Equine Radiology
Journal Club Resident Study Guide

Radiographic & Radiological Assessment of Laminitis

An interactive review of the standard projections, the normal reference measurements of the forefoot, and the radiological hallmarks of the laminitic horse. Click the pulsing markers on the foot diagrams to learn each measurement — how to obtain it, what is normal, and what changes in laminitis.

Adapted for study from Sherlock & Parks (2013), Equine Veterinary Education 25(10):524–535. For educational use.

Before you interpret

Obtaining diagnostic radiographs

Positioning and preparation errors mimic or mask disease. Standardize every series so that serial films are directly comparable.

🦶 Preparation & stance

  • Trim timing — angular measurements, dorsal wall thickness and sole depth are all altered by trimming:
    • Ideally acquire radiographs both before and after trimming
    • If only one set is affordable = the pre-trim study, because it guides the trim itself
  • Clean the foot before exposure:
    • Angles of the bars
    • Central and lateral sulci of the frog
  • Stance — even weightbearing is essential for both LM and DP views:
    • Stand squarely on two blocks of equal height
    • Metacarpus/metatarsus perpendicular to the ground and parallel to each other
    • Poor positioning alters the normal hoof-capsule/P3 and inter-phalangeal relationships
  • Which limbs to image:
    • Ideal to image the contralateral limb, even in unilaterally affected horses
    • In some cases all four limbs should be evaluated
  • Repeat frequency by stability — the interval depends on the individual case:
    • Clinically unstable = weekly radiographs
    • Clinically stable = re-radiograph at 3–4 month intervals
    • Any deterioration = re-image, regardless of the interval
  • Factors that shorten the interval:
    • Speed of hoof wall growth
    • Clinical progression of the horse
    • Need for radiographic control of trimming and shoeing
    • Weighed against the risk of exacerbating disease during transport if portable radiography is unavailable

📍 Markers

  • Digital radiography has reduced (not eliminated) the need for markers — no longer mandatory provided appropriate exposures are used and a thorough radiological evaluation is performed.
  • Use a marker of known dimension on the dorsal surface of the hoof wall to account for the effect of magnification on specific measurements.
  • Dorsal wall marker — barium paste or a metal strip:
    • Must sit on the dorsal sagittal midline
    • Barium is preferred on distorted walls — accurate placement of a metal strip on a distorted surface is difficult and may cause misinterpretation
    • Its proximal extent must be consistent between serial radiographs
  • Proximal landmark — at the most proximal extent of the hoof wall:
    • Identify by digital palpation
    • Rasp the periople at the coronary band to make it more readily identifiable
    • Mark with indelible ink to prevent interoperator variation across a series
  • Ground marker:
    • Mark with a shoe, or preferably a radiodense marker within the block
    • Marking the frog apex is controversial — an overgrown frog confuses identification of the apex
  • For horizontal DP views:
    • Bead of barium paste on the coronary band at the mid-quarter — clarifies the palmar process / ipsilateral coronary band relationship
    • A line of barium on the abaxial wall improves estimation of abaxial wall thickness

The three standard projections

↔️ Lateromedial (LM)

  • Centering:
    • Parallel to the ground and the heel bulbs
    • Midway between dorsal and palmar/plantar surfaces
  • Assesses: rotation, sole depth, CE distance, hoof width
  • Limitation: long considered essential, but allows assessment in one plane only

⬍ Horizontal dorsopalmar (DP)

  • Centering: ~15 mm above the ground surface
  • Assesses: medial–lateral (uniaxial) distal displacement and DIP joint-space asymmetry
  • Status: considered critical by several authors and gaining popularity

◣ Dorsal 45° Pr-PaDiO

  • Highlights: the solar margin of P3
  • Assesses: vascular channels, solar margin fractures, disuse osteopenia
  • Status: rarely part of a routine laminitic evaluation, but valuable for margin lesions
The core of the guide

Distal Phalanx Measurements

Figures 1a (distances) and 1b (angles & ratios) are the paper's normal reference diagrams. The paper provides no normal dorsopalmar diagram, so the DP view tab uses Fig 11 — a clinical radiograph — as its base; each DP marker still states the normal appearance first. Switch diagrams, then click each ● marker. Values shown are the center of the normal range — not absolute limits — and vary markedly with breed, size and farriery.

Figure 1a — lateromedial diagram of the normal forefoot showing measured distances
👆 Tap a marker to reveal its measurement, normal value & laminitic change
🐴

Select a measurement

Click any pulsing marker on the diagram to open its full breakdown here — technique, the normal reference value, and how it changes in the laminitic foot with example radiographs.

Table 1 · Quick reference

Normal radiological values — sound forefoot

Representative of the center of the range; marked breed/size variability and farriery effects mean there is significant overlap between normal and abnormal. Always interpret alongside clinical signs.

