Equine Orthopaedics

Lameness investigation •Observation at rest; posture muscle mass, limb alignment, hoof balance and shoeing •Palpation for joint distension, tendon enlargement, heat, increased digital pulse amplitude •Grading of lameness at walk and trot 1-5 •Lameness observation on soft/hard, circles etc •Flexion tests •Nerve/ joint blocks/tap •Application of hoof testers •Paring of foot

Careful observation and palpation at rest are important features to look for include.... Loss of muscle mass may indicate chronic lameness and disuse muscle atrophy. Thickening of a tendon or ligamnent may indicate injury (chronic or acute). Heat will indicate active inflammation of that structure. Distension of a synovial structure, (joint, bursa, tendon sheath) indicates inflammation of that structure, this is particularly significant if the structure is significantly more distended on the lame than the sound limb. Palpation of the digital artery in the abaxial sesamoid site will reveal increased amplitude if there is foot pathology such as laminitis or a foot abscess. Poor conformation which will result in abnormal loading of the limb and thus predispose to lameness

Recognising lameness It is normal for a horse to rest a hind limb, ‘locking’ the stifle on the opposite limb, however both forelimbs should be equally weight-bearing at all times. At walk all four limbs should be bear weight equally and have equal stride length, the hind feet should land in or in front of the hoof prints of the forelimb on the same side, this is called tracking up, failure to do this indicates a shortened stride length.

If there is a lameness in a foreleg the horse will tend to raise the head as this limb hits the ground, as the opposite sound leg hits the ground, the head will drop, ie the head will ‘nod’ down as the SOUND leg hits the ground. A hind limb lameness is appreciated by increased amplitude of the quarters (usually best appreciated by observing the top of the gluteal muscles) on the LAME side, most often the impression will be of the hip ‘dropping’ as the lame limb hits the ground.

Nerve block Injection of local anaesthetic close to a nerve will desensitise the structures distal to this site. If the horse goes sound subsequent to a nerve block, the source of pain must be distal to the site of the block. This is a useful technique to help localise the site of the pain. Sites of the most commonly used nerve blocks are described in The Equine Formulary which Dr Sefinew has available.

Joint Block Similarly injection of local anaesthetic into a joint will block pain from that joint, if the joint is the source of lameness, the horse will improve after a joint block.

Sterility is essential. Surgical preparation, sterile needle, syringe, gloves, new, unused bottle of local anaesthetic.

Further investigations Radiography Ultrasonography Scintigraphy CT scanning MRI

Very lame horse ‘three legged lame’

Fracture •Crepitus •Deformity •Swelling •Instability Most fractures require euthanasia

Sepsis •Abcess synovial sepsis •Cellulitis life threatening Easily treated

‘no foot no horse’ most lamenesses are due to foot problems

Good foot balance is essential to maintain soundness and working capacity

Foot imbalance predisposes to lameness

Trim hoof to achieve.............

•Dorsoplamar balance •Mediolateral balance •Hoof landing flat

Shoe for.......

•Good sole protection •Easy breakover •Heel support

Donkey foot care NB Dr Sefinew has available a DVD on donkey foot care, though it is slightly biased to British conditions, eg wet ground.

More upright and’ boxy’ than horse hoof Thick sole

Hoof abcess •‘pus in the foot’ •White line or sole •Very painful •Increased digital pulse •Response to hoof testers •Drain •Poultice/tub •Tetanus prophylaxis

Hoof wall cracks Cause pain due to instability and infection, to treat....

•Balance hoof •Trim and clean crack •Stabilise foot with a shoe •Unload affected area •Nutrition important, sulphur, Ca etc for horn quality

Corn Painful bruise located at ‘seat of corn, between bar and wall at heel, caused by poor shoeing, heel of shoe too short

White line disease Infection enters via ‘white line’ between wall and sole, chronic lamimitis cases very susceptible

Keratoma Benign tumour of hoof horn, can be cut out, may see radiolucency on p3 on radiographs

Canker • Anaerobic infection causing spongy abnormal horn production •Treat by debridement of abnormal horn, local iodine or metronidazole

Thrush •Fusobacterium necrophorum • Treat with Iodine

Pedal bone fracture Resent percussion of hoof wall Radiographic diagnosis

Usually heal well if hoof capsule stabilsed with a shoe

Ossification of the lateral cartilages ‘side bone’ (Infection=quittor)

Navicular disease

Pain from navicular bone and associated structures associated with poor hoof balance (broken back hoof –pastern axis.

