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Determinants of Fracture Healing Open Fractures. Open fractures also termed com- The following factors influence fracture healing: pound fractures are often infected and as such carry a The severity of the fracture greater potential for nonunion than closed fractures. Which bone is fractured Where in a particular bone the fracture occurs Age of the Horse. In people, pets, and cattle, the Whether or not the fracture is fresh young heal more rapidly and with fewer complica- Whether or not the fracture is open tions than do the old.

Thus foals, yearlings, and young The age of the horse adults usually heal more rapidly than older horses, Whether any other serious injuries or preexisting assuming a comparable degree of injury and similar disease are present treatment. How the fracture is repaired The skill of the surgeon Concomitant Injury. Concomitant injuries place an The quality of the aftercare additional demand on the bodys resources, especially the immune system, compromising healing to varying Fracture Severity.

Generally, comminuted and multi- extents. The greater the degree of Method of Repair. All things equal, a plated fracture fragment displacement, the greater the amount of will heal more rapidly and with less callus than one secondary muscle and vascular damageboth impor- that is pinned.

Surgical Skill. The skill of the surgeon may be the Fracture Location. Fractures that occur at the distal single most important variable in predicting the end of long bones often cannot be compressed because outcome of orthopedic procedures. C D Figure Radiographs of a horse that stepped in a hole and dislocated its pastern joint approximately a year ago. The animal is now mildly to moderately lame, especially after exercise.

Close-up lateral A and dorsopalmar B views of the pastern joint show advanced osteoarthritic remodeling as evidenced by 1 symmetric periarticular and extraarticular new bone deposition, 2 a narrowed cartilage space, and 3 subchondral sclerosis. Similar views C, D of the opposite normal pastern are provided for comparison. C D Figure Radiographs of a horse that completely severed its flexor tendons 2 to 3 years previously.

DIGITAL RADIOGRAPHY

As a result, both proximal sesamoids are severely deformed, as seen in close-up dorsopalmar A , true lateral B , lateral oblique C , and medial oblique D views, resembling what is often observed following displaced apical or body fractures. Adaptive remodel- ing of this sort is rarely documented radiographically because many horses with such injuries are destroyed.

Postoperative Aftercare. The type, amount, and readily recognized. Examples of short- and long-term quality of postsurgical aftercare strongly influence fracture healing are presented in the chapters that healing time. This is especially true of physiotherapy. Figure Lateral view of the fetlock of a horse that completely severed its right front flexor tendons 20 years ago.

As a result, the metacarpal condyle has drifted toward the palmar aspect of the proxi- mal phalanx, which now has a flatter articular surface, to better match the dorsal half of the overlying condyle, with which it now articulates. For their part, the sesamoids are fully and for the most part articulating with the palmar aspect of the canon bone, accommodating its forward inclina- tion and the hyperflexed attitude of the fetlock.

The flattened mound of new bone on the dorsal surface of the distal metacarpal metaphysis and a similar deposit on the underlying phalanx are impingement exostoses, a consequence of one surface striking the other. A B Figure A, What makes the previous case Figure an even better example of remodeling are the secondary changes to the opposite fetlock, which in many respects are more pronounced than those in the injured limb. Note the greater degree of hyperextension, and the extensive dystrophic calcification in the suspensory field.

B, A normal lateral view is provided for comparison. The most commonly accommodative remodeling is the sprain-fracture- affected bones in the horse are the third carpal, proxi- dislocation. The result is incongruency, one differences. Triggered by an articular mismatch, and to a lesser extent by any associated instability, each of the Traumatically Induced involved bone surfaces, injured and uninjured alike, Perhaps the best and most obvious example of skele- attempts to reach an anatomic accommodation tal remodeling is the fracture callus.

Take the case of a through the process of remodeling. In other words, simple two-piece distal extremity fracture treated with each surface tries to match that of the other, although a cast. The ends of the broken bone are first physio- usually not with the usual accoutrements of a normal logically fixed by a combination of clot and connective joint, such as articular cartilage.

Then, through a sur- Accommodative remodeling also can occur in unin- prisingly sophisticated process, the soft callus is trans- jured parts, especially joints in the opposite leg. Examples of Thought of most simply, fracture remodeling is a primary and secondary accommodative remodeling restorative process. Seemingly, the broken bone is are shown in Figures to Like any restoration, the process of fracture 1.

Kold SE, Hickman J, Melson F: Qualitative aspects of the healing is often slow and sometimes tedious, a little bit incorporation of equine cancellous bone grafts, Equine Vet of bone added here, a little bit subtracted there. In most J , Accommodative Remodeling may take another form, one predicated on the concept of accommodation. Smallwood and Holladay reported the normal xerographic appearance of the equine digit Conventional Radiography and fetlock. Busoni and Denoix reported the normal medial view centered as closely as possible on the sonographic appearance of what they termed the center of P3 Figures and Often studies of this podotrochlear apparatus, in three cadaver limbs and five type are of a survey nature, where there is no certain living animals.

In most instances a transverse tissue slices comparable to the scan planes. Areas of poten- The technique proved capable of displaying the fol- tial pathology are listed in Table The foot as well as other parts of the skeleton can also be imaged using computed radiogra- phy CR , in many respects a superior form of imaging Angiography. Coffman and co-workers described the compared with conventional radiography, but also a angiographic appearance of the laminitic horse.

