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Compendium April 2011 (Vol 33, No 4)

The Equine Pastern

by Ryan S. Carpenter, DVM, MS, DACVS, Gary M. Baxter, VMD, MS, DACVS

    CETEST This course is approved for 3.0 CE credits

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    Abstract

    Injuries involving the pastern region are a common source of lameness in many types of performance horses. Knowledge of the common breed- and activity-associated injuries can aid veterinarians in making an accurate diagnosis because injuries of the pastern region are often breed- or use-specific. The differential diagnosis for disorders of the pastern region includes osteoarthritis, osteochondrosis, fractures, infection, and soft tissue injuries. In general, soft tissue injuries of the pastern region can be difficult to diagnose, and affected horses have a reasonable chance of returning to their intended uses; osseous injuries are typically easier to diagnose and have a good prognosis if arthrodesis is an option.

    Anatomy

    The proximal interphalangeal joint (PIJ; pastern joint) is a diarthrodial joint formed from the distal aspect of the proximal phalanx (P1) and the proximal aspect of the middle phalanx (P2).1,2 The pastern region is bounded dorsally by the common or long digital extensor tendon. Palmar/plantar support structures of the pastern region are formed by the distal sesamoidean ligaments (DSLs; straight, oblique, and cruciate ligaments), digital flexor tendons (superficial digital flexor tendon [SDFT] and deep digital flexor tendon [DDFT]), and proximal and distal digital annular ligaments within the digital flexor tendon sheath (DFTS).1,2 The medial and lateral collateral ligaments provide support in the sagittal plane.1,2

    Physical Examination

    The physical examination begins with visual inspection of the limb and evaluation of range of motion and response to hoof testers. The pastern region should be symmetric and free of swelling or bony enlargement. Injuries involving the pastern region are rarely bilateral, but osteoarthritis (OA) may be; therefore, comparing the right and left limb or medial and lateral aspect of the same limb is helpful when identifying abnormalities. Abnormalities in the pastern region, such as swelling or bony enlargement, are usually obvious because of minimal soft tissue in the area.1,2 The severity of lameness associated with the pastern region ranges from subtle to severe, depending on the injury.1 Generally, injuries involving the PIJ or DFTS cause obvious lameness, whereas lameness due to early OA or strains of the sesamoidean ligaments may be mild. Pain in the pastern region is often exacerbated by distal limb flexion or lunging the horse with the affected limb on the inside of the circle. The differential diagnosis for disorders of the pastern region includes OA, osteochondrosis (OC), fractures, infection, and soft tissue injuries; however, the types of injuries are often breed- or use-specific.1,2

    Diagnostic Procedures

    Regional nerve blocks are an important technique for isolating lameness in any horse. The PIJ is not always completely anesthetized by perineural anesthesia at the level of either the basisesamoid or the abaxial nerve block; thus, a low, four-point nerve block may be necessary.1,2 However, a palmar/plantar digital nerve block can desensitize the pastern region, depending on the location of the block and the amount of anesthetic used. Schumacher et al3 reported that the PIJ is unlikely to be anesthetized when the palmar digital nerves are anesthetized at the proximal margin of the collateral cartilages of the foot. However, pain within the PIJ cannot be excluded when the palmar digital nerves are anesthetized at any site proximal to the proximal margin of the collateral cartilages of the foot.3 Therefore, in a horse with a suspected stress fracture of P1 or P2, it is important to avoid performing a nerve block because perineural anesthesia would likely cause the horse to become more comfortable and displace the fracture. Response to intraarticular anesthesia varies depending on the injury, but improvement of lameness by 50% or more implicates the PIJ and is essential for accurate diagnosis.1,2 Several imaging modalities, such as radiography or ultrasonography, are important for initial characterization of the injury. Ultrasonographic evaluation of the pastern is an integral part of characterizing the extent of the soft tissue injury. Additionally, nuclear scintigraphy, computed tomography (CT), magnetic resonance imaging (MRI), or tenoscopy of the DFTS may help make a more accurate diagnosis and prognosis.1,2 In general, osseous and joint abnormalities are best evaluated using radiography or CT, whereas MRI offers optimal evaluation of soft tissue injuries.

