Keratomas are an uncommon cause of lameness in equids.1 Although their pathogenesis has not been conclusively determined, keratomas are believed to develop secondary to inflammation induced by hoof wall trauma at the level of the coronary band or subsolar abscess. In most instances, keratomas manifest as an aberrant cylindrical growth of keratin that follows the horn tubules distally. Less commonly, keratomas can take the form of a solitary spherical mass within the hoof capsule. Because of their expansile nature, keratomas impinge on the distal phalanx, resulting in chronic inflammation, pressure resorption, and the characteristic semicircular lucency often observed radiographically.
Clinical signs of keratomas in equids include various degrees of lameness, recurrent foot abscesses, deformation of the hoof capsule adjacent to the underlying keratoma, and displacement of the white line toward the sole as it continues to grow distad. A diagnosis of keratoma is typically made on the basis of anamnesis, observation of the aforementioned clinical signs, radiographic findings, and, if necessary, additional imaging techniques, including CT, MRI, or, more uncommonly, nuclear scintigraphic evaluation.
Treatment to prevent recurrence requires en bloc surgical removal of the entire mass through either complete or partial hoof wall resection. Partial hoof wall resection appears to be the treatment of choice, given the lower complication rate and more rapid return to use for horses treated with this technique than for horses treated with complete resection.2–4
In a previous study,5 MRI (n = 7) or CT (3) was performed for 10 horses during surgery to more accurately define the margins of the keratoma, thereby decreasing the size of the hoof wall resection necessary to remove the keratoma, which subsequently resulted in a low complication rate (2/10; imaging modality not specified). In that study,5 barium paste had been applied to the hoof wall as a marker overlying the keratoma to guide hoof wall resection. The more common use of MRI versus CT in that study5 was reportedly attributable to the unavailability of CT at that time for most horses, and the investigators stated that they preferred the use of intraoperative CT, given the superior image quality of the hoof capsule than attainable with MRI. However, no conclusions could be drawn regarding the usefulness of CT-assisted keratoma removal specifically owing to various limitations.
Reported complication rates associated with surgical resection of keratomas in horses range from 20% to 71%.2,4,5 Such complications include excessive granulation tissue formation, hoof capsule instability, surgical site infection, and keratoma recurrence. This large degree of variability could be due to differences among studies in techniques used for keratoma removal (ie, partial vs complete hoof wall resection) as well as definitions of what constitutes a complication.
The objectives of the study reported here were describe the preoperative use of CT in the diagnosis of and surgical planning for keratoma removal in equids, describe the surgical removal techniques and postoperative patient management approaches, and determine the outcome for these patients. We surmised that preoperative CT would allow for accurate identification and delineation of keratomas, resulting in low postoperative morbidity and rapid return to previous use following surgical removal.
Regional limb perfusion
Large Animal Peters Carbon Fiber CT Table, Kimsey Welding Works, Woodland, Calif.
GE HiSpeed helical scanner FX/I, GE Medical Systems, Waukesha, Wis.
16-slice GE Lightspeed scanner, GE Medical Systems, Waukesha, Wis.
eFilm workstation, Merge Healthcare, Hartland, Wis.
Hall Surgairtome, Conmed, Largo, Fla.
Ridgid JobMax 3-amp multi-tool, Ridge Tool Co, Elyria, Ohio.
Kerlix gauze bandage roll, Covidien, New Haven, Conn.
Curasalt hypertonic saline dressing, Covidien, New Haven, Conn.
Rediroll, The Franklin-Williams Co, Lexington, Ky.
Brown cling gauze, Jorgensen Laboratories Inc, Loveland, Colo.
Elastikon, Johnson & Johnson, Skillman, NJ.
Dalric special cuff shoe, Nanric, Lawrenceburg, Ky.
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3. Honnas CM, Dabareiner RM, McCauley BH. Hoof wall surgery in the horse: approaches to and underlying disorders. Vet Clin North Am Equine Pract 2003;19:479–499.
5. Getman LM, Davidson EJ, Ross MW, et al. Computed tomography or magnetic resonance imaging-assisted partial hoof wall resection for keratoma removal. Vet Surg 2011;40:708–714.
6. American Association of Equine Practitioners. Definition and classification of lameness. Guide for veterinary service and judging of equestrian events. Lexington, Ky: American Association of Equine Practitioners, 1991;19.
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