Briefly, CR, as its name indicates, Ackerman and co-workers described the angiographic converts penetrated x-rays into numeric data that can appearance of both the normal and the foundered be manipulated by a computer to improve image con- foot. As an added benefit, lossless digital images can be readily Radionuclide Imaging Nuclear Medicine, Nuclear deployed to both intranets and the Internet, greatly Imaging, Nuclear Scintigraphy.

Nuclear scintigra- reducing the time-to-view waiting period for those phy, also known as nuclear medicine, provides another requesting the examinations.

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Roberts and imaging is not confined to the distal extremities, but Graham described the specific advantages of it can be used anywhere in the skeletal system. I hope limb scintigraphy, emphasizing the importance of no one takes offense. A B Figure Bones of an equine forefoot within the hoof corresponding to the lateral A and degree dorsopalmar B radiographs shown in Figure Scintigraphic activity ceases in within a specific part of a horses body is referred to as the distal femoral physis of a horse by 2.

Growth plates physes , especially in young foals, appear quite intense until they eventually disappear or close once the animal matures. Disappearance of Uptake Related to Breed and Usage growth plate radiopharmaceutical activity precedes In general, jumping horses show a greater amount of radiographic closure in the distal extremity of foals, as radiopharmaceutical uptake, in a greater number of demonstrated by Metcalf and co-workers. Conversely, bones, than Standardbreds or Thoroughbreds. Uptake Related to Earlier Nerve Block pain and lameness, bone stress, and abnormal radio- Regional Perineural Anesthesia graphs and nuclear uptake patterns.

Only later did regional nerve blocks. High and low palmar Subsequently, Twardock asserted that a similar rela- blocks caused an even greater increase in uptake. Bone-phase scinti- this type of abnormal uptake pattern was not merely grams were unaffected. Diseases that often fall into this category are listed in Box CR provides greater bone detail, for example, small chip fractures or detached osteochondral fragments. It optimizes both hard- and soft-tissue detail, eliminating Thermography of the Distal Limb the need for separate radiographic exposures. It allows for viewing of all areas of a specific image, Thermography has been used on a limited basis to including those typically overexposed or underex- diagnose a variety of equine foot diseases, including posed in a conventional radiograph.

Stromberg is one of the few veterinarians to report thermographic abnormalities obtained from a medium-sized group of horses Joints: Acute sprains as indicated by mild swelling showed an elevated temperature com- Anatomic Region of P3 Potential Pathology pared with the opposite control leg, even though Alignment with P2 Traumatic dislocation, lameness radiographs appeared normal. As the swelling sub- accommodation, flexural sided, the temperature gradually returned to deformity normal. Reinjury was diseases and injuries as they appear in CT images; and typically marked by a rise in temperature, as were a clear understanding of the physical principles that hairline articular fractures, the latter often being underlie the creation and appearance of CT images.

Also, as might be expected, rience, getting the affected part of the horse satisfacto- infectious arthritis caused an increase in joint tem- rily positioned in the bore of the gantry and keeping perature before radiographic alterations became it that way during the examination remains as, or evident. Long Bones: Recent periosteal new bone deposits examination. Likewise, getting the horse from where it appeared as hot spots on thermograms, as did is anesthetized to the CT machine, and later back to the splints in the active phase of development.

Mature recovery stall, can be particularly onerous depending splints were undetectable thermographically, even on the physical layout of the facility. Magnetography 3. Foot: The coronary band and sole were both Magnetic resonance imaging MRI provides superior amenable to thermographic interrogation; the hoof multiplanar soft-tissue imagery, but it has compara- was not.

The coronet temperature was elevated tively slow image acquisition and is very expensive with a variety of ailments but with none specifi- compared with other kinds of medical imaging. Using cally. Solar emissions also rose with a variety of a low-field-strength permanent magnet, we are able disorders, including the following: 1 subsolar to do no more than two cases per day. CT is much abscess, 2 subsolar hemorrhage, and 3 non- faster.

Park and co-workers have reported the emit heat when injured: the more severe the injury, MR appearance of the foot and fetlock in a dismem- the greater the amount of heat given off. This article is of special value because of the excellent Computed Tomography quality of the explanatory line drawings accompany- CT provides superior cross-sectional digital images of ing the included MR imagesindispensable normal complex extremital fractures, but the equipment is references for those undertaking such examinations.

Control over slice thickness effectively eliminates MRI T1-weighted images on the disarticulated lower superimposition by other nearby bones. Once forelimbs of three horses that had previously been acquired, individual images can be optimized for bone diagnosed with digital disease laminitis, navicular or soft-tissue viewing, termed bone or soft-tissue disease, and ringbone. Images may also be viewed three- at least in frozen, disarticulated horse limbs, it was dimensionally provided the slices are thin enough 2 possible to visualize most of the soft tissues of the foot millimeters or smaller and the necessary software is and to detect a variety of abnormalities not visible in available, a process known as three-dimensional 3D radiographs.

For example, altered signal intensity was reconstruction, which greatly enhances the understand- found in articular cartilage, joint capsule, ligaments, ing of spatial relationships, especially in planning frac- tendons, navicular bursa, and collateral cartilages. Lesions were also detected in the subchondral bone of Barbee reported that CT in horses is expensive, with the phalanges and the navicular bone.

For example, a T1-weighted especially important in providing data for outcome- image of a dismembered equine digit portrays syn- based decision making, Diagnostic claims made in ovial fluid as a bright, high-intensity signal but in a review articles on equine CT continue to be based living horse as a dark, low-intensity signal.


