BACK TO BASICS: LAMENESS AND PODIATRY


Fig. 2. Nonlaminitic venogram. A, Placement of inner tube tourniquet; B, catheter in lateral digital vein; C, coronary plexus and papilla; D, sublamellar zone; E, circumflex vessels and terminal papillae; and F, solar plexus and papillae.


The sublamellar venous plexus joins the solar plexus and the circumferential veins. Terminal and solar papillae are notable and are normally in the same plane as the dorsal surface of P3. The papillae are important, as they allow visualization of the growth centers for the production of a hard protective sole and horn.19 Typically, in hooves with a sole depth of 15 mm, approximately 10mmwill be contrast-filled solar corium and 5 mm of hard protective horn. Horses with a chronic thin sole will demonstrate very little to no papillae and have less than 2–3 mm of contrast- filled solar corium. One could hypothesize that this is why thin-soled horses appear to have minimal to no sole growth until sufficient mechanical solutions are applied to unload the compressed corium. The dorsopalmar view is very similar to the lat-


eral view but allows further visualization of the medial and lateral coronary venous plexus as well as the terminal arch. Oftentimes, the medial coro- nary plexus has decreased filling secondary to nor- mal loading in the healthy foot, as the medial aspect of the hoof bears a greater load. In the author’s experience, this is noted to improve in the unloaded and late lateral views in nonlaminitic cases. Using external characteristics, radiographs and


digital venograms in combination offer a vast amount of information relative to the level of struc- tural damage, allowing for a more precise pairing of mechanics to structural damage. Early in the au- thor’s career, a similar level of mechanics was ap-


382 2018  Vol. 64  AAEP PROCEEDINGS


plied to every case, without regard for the large spectrum of damage unique to each individual case. The result is that not all cases experienced as much success because many had a higher level of damage, indicating a higher degree of management needed. Comparative plain radiographs offer useful informa-


tion concerning the degree of displacement of P3 and level of bone damage that has occurred; however, sim- ilar levels of radiographic boney displacement can have very different venogram characteristics. Veno- grams can highlight the internal anatomy, which may be displaced and compressed once the suspensory ap- paratus has begun to fail. It has proven to be very helpful as an adjunct tool to follow cases in the acute phase, as soft tissue and vascular changes are noted prior to structural collapse.20 Simply put, the greater the structural damage, the greater magnitude of dis- placement of tissue highlighted by the venogram and higher levels of compression are noted under the tip of P3, solar corium, and the sublamellar zone. As the level of damage identified increases, the level of me- chanics prescribed must also increase. Ideally, the author performs plain film radiographs with ra- diopaque paste applied to the dorsal hoof wall from the coronary band to the tip of the toe, with a calibration tool in place for consistent measurements, as well as digital venograms on first examination. The amount of sole depth, degree of pain, and evaluation of four crucial regions of the venogram will aid in deciding an initial mechanical therapy.


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