Normal Musculoskeletal Radiographic Anatomy
(emphasis on equine)
CVM 6101, Fall 2011
Instructor: Kari L. Anderson, DVM, Dipl ACVR
Office: C350 VTH
Work Area: Medical Imaging
Phone Numbers:
Office: 5-3762
Medical Imaging: 5-1200
Email: kla@tc.umn.edu
Lecture Topic
Equine Skull and Spine
Equine Distal Limb
Equine Proximal Limb
Notes
Skull p.2
Spine p.11
p.14
p.20
Resources:
Course Moodle site
Laboratory packets on the Medical Imaging web site:
http://www.academic-server.cvm.umn.edu/radiology/CVM6101/Labs/6101Lab4F07/index.htm
Textbook of Veterinary Diagnostic Radiology, Thrall DE, 4th ed, WB Saunders, 2002, 5th ed, WB
Saunders, 2007
Clinical Radiology of the Horse, Butler JA, et al, 2nd or 3rd ed, Blackwell Science 2000, WileyBlackwell 2008
2
Radiography of the Equine Skull
Equipment
One can use relatively low-capacity equipment for many areas of the head. Most views
may be made with average portable x-ray units (especially if mounted on a stand). The
rostral mandible, calvarium, and frontal bones do not have much overlying soft tissue to
attenuate the x-ray beam. The normal air containing structures (nasal cavity, sinuses,
pharynx, guttural pouches) enhance the ability to examine these areas.
The nature of the x-ray tube suspension will determine whether it is convenient or even
possible to obtain the necessary views for a skull examination. A ceiling suspended tube
is the most user-friendly apparatus; however, this cannot be used in the field, and the tube
may not be able to be placed under the head. A portable unit on a stand with wheels can
be moved to the horse and multiple positions of the tube head can be made. On the
downside, this is difficult to use in a stall. A box-type portable hand-held unit is often
difficult to use because of the weight of the tube.
The size of the cassette is not critical. Use cassette holders as often as possible. A grid is
not recommended because often the beam will not be directed perpendicular to the
cassette. Use of a grid in this situation will often cause the artifact known as grid cut-off.
Most often a fast film/screen combination should be used in order to decrease the
exposure needed. Remember that this will result in some loss of detail.
Restraint
Restraint is difficult because of the placement of the cassette and tube head around the
patient’s head. It may be helpful to cover the patient’s eyes. Tranquilization or sedation
is always beneficial in obtaining a high quality study. The use of a rope halter is helpful,
but you will probably need to partially remove or modify its position for some views so it
does not create artifactual shadows on the radiograph. A rope halter causes fewer
artifacts than a nylon halter with metal. A hand placed on the poll or an ear twitch is
often helpful in restraint of the head. Be sure to keep hands (in lead gloves, of course)
out of the primary beam.
CVM 6101 Equine Skull Radiographic Anatomy
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Radiographic Views
Radiography of the skull requires skill and imagination in order to achieve diagnostic
radiographs of the area of interest. Often, the clinical signs of the patient will dictate the
radiographic positions to be made. Because the head is large, many oblique radiographic
views should be made with the x-ray beam in a tangential plane to the area of interest
(except for teeth). This accomplishes the following:
 Decreases tissue thickness
 Removes superimposed structures which hamper evaluation
Once abnormalities are found, you may need to tailor further radiographic projections.
The head is free to move in any direction and continually moves until you take the
exposure. Therefore, it may be difficult to reproduce exact positioning. A great deal of
ingenuity and freedom of choice must be exercised in order to achieve an appropriate
study.
Lateral views of the skull are important for a broad perspective, but due to
superimposition of structures, they are not as helpful. It is often helpful to use both right
and left projections in order to take advantage of both image sharpness and magnification
to localize lesion. DV or VD studies are of value, but are difficult to obtain in a standing
horse because of the thickness of the tissue and the need to position the tube under or
over head. The oblique views are often the most helpful, because each side of the skull
can be evaluated without superimposition of the opposite side. Remember to place the
area of interest next to the cassette for the most detail with the least amount of distortion.
Radiopaque markers to mark which side is being radiographed are mandatory. Consider
using metallic markers attached at the site of drainage or swelling for location on the
radiograph.