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Somewhat theatrically, the authors termed and limbs of horses; experience with various equine their finding the magic-angle effect. Live Horses. Dyson and co-workers performed taking the short, curvilinear, marginal lucency, nor- medical magnetography on 15 live sore-footed horses, mally found between the proximal and distal angles of concluding that MRI was capable of detecting navicu- the palmar processes of foals up to 3 months of age, lar lesions impossible to identify by any other means.

Veterinary Diagnostic Imaging - The Horse - E-Book - Charles S. Farrow - Google книги

Before considering the of the navicular bone, distal phalanx, distal sesamoid- many normal variations found in the distal phalanx, I ian ligament, navicular bursa, and deep digital flexor would like first to draw attention to one of its most tendon. Most lesions were of the degenerative type, as unique features: its lavish blood supply. Obviously, indicated by abnormal tissue water content. However, individual blood vessels are not visible in a plain it was conceded that CT would likely provide a more radiograph, but the canals through which they pass, detailed view of cortical bone surfaces.

Defleshed In conclusion, the authors emphasized that MRI bone specimenssome with overlying vascular corro- examination of horse feet was costly and time con- sion castsreadily reveal the sheer magnitude of this suming, and it requires a great deal of procedural and phenomenon. Also noteworthy is the extremely diagnostic experience. Magnetogaphy, in the authors roughened surface of P3, which becomes quite pro- opinion, was best suited to lesion confirmation or nounced distally, especially along its caudolateral wall denial , rather than preliminary screening.

Frontal Profile. The fore and hind distal phalanges exhibit subtle but consistent differences in frontal, III SOME USEFUL FOOT FACTS degree projections, with the solar margin of the rear phalanx appearing relatively more conical in shape, a As they have with other anatomic regions of the horse, difference that can sometimes be used to differentiate Quick and Rendano produced a list of diagnostically one from the other in the case of failed marking or valuable facts about the foot, which are listed below,33 mismarking.

The dorsal margin of P3 usually P3 has three designated surfaces: 1 articular, 2 appears relatively straight when viewed laterally, but parietal also termed the face , and 3 solar also occasionally it appears gently convex Roman-nosed or, known as the bearing surface. It most instances The parietal sulcusappearing in the dorsopalmar these are normal anatomic variants, but if there is view as bilateral notches in the lateral borders of P3 doubt, the opposite side can be radiographed for com- immediately distal to the lateral cartilagesharbors parison.

If both appear similar, they are probably the dorsal artery of the foot. The solar canal appears as a pair of small radiolu- cent ovals in the middle third of the distal phalanx. The solar margin is normally highly variable, and it must not be mistaken for disease. The size, shape, and number of vascular channels in P3 are also highly variable. The density of P3 is normally quite variable and can change with age and activity levels. The width of the distal interphalangeal joint often appears uneven as a result of the horse shifting its weight leaning off when the opposite foot is lifted.

Many but not all horses have a notched toe, termed a crena, which must not be mistaken for focal osteomyelitis. If the solar surface of the hoof is not cleaned and packed before being radiographed, a characteristic V-shaped gas shadow may appear in the high coro- nary view, the result of gas in the sulci.

The distal phalanx is relatively smaller and narrower in foals compared with juveniles Figure Corrosion cast demonstrates the rich distal phalangeal and periphalangeal blood supplies and the and adults. Likewise, the solar margin of a young foal myriad of bony channels through which the individual is considerably smoother and more conical than it is in vessels pass, accounting for the porous appearance of this adults. Kaneps and co-workers cautioned against mis- region of the bone. Cortical Thickness and Degree of Arch. Calcified thickness of the dorsal cortex of P3 is reported to be lateral cartilages, or side bones as they are commonly thicker in racehorses than in nonracing animals, a termed, can range from nonexistent to enormous, finding that I have not observed consistently.

Often one or both side bones are Normal Divergence and Convergence Rotation. Normal As far as I can determine, there is no evidence that convergence pivoting of P3 forward, toward the hoof ossification of one or both lateral cartilages causes wall has also been described dorsal rotation.

An lameness in horses, although there is published overgrown toe often creates the illusion of divergence, opinion to this effect. The outer edge of the distal phalanx, the lateral cartilages of Finnhorse cadaver limbs. Many horses feature a thumbprint-like impres- and osteoarthritis of the coffin joint in Finnhorse sion centrally, termed a crena Figure As already cadaver forefeet. Ossification of the collateral carti- suggested, where doubt exists about the normalcy of lages was found in 36 of feet; however, no demon- such a finding, the opposite limb can be imaged for strable link was found between the existence of side comparison.

Vascular Channels. The vascular channels or canals of Neither was there any evidence that side bones pro- the distal phalanx differ in size, number, and location. Extensor Process. The appearance of the extensor process of the distal phalanx, as seen in lateral profile, Trabeculation. As with vascular channels, the trabec- varies from rounded to conical. In some horses and ular pattern of P3 may differ considerably from horse ponies, the extensor process appears disproportion- to horse.

In some animals the trabeculae appear quite ately large compared with the remainder of P3. Other large and distinct, a pattern sometimes referred to as horses have a deep indentation in the periarticular coarse, whereas other horses have very thin, barely per- portion of the extensor process, an appearance ceptible trabeculae, termed fine Figure A B Figure A, Distal phalangeal close-up, frontal perspective, shows a distinctive crena, a shallow concavity located at the center of the solar margin, which is a normal anatomic variation in horses.

B, A deliberately underpenetrated degree dorsopalmar view of the distal phalanx in a normal horse shows a shallow crena at the center of the solar margin. C D Figure High coronary close-up views of the distal phalanges of four normal horses show variation in normal trabeculation ranging from fine A, B to coarse C, D. A B Figure Close-up degree dorsopalmar A and lateral B views of a sound horse with large side bone ossified collateral cartilages.

