Diseases of the Musculoskeletal System

Chapter 54 Diseases of the Musculoskeletal System


Disorders of the musculoskeletal system are of great importance to the equine industry. The main purpose of a horse is to work, and if it has lameness problems it will not be able to do much work. One of the first things that must be understood is the difference between a blemish and an unsoundness. A blemish is an alteration in the appearance that does not affect the horse’s serviceability. An unsoundness, in contrast, does affect the horse’s ability to do its job. Most unsoundnesses occur in the horse’s front limbs, distal to the knee.



SUBSOLAR BRUISING (“CORNS”)


Sole bruises are usually caused by trauma to the sole with subsequent hemorrhage between the sensitive and insensitive soles. Some factors that make an animal more likely to have bruising include:


• Exercise on hard ground

• Thin, flat soles

• Coffin bone rotation



CLINICAL SIGNS



• Horses may or may not show acute onset of lameness

• The lameness is usually chronic and low grade

• Bruises are often bilateral

• Sole pain is evident with hoof testers


DIAGNOSIS



• Visualization of bruise


TREATMENT



• Make sure of proper shoeing/trimming to support foot and protect sole

• Nonsteroidal antiinflammatory drugs (NSAIDs) to control pain


INFORMATION FOR CLIENTS



• The condition can be prevented by maintaining proper foot conformation so that the sole is concave and nonweight-bearing.


HOOF ABSCESSES


Hoof abscesses are the most common cause of acute, severe lameness in horses. Horses with a history of foreign body penetration into the hoof capsule and those with chronic laminitis are more likely to experience development of hoof abscesses. The condition occurs when bacteria gain access to hoof structures and form abscesses. Pain occurs because abscesses cannot expand due to the hoof’s rigid structure. Pain is relieved when abscesses rupture.




CLINICAL SIGNS



• Acute, severe lameness (3–5/5)

• +/− Heat in foot and over coronary band

• +/− Palmar digital pulses

• +/− Fetlock and pastern swelling

• Localized pain with hoof testers


DIAGNOSIS



• Visualization of draining tract

• Sometimes a radiograph of the hoof is taken to visualize how deep the tract extends


TREATMENT



• Localize pain and pare out abscess

• Epsom salt soaks

• +/− Drawing agent (Ichthammol)

• Antibiotics usually are not indicated, unless the horse is kept in dirty, unsanitary conditions

• Be aware of tetanus prophylaxis!


NAVICULAR SYNDROME


Navicular syndrome is most common in large-bodied horses, especially of quarter horse, Thoroughbred, and Warmblood breeding. Onset is most often seen in 6- to 8-year-old horses. The condition can occur when excessive stress and strain on flexor tendons puts pressure on navicular bursa or excessive concussion on coffin joint leads to inflammation of navicular bursa. This leads to inflammation and erosion of navicular bone. Heavily muscled horses with small feet, horses with short, upright pasterns, and horses with improperly trimmed hooves (long toe, low heel) are more likely to acquire the condition.




CLINICAL SIGNS



• Chronic, low-grade lameness, often bilateral

• Lameness may be intermittent

• Pointing

• Pain over frog with hoof testers


DIAGNOSIS



• Palmar digital nerve blocks

• Radiographs


TREATMENT



• NSAIDs (take care, some will cause gastric ulceration)

• Correct hoof imbalance

• Support heels

• Isoxsuprine

• Suspensory ligament desmotomy

• Palmer digital neurectomy


INFORMATION FOR CLIENTS



• Although there is no reliable way to prevent occurrence of the condition, its likelihood of occurrence can be reduced by maintaining proper hoof balance.


THRUSH


Thrush is a bacterial infection of sulci of frog and is usually found in horses that are kept in wet conditions. The most common bacterium isolated from horses with thrush is Fusarium necrophorum. A horse is more likely to contract thrush if it is kept in wet, dirty conditions, especially if the feet are not properly maintained.




CLINICAL SIGNS



• Foul-smelling black discharge from frog sulci

• Horse is usually not lame, unless severe

• Deep erosion of frog sulci


DIAGNOSIS



• Visual signs and smell

• Treatment

• Clean feet, removing necrotic tissue

• Apply topical astringents such as Koppertox, iodine, and others.


INFORMATION FOR CLIENTS



• Thrush is easily prevented by keeping the horse’s living conditions clean and sanitary. Daily cleaning of the feet will also reduce the occurrence.


SIDE BONE (CALCIFICATION OF LATERAL CARTILAGES)


Sidebone is usually found in the front feet of older horses. Draft breeds are overrepresented in the population of affected horses. Sidebones usually start as an unsoundness, then regress to a blemish. The inciting cause for a horse to experience development of sidebones is direct trauma to the foot.




CLINICAL SIGNS



• Lameness in the initial stages

• Evidence of trauma

• Occasionally a bulge just distal to the coronary band may be seen


DIAGNOSIS



• Radiographs of the affected foot


TREATMENT



• NSAIDs

• Rest (sometimes for as long as 6 months)

• Immobilize foot with bar shoe


PASTERN CHIP FRACTURES


Chip fractures of the pastern generally involve the long pastern bone. Repetitive stress and overflexing of the hock can cause these fractures. Horses that have long, weak pasterns are more likely to experience development of these fractures.




CLINICAL SIGNS



• Slight lameness, if any

• Swelling around dorsal aspect of fetlock joint

• Slight pain on fetlock flexion


DIAGNOSIS



• Radiographic evaluation


TREATMENT



• Most often accomplished by arthroscopic chip removal


PROXIMAL SESAMOID FRACTURE


Sesamoid bones are part of the suspensory apparatus. Wear and tear occurs at the abaxial surfaces where suspensory ligaments pass. Sesamoid bone fractures are most commonly seen in athletic horses. Stress and strain on the fetlock joint, often from repeated overextension of the joint, puts force on the suspensory ligaments, which, in turn, pull on the sesamoid bones, causing them to fracture. Performance horses with long, weak pasterns are more likely to fracture their proximal sesamoids than are other horses.




CLINICAL SIGNS



• The condition is more common in the forelimbs.

• A variable degree of lameness exists.

• Pain is evident on flexion of the fetlock and palpation of the sesamoid bones.


DIAGNOSIS



• Radiographic examination

• It is also advisable to perform an ultrasound of the suspensory apparatus


TREATMENT



• Surgery
Removal of fragment

Casting with rest for up to 1 year

Internal fixation

• Prognosis more favorable if caught early


SESMOIDITIS


Sesmoiditis is an osteitis of the proximal sesamoid bones, and it is most often encountered in racehorses. These horses often present with a history of gait restriction during training. Extreme stress and strain and repetitive loading lead to tearing of suspensory ligament attachments. This, in turn, leads to inflammation of the proximal sesamoid bones. Horses with long, weak pasterns are more likely to be affected by sesamoiditis.




CLINICAL SIGNS



• The condition is more common in the forelimbs.

• A variable degree of lameness exists.

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Aug 31, 2016 | Posted by in GENERAL | Comments Off on Diseases of the Musculoskeletal System

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