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How to Radiograph and Diagnose Fractures ofthe Tibia in the Field

Patrick Worden, DVM*; John Peloso, DVM, MS, Diplomate ACVS; andRodney Legg

Authors’ address: Equine Medical Center of Ocala, 7107 W Hwy 326, Ocala, FL 34482–1244; e-mail:[email protected]. *Corresponding and presenting author. © 2013 AAEP.

1. Introduction

Displaced and non-displaced fractures and proximalphyseal fractures of the tibia are occasionally en-countered in practice.1 Stress fractures of the tibiaare one of the most common causes for hind limblameness in the young Thoroughbred racehorse.2–5

Although making a diagnosis of a displaced fractureis self-evident, non-displaced and physeal fracturesof the tibia often cause non–weight-bearing lame-ness with a variable degree of swelling and few otherclinical signs, making diagnosis a challenge.2

Stress fractures of the tibia occur most commonlyin 2-year-old or unraced Thoroughbred racehors-es.3–6 They often give minimal to no clinical evi-dence of their presence with the exception oflameness and a recent history of high-intensity ex-ercise (racing or breezing). Diagnosis of stress frac-tures of the tibia in its upper portions of the limb isa clinical challenge because the site of pain is rarelyamenable to identification through palpation or re-gional anesthesia. Historically, nuclear scintigra-phy has been the imaging modality of choice for thediagnosis of stress fracture of the tibia, given itslocation on the upper portion of the limb and thehigh sensitivity of nuclear scintigraphy.3–6

Because nuclear scintigraphy is an expensive im-aging modality, the initial diagnosis is often notperformed, and follow-up scintigraphic examina-tions are rarely performed. Digital radiographyhas become commonplace in equine practice over thelast 6 years; therefore, collecting excellent qualityimages of the tibia has become a reality. In onestudy of 51 cases of tibial stress fracture, 33% (17cases) were diagnosed through the use of radio-graphs alone.3 Making an initial diagnosis of atibial fracture and return to exercise recommenda-tions can be tailored to patient needs on the basis ofthe results of serial radiographic examinations andnot standardized group recommendations.

Radiography of the tibia is often frustrating andtypically inconclusive for several reasons. Thetechnique is infrequently performed; therefore,questions regarding radiographic technique, platepositioning, and inexperience create uncertainty.The concave anatomy of the caudal aspect of thepelvic limb created by the musculature and the prox-imal tibia makes positioning of the cassette a chal-lenge. Fine-quality, motion-free radiographs areessential if subtle findings such as endosteal sclero-sis and periosteal new bone formation are to beidentified. Finally, if radiographs are attempted

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HOW TO TAKE AND INTERPRET RADIOGRAPHS OF THE YOUNG PERFORMANCE HORSE

NOTES

within days after the history of high-speed exerciseand lameness in the training Thoroughbred, theyare likely to be inconclusive.

The objective of this presentation is to provide theambulatory veterinarian with a simple technique tocollect excellent-quality radiographs of the tibia tofacilitate making the initial diagnosis. Another ob-jective is to outline an appropriate schedule for tak-ing follow-up radiographs after diagnosis so thatreturn to performance recommendations can bebased on findings of serial radiographic examina-tions tailored specifically to patient needs and notthe customary recommendations of 6 months of con-valescence after injury.

2. Materials and Methods

History and Physical ExaminationIndications for radiographing the tibia are youngThoroughbred horses (usually less than 2 years of

age) that have hind limb lameness on average ofgrade 3/5 within 4 days of any speed work (recentbreezing or racing). Typically, these horses3 havenot raced or are lightly raced before a diagnosis oftibial stress fracture. Many horses have a historyof more severe lameness soon after exercise thatimproves over a 24-hour period with stall rest andnon-steroidal anti-inflammatory drug treatment.

Horses rarely respond to firm palpation and per-cussion of the mid tibia, and lameness is exacer-bated by a spavin test in up to 76% of casesevaluated in one study.3 Another indication for tib-ial radiographs is lameness that persists after adiagnostic low, four-point nerve block. Nerveblocks performed in more proximal locations on thehind limb are difficult to perform reliably.

