This document discusses three uncommon causes of foot lameness: canker, keratoma, and quittor. [1] Canker is a chronic infectious disease of the epidermal tissues of the foot, usually originating in the frog and spreading. It presents as a fetid odor and granulation tissue in the frog. Treatment involves debridement, topical antibiotics, and keeping the foot clean and dry. [2] Keratoma is excessive keratin production between the hoof wall and distal phalanx, causing a hard mass. Diagnosis is via radiographs showing a radiolucent lesion. Surgical removal is required for resolution. [3] Quittor is chronic

1. UNCOMMON CAUSES OF FOOT LAMENESS:
Canker, Keratoma, Quittor, Corn
Dane Tatarniuk, DVM

2. CAUSES OF FOOT LAMENESS:
 Navicular Syndrome  Quittor
 DDFT  Sole Bruise
 Collateral Ligaments  Abscess
 Osteoarthritis  Corn
 Laminitis  Gravel
 P3 Fracture  Keratoma
 Navicular Fracture  Penetrating Injuries
 Pedal Osteitis  Canker
 White Line Disease
 Hoof Avulsion
 Sheared Heels /
Quarters
 P3 Subchondral Cysts
 Sidebone

3. 1. CANKER

4. CANKER
 Infectious process of the equine foot
 Chronic hypertrophic, moist pododermatitis of epidermal
tissues

5. CANKER
 Usually originates in frog, then spreads to sole, bars, hoof
wall
 Any breed; no difference between mares, geldings, studs.
 Higher prevalence seen in Draft Horses.
 Both fore and hind limbs
 Seen more commonly in the southern states, and more
humid regions
 History of being housed on moist pastures or kept in wet,
unhygienic conditions
 Canker has been seen in horses that receive routine hoof
care maintenance.

6. CANKER VS. THRUSH
 Canker is often misdiagnosed
initially as thrush
 Sometimes mild lesions are not
very distinct, visually
 If treating thrush and lesion not
resolving with routine treatment…
= be suspicious of canker

7. CANKER VS. THRUSH
 Thrush is limited to lateral and medial sulci, central sulci or
base of frog (if fissure present)
 Canker invades horn of frog anywhere.
 Biggest difference:
 Canker = Proliferation of tissue
 Thrush = Loss of tissue

8. CANKER – CLINICAL SIGNS
 Often a fetid odor
 Lesion bleeds easily when abraded
 Mild lesion - area of focal granulation tissue in frog
 Severe lesion - frog has ragged, filamentous appearance
 Proliferative frog with small finger like papillae of soft, off
white material that is “cauliflower” like
 Epidermis of frog is friable and is “cottage cheese” like.

9. CANKER

10. CANKER – CLINICAL SIGNS
 Early stages, not associated with lameness, as disease is
isolated to superficial epidermis
 Clinical signs (lameness) increase once lesion becomes
diffuse, involves other structures of foot
 Extremely painful when pressure applied!
 Sometimes is best indicator of canker.

11. CANKER - DIAGNOSIS
 Culture is unrewarding
 Mixed bacterial population isolated from stratum
germinativum layer.
 Biopsy can confirm canker lesion
 But not routinely required.
 If lesion does not have characteristic appearance, or if in
abnormal (non-frog) location = biopsy helpful.
 Must remove superficial necrotic tissue prior to biopsy
 Sample taken from margin of lesion
 6mm punch biopsy works well

12. CANKER - HISTOLOGY
 Histologic Diagnosis:
 Proliferative papillary hyperplasia of epidermis
 Pathogenesis:
 infection -> dyskeratosis -> creates filamentous “fronds”
of hypertrophic horn

13. CANKER - ETIOLOGY
 Etiology unknown.
 For the longest time, presumed to be anaerobic infection:
 Fusobacterium necrophorum
 Bacteroides
 Other anaerobic organisms
 Recent paper identifying bovine papillomavirus (2011)

14. CANKER - TREATMENT
 O‟Grady‟s Four Principles of Successful Treatment:
 1. Early recognition
 2. Debridement
 3. Routine topical treatment
 4. Keep wound clean & dry
 promotes cornification

15. CANKER - DEBRIDEMENT
 Tourniquet is essential
 Sedation vs. anesthesia
 Extent of lesion, clinician comfort level
 Trim horse, remove loose exfoliating sole, excess toe or heel.
 Remove abnormal tissue down to normal cornium
 Clear demarcation between abnormal and normal layers
 Try not to remove excessive amounts of cornium if possible
 Will retard cornification after surgery and decrease quality and
depth of new sole being produced
 Balancing act