Lateral view
 Permits evaluation of the air-filled paranasal sinuses
and nasal passages (superimposed)
 Malalignment of the incisor teeth may be seen
 Dental arcades are superimposed on this view, and
dental disease is difficult to identify
CVM 6101 Equine Skull Radiographic Anatomy
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Dorsoventral (ventrodorsal) view
 This view permits comparison of one side of the head
with the other
 Much of the nasal passage and paransal sinuses are
obscured by the mandible and teeth
 Usefulness is limited principally to evaluating midline
structures
 The nasal septum, common nasal meatus, and
maxillary sinus may be studied
 Bony structures are difficult to evaluate due to
superimposed teeth
 Teeth usually not studied with this view; however,
because they are seen en face, the surrounding alveoli
can often be studied
Oblique views
These views produce the best radiographs for evaluation of the maxillary sinuses,
frontal sinuses, and both dental arcades
 Bilateral studies should be made because there is great variation in the appearance of
the teeth with age (unaffected side for comparison)
 Important in evaluation of teeth roots since they are projected free of other bony or
dental structures

To visualize the maxillary sinuses and the nasal passages:
 Place the cassette ventrally against the affected side of the
head
 The cassette is angled against the head at approximately
15-30°
 Position the x-ray tube dorsolaterally above the head on the
opposite unaffected side
 The x-ray beam is directed downward toward the head,
centering on the third and fourth cheek teeth on the
affected side
CVM 6101 Equine Skull Radiographic Anatomy
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To visualize the upper dental arcade:
 Place the cassette against the affected side of the head
 Place the x-ray tube dorsolaterally against the unaffected
side of the head
 The x-ray beam is directed downward at a 30-45° angle
and is centered on the region of interest
 Make the oblique of the normal side in the same manner
 It is also possible to make this oblique view with the xray tube positioned laterally and ventrally below the
affected side with the cassette against the unaffected
side dorsally. The x-ray beam is directed upwardly.
To visualize the lower dental arcade:
 Place the cassette against the unaffected side ventrally
 Place the x-ray tube dorsolaterally to the affected side
 Direct the x-ray beam downward at a 45° angle
 It is also possible to make this oblique view by directing
the x-ray beam in an upward direction aiming at the
intermandibular area. The cassette is positioned
dorsally and laterally to the affected side.
To visualize the frontal region:
 Place the cassette against the horse’s head on the affected side slightly ventrally
 Place the x-ray tube on the opposite unaffected side slightly above the head
 Direct the x-ray beam obliquely downward at approximately a 30° angle and centered
on the midline just behind the eye on the affected side
CVM 6101 Equine Skull Radiographic Anatomy
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Views of the Oro- and nasopharynx and guttural pouch:
These structures can be evaluated with a lateral view. This is the only view that is
regularly made. If the lesion is most likely unilateral, place the affected side next to the
cassette. Center the x-ray beam just caudally to the mid-portion of the ramus of the
mandible. The head should be held slightly extended so as to move the vertical ramus of
the mandible so it is not superimposed over areas of interest.
When deciding which views to obtain, remember that the skull should be symmetric, and
you may use the other side of the head as a “normal control” (e.g., do oblique views of
both dental arcades for comparison).
Indications for radiography of the skull
The decision to make a radiographic study should be based upon a need to answer
specific questions indicated by clinical signs and physical examination. Use the results
from a radiographic examination in combination with clinical signs, endoscopic and
physical examinations, and clinical pathologic tests to arrive at an accurate diagnosis.
Specific indications would include:
 Nasal discharge
 Nasal airway obstruction/upper respiratory noise
 Facial swelling/deformity
 Epistaxis (particulary if unilateral)
 Dental disease
 Draining tracts
 Epiphora
 Trauma
CVM 6101 Equine Skull Radiographic Anatomy
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Radiographic Interpretation
The equine skull anatomy is complex and a thorough knowledge of normal anatomy is
most beneficial. The radiographic examination will be challenging to interpret; therefore,
one must be systematic. Remember that the skull is bilaterally symmetric and the
unaffected side may be used as a “normal control”. It will be helpful to consult a
reference on normal radiographic anatomy, remembering that there are slight individual
variations. Also, differences in positioning may radically alter the radiographic and
anatomic relationship of structures.