Radiographing the TibiaWhen obtaining radiographs of the tibia, we makethree changes to what is conventionally described inthe literature: (1) the perpendicular orientation ofthe cassette; (2) radiographing the tibia in halves;and (3) positioning the radiographer caudally be-hind the horse. Each of these is explained in detail.

Perpendicular Orientation of CassetteMost digital radiography plates are rectangular inshape, with a shorter and longer axis. With theserectangular shapes, it is easier to rotate the plate sothat the short axis of the plate is oriented up and downthe limb. In other words, the long axis of the cassetteis perpendicular to the long axis of the limb.

Fig. 1. A caudomedial-craniolateral oblique projection is takenfrom 45° medial to the dorsoplantar plane. Notice that the shortaxis of the plate is positioned perpendicular to the long axis of thetibia, the top portion of the tibia is being radiographed, and theradiographer is standing behind the horse with the cassette po-sitioned along the cranial aspect of the tibia. When radiographsare collected, the radiographic machine is positioned from a cau-dal perspective and the shorter plate perspective is rotated sothat it is parallel to the long axis of the tibia. When the plate canbe positioned closer to the tibia, the shorter plate-to-object dis-tance allows for a more diagnostic image to be taken with the useof lower exposure settings.

Fig. 2. Drawing taken from a dorsal perspective above thehorse. The circle represents the tibia and the arrows representthe caudal location of the radiographer standing behind the horsewith the horse’s head positioned cranially toward the top of theimage. Our four standard projections are Cd45M–CaLO projec-tion (red line), Cd10Pr–CrDiO projection (black line), Cd45L–CrMO (blue line), and an LM (green line). Most radiographiclesions are identified by the projection outlined by the red arrow(Cd45M–CaLO projection).

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Radiograph the Tibia in HalvesWe position the cassette and take radiographs of thetibia from two different perspectives: from the prox-imal aspect and from the distal aspect. This allowsthe entire tibia to be radiographed, given its length,and allows for higher technique settings on largerhorses that have more soft tissue associated with theproximal aspect of the tibia. When this techniqueis used , approximately two thirds of the tibia fits on

a standard-sized cassette; therefore, images of themiddle can be evaluated in the top and bottomprojections.

Position of the Radiographer and the CassetteThe radiographic machine and radiographer are po-sitioned behind the horse. Given the concave anat-omy of the musculature on the caudal aspect of thethigh, the dorsal position of the cassette allows it to

Fig. 3. These six projections are normal radiographs of the tibia. The top row is the medial and latter obliques, respectively; themiddle row is the top and bottom of the lateral-medial projection; and the bottom row is the top and bottom of the caudal-cranialprojection.



be positioned closer to the tibia in this location.In addition, this shorter plate-to-object distance al-lows for a more diagnostic image and lower tech-nique settings (Fig. 1). The insertion of the patellarligaments on the proximal aspect of the tibia is auseful landmark that allows for more exact position-ing of the plate with respect to the tibia during theinitial examination and during follow-upexaminations.

Standard ProjectionsThe operator stands behind the horse (Figs. 1 and 2)to collect our four standard projections.

(1) A caudomedial-craniolateral oblique projectionmade at 45° medial to the dorsoplantar plane(Cd45M–CaLO; Fig. 2, red line);

(2) A caudoproximal-craniodistal oblique projec-tion made at 10° proximal to the supporting surfaceand parallel to the dorsoplantar plane (Cd10Pr–Cr-DiO; Fig. 2, black line);

(3) A caudolateral-craniomedial oblique projectionmade at 45° lateral to the dorsoplantar plane(Cd45L–CrMO; Fig. 2, blue line);

(4) A lateromedial (LM) projection (Fig. 2, greenline).

Fig. 4. The four images are examples of the Ca45M–CaLO (red line in Fig. 2) projection. The red arrow identifies the endostealreaction created from a stress fracture in the racing Thoroughbred.