16. CANKER - DEBRIDEMENT
 Instruments for debridement:
 Scalpel blade
 Electrocautery in cut mode
 CO2 Laser
 Follow with cryotherapy:
 Liquid nitrogen most common
 Freeze area until it becomes hard – let it thaw – then
freeze one more time

17. CANKER – TOPICAL MEDS
 Systemic antibiotics not warranted
 Lesions resolve with topical only application
 Topical Options:
 Chloramphenicol
 Metronidazole powder
 2% metronidazole ointment
 Ketoconazole/rifampin/DMSO mix
 10% benzoyl peroxide in acetone and metronidazole
powder

18. CANKER – TOPICAL MEDS
 Clean area daily with surgical scrub (betadine)
 Rinse with saline
 Apply medication of choice to area
 Protect with sponge gauze
 Keep entire foot clean and dry
 Foot bandage
 Treatment plate
 Dry stall & stall rest

19. CANKER - LITERATURE
 O’Grady’s Study: 56 cases
 21 - single forelimb affected
 29 - single hindlimb affected
 1 - one forelimb and one hindlimb affected
 5 - bilateral forelimb affected
 All cases treated similar treatment protocol:
 „10% benzoyl peroxide in acetone + metronidazole
powder‟
 55 cases resolved successfully
 1 case reoccurred
 Responded the second time to laser photoablation

20. CANKER - LITERATURE
 Oosterlinck Study: 30 horses
 Only recognized as canker initially in 5 cases
 In 10 cases, thrush had been mis-diagnosed and treated
for several months
 Duration of hospitalization was significantly decreased in
horses receiving oral prednisolone for 3 weeks
compared to those without this additional systemic
treatment
 10 horses: No recurrence with treatment
 14 horses: Problems reoccurred within the first year
 6 horses: Subjected to euthanasia due to diagnosis

21. CANKER - PROGNOSIS
 Prognosis is favorable for complete
resolution if treatment instituted early in
course of disease
 Involvement of sole, bars, hoof wall
= prognosis goes down
 Multiple limbs affected
= prognosis goes down
 Duration of aftercare treatment can take
several weeks to months
 Very important to communicate this to
owner

22. 2. KERATOMA

23. KERATOMA - OVERVIEW
 Excessive keratin is
produced between the
hoof wall and distal
phalanx
 “Oma” implies neoplasia
– however this process
is not neoplastic
 Rather, morphological
process is hyperplasia

24. KERATOMA - SIGNALMENT
 Initial owner complaints:
 Lameness of unknown
origin
 Abnormal contour to the
hoof capsule
 Deviation of the
coronary band and hoof
wall
 Most common sites are
toe or quarter
 Chronic abscessation in
foot
 Affects any age, any breed
 Can be multifocal

25. KERATOMA - ETIOLOGY
 Unknown etiology
 Etiologies proposed include:
 Direct trauma to hoof capsule & associated structures
 Chronic irritation
 Sole abscessation
 “Chicken – Egg”
 …keratoma causing abscesses or abscesses
causing keratoma?
 Many cases where no history of insult to hoof is present

26. KERATOMA - DIAGNOSIS
 Hoof Tester:
 Painful response over lesion
 Diagnostic Analgesia:
 Block depends on location of keratoma
 PDN, Pastern Semi-Ring, Abaxial Sesamoid
 Radiographs:
 Discrete, semi-circular, radiolucent abnormality with a
non-sclerotic (smooth) rim
 Irregular, sclerotic margins = think pedal osteitis
 Dorsoproximal-65°-palmarodistal view
 Only see keratoma itself if mineralized

27. KERATOMA - RADS

28. KERATOMA – NOVEL IMAGING
 Ultrasound:
 If near coronary band, can ultrasound lesion
 Appears as hypo-echoic, well-delineated soft tissue
mass
 Computed Tomography
 Magnetic Resonance Imaging

29. KERATOMA - CT

30. KERATOMA - MRI

31. KERATOMA - DIFFERENTIALS
 DDx for focal, radio-lucent lesion on radiographs:
 Fibroma
 Mast cell tumor
 Squamous Cell Carcinoma
 Intra-osseous Epidermoid Cyst
 Melanoma
 Bone Cyst
 Calcified Hematoma
 Capsulated Abscess

32. KERATOMA - PATHOLOGY
 Histology reveals excessive amounts of keratin and
hyperplasia of the squamous epithelial cells.
 Occasionally see granulation tissue and inflammatory cell
influx (variable).
 Gross appearance is a firm, nodular, yellow-grey mass of
varying size.