In newborn foals, the extensor process has been Figure shows a defleshed distal phalanx reported as being incompletely mineralized, and thus emphasis on the extensor process from four different may be mistaken for osteochondritis or osteomyelitis. The uppermost aspect of the extensor process contains a small curl that functionally behaves as a kind of Simulated Lesions.

In degree dorsopalmar dorso- retainer during flexion. A B Figure A, Proximolateral view of a defleshed distal phalanx shows a distinctive channel running along the caudolateral aspect of the bone, the dorsal groove. B, A corrosion cast shows the associated vasculature. Packing end-on, resembling a small bone cyst or focal area of should be done with care, being sure to apply the filler bone loss in the center of P3 Figure See also Pedal evenly and leaving no misleading gas pockets that Osteitis to follow.

Figure Lateral view of the foot deliberately Figure Close-up caudolateral view of a defleshed underexposed of a recently foundered horse shows mild distal phalanx shows dorsal groove flanked by vascular distal phalangeal rotation and a faint laminitic lucency. The foramina. The latter may be mistaken for a bone cyst or toe is dangerously close to the sole as a result of the distal localized infection. Unfortunately, these supposed radiographic disease indicators are often found in normal horses.

This lack of diagnostic specificity has not only rendered such signs unreliable, but worse has led to false-positive diagnosis. Accordingly, I strongly recommend that this diagnosis be used with considerable caution or, better, avoided altogether. Because the Figure Sole of an adult horse seen from below, coronet is radiographically visible, and thus can be showing a toothbrush being used to remove soil from the used as a reference point in progress films, metallic sulci of the frog.

Unevenly applied packing material may cause focal Small fractures from the dorsal edge of the solar differences in bone density, depending on whether it margin are often visible as subtle, forward deflections is relatively thicker or thinner than the surrounding of the tip of P3 as seen in lateral projections.

Where packing. Starrak reported how such differences may be uncertainty exists, a degree dorsopalmar view mistaken for disease. Actually, it is the distal two channels. A B Figure High coronary A and high coronary close-up B views of the distal phalanx of a laminitic horse made with the shoes on. The focal concavity in the central solar margin is the crena, a normal variant in horses.

The relatively roughened lateral solar margin best seen in the close-up is also a normal variant. A,B C Figure Distal phalangeal radiometrics. A, Close-up lateral view of the distal phalanx of a foundered horse soft tissues emphasized. B, Lines drawn along the dorsal surfaces of the hoof wall and as corresponding surface of P3 diverge, consistent with mild rotation. C, A lateral radiograph of a healthy horse is provided for comparison.

In the latter distal phalangeal rotation are judged by the spatial instances, and depending on how the line is drawn, relationship between P3 and the hoof wall, specifically, false divergence may result. Finally, and as reported by the loss of a parallel alignment. As the laminitic foot Koblik and co-workers, if something less than a true degenerates and the distal phalanx detaches, the lateral projection of the distal phalanx is obtained, normal parallel relationship between the two is lost.

A B Figure Lateral A and lateral close-up B views of distal phalanx show moderate distal phalangeal rotation with a triangular gas pocket underlying the distal hoof emphasis zone. In the case of the hoof, begin the line just below the penetrated sole or coronary drainage. Gas may also be coronet, and extend it distally until reaching the flair released from hemoglobin secondary to disintegrating of the toe and then stop. Begin the line along the front surface of P3 just below the extensor process, and continue to the tip of P3.

Do the same if the surface is concave. With the exception of the extensor process, new bone Then compare the lines to see whether they are is not readily formed on the surface of the distal parallel. This is due in large part to its single layer of fibrous periosteum, which coats all but the extensor For more practical information on the balancing process.

The carpal and tarsal bones have a similar of horses feet with or without laminitis , I strongly primitive covering, which responds much more slowly recommend the review by Balch and colleagues. Accordingly, acute and subacute laminitis produces Distal Phalangeal Displacement no structural changes in the distal phalanx. The excep- Phalangeal Sinking tion to this rule is when there is severe rotation that As mentioned earlier, a single lateral image of the eventually leads to penetration of the sole, fracture of distal phalanx is usually sufficient to detect distal dis- the tip of P3, and secondary osteomyelitis.

Horses that placement of P3 within the hoof, provided the degree recover from these additional injuries are typically left of displacement is marked. Otherwise, an earlier or with a small, deformed foot or, in the severe instance, later comparison view is necessary. Metallic markers little more than a digital stump. There may also be large hoof defects, the the Linford method, in which the width of the soft tissue result of therapeutic trimming.

A B Figure A, Lateral view of laminitic front foot of a 2-year-old pony shows 1 distal phalangeal rotation, 2 secondary fracture of the tip of P3, 3 pronounced rocker sole, and 4 a badly overgrown toe. B, The opposite front foot is also badly deformed, but as yet it is not fractured.

Distal displacement sinking occurred before rotation. A radiometric value of greater than Initially Normal Foot Peloso and co-workers published their observations in 20 foundered horses that initially developed laminitis A wrinkled or deformed hoof wall in a single front foot and later in the other. Surprisingly, and contrary to the pre- Abbreviated size vailing belief at the time, being overweight was not a Abnormal shape factor. The authors made the following radiographic Various combinations of the foregoing radiographic observations regarding the potential development of disease indicators are shown in Figures to Radiographic Prognosis in Chronic Laminitis Use of Radiographs as an Aid to Corrective Shoeing and Trimming in Horses With Generally speaking, the combination of rotation, distal displacement, and laminar gas does not bode well for Chronic Laminitis functional recovery.