Use external landmarks:
Cheek teeth:
 These are readily apparent and provide a constant point of reference for lesion
placement
 Use a field of view of sufficient size so that either rostral or caudal cheek tooth is
identifiable
Zygomatic arch:
 Usually evident over caudal portion of nasal passage
 Superimposed over orbit
 Continues rostrally as a linear region of bone opacity, which represents the facial
crest
Use internal landmarks:
 Rostral limit of dorsal conchal sinus
th
 Usually dorsal to 4 cheek tooth
 Rostral limit of ventral conchal sinus
th
 Usually dorsal to 4 cheek tooth
 Rostral limit of maxillary sinus
rd
 Usually dorsal to 3 cheek tooth
 Ethmoid turbinates
 Most consistent landmark, marks caudal limit of nasal cavity
Radiographic Examinations:
1.
2.
3.
4.
5.
6.
Maxillary sinuses and nasal passages
Frontal studies
Incisors/rostral mandible
Maxillary cheek teeth
Mandibular cheek teeth
Oro- and nasopharynx, larynx, guttural pouch
CVM 6101 Equine Skull Radiographic Anatomy
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Normal Anatomy
There are six pairs of paranasal sinuses:
 Dorsal, middle, ventral conchal sinuses
 Maxillary sinus (divided into a rostral and caudal portion)
 Frontal sinus
 Sphenopalatine sinus
Maxillary sinus
 Dorsal to upper molars
 Bony septum dividing the rostral and caudal compartments is usually visible as a thin,
angled vertical bone plate dorsal to the 4th cheek tooth (1st maxillary molar)
 Infraorbital canal is superimposed over the central portion in a longitudinal manner
 Nasolacrimal canal is located at the dorsal rostral border
 Size of the sinus appears to increase as the horse ages because of a decrease in size of
the roots of the molars
 Important to determine which compartment is affected in a disease state in order to
plan treatment accordingly
Frontal sinus
 Outlined dorsally and caudally by the
frontal bone
 Located dorsocaudal to nasal cavity
 Radiographically divided into two parts:
a roughly triangular portion dorsal and
caudal to the ethmoid turbinates, and a
portion rostrodorsal to ethmoid
turbinates which has a scalloped cranial
margin that is dorsal to the 5th cheek
tooth
Sphenopalatine sinus
 Usually not radiographically recognized
 Small
 Vertical rami of the mandibles are
superimposed over this sinus
CVM 6101 Equine Skull Radiographic Anatomy
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In young horses, the long roots of the upper cheek teeth overlap and obscure much of the
ventral portion of the nasal passage and paranasal sinuses. Continuous tooth wear as the
animal ages results in shortening of these roots. By the time the horse is 15-20 years old,
the roots of the teeth do not obscure as much of the nasal passage and sinuses.
Teeth
Dental formulae:
Deciduous formula
Permanent formula
3–1–3
3–1–3
3 – 1 – 3(4) – 3
3 – 1 – 3(4) – 3
The eruption of the permanent teeth causes resorption of the roots of the 3 deciduous
premolars. This creates a “cap”, with “capping” of the occlusal surface of the erupting
permanent teeth. Normally these are broken off. If the “caps” remain, this creates
problems in the eruption of permanent teeth. The permanent teeth continue to grow with
lengthening of roots until about 6 years of age, at which time the teeth will then appear to
shorten due to attrition. The roots will become long and tapered.
The periodontal space is a radiolucent zone between the cementum/enamel on the root
and the trabecular bone forming the alveolus around the root. The periodontal space is
prominent in younger horses, and is less easily visualized in the older patient. The
radiolucent space around the tooth continues to and around the apex of the root, creating
a rounded radiolucent pocket in the younger horse. With age, this pocket disappears and
is replaced by sparse bony trabeculae surrounding the thin, tapering roots.
