exertion.
The affected muscles may appear harder than normally, and are painful on palpation. Usually the extensor muscles of the limbs are involved, and frequently those of the loins and quarters. The psoas muscles may also undergo inflam matory changes, more especially amongst race horses, steeplechasers in training, and hunters. Horses affected with myositis of fatigue show little desire to lie down. When they do so they manifest pain to an even greater extent than whilst standing, and thereby differ from horses suffering from laminitis, which, although fre quently loth to lie down, invariably obtain a certain amount of relief from pain when they do so.
Treatment. Rest is by far the most essential part of the treatment. The horse should pre ferably be stabled in a loose-box where he is free to move about and able to rise without difficulty, should he feel inclined to go down. The diet should be confined to loose, easily digested food, such as mashes, roots, and green food when obtainable. A gentle laxative is always advisable, and may take the form of aloes barb. 3ij. iv., calomel 3i. or mag. sulph.
When the muscular soreness is very marked sod. salicylas in hall-ounce doses repeated three times a day may give relief and combat the feverish symptoms which are frequently present.
The inflamed muscles may be massaged with a mild, stimulating liniment if desired, preceded, when pain is severe, by hot fomentation. _