The tarsus Flashcards by Sophie Robinson

The tarsus is also know as?

The hock

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Is the hock a common site of pathology?

Yes

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Which bones make up the tarsus

Tibia proximal, then talus
Central tarsal bone
3rd tarsal bone - Either side of it is the 4th tarsal bone and the fused 1st and 2nd tarsal bones
Distally = 3rd metatarsal bones + splint bones
On the plantar aspect is the calcaneus

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Describe the joints in the tarsus

Tibia proximal, then talus – between them is the tarsocrural joint
Talocalcaneal joint on the plantar aspect
Proximal intertarsal joint
Distal intertarsal joint
Tarsometatarsal joint

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Describe the tarsocrural joint in terms of motion

Large, high motion joint – where most of the flexion and extension of the tarsus comes from

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Which tarsal bone is involved in the majority of weightbearing?

3rd tarsal bone

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Which tissues articular with the calcaneus

Gastrocnemius muscle and SDFT

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Describe communication between the tarsal joints

Proximal intertarsal joint – always communicates with the tarsocrural joint
Tarsometatarsal joint – communicates with the distal intertarsal joint in about 40% of cases

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Name the tendons and ligaments found on the dorsal aspect of the tarsus

2 main extensors – tibialis cranialis and peroneus tertius
Also long extensor tendon – extends down to the pedal bone
Either side of the tarsus and short (deep) and long (superficial) collateral ligaments

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Name the tendons and ligaments found on the plantar aspect of the tarsus

Deep digital flexor tendon
Superficial flexor tendon
Tarsal sheaths

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Which structure inserts on the calcaneus?

Gastrocnemius muscle

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Where does the SDFT lie?

SDFT and its muscle lies over the top of the gastrocnemius, runs over the top of the calcaneus (held in place by a band of tissue)

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Where does the DDFT lie?

Deeper is the DDFT – runs over the sustentaculum tali= horizontal shelf that arises from the anteromedial portion of thecalcaneus

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Name the 3 calcaneal bursa - from superficial to deep

(Acquired) superficial bursae
Intertendinous bursa
Gastrocnemius bursa

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Describe the main features of the (Acquired) superficial bursae

Between SDFT and skin
“Capped” hock – due to fluid
Occurs right on the point of the hock

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Describe the main features of the intertendinous bursa

Between gastrocnemius and SDFT extending distally
Communicates with gastrocnemius bursa
Occurs slightly laterally on the point of the hock

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Describe the main features of the gastrocnemius bursa

Deep between gastrocnemius tendon and tuber calcis

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Describe the distribution of Osteochondritis Dissecans in the tarsus

Mostly: Distal intermediate ridge of the tibia (“DIRT” lesions)
Lateral trochlear ridge
(Medial malleolus)

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What are the clinical signs of Osteochondritis Dissecans in the tarsus

Usually young horse (6mo-3yr):
- As it is a developmental condition
- Often found on screening radiographs
Effusion of the tarsocrural joint
(Lameness)
Check other limb/joints!

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Describe how Osteochondritis Dissecans in the tarsus appears on radiography

Radiolucent osseous fragment located at the level of the distal intermediate ridge of the tibia = OCD DIRT lesion
Also small radiopaque osseous fragments associated with a larger radiolucent defect on the lateral trochlear ridge

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How is Osteochondritis Dissecans in the tarsus treated?

Arthroscopy treatment to remove fragments

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How old must a horse be to have Arthroscopy treatment for Osteochondritis Dissecans in the tarsus? Why?

Usually wait until 11 months+
As some subtle fragments may reattach and some may not have formed yet

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What are the causes of tarsal bone collapse?

Developmental condition
Incomplete ossification:
- Dysmature/premature foal
- Neonatal maladjustment
- Can present as angular limb deformities

Before diagnosis of tarsal bone collapse which DDx needs to be ruled out?

Septic physitis

If a foal is diagnosed with tarsal bone collapse what do you need to tell owners?

If seen need warn owners of arthritis in the future as these bones are damaged at a young age

How is tarsal bone collapse treated?

Supportive therapy until matures – load tarus symmetrically Prognosis: poor esp if >30% collapse/fragmentation

'bone spavin' is an equine term for which condition?

Osteoarthritis of the lower hock joints

Which joints of the tarsus are most affected by osteoarthritis?

Mainly tarsometatarsal joint, sometimes also distal metatarsal joint (also PIT/TC/talocalcaneal)

'Juvenile spavin' occurs as a result of?