Diagnostic imaging

A B Figure Lateral A and lateral close-up B views of a front foot in a foundered mare show: 1 distal phalangeal displaced, without rotation; and 2 a characteristic bone deposit just proximal to the tip of P3 emphasis zone. Mud on the upper part of the hoof emphasis zone mimics deformity often associated with chronicity. C D Figure Lateral close-up A and ultra-close-up B views of a pathologic distal phalangeal fracture in a foundered horse.

Lateral close-up C and ultra-close-up D views of the opposite front foot are provided for normal comparison. D E Figure Right A, B and left C, D lateral and lateral close-up views of a pony with laminitis show rotation and tip-fractures bilaterally tack marker was by special request. The animals recently trimmed and rasped left forefoot is also included E. The problem is made even greater when pain prevents the fractured leg from being posi- Fractures of P2, particularly avulsion fractures of the tioned in the standard manner.

In such circumstances, palmaromedial eminence, are most common in CT will often prove indispensable, provided the cutting, reining, and barrel racing horses, presumably animal can be put under general anesthesia and, the result of the tremendous force exerted on this part equally important, recovered. Predisposing factors include 1 racing on Normal Foot Laminitic Foot excessively hard surfaces; 2 blunt trauma, such as Complete filling of terminal arch Poor filling of terminal arch kicking a stall door or stock rail; 3 falling or colliding with another horse during a race; and 3 preexisting Eight to 10 primary arterial branches Larger but fewer arterial bone or foot disease, such as laminitis, nonspecific P3 between 0.

Less certain bio- corium of the hoof dense and disorganized mechanical influences include upright conformation, improper hoof trim, or unbalanced shoeing. A hind Numerous fine vessels in the Irregular vasculature in the corium of the coronary band corium of the coronary distal phalangeal fracture was reported in a 7-year-old band Tennessee Walker after it fell on pavement. The great majority of breaks were either through Regular, smooth corial vessels Irregular, tortuous vessels the left lateral or right medial surface of the bone, in corium of coronary band reflecting the uneven weight distribution that occurs when racing counterclockwise.

A B Figure Lateral A and lateral close-up B views of the right front foot of a chronically foundered Arabian gelding show a severely deformed distal phalanx, the combined result of rotation, distal displacement, multiple toe fractures, and a failed attempt at repair. Clinically, horses with acute P3 fractures typically Caution: Gas or dirt trapped in the sulci of the frog can be show one or more of the following abnormalities: 1 mistaken for a fracture, especially in the high coronary view lameness; 2 regional hyperemia, as indicated by a Figure Classification of Distal Phalangeal Fractures Generally, signs are less pronounced in chronic Scott and co-workers have numerically classified P3 injuries, especially if they are nonarticular.

As Box The oblique projections are a hedge against missing a minimally displaced articular frac- ture located in the outside third of the body of P3 or a Distal Phalangeal Fracture Types caudally located wing fracture. Most P3 fractures are complete, extending fully through the bone in the sagittal or parasagittal plane. Because these fractures enter the coffin joint proximally, they are also articular B o x 3 - 4 in nature. In my experience, fractures breaking into the Differential Diagnosis of Distal Phalangeal Fractures central third of the coffin joint are generally more Sole bruise severe painful, cause greater articular disruption, and are Sole abscess slower to heal than outer third fractures.

Small elliptical fractures from the Navicular infection dorsal-most aspect of the solar border of P3 as viewed Osteochondritis of subchondral bone of P3 laterally are known as toe fractures. Most toe fractures Osteochondritis of extensor process Laminitis are the indirect result of distal phalangeal rotation sub- sequent to laminitis and, as such, can be considered. A B Figure Sole of an adult horse viewed from below A shows deep, V-shaped crevices: the sulci flanking the caudally situated frog.

These channels should be cleaned and packed with radiotransparent material before radiography to avoid diagnostically confusing V-shaped artifacts exemplified in the accompanying radiograph B. When P3 penetrates the sole, Medial and Lateral Palmar Process Fracture becomes infected, and is structurally degraded, it Wing Fracture usually is subject to a similar fate. Complete fractures of the palmar plantar process often spare the coffin joint, making them less painful Marginal Sequestrum than articular P3 fractures. Because these fractures typ- Osteomyelitis of P3 secondary to a sole abscess or ically break through the wing transversely, they can be direct inoculation from a penetrating wound can lead difficult or impossible to visualize in standard frontal to the death and detachment of small pieces of the or lateral projections, especially if they are fresh.

For solar margin, so-called saucer fractures or sequestra. In instances in which the initial radiographic exam- ination appears normal as a result of insufficient frag- ment displacement, a follow-up examination made 2 to 4 weeks later will usually reveal the break. CT is usually definitive pro- vided that the slices are no more than 2 millimeters Type 1 Nonarticular fracture of the palmar or plantar process thick with a corresponding gap between slices. C D Figure Sixty-five-degree dorsopalmar DP oblique A and true lateral B views of the distal phalanx show a nonarticular, hairline fracture of the lateral wing.

An oblique view of the opposite wing C and degree DP view D fail to identify the break. Extensor Process Fracture type, the extensor process remained in a relatively normal position, whereas the rest of P3 and the navic- Fragmentation of the extensor process has been attrib- ular bone appeared detached and displaced in a cau- uted to at least five causes: 1 traumatic avulsion by doproximal direction.

