Introduction

• Cause: chronic inflammation of the sesamoid bones.
• Cause of lameness and incidental finding in the racing greyhound.
• Lameness in large pet breeds, eg Rottweiler.
• Signs: often an insidious onset, progressive forelimb lameness in young dogs, or can also be acute onset lameness in adults.
• Diagnosis: clinical signs and radiography.
• Treatment: conservative, or surgical removal of sesamoids.
• Prognosis: guarded for resolution.

Pathogenesis

Etiology

• Lytic lesions possible manifestation of osteochondrosis Osteochondrosis.
• Inflammatory changes seen with enthesiophyte formation, possible traumatic etiology.
• Degenerative secondary changes may be present in the metacarpo-phalangeal joint.

Pathophysiology

• Fragmentation of the sesamoid bone may be result of abnormal endochondral ossification, ie a manifestation of osteochondrosis.
• Multiple exostoses within the soft tissue attachments of the sesamoid may have a traumatic etiology.
• There may be calcification around the sesamoid bones or osteophytosis around the metacarpo-phalangeal joint.
• These changes may be secondary to joint trauma or instability.
• Repeated stress on palmar surface of sesamoids by digital flexor tendons during hyperextension of metacarpo-phalangeal joints may → fatigue fractures and degeneration of the underlying bone and soft tissues.
• Digits 2 and 5: flexor tendon pressure solely on inner sesamoids 2 and 7.
• Digits 2 and 5: metacarpal bones are asymmetrical so axial condyle bears more load.
• Histologically see bone fracture and necrosis supporting vascular compromise theory.

Timecourse

• Slow, progressive lameness seen over weeks to months in the young dog.

Diagnosis

Treatment

Outcomes