September 2014 Large animal case

September 2014

Quarter horse
Female intact
12 years of age
Chronic lameness hind right
Graded 2/5 and localised on the tarsus
Radiographs of the region were taken.

Radiographic examination

Lateromedial and dorsoplantar view of the right tarsus.

Radiographic findings and diagnosis

  • There is irregularly defined increased opacity of the medullary bone with loss of the trabecular pattern of the proximal metatarsus (MT, arrows).
  • There is very mild new bone formation on the proximodorsal periarticular border of the metatarsus (arrow head).
  • The radiographic findings are compatible with chronic proximal suspensory ligament desmitis and possible, minimal osteoarthritis of the tarsometatarsal joint.

 Radiographic examination

Close up of the lateromedial view of the left tarsus.

Diagnosis

An ultrasonographic examination of the origin of the suspensory ligament was performed.

Ultrasound image (long axis) of the origin of the suspensory ligament

Diagnosis

  • There is segmental reduction of the parallel fibre pattern mainly dorsally with ill defined hypoechogenic areas (arrows).
  • The plantar surface of the MT bone is irregular mainly at the origin of the ligament (empty arrow).

 

Close up of the ultrasound image

Comments

  • The diagnosis of chronic proximal suspensory desmitis was ultrasonographically confirmed.
  • Radiographic abnormalities involving the proximal aspect of the 3rd MT bone are often associated with proximal suspensory desmitis. Common abnormalities observed in the lateromedial projection include alteration of the trabecular orientation and new periosteal bone formation on the proximoplantar aspect of the 3rd MT bone. Trabecular sclerosis is frequently seen in the dorsoplantar projection. New bone formation (enthesiophyte formation) or small avulsion fragments on the plantar aspect of the 3rd MT bone can also be present.
  • Because the suspensory ligament consists of striated muscle, fat and connective tissue the ultrasonographic appearance has heterogeneous echogenicity and ultrasonographic assessment is very challenging.
  • In horses with proximal suspensory ligament desmitis, one or more of the following ultrasonographic findings have been described: Enlargement, possible reduced definition of the suspensory ligament margins¬† (especially dorsally), central hypoechoic areas, , irregular plantar cortex of the 3rd MT bone or decreased echogenicity. Avulsion fractures or enthesiophytes formation can also be present.