Transcript m5zn_a768cacd3acff8c

lameness
Def.


Lameness is the result of a change from
normal stance and gait caused by either a
structural or a functional disorder of one
or more of the limbs, the neck, or the
trunk.
It is not a disease, but a manifestation of
either pain or mechanical interference of
the musculoskeletal system, although a
combination of the two frequently exists .
 Mechanical
lameness is best
typified by fibrotic myopathy with
its characteristic gait abnormality,
 but can also be the result of a
restriction (eg, tendon sheath
restriction in annular ligament
syndrome).




Pain-related lameness can be classified as:
weightbearing (supporting leg) or
nonweightbearing (swinging leg)
lameness,
although lameness most often is
composed of both.
A
supporting leg lameness is seen
when the horse attempts to
reduce the amount of time a
particular limb is bearing weight.
 The horse elevates its head and
shifts its weight away from a
particular limb during
weightbearing for a forelimb
lameness, whereas the opposite is
true for a hindlimb lameness.
Factors that predispose to
lameness



physical immaturity :
eg, bones that are anatomically normal
but biomechanically weak due to the age
of the horse at the onset of training
or bone that is abnormally weak due to
developmental orthopedic disease),
Inciting factors in lameness



direct or indirect trauma,
incoordination of muscle action following
fatigue in racehorses racing over long
distances,
or inflammation—more often than not
without infection—of joints, tendons, and
ligaments in particular.
The Lameness Examination:
Overview

A systematic investigation of a lame horse
is time consuming.




The examination begins with a comprehensive
medical history; type, age, and training
regimen may give important clues to the
lameness as will the time since onset of
lameness and interim management.
The interval since the last shoeing should be
noted, as well as any suggestions that the
lameness may improve with either rest or
exercise.
Response to anti-inflammatory or analgesic
medications may provide useful information.
Results of hematologic and biochemical
analyses may shed light on other problems that
influence overall performance.




detailed visual inspection and thorough
manual palpation of the limbs in
weightbearing and nonweightbearing positions.
comparision with the contralateral limb should
always take place,
Any heat, joint distention, or abnormal tissue
tension should be noted, as well as the reaction
of the horse and range of flexion and extension
of all joints.
Specific areas of muscle wastage may also
provide useful information.



The feet should be thoroughly examined,
including compression of the walls and
sole with hoof testers.
Wear patterns of shoes and feet should be
noted.
A number of abnormalities such as broken
toe/pastern axis; mismatched hoof angles;
under-run, contracted, and sheared heels,
and disproportionate hoof size are seen
more frequently in lame than in sound
horses.
 Shoes
should be left on, as
removing them at this stage
might make the horse footsore
and thereby preclude further
examination.
 However, occasionally it may
prove useful to remove the front
shoes to demonstrate that the
shoeing was the cause of the
lameness.
Hoof testers are applied across the hoof wall and
the bottom of the hoof to check for painful areas .





The back and neck should be thoroughly
examined with the horse restrained and
standing square on a level surface.
The neck should be assessed for range of
movement in all planes and for evidence of
muscle asymmetry and pain.
The dorsal midline of the back should be
straight, and equal tone should be present in the
paravertebral musculature on either side of the
midline.
The same should be true of the gluteal
musculature and the hamstrings.
Spatial alignment of the tubera coxae and
sacrale should also be observed.
Thorough palpation of the back is an important
part of a lameness examination .



Examination during exercise becomes an
option only if the degree of lameness is
minor and chronic.
If lameness is major and acute (eg,
suspected fracture), additional exercise
could result in a catastrophic breakdown
with dire consequences for the horse.
It is important to check whether the
horse may have been given analgesic
medication prior to the lameness
examination.



Flexion tests are useful diagnostic tools.
The range of movement and response to
passive flexion, along with any suggestion
of increased lameness or onset of
lameness following flexion, should be
observed.
However, results of recent studies have
suggested that “false-positive” results may
be seen if excessive forces are applied.
The horse's leg is held in a flexed position to stress
the joint. The horse will be assessed at a trot to
determine if this flexion test accentuates the
lameness .

A ridden assessment of the horse is
often necessary, particularly with a subtle
lameness or a horse that is unwilling to
perform certain movements (eg, a
dressage horse). A multilimb lameness
without an obvious single-limb lameness
may also be involved. The clinical signs
may be minor (eg, signs of aversion as
opposed to lameness).
Imaging Techniques




Imaging techniques provide important
pathologic and physiologic information
necessary to treat specific conditions.
Imaging can be divided into anatomic and
physiologic methods.
Anatomic imaging methods include
radiology, ultrasonography, computed
tomography, and MRI.
Physiologic imaging methods include
scintigraphy and thermography.
Anatomic Imaging Techniques



Radiologic techniques are the methods most
commonly used to evaluate lameness in horses.
Plain film radiography requires multiple
projections to evaluate any area.
It allows assessment of bony tissues and reflects
chronic changes. Occasionally, radiographic
techniques that provide more information are
needed.
Contrast radiography provides information about
articular cartilage and surfaces and is of
particular value in determining whether
subchondral cysts communicate with the joint
and in delineating subcutaneous tracts.
The technician holds an x-ray plate behind the
horse's limb so that a radiograph can be
taken. Some horses may need to be sedated so they
stand quietly for the x-ray .