    Tendon and Ligament Injuries

    In general, injuries to the SDFT occur most frequently in the forelimb, followed by injuries to the oblique DSL, DDFT, and straight DSL. Injuries to the DDFT in the hindlimb are usually associated with a lower incidence of other soft tissue injuries compared with injuries to the DDFT in the forelimb.4–9 Collateral ligament injuries are more common in the forelimb but can occur in the hindlimb.4,6,10

    Superficial Digital Flexor Tendon

    SDFT injuries at the level of the pastern most commonly involve the branches of the SDFT in the forelimb.4–9 Abnormal conformation such as a long pastern or an underrun heel may predispose a horse to injury of the SDFT branch. Lameness usually occurs at the onset of injury, with focal heat, swelling, and sensitivity noted on palpation. However, because these injuries are often missed, careful palpation and comparison of the medial and lateral branches are important for detecting differences in size, heat, and pain. In general, swelling develops within 3 to 4 days. Ultrasonographic examination in the absence of swelling may produce false-negative results In general, swelling facilitates diagnosis of lesions because of a fluid–soft tissue interface. Core lesions, followed by diffuse injury to the affected branch, are the most common injuries identified by ultrasonographic examination.4,5 The medial branch of the SDFT appears to be injured more frequently than the lateral branch. Avulsion fracture of the insertion of the SDFT branch is not common.4,5 Horses with SDFT injuries in the pastern region have a poorer prognosis for return to racing and a higher recurrence of injury than horses with injuries in the metacarpal region.4,5 Conservative treatment options include a controlled rehabilitation program similar to that for any bowed tendon injury; however, 6 to 12 months of rehabilitation is typically needed. Surgical exploration of the DFTS via tenoscopy is often helpful for identifying the extent of the injury, recognizing longitudinal tears within the SDFT that are often missed with ultrasonography, and debriding the damaged tendon and possible adhesions.11,12 Additionally, annular ligament desmotomy may be performed during surgery, if appropriate. MRI may be superior to tenoscopy of the DFTS for characterizing the extent of damage to the SDFT; however, MRI does not allow debridement and treatment of the lesion. Regardless of treatment, routine ultrasonographic monitoring of tendon healing, typically at 30- to 60-day intervals, is very important for adjusting the rehabilitation process as needed. Additionally, it may be beneficial to medicate the DFTS with corticosteroids, hyaluronan, interlukin-1 receptor antagonist protein (IRAP), intralesional injection of platelet-rich plasma, or stem cell therapy.

    Deep Digital Flexor Tendon

    Deep digital flexor tendonitis affects various sport horses and typically presents as an acute-onset, persistent, unilateral, moderate to severe forelimb lameness.4,5 The lameness is often worse on a soft surface and generally improves with perineural anesthesia of the palmar/plantar nerves at the level of the proximal sesamoid bones.1,2 The DFTS is often distended in conjunction with the injury, possibly aiding the ultrasonographic evaluation. However, longitudinal tears of the DDFT cannot be definitively diagnosed using only ultrasonography, which typically reveals only nonspecific signs of chronic tenosynovitis.11,12 At the level of the pastern, the DDFT is bilobed, and the lobes are similar in size and shape. A lesion may involve one or both lobes and is typically characterized by enlargement and alteration of the tendon with or without a hypoechoic region. DDFT injuries are occasionally seen in conjunction with DSL injuries.2 In chronic injuries, dystrophic mineralization may be seen.4 Additionally, MRI is superior to ultrasonography for characterizing the extent of the damage to the DDFT. If the DFTS is distended, intrasynovial anesthesia of the sheath is preferred for confirming the location of the lameness. However, tenoscopy of the DFTS is important for making an accurate diagnosis and administering specific treatment. Therefore, if DFTS-associated lameness is confirmed and effusion is present, we strongly recommend tenoscopy despite equivocal ultrasonographic findings. Surgical exploration of the DFTS via tenoscopy is often helpful for identifying the extent of the injury, recognizing longitudinal tears within the DDFT that are often missed with ultrasonography, and debriding the damaged tendon and possible adhesions11,12 (FIGURE 1) . Treatment options for DDFT injuries are similar to those for the SDFT; however, recurrence of DDFT injuries is common.

