Ossa metatarsalia II et IV (MT2 + MT4)
The second (medial) and fourth (lateral) metacarpal bones in the forelimb and the corresponding metatarsal bones in the hindlimb are the vestigial splint bones. They run along the palmar (forelimb) or plantar (hindlimb) surface of the cannon bone (third metacarpal or metatarsal). They are approximately one-third shorter than the cannon bone and end in rounded nodules called buttons that are palpable landmarks. They are connected to the cannon bone by strong interosseous ligaments that typically ossify with age. Hindlimb splints (periostitis) are less common than forelimb splints.
Splints (periostitis or fracture of the interosseous ligament) are a common cause of lameness, especially in young performance horses. Diagnosis is clinical and radiographic. Most cases resolve with rest and appropriate management. Fractures of the splint bones can occur from trauma.
## Overview Splints are inflammation of the interosseous ligament and periosteum between the cannon bone and the small metacarpal (splint) bones, producing a bony swelling (exostosis). They are commo
Fractures or bony growths (splints) on the second or fourth metacarpal bones. Splints are common in young horses beginning work and are caused by tearing of the interosseous ligament between the splin
Sudden swelling or lameness along the side of the cannon bone should be evaluated. Most splints improve with rest. Protective boots can help reduce risk in some disciplines.
## Overview Splints are inflammation of the interosseous ligament and periosteum between the cannon bone and the small metacarpal (splint) bones, producing a bony swelling (exostosis). They are common in young horses and usually occur on the medial side. Lameness is present only while the splint is forming. Once the bone settles, most horses become sound unless the swelling interferes with the suspensory ligament. ## Causes Concussion, training stress in immature horses, conformation, or direct trauma. ## Diagnosis Palpation and radiographs to distinguish from fracture. ## Treatment Rest and anti-inflammatories. Intralesional corticosteroids are sometimes used. Surgery only if the exostosis impinges on the suspensory. ## Recovery and Prognosis Excellent. The bony lump usually remains but is not painful. ## Prevention Gradual training of young horses and balanced shoeing. Signs include: firm swelling on the medial cannon; lameness while forming; resolves once ossified; radiographic exostosis
Fractures or bony growths (splints) on the second or fourth metacarpal bones. Splints are common in young horses beginning work and are caused by tearing of the interosseous ligament between the splint and cannon bones. Signs include: Warm, painful swelling on the inside or outside of the cannon bone; lameness in acute phase; bony hard lump after healing (cosmetic blemish); usually resolves with rest; rarely causes long-term lameness unless near the knee or suspensory.; Consult veterinarian for specific symptoms.; Hard, warm, painful swelling on the side of the cannon bone; lameness (may be temporary); cosmetic blemish after healing; splint fractures can irritate the suspensory ligament if displaced.
Splints (periostitis or fracture of the interosseous ligament) are a common cause of lameness, especially in young performance horses. Diagnosis is clinical and radiographic. Most cases resolve with rest and appropriate management. Fractures of the splint bones can occur from trauma.
Sudden swelling or lameness along the side of the cannon bone should be evaluated. Most splints improve with rest. Protective boots can help reduce risk in some disciplines.
See the Second & Fourth Metatarsal Bones / Splint Bones (Left Hindlimb) on our interactive 3D horse model. Open 3D Model