A 7-year-old Quarter Horse gelding, which weighed 524 kg (1,153 lb) and was used for general-purpose riding, was evaluated at the University of Georgia Veterinary Teaching Hospital because of a 4-day history of sudden onset of severe left forelimb lameness (grade 4/51). The lameness was first noticed when the horse was brought in from pasture. Prior to referral, the left forefoot shoe had been removed and the foot had been pared; after a poultice had been applied, there was no evidence of discharge or improvement in lameness. However, treatment with phenylbutazonea (4.4 mg/kg [2 mg/lb], IV, q 12 h) resulted in reduction in lameness severity. The horse had no known previous history of lameness.
Signs of a mild diffuse pain were elicited in response to hoof testers, with a focal area of intense pain response on the lateral quarter of the affected forefoot. Administration of an abaxial sesamoid nerve block with 2% mepivacaine hydrochlorideb markedly improved the lameness (estimated reduction in severity, 80%). Further paring of the lateral aspect of the sole was performed; no purulent material was found, but severe profuse hemorrhage developed as the sensitive tissues were approached. A well-padded foot bandage was applied for hemostasis.
Once hemostasis was achieved, standard radiographic views of the foot were obtained. These included the following: lateromedial, weight-bearing dorsopalmar, 45° dorsoproximal-palmarodistal oblique, 45° dorsoproximomedial-palmarodistolateral oblique, and 45° dorsoproximolateral-palmarodistomedial oblique.2 Subsequently, the foot was placed in a water bath to displace gas artifact, and a dorsoproximal-palmarodistal oblique radiographic view was obtained. Assessment of the images revealed a radiolucent line that extended transversely across the distal phalanx approximately halfway between the extensor process of the distal phalanx and the dorsal solar border (Figure 1). To better define the radiographic abnormality, additional dorsoproximal-palmarodistal oblique views were obtained at multiple angles of obliquity ranging from 40° to 70°. The radiolucent line appeared to extend from the medial and lateral solar margins of the distal phalanx. The radiographic interpretation was a nondisplaced transverse fracture of the distal phalanx.
Dorsoproximal-palmarodistal 45° oblique radiographic view of the distal phalanx of the left forelimb of a horse that was evaluated because of sudden onset of severe lameness of 4 days' duration. Notice the radiolucent line traversing the distal phalanx suggestive of a transverse fracture (arrows).
Citation: Journal of the American Veterinary Medical Association 240, 1; 10.2460/javma.240.1.82
A rim cast was placed on the left forefoot.3 After placing orthopedic feltc across the heel bulbs, one 3-inch roll of fiberglass cast materiald was placed around the hoof of the left forelimb circumferentially. A cuff was formed over the heel bulbs, and the cast material was wrapped around the distal aspect of the foot so that approximately 1.5 inches of material covered the solar surface and 1.5 inches of material covered the distal hoof wall, thereby molding the material to the shape of the foot. Each sequential wrap was placed directly on top of the first. The hoof of the right forelimb was supported by packing the sole with impression material.e Treatment with phenylbutazonea (3.3 to 4.4 mg/kg [1.5 to 2 mg/lb], PO, q 12 h) was initiated. Over the following 24-hour period, improvement was marginal with persistence of grade 4/5 lameness. To create an approximately 12° heel elevation, wedge padsf were subsequently attached to the rim cast by use of standard 2-inch drywall screws drilled proximally to distally through the hoof wall, rim cast, and wedge pads. There was immediate improvement in the lameness with elimination of the lameness during walking. The horse was discharged from the hospital the following day; it was maintained in the elevated rim cast with strict stall rest and received a gradually tapering dosage of phenylbutazonea (2.2 to 1.1 mg/kg [1 to 0.5 mg/lb], PO, q 12 to 24 h) over a period of 3 weeks after injury, at which time administration of the drug was discontinued.
The horse appeared to remain comfortable, and on day 28, the rim cast was removed. There were no complications associated with the cast except for development of some mild cast sores over the heel bulbs (Figure 2). Follow-up radiographic views were obtained, which revealed a more radiographically apparent fracture line with no displacement (Figure 3). The foot was shod in a manufactured elevated heel shoe with 5 toe and quarter clips. The palmar half of an egg-bar shoe was welded to the palmar half of a full eggbar shoe to create a sagittally supported heel wedge of approximately 10° elevation. The horse was reevaluated at 14-day intervals, and progressive improvement in the lameness was evident. At 2 months, the cast sores had resolved and the horse had grade 2/5 lameness1 of the left forelimb. The horse was allowed controlled hand walking for 2 weeks, at which time it was allowed access to a small paddock. At 3 months after injury, the horse was no longer lame; the elevated heel shoe was removed, and the foot was shod in a flat steel bar shoe with a 3° wedge pad. At 4 months after injury, repeated radiographic examination did not reveal the presence of a fracture line. The horse was allowed a slow reintroduction to light work with increasing durations of walking and trotting. At 6 months, there was no detectable lameness under regular work at the horse's previous level of performance, including cantering and jumping fences up to 3 feet in height.