    Rupture of the DDFT in the pastern region or within the hoof capsule is an infrequent sequela of neurectomy of the palmar digital nerves and is more commonly due to lacerations in the palmar/plantar pastern region. Preexisting lesions of the DDFT are likely to predispose horses to tendon rupture. Complete rupture causes the toe of the affected limb to flip up when it is bearing weight.1,2 Depending on the integrity of the DDFT, radiographic evidence of subluxation of the distal interphalangealjoint may be present. The prognosis for these horses returning to athletic soundness is guarded; however, if support-limb laminitis does not develop, reasonable options for these horses include making them serviceably sound for breeding or retiring them to pasture. Corrective shoeing with an elevated heel and rolled toe can make these horses more comfortable.

    Distal Sesamoidean Ligaments

    Desmitis of the oblique, straight, and cruciate DSLs occurs in all types of performance horses, with injury to the oblique DSL being the most common.4–9 The medial branch of the oblique DSL is injured more often than the lateral branch, and injury to the medial branch is more common in the forelimb than the hindlimb.6 Hindlimb oblique DSL injuries are more common in horses that are not used for racing.2 Horses with a valgus or varus limb conformation or long, sloping pastern may be at increased risk for injury. Discrete core lesions, diffuse fiber tearing, and avulsion fractures at the base of the sesamoid bones are common ultrasonographic findings. However, because of the limitations of ultrasonography, MRI is often necessary for definitive diagnosis (FIGURE 2) .

    Injuries to the straight or cruciate DSL are infrequent and may occur alone or with other soft tissue injuries. Lameness is often present; however, soft tissue swelling may not accompany the injury. Avulsion fractures are less common at the origin of the straight DSL than at the origin of the oblique DSL.4–9 Ultrasonographic identification of cruciate DSL injuries is difficult due to the location of these ligaments; therefore, these injuries may be underdiagnosed.

    Regardless of which DSL is injured, affected horses have a reasonable chance of returning to their intended use; however, the incidence of recurrence appears to be high.4,5 A prolonged, controlled-exercise rehabilitation program with periodic ultrasonographic evaluations is part of the preferred treatment, similar to programs for other tendon and ligament injuries. Additional treatments that may augment healing include extracorporeal shock wave therapy and local injection of stem cells or platelet-rich plasma; however, no studies have evaluated these options for treating DSL injuries.

    Orthopedic Injuries

    Fractures

    P1 or P2 fractures are important causes of lameness in all breeds. P1 fractures occur most often in racing breeds, whereas P2 fractures occur most often in horses used for Western-type activities. However, either pastern bone may fracture in any horse during lunging or because of trauma (e.g., kicks, falls).1,2 In horses with incomplete P1 fractures, lameness may be subtle; however, substantial fetlock joint effusion is often present because nearly all of these fractures involve the fetlock joint and rarely enter the PIJ. Horses with complex P1fractures typically exhibit obvious lameness,pain during manipulation of the pastern, and fetlock joint effusion.1,2 Radiographic evaluation of the affected limb is critical for the initial diagnosis. Multiple views at differing angles may be necessary to completely determine the characteristics of the fracture. Treatment options for incomplete P1 fractures typically include lag screw fixation through stab incisions and are associated with a good prognosis. More complex fractures should be treated with open reduction and internal fixation or partial reconstruction together with a transfixation cast or external fixator, which can result in a good outcome. In our opinion, treatment with a half-limb cast alone is not the best option for these complex fractures, although successful outcomes have been reported.1,2

    Horses with P2 fractures typically demonstrate obvious lameness, severe pain when the pastern is rotated, and variable swelling of the pastern region. However, some horses with single P2 eminence fractures may not exhibit severe lameness but have persistent lameness that is localized to the pastern region. Typically, horses with any type of P2 fracture, including palmar/plantar eminence fractures or those involving the distal interphalangeal joint, should undergo arthrodesis of the PIJ with a single or double plate combined with a half-limb cast. Severely comminuted P2 fractures that are not amenable to internal fixation may be treated with a transfixation pin cast or external skeletal fixation. Although short-term survival was not improved by combined internal fixation and a transfixation pin cast in one study,13 we think that P2 fractures should be repaired with internal fixation when possible, especially when the distal interphalangeal joint is involved (FIGURE 3) .

    Because comminuted fractures of P1 or P2 are difficult to treat, CT evaluation before surgery may be helpful for presurgical fracture repair planning and may permit more precise screw placement for improved joint realignment (FIGURE 3) . It is realistic to expect affected horses to have a good prognosis for becoming serviceably sound for breeding or being retired to pasture; some affected horses may return to athletic performance.