The four standard projections taken from proxi-mal and distal perspectives typically create a mini-mum of eight radiographic images. Most of thepathology that we find (especially in the 2-year-oldThoroughbred racehorse) is in the mid diaphysis onthe Cd45M–CrLO projection (Fig. 2, red line); there-

fore, we usually recommend taking a few additionalviews, concentrating on the center of the tibia.The end result is up to 10 images per tibia. Be-cause the occurrence of bilateral tibial stress frac-ture can be high,1,3 it can amount to up to 20radiographs per patient.

Fig. 5. Example of a horse with a cortical fracture and the appearance of the fracture taken 30 days later.



3. Results

With hind limb lameness, the tibia is radiographedon day 1 of lameness if diagnostic blocks do notlocalize the lameness to the lower limb. Cases thatare radiographically negative on day 1 are radio-graphed again on day 10. The author (PW) hasradiographed approximately 100 tibias in 90 horsessince January 1, 2008. Most of these radiographswere taken on 2-year-old Thoroughbreds preparingfor an in-training sale. It is the presenting author’sestimation that when this combination of tibial ra-diographs is evaluated, approximately 50% of the 90horses radiographed have evidence of either a frac-ture line or endosteal reaction consistent with atibial stress fracture. If significant changes areidentified, the radiographs taken earlier in time areoften negative. In the presenting author’s experi-ence, radiographs taken on day 1 of lameness arehelpful in approximately 20% of cases and radio-graphs taken 10 days later are helpful in the re-maining 80% of cases. It is the presenting author’sopinion that follow-up radiographs should be re-peated for all cases that are negative initially.

Radiographic DiagnosisInitial radiographic changes include an endostealreaction that can progress to a periosteal reactionand a cortical fracture line originating from theouter cortex. Typically, bone develops on the en-dosteum and results in a sclerotic region that formssecondary to fatigue fracture.

Radiographic evidence of endosteal, focal perios-teal, or an intracortical fracture line is considereddiagnostic of a stress fracture, although it is recog-nized that some horses will only develop endostealreaction and never develop the periosteal reactionand/or a cortical fracture line.

Schedule of Initial Radiographs and Follow-UpRadiographsStress fractures can be difficult to detect early in theacute stages until the mineral content of the frac-ture line decreases by 30% of the total mineral con-tent of the bone—a phenomenon called radiographicrarefaction.1 Thus, a fracture line that was notradiographically apparent on the initial radiographsmay be detected on films obtained 5 to 10 days later.

Horses with non-displaced fractures and physealfractures are radiographed immediately after in-jury, and the diagnosis is often readily evident.In training, Thoroughbreds with the appropriatehistory should also be radiographed immediatelyafter injury, although these initial radiographs canoften be negative. These same horses should bere-radiographed in 10 days’ time and should be onrestricted exercise schedules until these radio-graphs are repeated. Some fractures are never vis-ible radiographically and may be preceded by thedevelopment of endosteal sclerosis.

Once the diagnosis of non-displaced or physealfracture is made, follow-up radiographs should be

taken every 30 days, and the results of these exam-inations should guide future exercise schedules.Non-displaced fractures can take up to 6 months toheal, but light exercise can begin at 3 months inadvance of radiographic evidence of fracture heal-ing. Physeal fractures can be returned to exercisein 4 to 6 weeks.

Once a diagnosis of tibial stress fracture is made,radiographs should be taken every 30 days and oncebefore the horse does any high-intensity exercise(racing or breezing). Current recommendationsare to stall-rest the horse until it is sound at the jog5 to 7 days, followed by 60 days of paddock exerciseor light galloping.2–8

Some suggest that training can be resumed 4 to 6weeks after diagnosis, although one author com-ments that training initiated sooner than 16 weeksafter injury predisposes the horse to the reoccur-rence of stress-related bone injury.8

4. Discussion

Tibial stress fractures are one of the most commoncauses for hind limb lameness in the young Thor-oughbred. Until digital radiography, the only wayto confirm a tibial stress fracture was with a bonescan. Today, many of the digital radiography unitson the market will produce very high-quality imagesof the tibia. In the presenting author’s experiencewith young Thoroughbred racehorses and 2-year-olds in training, approximately 90% of tibial stressfractures occur in the dorsal lateral aspect of themid-diaphysis, and this observation is supported inthe literature.3–8