Photograph of the lateral aspect of the left forefoot of the horse in Figure 1 at 1 month after injury. The rim cast has been removed, and a manufactured elevated heel shoe has been applied to decrease tension on the distal phalanx from the DSIL and DDFT. This shoe was a full bar shoe with additional quarter and toe clips placed to minimize expansion of the hoof capsule. Notice the granulating wound over the heel bulbs secondary to the rim cast.
Citation: Journal of the American Veterinary Medical Association 240, 1; 10.2460/javma.240.1.82
Dorsoproximal-palmarodistal 45° oblique radiographic view of the distal phalanx of the left forefoot of the horse in Figure 1 at 28 days after injury. The transverse fracture line through the distal phalanx is more radiographically apparent than it was at the initial examination (arrows).
Citation: Journal of the American Veterinary Medical Association 240, 1; 10.2460/javma.240.1.82
The horse was readmitted to the hospital 6 months after the injury because of severe colic that was unresponsive to analgesia. Financial limitations prohibited surgical intervention, and the horse was euthanized via IV injection of an overdose of pentobarbital sodium solution.g The forelimbs were removed immediately and frozen at −20°C. The limbs were subsequently defrosted and underwent MR imaging (by use of a 3.0-T magneth) in transverse, sagittal, and frontal (dorsal) planes in PD, T2-weighted, and STIR sequences. In PD, T2-weighted, and STIR sagittal images, a thin, moderate- to high-intensity signal through the solar surface of the distal phalanx at the distal aspect of the insertion of the DDFT of the left forefoot was visible. This was surrounded by a narrow area of low signal intensity on PD and T2-weighted images (Figure 4). Additionally, there was a region of moderately increased signal intensity approximately halfway between the extensor process and solar aspect of the dorsal surface of the distal phalanx. Signal changes were difficult to interpret through the body of the distal phalanx on sagittal images. There was a reproducible high-intensity signal on PD, T2, and STIR frontal sequences through the solar surface of the distal phalanx of the left forelimb.
Magnetic resonance images of the distal phalanx of the left forefoot obtained after euthanasia of the horse in Figure 1 for reasons unrelated to orthopedic disease. A—On a T2-weighted midsagittal MR image, notice the linear area of moderate- to high-intensity signal through the solar surface of the distal phalanx at the distal aspect of the insertion of the DDFT (white arrow). This is surrounded by a narrow, poorly demarcated area of low signal intensity. Additionally, there is a moderate increase in signal intensity approximately halfway between the extensor process and the solar aspect of the dorsal surface of the distal phalanx (black arrow). B—On a PD frontal MR image, there is a poorly demarcated linear high-intensity signal that extends transversely across the distal phalanx and is most noticeable within the dense bone of the solar surface of the distal phalanx (arrows).
Citation: Journal of the American Veterinary Medical Association 240, 1; 10.2460/javma.240.1.82
After MR imaging, the cadaveric limbs were dissected and photographed. Gross dissection revealed transverse linear disruption (most evident in the sagittal plane) of the normal appearance of the distal phalanx of the left forelimb (Figure 5). Histologic examination of this area after acid decalcification and staining with H&E stain revealed trabeculae that were broader and more irregular than those more distant from the fracture site. These trabeculae were composed of a large amount of central woven bone surrounded by a smaller layer of lamellar bone; the trabeculae further from the fracture site were composed of lamellar bone exclusively. The associated cortical bone was also composed of woven bone and lamellar bone. These findings were consistent with a healing fracture.
Photograph of a sagittal section of the distal phalanx of the left forelimb obtained after euthanasia of the horse in Figure 1 for reasons unrelated to orthopedic disease. Notice the linear disruption of the normal appearance of the cortical bone of the distal phalanx at the distal insertion of the DDFT on the solar surface and the middle of the dorsal surface of the distal phalanx, which correspond to the areas of increased signal intensity in the MR images (arrows).