    Osteoarthritis of the Proximal Interphalangeal Joint

    Horses used for jumping, dressage, and Western-type activities appear to be prone to OA of the PIJ (i.e., high ringbone).1,2 Lameness may range from 2 to 4 (on a scale of 0 to 5) and typically improves with perineural (basisesamoid) and intraarticular anesthesia. Obvious enlargement of the pastern and/or varus deformity of the phalanges may be present in horses with advanced disease (FIGURE 4) . Radiographic abnormalities include new bone formation, periarticular sclerosis, and loss of joint space, typically on the medial aspect of the PIJ1,2 (FIGURE 4) . Comparative radiographs of the contralateral limb should be obtained in most horses because the condition may be bilateral.

    Horses with mild OA of the PIJ that is unrelated to fracture are often good candidates for conservative management. Various treatment options are aimed at easing the breakover forces in the affected foot and decreasing the pain and inflammation associated with OA. Therapeutic shoeing is aimed at reducing toe length and elevating the heel to ease breakover forces. Intraarticular administration of corticosteroids and hyaluronan is most effective in horses with mild or moderate OA. NSAIDs are useful in the initial stage. The use of topical 1% diclofenac sodium cream (Surpass, Boehringer Ingelheim) may be a better option for local long-term pain relief; however, long-term use of systemic NSAIDs (e.g., phenylbutazone) can be successful if managed appropriately. Additional treatments that may be beneficial, depending on the severity of OA, include joint-oriented nutraceuticals, intramuscular glycosaminoglycans, and intravenous hyaluronan or intraarticular IRAP.

    In horses with advanced OA, particularly those with extensive periarticular boneproliferation and extensive loss of joint space, surgical arthrodesis is the preferred treatment. Natural ankylosis may occur but is often a long, painful process with variable results. Surgical arthrodesis is generally considered a better solution over the long term because it produces more consistent results. Many methods of arthrodesis have been described, and clinician preference varies. Current recommended techniques include a single dorsal midline plate with additional transarticular 4.5- or 5.5-mm screws or two dorsally applied plates with or without transarticular screws.14–16 We prefer a single, dorsally applied, 4.5-mm narrow, three- or four-hole plate with two 5.5-mm transarticular screws to try to improve patient comfort immediately after surgery and reduce the duration of casting (FIGURE 5) . This method requires cast coaptation for 2 weeks to protect the incision site17; however, we typically leave the cast in place for 3 weeks. After arthrodesis of the PIJ, 89% to 95% of horses with hindlimb lameness and 70% to 85% of horses with forelimb lameness return to their intended use, and 85% return to athletic soundness.17–20 The plate and two-screw method for arthrodesis of the PIJ is broadly applicable, including treatment of single eminence P2 fractures; however, comminuted P2 fractures are best repaired with two dorsally applied plates or specially designed plates such as a spoon plate.21

    There are anecdotal reports of intraarticular administration of ethyl alcohol in the PIJ, with or without cast immobilization, and the results have been variable. Intraarticular administration of ethyl alcohol into the tarsometatarsal joint can facilitate arthrodesis in a pain-free manner22; however, the tarsometatarsal joint is a relatively low-motion joint compared with the PIJ and may be better suited for this type of treatment. Based on the amount of motion of the PIJ, cast immobilization following injection has been used to help facilitate arthrodesis, and success has been variable. The use of ethyl alcohol may be considered in horses with aggressive degenerative changes and new bone formation, whereas horses with minimal radiographic changes typically do not do well after ethyl alcohol treatment. Because of very inconsistent results with using ethyl alcohol, we do not recommend it for arthrodesis of the PIJ.

    Osteochondrosis of the Proximal Interphalangeal Joint

    In horses, OC is less common in the PIJ than in other joints. Osteochondral fragments associated with OC tend to occur dorsally or on the palmar/plantar eminence of P2, causing variable lameness (FIGURE 6) . These fragments may be incidental radiographic findings but can be accompanied by mild changes consistent with OA.1,2 It is important to identify the true source of lameness because surgical removal of osteochondral fragments can be difficult; however, the dorsal and palmar/plantar pouches of the PIJ are accessible with an arthroscope.23 Subchondral cystic lesions are more common in the hindlimb than the forelimb and can occur bilaterally.2 Some cystic lesions can be traumatically induced, but affected horses are often more lame and older than horses with developmental subchondral cystic lesions.2 Therefore, the clinical relevance of these lesions should be established using diagnostic analgesia.2 Management of subchondral cystic lesions includes intraarticular medications, arthrodesis of the PIJ, or periarticular drilling of the cyst and injection of a steroid or cancellous bone if it does not communicate with the joint.1,2

