HOW TO MANAGE HOOF LAMENESS II


aspect of the procedure is management of the foot. Combination of surgery with the appropriate trim and therapeutic shoeing is imperative for long- term success. Performing the DDF tenotomy without realignment shoeing of the hoof capsule will have a short-term clinical improvement and most likely won’t affect the survival rate.1 Transection of the DDF tendon is a controversial treatment for chronic laminitis largely because of the variation in personal experience with the proce- dure and the varying success rates reported in pre- viously published data.1 Differences in reported success rates are more likely because of the dissim- ilarities in foot pathology and the foot management associated with the procedure. Outcomes are de- termined based on the degree of bone disease, solar penetration, degrees of rotation, sinking (distal dis- placement of the coffin bone but no rotation), num- ber of limbs involved, and front or hind feet affected. There are several issues to consider when making the decision to perform a DDF tenotomy: initial damage assessment, short- and long-term goals of the client, aftercare capabilities and responsibilities of the caretakers, mechanical knowledge, and skill level of the farrier and veterinarian relative to the patient, and financial impact. The DDF tenotomy has often been viewed merely as a salvage proce- dure. It is only considered late in case manage- ment and is often performed without considering the benefits of repositioning the palmar/plantar (herein referred to as palmar) and the articular surface of the coffin bone with healthy load zones. However, if performed early in case management, at the first indication that the vascular supply is not respond- ing to optimum mechanics before permanent dam- age occurs, the DDF tenotomy can greatly enhance the prognosis by increasing the potential for rapid vascular reperfusion to severely compressed ar- eas. This can preserve the integrity of the pal- mar rim and optimize solar and tubular papillae function, which accelerates sole and horn growth. Transection of the DDF tendon as a treatment for chronic laminitis has been reported with variable success rates in the previously published data. Eastman et al6 reported the results of 35 cases between 1988 and 1997. A total of 77% of the cases survived a minimum of 6 months, and 59% survived 2 years. Allen et al7 reported on 13 cases. Five of these (39%) returned to limited athletic activity, six (46%) were pasture sound, and the remaining two cases (15%) improved initially but were eventu- ally euthanized (one due to further deterioration after 9 months, and the other due to economic rea- sons). Hunt et al8 reported the experience with 20 cases. In these cases, 55% survived less than 1 month, 30% survived longer than 6 months, 15% of these remained lame. None of the cases in that study returned to athletic performance. These studies had a large variation in case specifics and included the degree of coffin bone injury at presentation, chronicity, shoeing and/or trimming protocols at the time the


400 2020  Vol. 66  AAEP PROCEEDINGS


DDF tenotomy was performed, and follow-up care. In Hunt’s study, there were several cases which all received the same shoeing protocol and postsurgical foot management. To better evaluate the efficacy of the tenotomy procedure, Morrison9 subclassified 245 cases that received a DDF tenotomy into the following catego- ries: degree of displacement of the coffin bone, cof- fin bone disease, medial, lateral, or vertical sinking of the coffin, and coffin bone that penetrated the sole.5 Of the 245 cases, 51% were considered a success. Success was defined as survival for 1 year after surgery, maintaining good body condition, and an Obel lameness Grade of 2 or less (moving freely at the walk but possibly having a stiff gait, sore on turning, and able to pick up each foot when asked). Cases with no coffin bone disease and no signs of sinking or solar penetration had an 83% success rate. Cases with moderate coffin bone dis- ease, and no sinking or solar penetration had a 93% success rate. Cases with severe coffin bone disease and no sinking or penetration had a 44% success rate. Cases with signs of sinking (medial, lateral, or vertical) had an overall success rate of 18%, while non-sinkers had a success rate of 71%. Cases with penetration and no sinking had an 88% success rate while cases with penetration and sinking had a 25% success rate. The number of limbs involved and their location was also associ- ated with outcome: success rate for one limb was 52%; two limbs, 50%; four limbs, 50%; front limb, 51%; and hind limbs, 50%. During laminitis and the rehabilitation process, it


is important to minimize further damage to the foot. As a team, the veterinarian and farrier should have an understanding of the normal supporting struc- tures of the digit, biomechanical forces on the foot, and the structural failure that results when these forces act on a diseased and damaged foot. In a healthy foot, the antagonistic forces between the laminae that support the coffin bone dorsally and the deep DDF tendon that pull palmarly are in bal- ance. In the laminitic foot, these forces are out of balance due to the loss of dorsal laminar support. This allows the unopposed palmar force of the DDF tendon to pull the coffin bone away from the hoof capsule and creates instability. Venograms clearly outline the blood circulation in the foot, and perfu- sion deficits that are a consequence of laminitis. This is an invaluable diagnostic that could help with prognosis. The clinical information gained from a physical examination of the foot, venograms, and radiographs will dictate which treatment modali- ties need to be implemented. The multitude of prognostic factors that affect outcome in the horse with laminitis make treating these cases a chal- lenge. Treating the horse with laminitis requires experience, expertise, realistic expectations, and a unified effort by the farrier, veterinarian, and owner.


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