Citation: Journal of the American Veterinary Medical Association 240, 1; 10.2460/javma.240.1.82
Discussion
The case reported here involved an unusual distal phalanx fracture in a mature horse. The fracture was identified on the basis of diagnostic imaging findings, and at 6 months after injury, treatment had successfully resolved the associated lameness. Unfortunately, long-term (> 6 months) follow-up information was not available because the horse was euthanized for reasons unrelated to orthopedic disease.
Given the clinical signs of sudden onset of severe lameness, which was localized to the horse's left forefoot on the basis of results of physical examination and perineural analgesia, a fracture of the distal phalanx was included as a differential diagnosis along with foot abscess, puncture wound, sepsis of a synovial structure within the foot, sole bruising, laminitis, distal sesamoid bone fracture, and severe soft tissue injury.4–8 Distension of the distal interphalangeal joint was not evident, most likely because the fracture was nonarticular.9 The severe hemorrhage that was encountered during superficial debridement of the sole was attributed to hematoma formation secondary to soft tissue disruption and fracture of the distal phalanx.
Definitive diagnosis was achieved via radiography; however, a thorough radiographic examination with particular attention to exclusion of gas artifact was necessary.6 Distal phalanx fractures can be difficult to identify radiographically, especially when they are minimally displaced because of the superimposition of the surrounding keratinized hoof wall and the propensity for gas artifacts.5,6,10 For the horse of this report, the radiographic diagnosis was best achieved when imaging was performed during placement of the foot in a water bath.11 Nuclear scintigraphy is a more sensitive imaging technique for detection of distal phalanx fractures in the acute phase; in 1 study,4 nuclear scintigraphy revealed fractures in 3 of 25 horses for which the fractures were not evident radiographically. Other advanced imaging techniques such as computed tomography and MR imaging have also been used to ascertain more information about foot lameness in horses.12–19 Although these advanced diagnostic imaging methods were unnecessary for an antemortem diagnosis in the horse of this report, the superior anatomic detail that they can provide would have improved the sensitivity and specificity of lesion detection.19 Additional information regarding the exact anatomic location of the fracture may have been helpful in formulating the treatment plan for this horse. When the cadaveric left forelimb was examined, the fracture was not apparent radiographically; however, there remained some evidence of the fracture on MR images, which supports the superior sensitivity of MR imaging for lesion detection.13–16,19,20
Fractures of the distal phalanx have been described and are most commonly categorized on the basis of their configuration defined by their anatomic location and articular involvement.5–8 The fracture in the horse of this report appeared radiographically as a transverse radiolucent line spanning the distal phalanx. A similar fracture orientation has been reported previously; 1 horse was reported to have a distal phalanx fracture through the solar canal, close to the insertion of the DDFT described as a frontal plane fracture,3 and a foal was reported to have a transverse distal phalanx fracture secondary to septic pedal osteitis caused by a previous traumatic injury.21
The nomenclature for fractures in similar anatomic planes appears to be variable. In this report, the fracture is described as transverse because it was perpendicular to the median plane and crossed the distal phalanx at a right angle to the long axis of the hoof and proximal interphalangeal (pastern) joint.22 In contrast, the frontal plane is perpendicular to both the median and transverse planes and would therefore divide the pedal bone into a dorsal and palmar half22 as described previously23; however, describing this orientation as being in the dorsal plane would be more technically correct.24
It is interesting to speculate as to the cause of the fracture in this particular orientation. In the absence of evidence of a pathological fracture in the horse of this report, it seems likely this fracture was caused by trauma. The orientation of the fracture was presumably associated with excessive force across either the solar aspect3 or dorsal aspect of the distal phalanx. This may have been associated with hyperextension of the distal interphalangeal joint (possibly exacerbated by toe elevation) in combination with the opposing force of the DDFT and DSIL3 or, alternatively, with a large force applied dorsally on the distal aspect of the hoof wall.
Treatment of the transverse distal phalanx fracture in the horse of this report commenced with application of a rim cast to minimize movement of the hoof capsule. This did not alleviate the lameness to any great extent; however, application of a wedge pad to elevate the heels made a marked difference in the severity of the horse's lameness. We hypothesized that elevating the heels decreased tension on the DDFT and DSIL, which neutralized forces acting on the fracture line.3,25,26 This marked reduction in lameness facilitated improved weight bearing and contributed to the prevention of overload laminitis in the contralateral limb without the necessity for administration of high doses of analgesic drugs.