Nasopharynx
 Upper airway between nasal choanae and glottis
 Single undivided passage
 Extends from rostral margin of vertical ramus of mandible to laryngeal cartilages
 Dorsal boundary is the basal bones of the skull and the ventral margins of the guttural
pouches
 Ventral margin is the soft palate
 Dorsal and ventral margins of epiglottis usually visible just dorsal to soft palate
Oropharynx
 Radiographically indistinguishable due to the fact that the base of the tongue
silhouettes with the soft palate (no air for definition)
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Larynx
 Epiglottis
 Arytenoepiglottic folds
 Corniculate process of the arytenoid cartilage
 Lateral ventricles
Guttural pouches
 Large, thin-walled, air-filled extensions of the auditory tube
 Smaller lateral and larger medial compartment, incompletely divided by stylohyoid
bone
 Bordered dorsally by base of skull and atlas
 Bordered ventrally by pharynx and commencement of esophagus
CVM 6101 Equine Skull Radiographic Anatomy
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Radiography of the Equine Spine
Equipment
High quality radiographs may be made using portable x-ray machines and fastintensifying screens. It is most helpful to have a stand for the x-ray unit and the cassette.
A grid is not necessary for the cranial part of the neck, but is necessary for the caudal
portion of the neck.
Restraint
It may be helpful to restrain the patient in stocks to minimize movement. Sedation is also
generally useful as it causes the horse to lower its head and neck. The disadvantage is
that the neck may be flexed relative to the normal standing position with altered
alignment of the vertebrae.
Radiographic Views
Several radiographs are needed in order to evaluate the entire cervical spine. An
overlapping series of films provides good evaluation of bony segments and the interposed
radiolucent intervertebral discs. Generally, survey radiographs are made in the standing
patient. If the patient is recumbent, use pads under the patient to position the spine
parallel to the cassette.
The most often obtained view is the lateral view. True laterals are essential, as slightly
obliqued views are difficult to interpret. Generally, at least three views are made to cover
the entire spine. The cranial view is centered on C2. The middle view is centered on C4.
The caudal view is centered on C6. As you proceed caudally, you will need to increase
the technique as the soft tissues get thicker.
It is helpful to place lead markers on the neck so that similarly appearing cervical
segments can be identified without question.
Myelography is often used as an adjunct to survey cervical spinal radiographs.
CVM 6101 Equine Spine Radiographic Anatomy
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Indications for radiography of the cervical spine:
 Abnormal head or neck posture
 Cervical pain, swelling or stiffness
 Neurological deficits (ataxia)
 Acute traumatic event (most often in young foals)
 Suspected developmental cervical spondylopathy (generally yearlings or 2 year olds)
CVM 6101 Equine Spine Radiographic Anatomy
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Normal Anatomy
Four cervical vertebrae (C1, C2, C6, C7) have characteristic shapes and are used as
landmarks to identify individual vertebrae when no other reference point is included on
the radiograph. C3, C4, and C5 are very nearly identical in appearance.
C1 (atlas)
No radiographically visible dorsal spinous process
Two large articular fossae enclosing most of the occipital condyles
Two large lateral processes (wings), each with two foramina
A suture between the separate ossification centers of the dorsal arch is present in foals
younger than 6 months (do not mistake for fracture)




C2 (axis)
 Large dorsal spinous process
 Cranial extension of the body (dens or odontoid process) articulates with the
ventrocaudal portion of C1
 A suture between two separate ossification centers of the dens is visible in young
horses (do not mistake for a fracture)
 The cranial arch has lateral vertebral foramina, the cranial borders of which are
incomplete in young horses, and may remain as a notch in the adult
C6



Large lateral processes with three projections
The caudal lateral process has a separate ossification center at birth (noted ventrally,
do not confuse with a fracture)
The caudal lateral process is seen ventral to the caudal aspect of the vertebral body
(distinctive)
C7


More prominent dorsal spinous process than the other cervical vertebrae
Caudal endplate is situated just cranial to the first rib
Closure of the cranial physes of C3 to C7 fuse ventrally intially and is complete at about
2 years of age. The caudal endplates fuse at their dorsal aspect initially around 4-5 years
of age, but the ventral portion may still be open at 5 years of age.
During flexion of the neck, apparent subluxation of adjacent vertebral bodies is
commonly seen, even in neurologically normal horses. This may occur at C2-3 and C34.
