Surgical management of specific equine lameness disorders (Proceedings)
Most cases of equine lameness are treated with a combination of medical and other non-surgical methods. However, there are a few specific cases in which surgical management is the treatment of choice. The surgical procedures that will be discussed in this paper include arthroscopy/tenoscopy/bursoscopy, palmar digital neurectomy, plantar fasciotomy with or without neurectomy of the deep branch of the lateral plantar nerve, pastern arthrodesis, and tarsal arthrodesis.
Arthroscopy involves the surgical exploration of a joint using a small telescope enabling a thorough examination of the joint without the need for a large surgical approach. Tenoscopy/bursoscopy involves the surgical exploration of tendon sheaths and bursae using the same surgical method. Using a technique called triangulation, additional small portals can be made that allow for surgical instruments to be placed within the synovial structure. The most common condition for the utilization of arthroscopy is for fragment removal. Fragments in equine joints arise from 2 main sources: traumatic injury and osteochodritis dissecans. The most common instances of traumatically induced osteochondral chip fragmentation are in the carpal and fetlock joints. Although chip fractures have been frequently considered acute injuries and recognized with acute clinical signs, it has been suggested that they are a secondary complication affecting joint margins previously altered by subchondral bone disease. Exercise causes microdamage within the joint which can lead to microcracks, more diffuse microdamage, and subchondral bone sclerosis. Therefore the ÒacuteÓ chip fracture typically occurs through this abnormal bone.
When accompanied by lameness, joint effusion, and pain upon flexion, the management of intra-articular joint fragments is relatively straight forward. These types of cases are most common in horses that perform at speed (race horses). In these cases, arthroscopic fragment removal and joint exploration is indicated. If not treated in a timely fashion, the inflammatory mediators that are released from the damaged bone and cartilage can lead to further cartilage damage, chronic proliferative synovitis, and joint capsule fibrosis leading to a decreased range of motion. When the lameness and effusion are significant, usually there is damage to the joint in addition to the fragmentation seen radiographically. Therefore, a thorough exploration of the joint should be performed.In many cases of intra-articular fragmentation, the management may not be straight forward. In my practice, there are many sound horses with intra-articular chip fragments that are found incidentally on pre-purchase examinations or in lameness examinations where the lameness is being caused by a different problem. Sometimes it is hard to recommend surgery and the accompanying down time in an otherwise sound horse that has been competing regularly. Decision making depends on the specific joint involved or the location of the fragment. I find that chip fragments in low motion joints, such as the pastern joint, rarely cause lameness problems and therefore are usually left in place, unless diagnostic intra-articular anesthesia confirms that the lameness is originating from the fragment. In high motion joints, such as the fetlock joint, I feel that location within the joint is particularly important, in addition to the discipline of the horse. I recommend that dorsal articular chip fragments within the fetlock joint be removed, even in the absence of clinical disease. These fragments over time can cause articular surface damage to the adjacent metacarpal condyle leading to osteoarthritis in the athletic horse. They also serve as point to decline purchase when found on a pre-purchase examination. Despite this recommendation, I have seen several horses with dorsal fetlock osteochondral fragments that have maintained athletic careers for years in the absence of clinical lameness. This is particularly true in horses that perform at low speeds (western performance horse). Palmar or plantar osteochondral fragmentation off of the proximal palmar or plantar eminence of the first phalanx are also common incidental findings in otherwise sound horses. Again, these are generally removed in horses that perform at speed. However, in horses involved in other disciplines, particularly those that work at lower speeds, I generally do not recommend surgical removal when there is clinical soundness. If lameness is present, the palmar/plantar fetlock fragment must be confirmed as the cause of the lameness using intra-articular anesthesia prior to recommending surgical removal. This is because these fragments are embedded within the distal sesamoidean ligaments in an area of the joint that is difficult to surgically access. The surgical removal of these fragments can be associated with some damage to the articular surface as well as to the distal sesamoidean ligaments, resulting in a longer post-operative convalescent periods. There are many horses in my practice that perform in disciplines at lower speeds that have these palmar/plantar osteochondral fragments with no apparent lameness or performance problems. Many of these fragments may have been present in the joint since they were yearlings or even weanlings.