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Normal Musculoskeletal Radiographic Anatomy (emphasis on equine) CVM 6101, Fall 2010

Instructor: Kari L. Anderson, DVM, Dipl ACVR Office: C350 VTH Work Area: Medical Imaging Phone Numbers: Office: 5-3762 Medical Imaging: 5-1200 Email: [email protected] Lecture Topic Equine Skull and Spine Equine Distal Limb Equine Proximal Limb Notes Skull p.2 Spine p.11 p.14 p.20

Resources: Normal large animal anatomy web materials accessible through WebCT/Vista 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 Imaging Anatomy web site of the College of Veterinary Medicine of University of Illinois http://vetmed.illinois.edu/courses/imaging_anatomy/index.html

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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 cutoff. 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

3 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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CVM 6101 Equine Skull Radiographic Anatomy

6 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

8 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 Usually dorsal to 4th cheek tooth Rostral limit of ventral conchal sinus Usually dorsal to 4th cheek tooth Rostral limit of maxillary sinus Usually dorsal to 3rd 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

9 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 3­1­3 3­1­3 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

CVM 6101 Equine Skull Radiographic Anatomy

11 Oropharynx Radiographically indistinguishable due to the fact that the base of the tongue silhouettes with the soft palate (no air for definition)

CVM 6101 Equine Skull Radiographic Anatomy

12 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

15 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) More prominent dorsal spinous process than the other cervical vertebrae Caudal endplate is situated just cranial to the first rib

C7

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 45 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 C3-4. The sagittal diameter of the vertebral canal tends to be slightly smaller in the midcervical region compared with more cranial and caudal levels.

CVM 6101 Equine Spine Radiographic Anatomy

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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

18 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

20 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

21 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

22 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

23 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

24 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

28 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

29 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 MP L = dorsolateral = 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

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