Honnas and co-workers eral involvement should be anticipated, which if evaluated the healing of 36 distal phalangeal fractures absent should cast serious doubt on the diagnosis. As recognized previously, fracture lines appearance of what was presumed to be a pathologic widened during the first few weeks after the initial fracture of P3, through a bone cyst located just beneath injury, achieving a maximum width at between 4 and the extensor process. As with most fractures of this 6 weeks. A B Figure The clarity of distal phalangeal wing fractures, and thus their identification, changes with the projection angle, as illustrated in this pair of films made directly from in front of the foot A and at a degree angle B.

Figure Sixty-five-degree dorsoplantar oblique view of the distal phalanx shows an articular wing fracture not Figure Displaced, parasagittal, articular fracture of visible in the nonobliqued projection. Scintigraphic Assessment. Keegan and co-workers described the scintigraphic appearance of 27 distal phalangeal fractures finding, not unexpectedly, that the fresher the fracture, the greater the isotopic uptake.

Compared with radiographs showing the fracture, the palmar scintigraphic projection proved the most accu- rate in depicting the break. These stress maneu- vers can be painful and sometimes cause the horse to B stumble or fall. Analgesia and increased caution during the procedure are advisable. Examples of coffin joint dislocation are shown in Figures and For example, surface infection presumed to involve only the periosteum is termed periostitis, sub- surface or cortical infection is termed osteitis, and deep infection involving both the medullary cavity and the cortex is termed osteomyelitis.

C Figure Close-up, degree dorsopalmar DP view Periosteal Difference A shows a displaced midsagittal, articular fracture of the distal phalanx extending well into and probably through The value of the foregoing classification is somewhat the extensor process, a fact not appreciable in the limited in the case of P3 infection because all but the degree DP B and lateral C views. In eight horses with com- This means that, unlike infected long bones, which plete parasagittal fractures, all but the articular portion usually show new bone deposition within a week or of the fracture line disappeared at a mean of 11 so of becoming infected, most distal phalangeal months.


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All the fractures that eventually healed infections do not become apparent for a month or showed some signs of healing by 6 months. The carpal and tarsal bones are also covered by Nonarticular fractures were more likely to heal com- a single-layer, fibrous periosteum and typically do not pletely than those that entered the coffin joint. Only show postinfectious new bone for at least a month. C Figure Sixty-five-degree, mild oblique A , degree, moderate oblique B , and degree dorsopalmar C views of the distal phalanx show a displaced parasagittal articular fracture, the clarity of which is highly dependent on projection angle.

A,B C Figure Lateral A , lateral close-up B , and degree dorsopalmar views of a cranially dislocated P3 secondary to ruptured flexor tendons. A B Figure Nonweight-bearing, lateral close-up A view of caudally dislocated P3, secondary to septic arthritis. Normal opposite coffin joint is provided for comparison B.

A B Figure Lateral close-up A and ultra-close-up B views of the hoof and distal phalanx deliberately underexposed to emphasize soft tissues show large gas-filled defect, accompanied by numerous small gas pockets situated between the solar defect and the tip of P3 emphasis zone. It is therefore my opinion that the term infection is Direct and Indirect Radiographic Indicators both the simplest and most direct radiographic means of P3 Infection of describing sepsis of the distal phalanx.

A band of gas located beneath P3 as seen in lateral Points of Attack projection is a reliable indicator of sepsis. Such a finding Most P3 infections develop secondary to a sole abscess. Likewise, discrete gas pockets, especially those that penetrate the navicular bursa or especially when situated along the outer surface of P3, coffin joint, can result in septic arthritis, which then are strongly indicative of infection, even in the absence may spread to the adjacent phalanges. C C Figure Sixty-five-degree A , degree oblique B , Figure Lateral A , lateral close-up B , and and true lateral C views of the foot of year-old degree dosopalmar oblique C views show gas pockets Thoroughbred gelding with a draining sinus in the medial surrounding the tip of P3 and extending along the lateral sulcus show a large gas pocket beneath the medial wing of solar margin emphasis zone.

P3 emphasis zone. The involvement. Probe marking as opposed to sinogra- depth, extent, and intercommunication of related sinus phy nearly always underestimates the full extent of a tracts and cavities can be established only using particular lesion Figures and A B Figure Lateral A and degree B marking studies of the horse in Figure show that a metallic probe can be extended from the drainage site to a point immediately caudal and proximal to the proximal border of the navicular bone.

Currently there is no evidence of osteomyelitis. B C Figure Lateral A and degree dorsopalmar B views of the forefoot of a severely lame horse show asymmetric narrowing of the coffin joint, without concomitant signs of arthritis, strongly suggesting septic arthritis. A lateral bursagram C confirms the suspicion of infection, with contrast solution present in both the coffin joint and distended navicular bursa. Baird pointed out the strong resem- Metallic foreign bodies, such as wires, show clearly, but wooden splinters are radiographically invisible Septic Arthritis, Osteomyelitis, and Figure Dislocation of the Coffin Joint One of the first radiographic indicators of a coffin joint Focal Marginal Bone Loss infection is narrowing of the cartilage space.

However, Localized bone loss from the solar margin of P3, as it is important not to mistake postural-related joint seen in frontal projection, is a convincing sign of infec- narrowing usually asymmetric for disease Figure tion. However, because of a marked individual vari- Once The best solution to this problem is radiographic com- a full-blown osteomyelitis is under way, the subchon- parison, for example, comparison of a suspected area dral bone begins to disintegrate and the cartilage space of bone loss in the right half of the solar margin with widens and often subluxates.

