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Proximal sesamoid: sesamoiditis
Introduction
- Local inflammation of the proximal sesamoid bones at the site of ligament attachment in racing horses.
- Two forms of the disease have been described.
- Signs: can present as an acute, or more usually chronic, forelimb lameness in horses in race training with swelling of the palmar fetlock and palpable pain.
- Diagnosis: regional anesthesia, radiography and ultrasonography are essential.
- Treatment: involves rest, modification of work programmes, cold therapy, support bandaging and topical/systemic anti-inflammatory medications.
- Prognosis: guarded.
Presenting signs
- Racing animals in training, eg Standardbreds, Thoroughbreds.
- Chronic lameness.
- Often low grade lameness or performance-limiting.
- Acute lameness.
- Associated with injuries to the suspensory apparatus.
- Fetlock flexion and palpable pain.
- Enlargement of suspensory structures of palmar fetlock.
Age predisposition
- Horses in race training: 2-5 years old.
Breed/Species predisposition
- Thoroughbred Thoroughbred .
- Standardbred Standardbred .
Cost considerations
- Loss of training days/earnings.
- Treatment.
Pathogenesis
Predisposing factors
General- Hard training or racing.
- Abnormal limb conformation.
- Previous injury to suspensory apparatus.
Pathophysiology
- Term used to describe proliferative or degenerative bony changes of the proximal sesamoid bones.
- Two forms have been described:
- Periostitis.
- Osteitis.
- 2 forms of seamoiditis have been described.
Periostitis form
- Acute or chronic injury to the suspensory ligament, distal sesamoidean ligaments and/or palmar/plantar annular ligament of fetlock.
- Leads to damage at bone-ligament interface (entheses) with proximal sesamoid bones.
- Osseous metaplasia of fibrous scar tissue and periostitis → formation of enthesiophytes + changes in bone contour.
Osteitis form
- Degenerative condition - is sesamoiditis the right term?
- Arteriosclerosis and thrombosis of nutrient arteries with subsequent local ischemic necrosis has been suggested as causing demineralized vascular channels within sesamoid bones.
- Others have suggested that they are normal variations in appearance.
- Enthesiopathy at the insertion site of the suspensory ligament branches between the nutrient foramina may → to the impression of radiolucency and enlargement of vascular channels.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- McLellan J & Plevin S (2014) Do radiographic signs of sesamoiditis in yearling Thoroughbreds predispose the development of suspensory ligament branch injury? Equine Vet J 46 (4), 446-450 PubMed.
- Zekas L J et al (1999) Characterization of the type and location of fractures of the third metacarpal/metatarsal condyles in 135 horses in central Kentucky (1986-1994). Equine Vet J 31 (4), 304-308 PubMed.
- Trumble T N et al (1995) Clinical relevance of the microvasculature of the equine proximal sesamaoid bone. Am J Vet Res 56 (6), 720-724 PubMed.
- Reeves M (1991) Sesamoiditis. JAVMA 199 (6), 682-683 PubMed.
- Hardy J et al (1991) Clinical relevance of radiographic findings in proximal sesamoid bones of two year-old Standardbreds in their first year of race training. JAVMA 198 (12), 2089-2094 PubMed.
- Nemeth F (1973) Sesamoiditis in the horse. Tijdschr Diergeneeskd 98 (20), 988-994 PubMed.
- Nemeth F (1973) The pathology of sesamoiditis. Tijdschr Diergeneeskd 98 (20), 1003-1021 PubMed.