History
A 12-year-old Quarter Horse gelding was examined for bilateral forelimb lameness of 5 years' duration that had increasingly worsened over 4 months, especially when the horse was on hard ground. Previous treatments including corrective shoeing, injection of corticosteroids into the distal interphalangeal joint (DIPJ) and navicular bursa, and administration of phenylbutazone had not improved the lameness. The horse would rock back on its hind limbs on occasion. Bilateral forelimb digital flexor tendon sheath effusion, varus of the metacarpophalangeal joints, and coronary band swelling were detected. Additionally, the horse had small forefeet for its size and bilateral over-at-the-knees conformation. Hoof-tester application across the frog and heels resulted in a strong positive response on the left forefoot and a mild positive response on the right forefoot. Bilateral forelimb lameness, which was greater in the right forelimb, was observed while walking, trotting, and turning the horse in circles. The lameness decreased after bilateral palmar digital perineural anesthesia to the point that the horse was practically sound. Radiographic views of the forefeet were obtained (Figure 1).
Lateromedial (A) and dorsopalmar (B) radiographic views of the distal portion of the right forefoot of a horse with a 5-year history of bilateral forelimb lameness.
Citation: Journal of the American Veterinary Medical Association 230, 9; 10.2460/javma.230.9.1307
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Radiographic Findings and Interpretation
Mild hyperextension and narrowing of the DIPJ are seen on the lateromedial radiographic view of the right forefoot (Figure 2). The palmar angle of the right forefoot is approximately 0°.1 In addition, sclerosis along the proximal aspect of the distal phalanx and periosteal reaction on the dorsal surface of the middle phalanx are evident. Incongruency and narrowing of the DIPJ evident in the dorsopalmar views are indicative of medial-to-lateral subluxation of the distal phalanx (Figures 2 and 3). Findings on radiographic views of the left forefoot (not shown) were suggestive of navicular syndrome.
Same radiographic views as in Figure 1. A—Notice mild hyperextension and narrowing of the DIPJ (black arrowheads), sclerosis along the proximal aspect of the distal phalanx, and periosteal reaction on the dorsal surface of the middle phalanx (arrow). Palmar angle is approximately 0°. B—Incongruency of the DIPJ (arrow) and narrowing (white arrowheads) are suggestive of medial-to-lateral subluxation of the distal phalanx.
Citation: Journal of the American Veterinary Medical Association 230, 9; 10.2460/javma.230.9.1307
Dorsopalmer oblique (65° proximal) radiographic view of the right forefoot of the horse in Figure 1. Notice DIPJ incongruency (arrow; pointing to the lateral aspect of the distal middle phalanx) and narrowing (arrowheads), which are consistent with medial-to-lateral subluxation of the distal phalanx.
Citation: Journal of the American Veterinary Medical Association 230, 9; 10.2460/javma.230.9.1307
Comments
Subluxation of the DIPJ is an uncommon cause of lameness in horses; however, when present, it may mimic clinical signs of chronic navicular syndrome. The horse of this report had been managed appropriately for navicular syndrome for many years but consequently developed DIPJ subluxation. Ultrasonography may have helped in the diagnosis of DIPJ collateral ligament injury, but it was not performed. Without computed tomography or magnetic resonance imaging, we could only speculate that the subluxation occurred because of chronic tearing of the DIPJ lateral collateral ligament or excessive loss of DIPJ articular cartilage secondary to long-term intra-articular treatment with corticosteroids. It is unknown whether intra-articular administration of corticosteroids perpetuated this pathologic progress. The cause of the periosteal reaction along the dorsal aspect of the middle phalanx is uncertain.
Few indications exist for DIPJ arthrodesis in horses; however, irreversible joint damage attributable to septic arthritis, osteoarthritis, articular fractures, osteochondrosis, luxation, or traumatic injury to the periarticular ligaments and soft tissue structures may require surgical intervention. Arthrodesis of any joint is indicated to relieve pain and improve limb function, but when attempting DIPJ arthrodesis, attaining pasture soundness should be the goal.2
Limited attempts to perform DIPJ arthrodesis by use of various techniques have been reported. Surgical treatments performed include insertion of transarticular 5.5-mm cortical bone screws,2,3 insertion of stainless steel baskets and transarticular 4.5-mm cortical bone screws,4 or facilitating ankylosis by use of cancellous bone grafting and transfixation casting.5 Reportedly, all horses undergoing DIPJ arthrodesis have responded favorably to surgical treatment for at least 10 months, but only 2 of 5 horses have survived long term (24 months).2,5 Complications associated with DIPJ arthrodesis have been recurrent lameness secondary to incomplete joint fusion, implant infection, and contralateral limb laminitis.3,4
Without surgical arthrodesis, prognosis for regaining soundness in the horse of this report was poor. If the DIPJ could completely ankylose on its own, the prognosis for achieving pasture soundness would have been more favorable, as has occurred in 1 horse6 following septic arthritis and septic navicular bursistis.
Because the pathologic changes in the foot were not limited to the heels, palmar digital neurectomy was discouraged for the horse of this report. The owner did not wish to pursue DIPJ arthrodesis; therefore, administration of phenylbuta-zone, corrective shoeing that could offer caudal heel support, and restricted exercise were recommended. Optional treatment included intra-articular administration of hyaluronic acid and application of a 1% diclofenac liposomal suspension. The horse was euthanized approximately 6 months after examination because the lameness became more severe. A necropsy was not performed.
- 1↑
Eliashar E, McGuigan MP, Wilson AM. Relationship of foot conformation and force applied to the navicular bone of sound horses at the trot. Equine Vet J 2004;36:431–435.
- 2↑
Busschers E, Richardson DW. Arthroscopically assisted arthrodesis of the distal interphalangeal joint with transarticular screws inserted through the dorsal hoof wall approach in a horse. J Am Vet Med Assoc 2006;228:909–913.
- 3
Schneider RK, Bramlage LR, Hardy J. Arthrodesis of the distal interphalangeal joint in two horses using three parallel 5.5-mm cortical screws. Vet Surg 1993;22:122–128.
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Honnas CM, Vacek JR, Schumacher J. Arthrodesis of the distal interphalangeal joint in a horse using stainless steel baskets and transarticular 4.5-mm cortical screws. Vet Comp Orthop Traumatol 1995;8:46–51.
- 5↑
Lescun TB, Morisset SM, Fugaro MN, et al. Facilitated ankylosis of the distal interphalangeal joint in a foal. Aust Vet J 2004;82:282–285.
- 6↑
Honnas CM, Schumacher J, Kuesis BS. Ankylosis of the distal interphalangeal joint in a horse after septic arthritis and septic navicular bursitis. J Am Vet Med Assoc 1992;200:964–968.
