Keratoma

Question 1

Pathogenesis

Answer 1

§ Hyperplastic keratin mass within the hoof

§ Originate from epidermal horn producing cells of coronary band

§ May be a benign neoplasm

§ Grow distally towards the toe with the hoof

§ Act as a space occupying lesion within the hoof capsule
- Pressure necrosis in adjacent distal phalanx
- Hoof deformation
- Loss of white line integrity → entry of bacteria → hoof abscess

Question 2

Where are keratomas most commonly found?

Answer 2

• in the toe region of the hoof

Question 3

Keratomas commonly occur due to an insult where? Examples of insults

Answer 3

• to the germinal cells at the coronary band
• hoof abscess that bursts out at the coronary band
• trauma
• hoof crack that propagates upwards towards the coronary band

Question 4

History

Answer 4

§ Maybe mild intermittent long term lameness
– May represent the time the keratoma was moving down the hoof and causing damage to the pedal bone
– Osteolysis is a painful process, therefore fits with the mild lameness
§ Usually recurrent severe lameness
– recurrent hoof abscesses at the same location

Question 5

CS / CE

Answer 5

§ Raised digital pulse (single foot)
§ Possible hoof wall distortion (of the dorsal wall)
§ Deviation of white line with ‘Cork like’ growth visible
§ Localised pain with hoof testers
§ Drainage from abscess
§ Lameness abolished by peri-neural anaesthesia
of the foot (abaxial sesamoid nerve block or potentially higher [to get the dorsal structures of the foot])
§ Keratoma is flexible to touch

Question 6

Diagnosis by radiography

Answer 6

§ Dorso 60°proximal – palmar/plantar distal oblique view (upright pedal)
§ Smoothly demarcated radiolucent lesion in the distal border of distal phalanx

Question 7

2 forms of keratoma

Answer 7

• tubular
• spherical

Question 8

Tx

Answer 8

Surgical excision
- Partial hoof wall resection through the dorsal hoof wall (full thickness)
- Under GA, foot numbed under perineural anaesthesia also likely
- Using an oscillating saw to cut a window
- Leave a bridge of intact hoof wall underneath/at the bottom to allow stability in the hoof
- Another bridge at the top of the hoof wall again for stability in the hoof

Question 9

Why is it important to try and remove the proximal extent of the keratoma during surgical excision?

Answer 9

• to prevent recurrence

Question 10

Tx aftercare

Answer 10

• hydrogel into the wound/defect to try stimulate granulation tissue in the wound
• gauze swab plugged into wound
• bandages over test op
• eventually once a nice granulation tissue bed has formed within the wound will replace the hydrogel with iodine
• as weeks pass will gradually be able to remove the bandaging altogether

Question 11

Prognosis

Answer 11

§ Takes several months (to a year) for hoof defect to grow out
§ Good prognosis
- Keratoma recurrence in <20% cases