33. KERATOMA - GROSS PATHOLOGY

34. KERATOMA - HISTOLOGY
Hematoxylin &
Eosin,
2x
magnification

35. KERATOMA - HISTOLOGY
Hematoxylin &
Eosin,
10x
magnification

36. KERATOMA - TREATMENT
 Complete surgical removal is required
 Incomplete removal = re-growth
 Surgery performed standing or under general anesthesia
 Partial or complete hoof wall resection
 Create two parallel vertical incisions on either side of keratoma
 3rd cut made distally at base of the mass
 4th cut made proximal to mass (but under coronary band)
 Depth – down to the sensitive laminae
 Cut using motorized burr (dremel), cast cutters, osteotome

37. PARTIAL VS. COMPLETE
Partial
Complete

42. KERATOMA – POST OP
 Hoof stabilization
 Prevents exuberant granulation tissue
 Minimizes pain
 Methods:
 Bar shoe with clips on either side of the defect
 Prevents independent movement of two portions of
hoof wall
 Bridge two sides of hoof wall together
 Metal strip spanning defect
 Screws & figure-8 wire spanning defect

43. Metal Strip
Figure 8 wire

44. KERATOMA - LITERATURE
 Boys Smith Study: 26 cases
 Complication rate from partial resection = 25%
 Complication rate from complete resection = 74%
 Complications:
 Excess granulation tissue
 Hoof crack formation
 Keratoma reoccurrence
 Time back to work shorter with PR over CR
 Median time 8 months (PR) vs. 10 months (CR)

45. KERATOMA - LITERATURE
 Cont… Boys Smith study: 26 cases
 History of abscessation in 92% of cases
 Radiographic signs present in 96% of cases
 Reoccurrence of keratoma in 11% of cases
 Higher occurrence with PR
 Limited surgical exposure…?
 Excessive granulation tissue in 32% of cases
 Higher occurrence with CR
 More hoof wall instability / movement

46. KERATOMA - LITERATURE
 Gasiorowski Study: 2 cases
 Supracoronary removal of keratomas
 Keratomas diagnosed behind or proximal to coronary
band (atypical)
 Inverted T-incision made 2cm proximal to coronary band
 Transect the common digital extensor (V shape)
 Body of mass elevated with periosteal elevators
 Primary closure

47. KERATOMA - LITERATURE
 Dead space present distally
 3mm groove burred out
 Creates instability
 Countered by placing 1.25mm
steel wire sutures
 Wire loose enough to allow
drainage, but tight enough to
prevent shearing forces

48. KERATOMA - PROGNOSIS
 Prognosis is good for return to previous function
 IF all the abnormal tissue is removed
 Hoof wall healing will take 10 - 12 months
 Inform owners that horse will be rested for at least 12 months
time

49. 3. QUITTOR

50. QUITTOR
 “Quittor” describes
chronic, purulent
inflammation of
the collateral
(ungual) cartilage
of distal phalanx.

51. QUITTOR - SIGNALMENT
 Lateral cartilage of
forelimb most
commonly affected
 History of reoccurring
drainage from fistulous
tracts that overly the
affected cartilage

52. QUITTOR – CLINICAL SIGNS
 Abscess formation
within collateral
cartilage
 Break open and drain
proximal to coronary
band
 Owners note drainage
from fistulous tracts
 Often history of
intermittent, severe
lameness

53. QUITTOR – CLINICAL SIGNS
 Degree of lameness is variable
 Patency of fistulous draining tracts = less severe
lameness
 Non-patent = no drainage of abscesses = more
severe lameness
 Pain on hoof tester over affected quarter
 Chronic inflammation may lead to permanent foot
damage = deformities in hoof wall and soft tissue

54. QUITTOR - ETIOLOGY
 Direct trauma to cartilage or soft
tissue overlying cartilage
 Penetrating wounds and
lacerations
 Blunt trauma  bruising 
damages blood supply
 Foot abscesses
 Chronic ascending infection of
the white line in the quarters
 Deep hoof cracks

55. QUITTOR - DIAGNOSIS
 Recurrent swelling of collateral
cartilage
 1+ fistulous tracts proximal to
coronary band
 Swelling and pain over collateral
cartilage
 Hoof tester sensitive over
affected quarter