    Subluxation of the Proximal Interphalangeal Joint

    Subluxation of the PIJ is uncommon, occurring in a medial/lateral or dorsal to palmar/plantar direction. Medial/lateral subluxation is due to severe injury to the collateral ligaments. Palmar/plantar subluxation usually follows a severe, traumatic soft tissue injury, such as a complete tear of the DSL, an SDFT branch injury, or a combination of these injuries.2 Treatment options for medial/lateral or palmar/plantar subluxations include conservative and surgical management. External coaptation is often successful in adult horses that receive acute care. Application of a Kimzey Leg Saver Splint (Kimzey, Inc., Woodland, CA) is an excellent method of external coaptation of this injury. Cast immobilization can be successful, but instability of the PIJ may preclude successful realignment with this method, and surgical arthrodesis is usually the best option.

    Dorsal subluxation can occur without any identifiable structural abnormalities of the pastern or metacarpal/metatarsal soft tissue structures. It occurs primarily in the hindlimbs in young horses, and lameness is usually absent or mild. This type of subluxation is dynamic and usually resolves during full weightbearing of the PIJ. The presence of changes consistent with OA, such as osteophyte formation, subchondral bone sclerosis, or joint space narrowing, worsens the prognosis. However, dorsal subluxation often occurs after traumatic disruption of the suspensory apparatus and arthrodesis of the fetlock joint or progressive, severe suspensory desmitis.2

    Dorsal subluxation of the PIJ was reported in the hindlimbs of three horses with mild flexural deformity.24 In these horses, aged 5 months to 4 years, subluxation was thought to be caused by mild contraction of the DDFT without compensatory contraction of the SDFT. Tenotomy of the medial head of the DDFT in the proximal metatarsal region resolved the dynamic dorsal subluxation.24 Other treatment options for dorsal subluxation of the PIJ include conservative and surgical management. The more chronic the subluxation, the more likely it will damage the soft tissue stabilizing the joint and require surgical arthrodesis for stability.

    Conclusion

    Injuries involving the pastern region are a common source of lameness in many types of performance horses. Knowledge of the common breed- and activity-associated injuries can aid veterinarians in making an accurate diagnosis. Pain within the PIJ cannot be excluded when the palmar/plantar digital nerves are anesthetized at any site proximal to the proximal margin of the collateral cartilages of the foot. Therefore, when anesthetizing the palmar/plantar digital nerves, it is important to administer the anesthetic at the level of the collateral cartilages to minimize the effect on the PIJ. In general, soft tissue injures of the SDFT, DDFT, and DSL of the pastern region can be difficult to diagnose and can recur, and affected horses have a reasonable chance of returning to their intended use. Osseous injures such as PIJ OA and phalangeal fractures typically have a better prognosis because horses can do very well after surgical arthrodesis of the PIJ. However, secondary involvement of the distal interphalangeal or metacarpal/metatarsophalangealjoint is often the limiting factor in horses with P2 and P1 fractures, respectively.

    Critical Points

    • Tenoscopy can be helpful for diagnosis and therapy in horses with equivocal ultrasonographic findings with effusion and lameness localized to the digital flexor tendon sheath.
    • Multiple views at different angles are often necessary to completely characterize first and second phalangeal fractures.
    • Osteochondrosis of the proximal interphalangeal joint (PIJ) may cause variable lameness, making it important for the clinician to identify the true source of lameness.
    • MRI is more accurate than ultrasonography for diagnosing soft tissue injuries of the pastern region.
    • Pain within the PIJ cannot be excluded when the palmar/plantar digital nerves are anesthetized at any site proximal to the proximal margin of the collateral cartilages of the foot. Therefore, when the palmar/plantar digital nerves are anesthetized, it is important to inject the anesthetic at the level of collateral cartilages to minimize the effect on the PIJ.
    • Injuries involving the pastern region are rarely bilateral, but osteoarthritis may be; therefore, comparing the right and left limb or medial and lateral aspect of the same limb is helpful when identifying abnormalities.
    • Treatment options for DDFT injuries are similar to those for SDFT injuries.