ParameterNormal valueNote
Dorsal hoof wall angle48–54°Mean 52.2 ± 3.7°
Heel angle43.5 ± 6.3°Slightly more acute than dorsal wall
Coronary extensor (CE / founder) distance−2 to 15 mmStrongly breed-dependent:
  • Thoroughbreds — mean 3.5 mm (0–10)
  • Mixed-breed — mean 4.1 mm (−1.8 to 9.7)
Dorsal hoof width14–22 mmBy breed:
  • Light breeds — 14–18 mm
  • Warmbloods — 18–20 mm
  • Standardbreds / heavy breeds — 20–22 mm
Hoof capsule as % of hoof width50–65%Capsule usually slightly >50% of thickness
Dorsal hoof width : palmar length P3<30%Ratio negates magnification
Sole depth at toe>11–15 mmBy breed:
  • Most horses — >15 mm ideal
  • Thoroughbreds — may be thinner (mean 11.1 mm)
Angle: solar margin of P3 to ground3–8°Positive; mean 6.1 ± 2.84°
Maximum vascular channel diameter3.5–4.5 mmOn D45° Pr-PaDiO
Pattern recognition

Additional laminitic signs

Cross-cutting findings that are not tied to a single measurement. Each is assessed alongside the position of P3 within the capsule.

💨 Gas (radiolucent) lines

  • Early, severe acute (20–40 h):
    • Communicate with the coronary band
    • Associated with a poor prognosis
  • Sub-acute (2–18 days):
    • Thin line parallel to the wall, ~2.2 cm below the coronet
    • Represents mummified lamellae
    • Not useful prognostically
  • Chronic:
    • Large irregular submural/subsolar lucencies
    • Follow significant P3 movement
    • Not useful prognostically

🔆 Coronary band halo

  • Radiolucent band at the coronet, visible on LM or DP views
  • Occurs as the pastern skin is drawn distally past the coronet — a sign of distal displacement
  • Indicates circumferential loss of lamellar structural integrity
  • Carries a poorer prognosis than dorsal rotation
  • Easier to detect with windowing on digital images

🦴 Osseous change (chronic)

  • Modeling of P3:
    • Loss of solar concavity / flattened solar border
    • Shortened solar and parietal surfaces
    • Dorsal-distal lipping (osteoproliferation)
  • Destructive change:
    • Osteitis of the parietal surface
    • Disuse rarefaction / osteopenia
    • Sequestra and necrosis
    • Solar margin fractures
  • Margin lesions are best seen on D45° Pr-PaDiO
What predicts outcome

Radiological signs as prognostic indicators

Studies conflict because they measured different parameters, and clinical evaluation may predict outcome better than any single radiological value. Listed strongest first.

  1. 1 CE (coronary–extensor) distance Strongest
    • The most significant prognostic parameter by stepwise regression (Cripps & Eustace)
    • Chronic cases with CE <7.9 mm were treatable
    • Very few with CE >15.2 mm survived or became rideable
    • More significant than severity of lameness, sole perforation or number of feet affected — all of which were themselves significant
  2. 2 Sole depth & solar margin angle Guides treatment
    • Sole <15 mm plus a high solar margin angle indicates difficult treatment and rehabilitation
    • Sole <10 mm with a solar margin angle >15° → recommended candidate for DDF tenotomy with immediate digit realignment
    • Other tenotomy indications: progressive rotation unresponsive to conservative treatment, unremitting pain with capsular rotation, secondary flexural deformity
  3. 3 Coronary band halo Poor
    • Suggests circumferential loss of lamellar structural integrity
    • Associated with a poorer prognosis than dorsal rotation
  4. 4 Uniaxial (asymmetric) distal displacement Inferior
    • Carries an inferior prognosis to the other displacement patterns
    • Only 65% of 11 horses were treated successfully with a wooden shoe
    • Less well recognized than rotation or symmetrical sinking, so evidence is limited
  5. 5 Gas lines Timing-dependent
    • Early lines in acute severe disease = poor clinical prognosis
    • Slowly developing thin lines after the initial episode = not prognostically useful
    • Large irregular lucencies of chronic disease = not prognostically useful
  6. 6 Symmetrical distal displacement (sinking) Debated
    • Commonly considered a poor prognosis, but this has been questioned more recently
    • Generally requires longer medical management; surgery is seldom indicated
  7. 7 Dorsal rotation angle Debated
    • Prognostically significant in one study — but other parameters were more significant
    • Stick et al.: <5.5° returned to function, >11.5° did not
    • Others returned horses to work after 11.5° using heart-bar shoes
    • More recent work has not found rotation angle useful for predicting survival
    • Height of horse/pony does not significantly change prognosis, though ponies rotate more
  8. 8 Osteoproliferation (lipping) None
    • Lipping at the distal dorsal parietal surface of P3 appears to have no prognostic significance
Bottom line: the key long-term factor is the extent of lamellar pathology (the degree of P3–hoof-wall instability), which is hard to quantify radiologically. Interpretation depends on close attention to serial plain radiographs, clinical evaluation, and sometimes venography.
All figures in one place

Figure gallery

Every figure from the source paper — the two reference diagrams and the twelve annotated radiographs — with a short description of what each one demonstrates. Click any image to enlarge.

Test yourself

Rapid-fire self-assessment

Ten questions drawn at random from a pool of 0, balanced across technique, measurements, displacement patterns and prognosis. Answer options are shuffled too, so the set is different every time. Pick an answer to reveal the explanation.

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