Swelling is typically con- a comparable area in the left half of the same bone or fined to the soft tissues proximal to the coronary band comparison of a suspicious area in the right front as the result of the confining quality of the hoof wall.

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Figures to show four examples of the extensor process. New bone deposition is also marginal bone loss due to infection. Infectious Sequestration In adult horses, coffin joint infections normally take Infectious sequestration from the solar margin of P3 is a month or more to reveal their presence, usually in rare in horses, occurring more commonly in cattle. The delayed. A B Figure Large lucency superimposed on the lateral wing of the distal phalanx emphasis zone in the degree dorsopalmar view A and a generalized decrease in caudoventral density in the lateral view B are the result of partial removal of the lateral aspect of the hoof.

C D Figure Foreign bodies. Case 1: Forefoot of a lame horse with drainage from the dorsolateral aspect of the coronet A. Close-up lateral B , ultra-close-up lateral C , and degree dorsopalmar D views show a small gas pocket in contact with the base of the extensor process. In tilage as the skeleton matures.

Eventually, intraarti- the case of P1, most cysts are usually situated prox- cular bacteria enter the synovial capillaries, and from imally, just below or to one side of the overlying there they move into the capsular tissues. Thrombosis, sagittal ridge, which may also appear defective. In such circumstances, gas often opposite foot should raise some question as to the clin- accumulates in what was formerly called the cartilage ical importance of either lesion. Verschooten contends that subchondral Absence of P3 bone cysts are caused by subchondral bone necrosis Taylor reported the congenital absence agenesis of a resulting from joint injury.

Although infection angular limb deformity. A vestigial P3 was found on the opposite side. G Figure , contd Surgical exploration revealed an abscess containing a small wooden splinter E. Case 2: Lateral F and forty-five-degree dorsopalmar G views show a metal rod fragment imbedded in the heel of a horse.

Lateral arthrocentesis has been associated with contrast spillage or diffusion of contrast solution into the navicular bursa and digital synovial sheath in about a third of cases, whereas a dorsal approach usually results in no such problems. Bertone and Aanes described the radiographic appearance of congenital phalangeal hypoplasia of P3 in a mule and two foals. All were unilateral. Figure Sixty-five-degree dorsopalmar DP oblique deliberately underexposed shows subtle bone loss along the caudal aspect of the lateral solar margin A , destruction not appreciable in either the opposite oblique C B or true DP projections C.

Figure A, Sixty- five-degree dorsopalmar DP oblique view of the right front distal phalanx A shows bone destruction along the dorsolateral aspect of the solar margin. B, Lateral close-up view shows a gas pocket in the caudoventral aspect of the heel emphasis zone. C, Forty-five-degree DP view shows narrowing of the medial aspect of the coffin joint, the result of a compensatory weight B C shift.

C Figure Sixty-five-degree dorsopalmar DP oblique view shows localized bone destruction emphasis zone along the dorsolateral border of P3 A. The opposite oblique B appears normal, as does the straight degree DP C. B D Figure Lateral A , lateral close-up B , and dorsopalmar DP oblique C views of what remains of the left front forefoot of a horse with severe laminitis. The hoof and distal phalanx have been lost to a combination of events, including 1 distal phalangeal rotation, 2 distal displacement, 3 solar penetration, 4 osteomyelitis, 5 insufficiency fracture, and 6 massive vascular thrombosis.

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A close-up DP view D of proximal P1 and the fetlock joint show intermediate-duration new bone just below the lateral palmar protuberance, indication the infection has nearly reached the fetlock. Figure Pathology specimen sagittal section viewed laterally of the horses foot shown in Figure shows little recognizable tissue below the pastern. Figure Dorsopalmar view of the foot of a normal horse shows narrowing of the lateral half of the coffin joint, the result of a compensatory weight-shift caused by lifting the opposite foot, This phenomenon is known as leaning off and must be distinguished from permanent narrowing resulting from disease.

A B Figure Lateral A and dorsopalmar B views of an infected coffin joint show 1 partial dislocation, 2 extensive subchondral bone destruction, 3 new bone deposition over much of the exterior of P2, 4 insufficiency fracture of the extensor process, and 5 massive proximal swelling to the level of the coronet. A B Figure Lateral A and dorsopalmar oblique B views of the foot of a 7-year-old American Saddle Horse that caught its foot in a barbed wire fence 6 weeks ago, cutting it deeply and subsequently developing an infection. Radiographs show the following: 1 complete dislocation of the coffin joint, including the navicular bone; 2 gas in the coffin joint atmospheric contamination of a draining wound ; 3 a cloud of new bone enveloping the middle phalanx; and 4 severe regional soft- tissue swelling.

Most resemble either infection or tumor, The Standard Navicular Series although the distinction is often unclear. Deep bony cavitation with associated cortical thinning and expan- In most practices, a standard navicular series consists sion resembling a bone cyst are often present Figure of four views: a true lateral, two dorsopalmars 45 and A fifth view is occasionally added, a penetrated body. Most keratomas are painful, but because of their high coronary, to evaluate P3. A standard navicular slow growth, typically lead to a gradually developing series and the purpose of each view are as follows lameness, unlike infections or tumors in which Table Keratomas involving the solar margin are often mistaken for osteomyelitis, or localized bone reabsorption second- Normal Anatomic Variations That May Mimic ary to a chronic sole abscess.