    Downloadable PDF

    1. Baxter GM. Adams and Stashak’s Lameness in Horses. Ames, IA: Wiley-Blackwell; 2011.

    2. Ross MW, Dyson SJ. Diagnosis and Management of Lameness in the Horse. Philadelphia: WB Saunders; 2002.

    3. Schumacher J, Livesey, F, Degraves, et al. Effect of anaesthesia of the palmar digital nerves on proximal interphalangeal joint pain in the horse. Equine Vet J 2004;36:409-414.

    4. Reef VB. Equine Diagnostic Ultrasound. Philadelphia: WB Saunders; 1998.

    5. Reef VB. Current Practice in Equine Surgery. Philadelphia: JB Lippincott; 1990.

    6. Denoix J, Crevier N, Azevedo C. Ultrasound examination of the pastern in horses. Proc AAEP 1991;37:363.

    7. Dyson S. Ultrasonographic examination of the pastern region. Equine Vet Educ 1992;4:254.

    8. Dyson S, Denoix J. Tendon, tendon sheath, and ligament injuries in the pastern. Vet Clin North Am Equine Pract 1995;11:217.

    9. Redding NW. Sonographic exam of the digital flexor tendon sheath, distal flexor tendons, and soft tissues of the palmar pastern region. Proc AAEP 1993;39:11.

    10. Denoix JM, Audigie F. Ultrasonographic examination of joints in horses. Proc AAEP 2001;46:366.

    11. Wright IM, McMahon PJ. Tenosynovitis associated with longitudinal tears of the digital flexor tendons in horses: a report of 20 cases. Equine Vet J 1999;31:12-18.

    12. Wilderjans H, Boussauw B, Madder K, et al. Tenosynovitis of the digital flexor sheath and annular ligament constriction syndrome caused by longitudinal tears in the deep digital flexor tendon: a clinical and surgical report of 17 cases in Warmblood horses. Equine Vet J 2003;35:270-275.

    13. Joyce J, Baxter GM, Sarrafian TL, et al. Use of transfixation pin casts to treat adult horses with comminuted phalangeal fractures: 20 cases (1993-2003). JAVMA 2006;229:725-730.

    14. Nixon AJ. Equine Fracture Repair. Philadelphia: WB Saunders; 1996.

    15. Genetzky RM, Schneider EJ, Butler HC, et al. Comparison of two surgical procedures for arthrodesis of the proximal interphalangeal joint in horses. JAVMA 1981;179:464-468.

    16. Crabill MR, Watkins JP, Schneider RK, et al. Double plate fixation of comminuted middle phalangeal fractures in horses (1985-1993). JAVMA 1995;207:1458-1461.

    17. Knox PM, Watkins JP. Proximal interphalangeal joint arthrodesis using a combination plate-screw technique in 53 horses (1994-2003). Equine Vet J 2006;38:538-542.

    18. Martin GS, McIlwraith CW, Turner AS, et al. Long term results and complications of proximal interphalangeal arthrodesis in horses. JAVMA 1984;184:1136-1140.

    19. Schaer TP, Bramlage LR, Emertson RM, et al. Proximal interphalangeal arthrodesis in 22 horses. Equine Vet J 2001;33:360-365.

    20. MacLellan KNM, Crawford WH, MacDonald DG. Proximal interphalangeal joint arthrodesis in 34 horses using two parallel 5.5-mm cortical bone screws. Vet Surg 2001;34:454-459.

    21. Sod GA, Mitchell CF, Hubert JD, et al. In vitro biomechanical comparison of equine proximal interphalangeal joint arthrodesis techniques: prototype equine spoon plate versus axially positioned dynamic compression plate and two abaxial transarticular cortical screws inserted in lag fashion. Vet Surg 2007;36:792-799.

    22. Shoemaker RW, Allen AL, Richardson CE, et al. Use of intra-articular administration of ethyl alcohol for arthrodesis of the tarsometatarsal joint in healthy horses. Am J Vet Res 2006;67:850-857.

    23. Radcliffe RM, Cheetham J, Bezuidenhout AJ, et al. Arthroscopic removal of palmar/plantar osteochondral fragments from the proximal interphalangeal joint in four horses. Vet Surg 2008;37:733-740.

    24. Shiroma JT, Engel HN, Wagner PC, et al. Dorsal subluxation of the proximal interphalangeal joint in the pelvic limb of three horses. JAVMA 1989;195:777-780.

    References »

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