Historically, radiography of the tibia was not prac-ticed in the field because of the limitations of stan-dard radiography: inexperience with radiographictechnique, large cassette sizes, and the number ofexposures needed and time delays in determiningwhether quality images were collected. Digital ra-diography has made high-quality, motion-free radio-graphs of the tibia a reality, so that endostealsclerosis and periosteal new bone formation is sig-nificantly easier to identify. In one study, 45 of 58(76%) tibial stress fractures were identified radio-graphically,5 and in another study, 33% of horseswith tibial stress fractures were identified on thebasis of radiographs alone.3 Most studies agreethat stress fractures and non-displaced fractures ofthe tibia are significantly more common in proximaland mid-diaphyseal locations.

The three techniques used in this report allow theambulatory veterinarian with a simple means tocollect excellent-quality radiographs of the tibia tomake the initial diagnosis. It also offers a schedulefor serial follow-up radiographs after diagnosis so thatreturn to performance recommendations can be basedon patient needs (also see Figs. 3–6).

5. Conclusions

Hind limb lameness that originates in the tibia iscommon in the young Thoroughbred racehorse.



Aside from hind limb lameness, the absence of phys-ical examination findings and clinical signs makefractures of the tibia a diagnostic challenge.

Taking quality radiographs is crucial when mak-ing an initial diagnosis of non-displaced fracturesand stress fractures of the tibia. When obtainingquality radiographs of the tibia, three technical de-tails will improve image quality and reproducibility:(1) turn the cassette so that the long axis is perpen-dicular to the tibia; (2) radiograph the tibia in prox-imal and distal halves; and (3) position theradiographer behind the horse and the cassette onthe cranial aspect of the tibia.

Although four standard projections are taken, le-sions are most often identified in the mid-diaphysis(70%), which suggests that the caudomedial-cranio-lateral oblique projection (Ca45M–CaLO; Fig. 2, redline) is the most useful projection. Typically, thetibia is radiographed on day 1 of lameness if diag-nostic blocks do not localize the lameness to thelower limb. Significant pathology is identified insome of the cases, and a course of action is outlinedon the basis of these radiographs. If significantchanges are not identified, then radiographs are re-peated in 10 days. In the presenting author’s opin-ion, the value of the technique is not to make anearly diagnosis but to make a diagnosis in the field

without a bone scan, and, if successful, to providea radiographic lesion that can be followed overtime with recovery recommendations that areindividualized.

References1. Butler J, Colles C, Dyson S, et al. General principles. In:

Clinical Radiology of the Horse. 2nd edition. Blackwell Pub-lishing Company, Wiley and Sons; 2001;1:1–26.

2. Watkins JP. Fractures of the tibia. In: Nixon AJ, editor.Equine Fracture Repair. 1st edition. Philadelphia: WBSaunders; 2006:273–284.

3. Spike DL, Bramlage LR, Embertson RM, et al. Tibial stressfractures in 51 racehorses, in Proceedings. Am Assoc EquinePract. 1996;42:280–281.

4. Arthur RM, Constantinide D. Results of 428 nuclear scinti-graphic examinations of the musculoskeletal system at aThoroughbred racetrack, in Proceedings. Am Assoc EquinePract 1995;41:84–87.

5. O’Sullivan CB, Lumsden JM. Stress fractures of the tibiaand humerus in Thoroughbred racehorses: 99 cases (1992–2000). J Am Vet Med Assoc 2003;222:491–498.

6. Ruggles AJ, Moore RM, Bertone AL, et al. Tibial stressfractures in racing Standardbreds: 13 cases (1989–1993).J Am Vet Med Assoc 1996;209:634–637.

7. Peloso JG, Watkins JP, Keele SR, et al. Bilateral stressfractures of the tibia in a racing American Quarter Horse.J Am Vet Med Assoc 1993;203:801–805.

8. Ross MW. The crus. In: Ross MW, Dyson SJ, editors. Diag-nosis and Management of Lameness in the Horse. 2nd edition.St Louis: Elsevier Saunders; 2011:526–532.

Fig. 6. Example of a tibial crest fracture of the tibia.



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