Severe degeneration of navicular bone

Laminitis Interdigitating laminae hold the pedal bone suspended within the hoof capsule

If there is breakdown of the dorsal laminae, the pedal bone will rotate due to the ‘pull’ of the deep digital flexor tendon being unopposed by the dorsal laminae. This is a common result of laminitis and results in ‘stretching of the white line at the toe and pressure on the sole at the tip of the pedal bone , sometimes seen a sensitivity or bruising in an arc just in front of the tip of the frog. Treatment includes addressing the underlying cause of the laminitis, support of the frog and caudal 1/3 of the sole (pads, soft bedding, sand). Corrective trimming is essential to trim back the wall of the foot at the toe and to lower the heels in order to restore normal foot balance.

Sinking occurs when the laminae all the way around the hoof break down and the pedal bone sinks within the hoof capsule. It is a serious consequence of laminitis which requires aggressive treatment of the underlying cause and foot support. It can carry a hopeless prognosis.

Causes of laminitis •Grain overload endotoxin released due to overgrowth then death of gram negative badteria in the caecum and colon •Endotoxaemia caused by retention of placenta,peritonitis, pleuropneumonia etc •Concussive trauma tearing the laminae ‘road founder’ •Metabolic disorders insulin reisitance, Cushings etc

Laminitis symptoms • Land heel first to relieve the toe •Typical stance, rock back to take weight off front limbs •Raised digital pulse •Laminitic rings on hoof wall which diverge at the heel •Sweat, blow in pain

Chronic laminitis.. rotated pedal bone Aims of trimming:- Realignment of P3 Lower heels Trim back dorsal wall Un-weight laminae (frog /sole support) Deep digital flexor tenotomy last resort

Re-modelling at tip of pedal bone ‘ski-tipping’

Treatment of laminitis •Treat underlying cause •Frog and sole support •Box rest •Corrective trimming

Frog and caudal sole support are an essential part of the treatment of laminitis. Support pads can be used or supportive bedding such as sand. So that some weight can be taken by the sole and frog in order to unload the compromised laminae.

Synovial Joint Structure

Synovial fluid analysis

Septic Inflammatory •Sterile lavage

•Antibiotics (intrathecal, systemic,IVRA)

Glucosamine PGAGS

•Rest •Hyonate •Corticosteroids

Synovitis (distended synovial structure)

Degenerative joint disease

•Synovitis •Synovial fluid changes •Cartilage breakdown •Capsulitits

Osteoarthritis eg spavin (hock), ring bone (pastern and coffin joints) •Destruction of articular cartilage • subcondral bone sclerosis •Osteophyte formation •Steroids, NSAIDS

ringbone

Hock Problems Spavin (osteoarthritis of lower tow hock joints) Sepsis of synovial structures Osteochondrosis... Failure of endochondral ossification of cartilage in young horses , developmental orthopaedic disease Fractures usually a kick from another horse Cellulitis the hind limb and hock are a common site for cellulitis

Carpus ‘Knee’ Synovial sepsis Trauma (falling on road etc) Chip fractures

Stifle Femur,Tibia and Patella Three separate joint compartments, femuropatella, medial and lateral femurotibial. Problems include • Synovial sepsis •Bone cysts (developmental •Orthopaedic disease) •‘Locking patella’

Upward fixation of patella ‘locked stifle’ ‘Clicking’

Medial patella ligament hooks over medial trochlear ridge This is normal when a horse rests the contralteral leg but sometimes fails to release, the horse then cannot flex the leg and will drag the toe

Locking patella is more common in young horses, the problem often stops happening when the horse matures and gains weight and muscle strength. When a horse has a locked patella, it can be encouraged to release by making the horse step backwards or suddenly startling the horse. In recurrent cases good nutrition to improve body condition and training to improve muscle strength help. In problem cases the MEDIAL patella ligament can be transected but this can have unwanted consequences on patella and joint integrity and should be a last resort.

