HOW-TO SESSION: FIELD SURGERY


similar for treating the chronic stable and chronic unstable horse (with dorsal capsular rotation) but special attention must be placed on managing sec- ondary infections and complications in the chronic unstable horse. Horses with mediolateral and/or distal displacement (sinkers) often require a differ- ent mechanical approach and will be covered sepa- rately from those with dorsal capsular rotation.


Modifying Hoof Boots to Treat Horses With Chronic Stable and Chronic Unstable Laminitis That is Predominantly Dorsal Capsular in Nature


With experience, hoof morphology (growth rings, stretching of the white line, solar prolapse, etc.) can give the practitioner great insight into what is going on inside the hoof capsule. A horse with unstable laminitis can displace in a matter of days and even hours. It can take weeks to months before hoof morphology will reflect these changes. Considering this, the author prefers to take quality radiographs prior to trimming horses with laminitis. The author approaches the treatment of dorsal capsular rotation with well-recognized biomechani- cal principles as described previously by Morrison5 and O’Grady.6 The hoof boot is simply going to provide a novel means of applying shoeing mechan- ics. It bears repeating that the efficacy of shoeing approaches as they relate to chronic laminitis re- mains anecdotal.2 Generalizing when talking about laminitis is dangerous given that each case is different and deserves an individualized approach. Having said that, the process can be broken down into the trim (wall sculpting and heel trim), support, and the application of mechanics (altering anterior breakover, mediolateral breakover, and heel eleva- tion when necessary). When treating horses with dorsal capsular displacement, the author trims the heels in an effort to recruit the healthier caudal portion of the foot to share more load (Fig. 3). Ex- cessively long toes and flares are sculpted with a rasp. Because this technique is not dependent on the hoof wall for shoe attachment, the ground sur- face of the wall can be rounded in an effort to move weight bearing axially (Fig. 4). The frog and bars are often recruited to bear weight by adding support material (covered in the section above, “Choosing Case-Appropriate Sole Support”). The foot is wedged to varying degrees in most cases. This is in an effort to get the solar margin angle of the distal phalanx near its pre-trim state (Figs. 5A and B). This negates the effects that the heel trim has on tension in the DDFT and consequently the dorsal lamellae. A rolled and/or rockered toe is used to enhance digital breakover and reduce the moment arm around the distal interphalangeal joint. This is thought to decrease stresses within the dorsal lamellae. In most cases the author chooses to place the point of breakover as far back as possible with- out the horse tipping forward onto the rocker in the stance phase. The anterior coronary band can be used to approximate this point (Figs. 5A and B).5


Fig. 3. Illustration of how trimming the heels, especially run- forward heels, can recruit more of the caudal portion of the foot for weight bearing and support. The shoe pictured fit the foot prior to trimming the heels.


A shoe is chosen or modified that fits the boot and eases mediolateral breakover in an effort to reduce torque placed on the lamellae in turns. Clogs, rail shoes, and half-round shoes, for example, accom- plish this well. The shoe is rockered, rasped, or ground to provide the desired breakover. Methyl- methacrylate hoof gluesh,i adhere well to boot bot- toms constructed of polyurethane. You must also be sure that the glue will adhere to your shoe choice. Methylmethacrylate bonds well to aluminum, poly- urethane, and wooden shoes. Approximately 5


Fig. 4. Wall sculpted or rounded to move weight distribution axially.


AAEP PROCEEDINGS  Vol. 61  2015 235


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