Equine Fractures Study Guide

Overview and Clinical Importance

Equine fractures represent one of the most challenging aspects of equine practice and are a major cause of morbidity and mortality in horses. The unique anatomy and biomechanics of the equine limb, combined with the horse's size and flight response, create significant challenges for fracture management. Understanding fracture classification, emergency stabilization, treatment options, and prognosis is essential for the NAVLE examination.

Fractures in horses can be classified as traumatic (kicks, falls, racing injuries) or stress-related (accumulated microdamage from repetitive loading). The location, configuration, and whether the fracture is open or closed significantly impact treatment decisions and prognosis.

Fracture Classification

Understanding fracture terminology is essential for communication and treatment planning. Fractures are described by multiple characteristics.

Distal Phalanx (P3/Coffin Bone) Fractures

Fractures of the distal phalanx (P3, coffin bone, pedal bone) are relatively common in horses. They occur in forelimbs or hindlimbs after concussive injury during exercise or from kicking solid objects. Thoroughbreds and Standardbreds (racing breeds) are most commonly affected.

P3 Fracture Classification (Types I-VII)

Clinical Signs and Diagnosis

• Mild to severe lameness (often sudden onset after exercise)
• Sensitivity to hoof testers (especially over affected area)
• Digital pulse may be increased
• Positive response to palmar/plantar digital nerve block
• Radiography: multiple views needed; fracture may not be visible initially (repeat in 2 weeks if suspected)
• Chronic extensor process fractures may cause "buttress foot" (triangular hoof shape)

Treatment Options

• Conservative: Box rest 6-12 months, bar shoe with clips, rim shoe, or hoof cast for immobilization
• Surgical (Types II, III, IV): Lag screw fixation for articular fractures; fragment removal for Type IV

Proximal Sesamoid Bone (PSB) Fractures

Proximal sesamoid bone fractures are predominantly an injury of racehorses due to the extreme forces placed on the fetlock joint during high-speed exercise. The PSBs are part of the suspensory apparatus and can fail catastrophically ("breakdown") when both bones fracture simultaneously.

PSB Fracture Classification

Clinical Signs

• Acute onset moderate to severe lameness (exacerbated by fetlock flexion)
• Heat, pain, and swelling over fetlock joint
• Hemarthrosis and synovial effusion of the metacarpophalangeal/metatarsophalangeal joint
• CRITICAL: Always perform ultrasonography to assess suspensory ligament (desmitis worsens prognosis)

Third Metacarpal/Metatarsal Condylar Fractures

Condylar fractures of MC3/MT3 (cannon bone) are common in racehorses and are typically the result of accumulated stress (fatigue fractures) rather than single traumatic events. They are classified as lateral or medial, and complete or incomplete.

Clinical Signs

Acute lameness after exercise (or race) with marked fetlock effusion. Horses may finish exercise appearing sound but become progressively lame. Diagnosis requires full radiographic series of the fetlock, including flexed dorsopalmar view.

Proximal Phalanx (P1) Fractures

Proximal phalanx (P1) fractures can occur in any performance horse but are most common in racehorses. The "split pastern" (short incomplete sagittal fracture) is the most common configuration and carries a good prognosis.

P1 Fracture Types

• Dorsal chip fractures: Dorsoproximal margin; hyperextension injury; typically medial aspect; removed arthroscopically (excellent prognosis)
• Palmar/Plantar osteochondral fragments: Type I (axial, articular) or Type II (abaxial); may be OCD or trauma; hindlimb more common
• Sagittal fractures: Short incomplete (good prognosis) to complete (requires lag screw fixation). Originates in sagittal groove, extends distally.
• Complete/Comminuted fractures: "Bag of ice" injury in severe cases. May require arthrodesis or euthanasia. Poor prognosis for athletic function.

Clinical Signs and Diagnosis

Acute onset lameness during or after high-speed exercise. Non-weight bearing with complete fractures. Pain on fetlock flexion and pressure over dorsal P1 midline. Incomplete fractures may require special radiographic views or nuclear scintigraphy. CT is valuable for occult fracture lines and surgical planning.

Treatment

Chip fractures: Arthroscopic removal. Short incomplete sagittal: Stall rest or lag screw fixation (surgical repair yields better outcome). Complete sagittal: Lag screw fixation via stab incisions. Comminuted: Consider breeding soundness only.

Splint Bone (MC2/MC4, MT2/MT4) Fractures

The second and fourth metacarpal/metatarsal bones (splint bones) are vestigial weight-bearing bones that are frequently injured. Fractures typically occur in the distal third and can be caused by external trauma (kicks) or internal trauma (associated with suspensory desmitis).

Long Bone Fractures (Radius, Tibia, Humerus)

Long bone fractures in adult horses carry a guarded to poor prognosis due to the challenges of adequate stabilization and the risk of contralateral limb laminitis during recovery. Foals have significantly better outcomes due to smaller size and more rapid healing.

Emergency First Aid and Stabilization

Proper emergency stabilization of equine fractures is critical to prevent closed fractures from becoming open, minimize soft tissue damage, and allow safe transport to a referral hospital. The Robert Jones bandage with splints is the mainstay of field stabilization.

Stabilization Principles

• SEDATE the horse: Use potent, long-lasting sedation (detomidine + butorphanol). Do NOT be conservative; these horses are anxious and in severe pain.
• Immobilize joints ABOVE and BELOW the fracture site
• Robert Jones bandage: Multiple layers of alternating cotton and elastic gauze, applied VERY tightly. Should make you sweat during application.
• Splints: PVC pipe, boards, or commercial splints. Apply caudally, laterally, or both depending on fracture level.
• Bandage cast: Superior stabilization if casting material available. Two layers cotton/elastic gauze, then 3 layers fiberglass tape.

Fracture Stabilization Levels

P3 Fracture Types - "Wing It 1-2-3": Type 1 = Non-articular wing (Good prognosis) Type 2 = Articular wing (Most common, Fair prognosis) Type 3 = Midsagittal (Poor prognosis)

PSB Fractures - "AABMC" (Apical, Abaxial, Basilar, Midbody, Comminuted): Apical = Most common (81%), Arthroscopic removal, Awesome prognosis Abaxial = Assess suspensory, Arthroscopic removal Basilar = Base, fair prognosis Midbody = needs lag screw Comminuted = Catastrophic breakdown

Condylar Fractures - "Lateral = Lag, Medial = Metal": Lateral condylar fractures = Lag screw fixation Medial condylar fractures = Metal plate fixation (propagating)

Splint Bone Prognosis - "Suspensory Status": The prognosis for splint bone fractures depends on the SUSPENSORY LIGAMENT, not the fracture itself. Always ultrasound the suspensory!

Robert Jones Bandage - "Sweat While You Wrap": If you're not sweating while applying a Robert Jones bandage, it's not tight enough. Multiple layers of cotton compressed by elastic gauze. Add splints for rigidity.