The sagittal diameter of the vertebral canal tends to be slightly smaller in the mid-cervical
region compared with more cranial and caudal levels.
CVM 6101 Equine Spine Radiographic Anatomy
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Radiography of the Equine Limb
Equipment
High quality radiographs may be made using portable x-ray machines and fastintensifying screens. Slower speed screens may be used in order to obtain greater detail.
It is most helpful to have a stand for the x-ray unit. Cassette holders are available and
should be used in order to practice safe radiography. Additionally, wooden blocks are
often used in order to elevate the foot for radiographic procedures of the distal limb.
Special cassette holders that allow one to place the foot directly on the cassette will be
used for several views.
Restraint
A cooperative patient may not need restraint. It is often helpful to hold up one of the
other limbs in order to encourage the horse to bear weight fully on the limb of interest
and to discourage movement of the limb of interest. Sedation is helpful with an
uncooperative patient and when radiographs of the hind limbs are being made (to avoid
being kicked).
Radiographic views
Standard radiographic views are made depending upon the area of interest. Remember
that orthogonal views are always indicated, but in the case of a horse, oblique views are
very common. The oblique views enable the interpreter to visualize many of the surfaces
of the large bones. Additionally, skyline views are commonly made in order to inspect
certain surfaces of interest. The standard radiographic views are listed for each area of
interest. “Standard” views will be variable depending upon the radiologist or equine
practitioner, but the listed views are what I have found to be most helpful.
Indications
Radiography of the equine limb is often used in order to investigate a lameness.
Generally, radiographs are made after a complete physical and lameness examination.
This will obviously help one localize the cause of the lameness. Radiographs are also
made after a traumatic episode (kick, laceration, etc) in order to evaluate the soft tissues
and bones. Additionally, it is common to make radiographs of certain areas of the limb
as part of a prepurchase examination of a horse.
CVM 6101 Equine Limb Radiographic Anatomy
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Normal Anatomy
Distal Phalanx (third phalanx, P3)
Radiographic views:
 standard: lateral and 45° dorsopalmar/plantar (DP)
 additional: horizontal beam DP, D45°P obliques
Normal appearance:
 rear P3 somewhat narrower than front P3
 smooth, opaque dorsal surface parallel to hoof wall
 extensor process is variable, should be bilaterally symmetric




well defined solar margin, some irregularity normal
tapering, symmetric vascular channels
a crena may be present on midline of the tip of P3
the solar canal may appear as a distinct radiolucent zone in
the middle of the bone
Normal variations and incidental findings:
 small, well circumscribed fragment palmar to the palmar
process
 small, radiopaque fragment proximal to the extensor
process on midline
 mineralization of the collateral cartilages (side bone)
 usually incidental
 incomplete ossification may be misinterpreted as fracture
 assess radiographic findings in light of clinical findings
CVM 6101 Equine Limb Radiographic Anatomy
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CVM 6101 Equine Limb Radiographic Anatomy
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Navicular Bone
Radiographic views
 standard: lateral, 65° dorsopalmar/plantar (DP), flexor tangential
 additional: horizontal beam DP, 45°DP, 65°DP obliques
Normal appearance:
 regions of interest include: proximal and distal borders, flexor and articular borders,
body and extremities
 mild irregularities of distal border may be considered normal depending on size and
shape; age related
 findings should be interpreted in light of age, breed, clinical examination
Normal variations and incidental findings:
 occasionally the navicular bone is absent, bipartite or tripartite
 a small smooth-edged depression is present in the sagittal ridge of at least 50% of
normal horses (lateral view); seen as a crescentic or oval lucency in the sagittal ridge
on the flexor tangential view
 smooth, opaque entheseophytes along proximal border
 variable number and size of distal synovial invaginations (up to 7)
CVM 6101 Equine Limb Radiographic Anatomy
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Proximal and Middle Phalanges; Proximal and Distal Interphalangeal Joints
Radiographic views:
 standard views: lateral, dorsopalmar/plantar (DP), DLPMO, DMPLO
 additional views: special oblique views to detect fractures, osteochondrosis lesions
Normal appearance:
 region devoid of trabeculae in central P1 (marrow or fat cavity)
 ergot may be superimposed over proximal P1 on DP view
 row of nutrient foramina at proximal and distal ends of P1 and P2
 bony prominence on palmar/plantar aspect of P1 (attachment of oblique sesamoidean
ligament)
 bony ridge on dorsomedial and dorsolateral aspect of P2 (origin of collateral
ligaments of the distal interphalangeal joint)
 prominent extensor process of P2
CVM 6101 Equine Limb Radiographic Anatomy