56. QUITTOR - DIAGNOSIS
 Need to differentiate between shallow abscesses or
ascending infection of the white line (gravel):
 Gravel – inflammatory process is often more localized,
one fistulous tract
 Quittor – inflammatory process is more diffuse, multiple
fistulous tracts

57. QUITTOR - IMAGING
 Radiographs:
 Useful to rule out bone involvement
 However lysis of collateral cartilage from infection can‟t
be seen on rads
 If collateral cartilage has ossified, can see evidence of
osteomyelitis
 Can determine depth and dimension of draining tract
using fistulography (flexible sterile probe)

58. QUITTOR - TREATMENT
 Treatment of
choice is surgical
excision of
necrotic collateral
cartilage and
fistulous tracts

59. QUITTOR - TREATMENT
 Medical management includes systemic and topical
antibiotics, foot soaks, and injection of fistulous tracts with
anti-septic
 Overall, medical management usually fails
 May temporarily suppress clinical signs but symptoms
reoccur
 Regional limb perfusion may be best medical approach
 Poor blood supply to collateral cartilage

60. QUITTOR - SURGERY
 Hold toe in rigid extension by drilling holes through hoof
wall  thread wire through holes  place traction on foot to
maintain extension
 Tenses joint capsule & retracts it from surgical dissection
plane
 Decreases chance of entering distal inter-phalangeal
joint
 Curve incision over affected cartilage, reflected proximally
 Necrotic tissue will be dark blue or red in color
 Close incision primarily and place foot in foot cast or
bandage

61. QUITTOR - LITERATURE
 Honas Study: 16 cases
 66% of cases became sound after surgical treatment
 If drainage less than 1 month, better prognosis for return
to soundness versus drainage for more than 1 month
 Lateral cartilage was affected in 88% of cases
 More trauma sustained laterally?

62. QUITTOR - PROGNOSIS
 Prognosis is excellent if complete removal of necrotic tissue
is achieved
 Secondary complications reduce prognosis:
 Osteomyelitis of distal phalanx
 Septic arthritis of distal inter-phalangeal joint
 Infection of digital cushion or other surrounding soft
tissue structures

63. 4. CORN

64. CORN
 A corn is a bruise that involves
the tissues of the sole
 Specifically at the angle
formed by the wall and bar
 Occur more commonly on the
medial angle on the forelimbs,
however occasionally are seen
in the hind
 If the bruised (corn) site
becomes infected -> abscess

65. CORN - TYPES
 Corns are divided into 3 categories:
 Dry
 Red stains, may not have any clinical significance
 Moist
 Serum accumulates beneath injured epidermis
 May cause mild lameness
 Suppurative
 Infected
 Usually more severe lameness

66. CORN - ETIOLOGY
 Corns caused by:
 Pressure from horse shoe
 If shoe left on too long, heel may overgrow the shoe
 Creates selective pressure on the sole at the angle of
the wall and bar
 Application of a shoe that is one half to one full size
too small can also increase pressure
 Stone wedged between shoe and sole

67. CORN – CLINICAL SIGNS
 Variable
 Varying degrees of lameness
 Usually mild to moderate
 If acute or infected
 May get warmth in hoof
wall
 Increased digital pulse
often present

68. DIAGNOSIS & TREATMENT
 Often diagnosis can be made by history and visualizing
lesion
 If lesion not apparent….
 Shoe should be removed and exfoliating sole removed
 Hoof testing parallel to sole of the foot will sometimes cause
a more significant pain response (vs. perpendicular)
 Lesions can resolve if source of trauma is removed and
horse is rested from heavy work
 ie. pull shoe
 Can also place frog support that will absorb concussion that
would normally distribute to the corn site
 Prognosis: Excellent

69. REFERENCES:
 Adams Lameness in Horses, Sixth Ed. Gary Baxter. Wiley-Blackwell
Publishing (2011).
 O‟Grady, S. “How to treat equine canker“ American Association of
Equine Practitioner Proceedings. Denver, CO. 1994.
 Oosterlinck, M. “Retrospective study on 30 horses with chronic
proliferative pododermatitis (canker).” EVE 2011.
 Boys Smith, S. “Complete and partial hoof wall resection for keratoma
removal: post-operative complications and final outcome.” EVJ 2006.
 Gasiorowski, J. “Supracoronary approach for keratoma removal in
horses: 2 cases.” EVE 2011
 Honnas, C. “Necrosis of the collateral cartilage of the distal phalanx in
horses: 16 cases.” JAVMA 1988
 Moyer W. “Bruising & Corrective shoeing” Vet Clin North America 1980