Osteoarthritis of the small tarsal joints in young horses seen secondary to tarsal bone collapse

How does Osteoarthritis of the small tarsal joints occur?

Poor conformation can lead to increased stress on the joint Compression and rotation of small tarsal bones when stops/jumps? Heritable?

Describe the findings on a clinical exam in a horse with Osteoarthritis of the small tarsal joints

1. Palpable exostoses; squared off toes or commonly NAD! 2. Lameness (mild-moderate) - Unilateral/bilateral - “choppy, stabby gait” - Worse on inside/hard surface 3. Poor performance/“stiff” - “back pain” 4. Flexion test +ve - Not specific!!! 5. Tarsocrural effusion esp with Proximal intertarsal OA

Describe the 'triad of disease' seen with osteoarthritis of the tarsus

If a horse has tarsal pathology it is likely they will sacroiliac pathology and back pain If the tarsus isn’t generating enough power this has to be made up by other parts of the body to compensate – causing them to strain

Describe the use of diagnostic analgesia for Osteoarthritis of the small tarsal joints

Intra-articular versus perineural!! - Joint blocks over nerve blocks TMT/DIT anaesthesia

Why is radiography performed after diagnostic analgesia in osteoarthritis cases?

A lot of horses with osteoarthritis have radiographic changes but not significant pain – so need to prove the radiographic changes are significant

Describe the use of radiography for Osteoarthritis of the small tarsal joints

Four standard views: DP, LM, DMPLO, DLPMO Poor correlation with clinical signs

Describe the radiographic findings of TMT/DIT osteoarthritis

- Complete loss of joint space - Mottling and sclerosis of tarsal bones – joint spaces should be crisp black lines

Describe systemic medication treatment options for small tarsal osteoarthritis

NSAID’s PSGAGs/HA Bisphosphonates Nutraceuticals

Describe other treatment options for small tarsal osteoarthritis

- Intra-articular medication = Corticosteroids +/- HA - Farriery: Improve breakover; lateral width - Chemical arthrodesis with Ethyl alcohol - Surgical arthrodesis

Describe how ethyl alcohol is used to treat small tarsal OA

Alcohol will destroy cartilage and then fuse the tarsal joints - Pain comes from bone grinding on bone and this will no longer happen - Do not want to get alcohol in the tarsocrural joint as this is a high motion joint - Contrast study performed to make sure its going into the right place

In which locations can tarsal fractures occur?

Malleolar (of the tibia) Calcaneal Small tarsal bones

How are malleolar fractures treated?

Can remove arthroscopically

How are calcaneal fractures treated?

May be unstable and therefore euthanasia

How are small tarsal bone fractures treated?

Conservative or internal fixation

Describe tarsal Luxations locations

Usually TMT or PIT

How are distal intertarsal joint luxations prevented?

4th tarsal bone

How do tarsal luxations present?

Severe lameness+ swelling Stress radiographs

How are tarsal luxations treated?

Cast +/- internal fixation Or euthanasia

Name 3 soft tissue injuries of the tarsus

Collateral ligament injuries Tarsal sheath swelling Calcaneal bursa/lateral luxation of SDFT

Describe treatment options for Collateral ligament injuries

Rest NSAIDs; cold hosing; bandaging Physiotherapy Intra-articular medication? Monitor with ultrasound Poor px if OA of joint develops

The term 'thoroughpin' refers to which condition?

Tarsal sheath synoviocoele

How does Tarsal sheath synoviocoele present?

Mild or no lameness Large unilateral swelling in caudodistal crus - Tear in synovial wall - Valve effect leads to fluid build up Usually no osseous pathology

How does Tarsal sheath synoviocoele present on ultrasound?

Effusion+++ with fibrinous deposits Usually no DDFT lesion

Describe management of Tarsal sheath synoviocoele

1. Conservative management - Drainage and corticosteroids - Tends to recur 2. Surgical management – enlarge communication tenoscopically

Where does a Calcaneal bursa/lateral luxation of SDFT most commonly occur?

Tend to tear medial attachment leading to lateral luxation

Describe the clinical presentation of a horse with calcaneal bursa/lateral luxation of SDFT

Often lots of swelling Bursal effusion ++ Horse agitated ++ - Don’t want to put their foot down - May see SDFT “sliding off” point of hock as walks

How is calcaneal bursa/lateral luxation of SDFT treated?

Rest, NSAIDs Surgery (debride tear)