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Metacarpo(tarso)phalangeal joint (fetlock)
Radiographic views:
 standard views: lateral, DP, DLPMO, DMPLO
 additional views:
flexed lateral: permits evaluation of margins and articular surface of proximal
sesamoids and dorsal articular surfaces of fetlock joint
tangential DP views: allows evaluation of multiple surfaces of condyles and sagittal
ridge of MC/MT III
Normal appearance:
 two distinct articulations:
 MC/MT III with P1
 MC/MT III with proximal sesamoids
 junction of articulations mistaken for flattening of distal condyles of MC/MT III
 sagittal ridge articulates with groove in proximal P1
 proximal sesamoids
 forelimb proximal sesamoids are larger and more triangular in appearance than than
the hindlimb
 the lateral proximal sesamoid bone is more pointed and “L-shaped” than the medial
 contain faint, thin, radiating lucent lines (vascular channels)
 axial and abaxial surfaces may show some unevenness, but should not show marked
roughening (suspensory ligament attachments)
CVM 6101 Equine Limb Radiographic Anatomy
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Metacarpus / Metatarsus
Radiographic views:
 standard views: lateral, DP, DLPMO, DMPLO
 additional views: as dictated by specific abnormality
Normal appearance:
 dorsal cortical contour of MC III is straight; dorsal cortical contour of MT III is
convex
 midportion of dorsal cortices are thicker than palmar/plantar cortices
 nutrient foramen is at junction of proximal and middle thirds on palmar/plantar cortex
 small circular lucent zones (nutrient foramina) may be seen in the proximal third
metacarpus/metatarsus on the DP view
 superimposition of second and fourth metacarpal/metatarsal bones give the optical
illusion of a linear radiolucent line at the junction of the margins of the bones (mach
line); do not mistake as a fracture
CVM 6101 Equine Limb Radiographic Anatomy
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Carpus
Radiographic views:
 standard views: lateral, DP, DLPMO, DMPLO, flexed lateral
 additional views: proximodorso-distodorsal skyline vies of distal radius, proximal
row of carpal bones, and distal row of carpal bones
Normal appearance:
 the intermediate carpal bone has a concave dorsal margin while the radial carpal bone
has a relatively convex dorsal margin
 on the flexed lateral view:
 the radial and third carpal bones are projected distally
 the intermediate and fourth carpal bones are projected proximally
 fat is present in the tendon sheath of the extensor carpi radialis tendon; displacement
of fat is a marker for intra-capsular soft tissue swelling
 three carpal joints:
 antebrachiocarpal (radiocarpal) joint: no communication with others
 middle carpal (intercarpal) joint: communication with carpometacarpal
 carpometacarpal joint: communication with middle carpal
 large circular lucent zone in the center of the distal radius on DP view
 the distal caudal aspect of the radius may be irregular; site of attachment of the
accessory ligament of SDF tendon
 there may be incomplete fusion between the lateral styloid process and the distal
epiphysis of the radius (radiolucent line)
 a first carpal bone may be present
CVM 6101 Equine Limb Radiographic Anatomy
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Tarsus
Radiographic views:
 standard views: lateral, DP, DLPMO, DMPLO
 additional views: flexed lateral (proximal trochlear ridges), flexed skyline of plantar
surface (calcaneus and sustentaculum tali)
Normal appearance:
 large bony prominence on the dorsomedial aspect of the third tarsal bone
 lateral trochlear ridge has a hook-like distal aspect
 medial trochlear ridge may have a small bony projection on distal aspect
 an incompletely mineralized distal fibula may be present
 the lateral and medial malleoli form from separate centers of ossification and may
appear as separate structures prior to skeletal maturity
 four tarsal joints:
a. tibiotarsal (tarsocrural) joint: communicates with proximal intertarsal
b. proximal intertarsal joint: communicates with tibiotarsal
c. distal intertarsal joint: variable communication with tarsometatarsal
d. tarsometatarsal joint: variable communication with distal intertarsal
CVM 6101 Equine Limb Radiographic Anatomy
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Stifle
Radiographic views:
 standard views: lateral, caudo-cranial (Cd-Cr)
 additional views: CdL-CrMO, skyline view of the patella
Normal appearance:
 margins of incompletely mineralized bones in immature horses appear ragged; do not
confuse this for a destructive process
 separate centers of ossification of the fibula; mistaken for fracture
 medial trochlear ridge of distal femur larger than lateral
 medial condyle of distal femur round, lateral condyle relatively flat (Cd-Cr view)
 extensor fossa of lateral condyle of femur
 medial intercondylar eminence of the tibia is larger and more pointed than the lateral
intercondylar eminence
 two joint articulations and three joint pouches:
 femoropatellar articulation and joint pouch
 femorotibial articulation with separate medial and lateral joint pouches
In most horses (80-90%) the femoropatellar and medial femorotibial joint pouches
communicate. The medial and lateral femorotibial pouches will communicate in
approximately 20% of horses.