Ultrasonographic examination can be
used to assess any soft tissues.
Ultrasonography is most useful in the
evaluation of tendons and ligaments but
can also be used to evaluate muscle and
cartilage.
It can also help determine whether a
lesion is active or chronic .


.MRI and computed tomography are highdetail anatomic imaging tools.
They are not currently used in clinical
practice but may be useful in research.
This is an MRI of a horse with bone inflammation
in the front of the pastern (light grey region) that
could not be detected on radiographs .
Physiologic Imaging Techniques
These techniques provide images that
reflect physiologic processes.
 Unlike anatomic imaging, which
reflects structure, physiologic imaging
techniques assess metabolism or
circulation.
 Thermography and scintigraphy allow
examination of the entire horse.




Thermography is the pictorial representation
of the surface temperature of an object. It is a
noninvasive technique that measures emitted
heat and is useful for detecting inflammatory
changes that may contribute to lameness.
Thermographically, the “hot spot” associated
with the localized inflammation generally is seen
in the skin directly overlying the injury.
However, diseased tissues may have a reduced
blood supply due to swelling, vessel thrombosis,
or tissue infarction. With such lesions, the area
of decreased heat is usually surrounded by
increased thermal emissions, probably due to
shunting of blood.




During scintigraphy, polyphosphonate
radiopharmaceuticals are given IV.
Their distribution is then measured by a
gamma camera.
The polyphosphonates bind rapidly to
exposed hydroxyapatite crystal, generally in
areas where bone is actively remodelling.
Because inflammation causes an increase in
blood flow, capillary permeability, and
extracellular fluid volume, inflamed tissues
accumulate high levels of
radiopharmaceutical during the soft-tissue
phase of scintigraphy, allowing evaluation of
soft-tissue injuries.
During the bone phase, the
radiopharmaceutical accumulates in
areas of increased remodelling or
vascularity.
 Because injured bone is remodelled
more rapidly, scintigraphy is useful
for detecting lesions in bone and
ligaments, particularly in identifying
enthesopathy (damage to the
insertions of tendons and ligaments
on bone).

Arthroscopy
)Tenoscopy, Bursoscopy(



Arthroscopy is the ultimate way of
assessing the soft tissues of a joint.
It often combines diagnosis with therapy
(surgery), with one procedure often
following the other during the same
anesthetic procedure.
Arthroscopy provides the only option for
examining all the soft tissues of the joint
interior and enables minimally invasive
surgical techniques, ensuring rapid healing of
soft tissues, as only minute stab incisions are
required.



It enables access to parts of joints not
accessible during an arthrotomy and
allows for detailed magnified images to be
stored and reproduced.
Arthroscopy also provides increased
cosmetic and functional advantages and
has lower postsurgical morbidity, while
decreasing convalescence time and
ensuring an earlier return to work.
It allows much improved mechanical
lavage of joints (eg, use of 10-20 L of
saline under up to 300 mm Hg).
 Most
equine joints of the
appendicular skeleton are large
enough to allow arthroscopy using
a rigid endoscope of 2.5-5 mm
diameter, inserted through a rigid
sleeve.
 Camera attachments transmit the
images to a monitor from which
still or video images can be
obtained.



Diagnostic and surgical tenoscopy and
bursoscopy are also used, often for cases
of sepsis of synovial structures.
Bursoscopy of the navicular bursa has
almost eliminated the “streetnail procedure”
for surgical treatment of sepsis, as has
calcaneal tenoscopy for infections that often
follow kicks to the hock.
The minimal soft-tissue trauma described
with tenoscopy is invaluable in restoring the
normal intrasynovial environment and has
revolutionized the recovery rate from septic
tenosynovitis.
Regional Analgesia
Diagnostic local analgesia is an
important component of the equine
lameness examination if the site of
pain is uncertain after a thorough
clinical examination.
 The appendicular nervous system is
quite consistent, and there are few
indications for ringblocks.

It should be used with care in horses
with severe lameness as, for example, a
simple fracture may become
comminuted if the protective effect of
pain is lost.
 Common conditions in which regional
analgesia is important in determining an
accurate diagnosis include superficial
foot pain, navicular disease, traumatic
joint disease, and proximal suspensory
desmitis.

 Perineural
analgesia should
start distally and progress
proximally.
 Intrasynovial analgesia may
start proximally if indicated by
clinical findings, as this does
not preclude subsequent distal
analgesia.
Nerves to a portion of the foot are blocked with a
local anesthetic to see if the lameness resolves .
Landmarks, forelimb nerve block, horse
Anatomy for nerve block in medial arm and
forearm, horse
Anatomy for nerve block of distal forelimb, horse
Anatomy for nerve block, digital area, forelimb,
horse
Landmarks, pelvic limb nerve block, horse
Anatomy for tarsus nerve block, horse
Anatomy for lateral crus nerve block, horse
Anatomy for medial crus nerve block, horse