Other treatment options for distal phalanx fractures in adult horses include fragment removal, specialized shoeing techniques, lag screw fixation, and neurectomy. In the report21 of a pathological transverse fracture in a yearling, a portion (45%) of the pedal bone was removed because septic osteitis prohibited salvage, but it is preferable to retain the bone and facilitate healing to preserve normal anatomic structure. Preservation of the normal anatomic structure reduces the risks for both mechanical laminitis and prolonged management.21 In the horse of this report, it appeared that the degree of pain would preclude application of a traditional metal shoe held with nails because percussion of the foot frequently worsens the discomfort,10 although desensitization of the foot through perineural analgesia at the level of the proximal sesamoid bones may have facilitated shoeing. Alternatively, a shoe applied with glue or acrylic hoof material could have been used to minimize percussion of the fracture; however, application of the rim cast was chosen as a cost-effective alternative that could easily be applied and changed when necessary. The only complication encountered was development of cast sores at the heel bulbs, which resolved after removal of the cast.
For this horse, attention was paid to contraction of the heels, which can develop in horses that are bearing less weight on an affected limb, in horses shod with bar shoes,10 and in horses with elevation of the heels for extended periods.27 The shoe was placed wide on the heels to prevent contraction of the heels, and the heel wedge was gradually reduced and eventually removed. Adhering to the principles of lag screw fixation for internal fixation of this fracture would have been technically challenging even with the use of computer-assisted surgery.28 Additionally, the degree of comfort after placement of the rim cast and wedge did not necessitate further stabilization during fracture healing. Palmar digital neurectomy has been used for type 1 fractures (nonarticular fractures of the palmar or plantar process) that are refractory to treatment or for fractures in horses for which a rapid return to function is required.5,8 Neurectomy was considered inappropriate in this case because a rapid return to function was not necessary and the location of the fracture close to the insertion of the DDFT and DSIL may have caused biomechanical instability within the hoof, especially if the horse resumed work prior to fracture healing.
Commonly, distal phalanx fracture lines are more radiographically apparent 1 month after injury because osteolysis at the fracture margins enlarges the fracture gap; 4 to 6 weeks after injury has been reported as the time of maximum radiographic fracture width.6 However, by 10 to 14 days after injury, considerable osteolysis has frequently developed, which aids recognition of a previously unidentified distal phalanx fracture.5,8,10,29,30
Overall, conservative treatment of the horse of this report resulted in radiographic evidence of a healed fracture, resolution of lameness, and a return to function at 6 months after injury, all of which are indicative of a successful outcome. As highlighted by this case, conservative management of a mature horse with an unusual transverse fracture of the distal phalanx can be worthwhile.
ABBREVIATIONS
| DDFT | Deep digital flexor tendon |
| DSIL | Distal sesamoidean impar ligament |
| MR | Magnetic resonance |
| PD | Proton density |
| STIR | Short tau inversion recovery |
Phenylbutazone, Butler Schein Animal Health, Dublin, Ohio.
Mepivacaine hydrochloride, Pfizer Inc, New York, NY.
Orthopedic felt, 1/4 × 36 × 21 inches, Hartmann-Conco Inc, Rock Hill, SC.
Fiberglass casting tape, BSN Medical Inc, Rutherford College, NC.
SciCan Select Polysil, SciCan Inc, Canonsburg, Pa.
Nanric Ultimate Pads, Nanric, Lawrenceburg, Ky.
Pentobarbital sodium solution, Virbac AH, Fort Worth, Tex.
16-channel fixed site SignaHDx, GE Health Care, Chalfont St Giles, Buckinghamshire, England.
References
- 1.↑
American Association of Equine Practitioners. Guide for veterinary service and judging of equestrian events: definition and classification of lameness. 4th ed. Lexington, Ky: American Association of Equine Practitioners, 1991; 19.
- 2.↑
Butler J, Colles C, Dyson S, et al. Chapter 2. Foot, pastern and fetlock: clinical radiology of the horse. 3rd ed. Chichester, West Sussex, England: John Wiley & Sons, 2008; 53–187.
- 3.↑
Anderson BH, Turner TA, Kobluk CN. Treatment of a comminuted frontal-plane fracture of the distal phalanx in a horse. J Am Vet Med Assoc 1996; 209: 1750–1752.
- 4.↑
Keegan KG, Twardock AR, Losonsky JM, et al. Scintigraphic evaluation of fractures of the distal phalanx in horses: 27 cases (1979–1988). J Am Vet Med Assoc 1993; 202: 1993–1997.
- 5.
Gabel A, Bukowiecki C. Fractures of the phalanges. Vet Clin North Am Equine Pract 1983; 5: 233–260.