Navicular Disease Monticello and co-workers described a malignant Kaser-Hotz and Ueltschi reviewed the navicular bones melanoma in an year-old American Paint. Radiographically the lesion resembled a bone lateral projection. Unfortunately, a similar finding cyst, being lytic, expansive, and involving the entire may also be found in horses with navicular disease.

When associated or concomitant bone or joint V-shaped lines or bands over the edges of the central disease is present, it can range from fracture to third of the navicular bone as seen in the high coro- osteoarthritis to osteochondritis. B D Figure Lateral A and sixty-five degree DP oblique B radiographs of the distal phalanx of a horse with a large keratoma show extensive, deep bone destruction accompanied by an ineffective reparative effort.

The new bone deposits on the dorsal surface of P2 are unrelated. Axial C and coronal D computed tomograms show the true extent of the tumor, which has destroyed much of the interior of the affected bone. D,E F Figure Lateral view of a lame horse with a clubfoot shows a distal phalanx with a Roman-nose profile and a moderate downward inclination A. A second horse, radiographed because of its clubbed foot B , was found to have osteochondritis fragmenting form of the extensor process C, D.

Subsequent screening of the presumably normal opposite foot reveled it too had a detached extensor process E, F , although lameness was not observed when the horse was examined earlier. Poorly defined, localized gas pockets trapped Underexposed, decentered, and obliqued lateral beneath the sole can mimic navicular cysts. Superimposition Projectional Variations That May Mimic of the proximal third of the extensor process on the Navicular Disease proximal border of the navicular bone can mimic a Nearly all the serious projectional problems associated bone deposit secondary to a sprain or avulsion with navicular radiography involve the skyline view, fracture.

This is true of both normal and abnormal the central ridge of the flexor cortex of the navicular animals, especially horses with navicular disease, in bone as seen in the skyline projection. The apparent defect was attributed to a requires that the x-ray beam pass through the center of normal focal concavity in the center ridge, not to the bone, as parallel as possible to its cortical surfaces. To do otherwise is to invite obliquity and projections Ruohoniemi and Tervahartiala reported that many that closely simulate corticomedullary indistinctness supposed radiographic abnormalities identified along and medullary sclerosis opacification as seen with both the proximal and distal navicular margins of fresh some forms of navicular disease.

Unrecognized obliq- Finnhorse forefeet could not be corroborated in follow- uity in the lateral projection may also lead to the false up CT examinations. A B Figure A, Lateral close-up view of a normal navicular bone in a 6-year-old Quarter Horse gelding shows the clear distinction between the high-density cortical bone of the flexor cortex and low-density bone of the medulla. B, A defleshed navicular bone is provided for comparison. A B Figure A, Forty-five-degree, close-up dorsopalmar view low coronary of a normal navicular bone of the horse described in Figure B, A caudal view of a defleshed navicular bone and associated phalanges is provided for comparison.

These findings suggest that some previous claims made for this view have been exaggerated. More than any other common skeletal disorder of the horse, with perhaps the exception of osteochondritis, navicular disease has been the recipient of numerous A recent makeovers in terminology: navicular syndrome and caudal heel pain syndrome, to name but two, neither of which appears to have shed any further etiologic light on the actual cause or causes of the disease. The latest appellation, caudal heel pain syndrome, is especially troubling because at best it suggests that many regional disorders are capable of producing a similar clinical profile and, at worst, exonerates the navicular bone altogether, depending on ones per- sonal interpretation of the expression and, in particu- lar, the meaning of the word syndrome.

A comparable view of a navicular bone is the least medically pretentious term available. Later the carti- nary, and skyline projections. B B Figure A, Incorrect skyline views: In the first instance, the angle of the x-ray beam was too shallow. B, In the second, the horses leg was not drawn back far enough.

In both cases, the result is the same: poor corticomedullary definition mimicking disease. C leaving a shallow depression in the underlying cortex Figure The associated vasculature appeared hyperemic. Initially the deep flexor tendon also stained brown where it contacted the central ridge of the navicular bone. As the disease worsened, part of the adjacent peritendineum disappeared and small tears appeared in the tendon, sometimes accompanied by adhesions. It is a routine procedure here and is performed standing with sedation. MRI magnetic resonance imaging involves putting the body part of interest in a magnetic field while using radio waves to help generate images of the region.

Various sequences are obtained which highlight specific tissue characteristics example STIR sequence highlights fluid both in bone and soft tissue. It is imperative to have a detailed lameness exam most often with joint and nerve blocks prior to an MRI.

Nuclear Scintigraphy

An MRI is most beneficial when the location of the lameness has been localized as much as possible. A typical MRI scan is sites, but is dependent on the lameness examination. MRI cases typically spend one night in the hospital to ensure the highest quality images are obtained. A single site MRI scan example 1 front foot can generate images that need to be interpreted. All MRI examinations are read by two people Dr.

Pigott and a board certified radiologist to provide the most amount of information for each case. Pigott works with the client and the local veterinarian to come up with treatment and rehabilitation protocols that optimize healing and return to function. Fluoroscopy is a technique that uses x-rays to generate real time moving images inside the body. At CRES, fluoroscopy is used routinely intraoperatively during fracture repair, joint fusion arthrodesis or ankylosis and certain orthopedic conditions to allow for the most anatomic repair possible.

It is used to help guide screw or plate placement based on the exact fracture configuration or condition. Ruffian Home. Ultrasonography At CRES, we have multiple high performance ultrasound machines capable of imaging various areas of the horse. Contact Us.