HOW TO MANAGE HOOF LAMENESS II


by itself can be misleading unless used in conjunc- tion with other soft tissue parameters. In the past, “capsule rotation” was considered pa- thognomonic for laminitis; however, other common foot issues result in horn alterations that may re- semble laminitis at first glance, yet not involve the laminae. For example, white-line disease fre- quently has capsule rotation radiographically but as a rule, the disease process is limited to the horn wall and the laminae only become altered to some degree in the ultra-chronic case. Clinically, white-line dis- ease can resemble laminitis and require similar me- chanical benefits as the wall is also an antagonist to the DDFT, and once it loses its natural function due to invading bacteria and fungi, the wall fails to re- sist the relentless pull of the tendon. Radiograph- ically, the gas line is distinctly different from white- line disease as it is within the inner non-pigmented horn, starts at the ground surface and has an erratic pattern of destruction. The etiology of capsule ro- tation and lesion intensity sets the stage for specific shoeing recommendations and goals. The farrier should be involved with formulating the mechanical plan based on the radiographic data that relates specifically to the trim, shoe design, and application.


Digital Breakover


Digital breakover is the distance from a vertical line drawn at the tip of the coffin bone and 90° to the point of break-over or the most dorsal location of the solar aspect of the hoof or shoe that contacts the ground. The point of break-over can be variable based on whether or not the shoe is flat or has a radius (rocker-type shoe). It is common practice to back the toe up to enhance break-over and to make the low-profile foot with crushed heel appear to have a stronger toe angle. Unfortunately, it is not a problem with the toe but a stark loss of heel mass. The natural heel-to-toe ratio is out of balance and reducing the strategic strength of the dorsal wall for the sake of making the heel appear stronger can be counterproductive. This practice fails to remark- ably improve mechanics and it can be counterpro- ductive (Fig. 8).


Medial/Lateral Balance


Balance is defined as even distribution of weight. This term is frequently used by farriers and vets with a wide range of interpretation based on a vari- ety of external and radiographic reference points. Even though subjective and without regard to sole depth, bone asymmetry, and PA, it is commonly thought that radiographic medial/lateral imbalance of the solar rim of the coffin bone is the cause for unsoundness. Therefore, oftentimes the farrier is instructed or inclined to remove foot on the longer side and/or add shims to the lower side in an effort to leave the wings horizontal with the ground surface. Unfortunately, when the foot has less than adequate mass (depth of sole and heel) removing more sole that is the first line of defense for the underlying


Fig. 8. The lateral image reveals that the wall was backed up with a rasp along the distal 2/3 of the dorsal face. Note the location of the dermal/epidermal opaque line relative to what was removed. The dorsal wall is the thickest and apparently the most strategic part of the capsule and removing it has little if any benefit.


sensitive structures is counterproductive. Discre- tion is due as there are more points of interest to consider when assessing static radiographic bal- ance. The DP view for podiatry issues requires as- tute attention to assure the horse is standing as square as possible, with each foot on a proper posi- tioning block and with the head straight forward to assure the most accurate representation of rim and joint balance. The slightest shift of load will alter both rim and joint balance. Coffin bone asymmetry frequently occurs with toe out conformation. Often there is less sole depth medial versus lateral and the bone is remarkably smaller in the vertical and hor- izontal plane than the lateral half. A large major- ity of these will also have medial joint listing along the same plane as the solar rim. Despite the ver- tical bone asymmetry and/or medial listing, the joint space will often be uniform. This description of imbalance can be consistent with sound, top athletic horses provided they have adequate foot mass. A more descriptive term may be natural imbalance as it is apparent that it is the result of permanent congenital limb and hoof deformities that we aren’t going to change but can manage the ill effects (Fig. 9 and Fig. 10). The growth rings along the medial lateral quarter


will also reflect a despairing rate of growth between them when load distribution is altered by undesir- able limb conformation. The excessively loaded side will have less distance between the rings. This deficit in medial wall growth is consistent with the lighter breeds that have toe-out conformation due to a valgus carpus, outward rotation of the en- tire limb (extorsion), or both. When the conforma- tion defect is more severe, a pushed up or displaced medial heel with this conformation can be seen as well. The pushed up or displaced heel is often erroneously referred to as a sheared heel. The pushed-up heel remains firmly attached to the op- posing quarter, whereas the sheared heel no longer remains firmly attached to the adjoining heel bulb


AAEP PROCEEDINGS  Vol. 66  2020 395


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