- 6.↑
Honnas C, O'Brien T, Linford R. Distal phalanx fractures in horses: a survey of 274 horses with radiographic assessment of healing in 36 horses. Vet Radiol 1988; 29: 98–107.
- 7.
Yovich J, Hilbert B, McGill C. Fractures of the distal phalanx in horses. Aust Vet J 1982; 59: 180–182.
- 8.
Scott EA, McDole M, Shires MH. A review of third phalanx fractures in the horse: sixty-five cases. J Am Vet Med Assoc 1979; 174: 1337–1343.
- 10.↑
Yovich J. Fractures of the distal phalanx in the horse. Vet Clin North Am Equine Pract 1989; 5: 145–160.
- 11.↑
Stashak T. Navicular disease (podotrochleosis). Adams' lameness in horses. 4th ed. Philadelphia: Lea & Febiger, 1987; 505–506.
- 12.
Martens P, Ihler C, Rennesund J. Detection of a radiographically occult fracture of the lateral palmar process of the distal phalanx in a horse using computed tomography. Vet Radiol Ultrasound 1999; 40: 346–349.
- 13.
Dyson S, Marks D. Foot pain and the elusive diagnosis. Vet Clin North Am Equine Pract 2003; 19: 531–565.
- 14.
Dyson S, Murray R, Schramme M, et al. Magnetic resonance imaging of the equine foot: 15 horses. Equine Vet J 2003; 35: 18–26.
- 15.
Mair T, Kinns J, Bolas N. Magnetic resonance imaging of the distal limb of the standing horse: technique and review of 40 cases of foot lameness, in Proceedings. 49th Annu Meet Am Assoc Equine Pract 2003; 29–41.
- 16.
Widmer A, Buckwater K, Fessler J, et al. Use of radiography, computed tomography and magnetic resonance imaging for evaluation of navicular syndrome in the horse. Vet Radiol Ultrasound 2000; 41: 108–116.
- 17.
Whitton R, Donovon C, Buckley T, et al. The diagnosis of lameness associated with distal limb pathology in a horse: a comparison of radiography, computed tomography and magnetic resonance imaging. Vet J 1998; 155: 223–229.
- 18.
Puchalski S, Galuppo L, Hornof W, et al. Intraarterial contrast-enhanced computed tomography of the equine distal limb. Vet Radiol Ultrasound 2007; 48: 21–29.
- 19.↑
Murray R, Mair T. Use of magnetic resonance imaging in lameness diagnosis in the horse. In Pract 2005; 27: 138–146.
- 20.
Schneider R, Gavin P, Tucker R. What MRI is teaching us about navicular disease, in Proceedings. 49th Annu Meet Am Assoc Equine Pract 2003; 210–219.
- 21.↑
Klohnen A, Trostle S, Stone W, et al. Management of a transverse fracture in the distal phalanx of a horse. Can Vet J 1997; 38: 561–563.
- 22.↑
Pasquini C, Spurgeon T, Pasquini S. Descriptive terms. In: Pasquini C, Spurgeon T, Pasquini S, eds. Anatomy of domestic animals. 5th ed. Pilot Point, Tex: Sudz Publishing, 1997; 15–20.
- 24.↑
Notes to termini generales. In: Nomina anatomica veterinaria. 5th ed. Ithaca, NY: International Committee on Veterinary Gross Anatomical Nomenclature, 2005; 11–15.
- 25.
Lochner FK, Milne DW, Mills EJ, et al. In vivo and in vitro measurement of tendon strain in the horse. Am J Vet Res 1980; 41: 1929–1937.
- 26.
Thompson K, Cheung K, Silverman M. The effect of toe angle on tendon, ligament and hoof wall strains in vitro. J Equine Vet Sci 1993; 13: 651–654.
- 27.↑
Ramos Bellenzani M, D'andrea Greve J, Pereira C. In vitro assessment of the equine hoof wall strains in flat weight bearing and after heel elevation. J Equine Vet Sci 2007; 27: 475–480.
- 28.↑
Rossol M, Gygax D, Andritzky-Waas J, et al. Comparison of computer assisted surgery with conventional technique for treatment of abaxial distal phalanx fractures in horses: an in vitro study. Vet Surg 2008; 37: 32–42.
- 29.
Furst A, Lischer C. Foot. In: Auer J, Stick J, eds. Equine surgery. 3rd ed. St Louis: Saunders, 2006; 1184–1217.
- 30.
Bertone A. Fractures of the distal phalanx. In: Nixon A, ed. Equine fracture repair. Philadelphia: Saunders, 1996; 146–152.