Fetlock P 1,Metacarpal/metatarsal ,Sesamoid bones. • Synovitis • Synovial sepsis • Arthritis

Digital flexor tendon sheath •Windgalls ( benign strain induced synovial distension) •Deep digital flexor tendon injury •Septic tenosynovitis •Annular ligament syndrome (chronic thickening of annular ligament associated with DFTS distension)

OCD (osteochondrosis) Usually a problem in large, fast growing horses. Developmental orthopaedic disease Genetic and nutritional factors Failure of endochondral ossification, cartilage flaps Bone cysts Free floating fragments of cartilage Joint distension Lameness

Synovial fluid normal.... •Clear •Pale yellow •Viscous

Septic • Cloudy •Watery •>10x109 cells /l

Synovial structures

SYNOVIAL SEPSIS •Life threatening •Anatomical knowledge, wounds near synovial

structures require careful examination

•Diagnosis.. synoviocentesis

•Emergency treatment .. Flush synovial

structure with large volumes of sterile saline

•Euthanasia if severe established infection, hopeless prognosis

Synovial structures

Sole Penetration In this site can result in contamination of the navicular bursa. This is a life threatening condition as it is extremely difficult to clear the infection. The bursa must be surgically debrided and flushed.

Synovial distensions

Synovial sepsis treatment •Realistic prognosis, established infection can be impossible to clear due to fibrin deposition etc •Lavage with large volumes of sterile saline •Intra-articular antibiotics •Intavenous regional antibiotic •Arthroscopy to debride fibrin, synovial villae etc

Splint bones (metacarpals 2 and 4 )

•‘Splints’ bony enlargement due to excess loading, may be lame while forming but once settled non significant •Fractures, often due to a kick.

Suspensory ligament Modified muscle More cellular then tendons Slow to heal Injury risk increased by soft going, long pasterns,poor shoeing, long toe, low heel

Suspensory ligament breakdown Results in dropping of the fetlock • Acute rupture • Chronic breakdown

•Maintain limb alignment ,store energy , initiate breakover •Don’t adapt to exercise in adult horses •Cannot regenerate •Accumulative degeneration over time •Speed major risk factor for injury •Prompt and aggressive treatment after injury will limit inflammatory damage

Flexor tendons

Enlarged superficial digital flexor tendon

Superficial flexor tendon Deep flexor tendon Check ligament Suspensory ligament

Ultrasonographic views of the flexor tendons in the proximal metacarpal region, cross sectional and longitudinal views

Scanning •Cross sectional area, enlarged in damaged tendon compared to contralateral limb •Fibre alignment, disrupted in injured tendon • Core lesions black area, absence of fibre pattern

Core Lesion

Tendon injury •Anti-inflammatories •Rest •Cold •Support •Shoeing •Polysulphatedglycosaminoglycans •Stem cell therapy •Platelet rich plasma •‘firing’ application of hot metal is useless and cruel

Myopathies •Recurrent Exertional Rhabdomyolysis •Vit E deficiency •Trauma •Clostridial myositis Can be caused by intramuscular injection

•Monensin toxicity myoglobinuria

Recurrent Equine Rhabdomyolysis Signs include muscle stiffness, soreness, short stride, sweating, myoglobinuria

•‘leaky’ sarcoplasmic reticulum •PSSM

Risk factors • High grain diet • Stress • Work after rest • Electrolyte imbalance

Treatment • Rest • Anti-inflammatories • Fluids

Control • Exercise • Diet • Dantrolene

Limb deformity result s in abnormal loading of structures pain and lameness

Early intervention In cases of congenital deformity can allow the limb to develop normally

Flexural limb deformities Congenital ‘contracture of the deep digital flexor tendon’

•Physiotherapy •Oxytetracycline i/v will help straightening of limb •Extension of toe (shoe, glue etc)

Sudan grass Can cause flexural deformity

Tendon ‘ laxity’ Hyperextension This will often resolve itself, it may be necessary to protect the heels from trauma

Angular limb deformities •Corrective trimming/ shoeing •Surgery

The hoof is trimmed to lower the wall on the side which the hoof is deviating from ie the lateral side in valgus. Shoes, glue, resin or even rigid material such as plastic taped to the foot is used to form a medial or lateral hoof extension to support the side to which the hoof is collapsing, eg the medial side of the hoof in valgus deformity. The aim of surgery is to slow growth rate of the bone on the convex side (by plating or using screws and wire to restrict the growth plate or by enhancing growth on the concave side ( by releasing and elevating the periosteum)

Valgus.. limb deviates laterally

Varus.. Limb deviates medially

• Carpus rapid growth of radius up to 6 months

• Fetlock only up to 2 months Correction is more urgent at an early stage

Careful support bandaging can be helpful in limb deformities, using materials such as plastic guttering as splints but care must be taken to avoid causing sores (eg avoid pressure on the accessory carpal bone). Bandaging should be avoided if possible in cases of tendon laxity as it will make the situation worse, most such cases wil resolve themselves.