Changes

==Distal Sesamoid (Navicular) Bone==

==Distal Sesamoid (Navicular) Bone==

The distal sesamoid in horses is known as the navicular bone. It is elongated transversely and articulates with both the distal and middle phalanx. The navicular is separated from the deep digital flexor tendon by a bursa; the flexor surface of the navicular is covered by cartilage. The proximal and distal ends are grooved and possess large foramina. The bone also has a sagittal ridge.

The distal sesamoid in horses is known as the navicular bone. It is elongated transversely and articulates with both the distal and middle phalanx, lying palmar to the distal interphalangeal joint.  

 

Dorsally, the articular surface is covered by hyaline cartilage. It articulates with the palmar aspect of the middle phalanx.  The palmar flexor surface is characterised by a prominent '''sagittal ridge''' and is covered by fibrocartilage; providing a smooth surface for the deep digital flexor tendon to glide during weightbearing.  The distal border contains a small articular facet of hyaline cartilage for articulation with the distal phalanx. The distal border contains numerous, synovium-lined, nutrient foraminae.

 

*Paired '''collateral sesamoidean ligaments''':  Originate from depressions on either side of the distal aspect of the proximal phalanx. They extend in a palmar direction to insert on the extremities and proximal border of the navicular bone; thereby acting to suspend the navicular bone.

*A branch from each '''collateral sesamoidean ligament''' originates at the palmar process (angle) of the distal phalanx (pedal bone)and inserts on the axial surface of the hoof cartilage.

*The '''distal sesamoidean (impar) ligament''' originates from the distal margin of the navicular bone and deep digital flexor tendon. It extends from the navicular bone proximally for 1.0-1.5cm and distally to the insertion of the deep digital flexor tendon on the distal phalanx (pedal bone).

 

The navicular is separated from the deep digital flexor tendon by the '''navicular bursa'''.  There is no communication between the navicular bursa and the distal interphalangeal (coffin) joint.