CANKER Infectious process of the equine foot Chronic hypertrophic, moist pododermatitis of epidermal tissues
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.
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
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
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.
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.
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
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)
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
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
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
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
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
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
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
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
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
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
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
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.
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
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
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)
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
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
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
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
QUITTOR “Quittor” describes chronic, purulent inflammation of the collateral (ungual) cartilage of distal phalanx.
QUITTOR - SIGNALMENT Lateral cartilage of forelimb most commonly affected History of reoccurring drainage from fistulous tracts that overly the affected cartilage
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
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
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
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
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
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)
QUITTOR - TREATMENT Treatment of choice is surgical excision of necrotic collateral cartilage and fistulous tracts
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
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
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?
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
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
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
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
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
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
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