CVM 6101 Equine Limb Radiographic Anatomy
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Oblique Radiographs of the Carpus and Tarsus Explained
RL Toal and KL Anderson
Remember:
The name of the radiographic view is derived from the path of the central x-ray beam.
 Example: dorsopalmar view: x-ray beam enters the dorsal aspect and exits the
palmar aspect.
The size and morphology of the bones and joints in the equine carpus and tarsus requires
that oblique views be made in order to study all bony surfaces and joint surfaces as
completely as possible. Each radiographic view will present a portion of the
carpus/tarsus in a slightly different orientation. Thorough knowledge of anatomy will
facilitate identification of the various views. Once the view is identified, it will be easy
to name the various bones and their corresponding surfaces in profile.
CVM 6101 Equine Limb Radiographic Anatomy
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The views:
DLPMO = Dorsolateral-palmaromedial oblique (thoracic limb)
Dorsolateral-plantaromedial oblique (pelvic limb)
x-ray beam enters dorsolateral aspect, exits palmaor/plantaromedial aspect
DMPLO = Dorsomedial-palmarolateral oblique (thoracic limb)
Dorsolateral-plantaromedial oblique (pelvic limb)
x-ray beam enters dorsomedial aspect, exits palmaro/plantarolateral aspect
The explanation:
DLPMO: A DLPMO view profiles the palmaro/plantarolateral and dorsomedial surfaces
of the carpus/tarsus. A simple way to remember this is to circle the two center letters and
draw an arc to connect the two outer letters.
D
LP
M
Oblique = D
LP
M = dorsomedial
= palmaro/plantarolateral
Now consider the palmaro/plantarolateral aspect. In the carpus/tarsus, the fourth
carpal/tarsal bone articulates with both the metacarpal/tarsal 4 and the metacarpal/tarsal
3. Also, the fourth carpal/tarsal bone is a large cuboidal bone. The articulation with
metacarpal/tarsal 4 forms a prominent ledge that extends beyond the surface of the fourth
carpal/tarsal bone. Recognition of these bones in profile signals a DLPMO view.
CVM 6101 Equine Limb Radiographic Anatomy
26
DMPLO: A DMPLO view profiles the palmaro/plantaromedial and dorsolateral surfaces
of the carpus/tarsus. A simple way to remember this is to circle the two center letters and
draw an arc to connect the two outer letters.
D
MP
L Oblique = D
L = dorsolateral
MP
= palmaro/plantaromedial
Now consider the palmaro/plantaromedial aspect. The second carpal/tarsal bone is in full
articulation with the corresponding metacarpal/tarsal 2. Also, the second carpal/tarsal
bone is smaller than the fourth carpal/tarsal bone. Recognition of these bones in profile
signals a DMPLO view. Another hint for the recognition of a DMPLO view of the tarsus
is to notice that the lateral trochlear ridge is profiled on the dorsolateral side in this view.
It has a prominent notch at its distal aspect.
CVM 6101 Equine Limb Radiographic Anatomy