Lameness - Navicular Syndrome

Question 1

About

Answer 1

• aka chronic heel pain or palmer foot syndrome
• horse shifts gait to a toe-first landing rather than heel first
• cause further pressure on navicular bone

Question 2

Causes and structure of navicular

Answer 2

• multiple causes - heel pain
• diagnosis difficult (small bone hard to get to)
• treatment may not be aimed at correct problem
  Poorly understood needs more research
• navicular held by ligaments deep digital flexor
• empire ligament connects navicular bone to P3
• navicular bursa = flu so all structures move easily without grinding
• next to interflangeal joint and sesamoid ligaments

Question 3

Navicular hypotheses

Answer 3

• vascular = blood flow too high (erosion) or too low (ischaemia)
• biochemical = pressure on bone
• multifactorial
• hereditary = shape of bone
• showjumping and activities where use fore legs pressure
• does heel pain come first and animal changes gait/posture therefore causing more damage or damage to navicular done first and heel become painful
• step on toe more, DDFT rub and create more pressure on navicular

Question 4

Abnormal forces maybe a result of…

Answer 4

• excessive forces applied to normal foot (landing after jump)
• normal forces applied to poorly conformed foot (walking)

Question 5

Poorly conformed feet and how to improve

Answer 5

• long toe, low heel
• collapsed heel affects blood flow to foot and nav bone
• digital cushion small - concussion
• ligaments/DDFT stretched
• result in pressure in area and inflamation
• excessive pressure on DDFT and nav bone
• pressure excessive in stance phase and at break over
• force and stress over navicular double in affected horses early in stance, pressure on soft tissues
• toe stance breakeven point higher
• use of wedges, raised heels and eggbar shoes to relieve pressure
• fix immediate problem and pressure, long term can continue to cause pressure on heel and cause to collapse even further
• animal may be more comfortable as shortend the toe and raised BUT done artificially
• long term = encourage heel growth

Question 6

Questions around navicular syndrome

Answer 6

Many favavour heel pain first and favourite toe first landing pressure changing on nav bone

Question 7

Diagnosis

Answer 7

Can’t reverse what has happened to navicular
Slow down and comfortable as possible
- MRI, scintigraphy and CT
- biochemical markers or joint and bone remodeling
~ indicate where damage occurring
~ ossification fragments where smooth bone edges should be

Question 8

Hereditary navicular

Answer 8

• shape of navicular bone is hereditary (estimated heritability = 0.26 - 0.3)
• navicular bone graded 0-4 (excellent to bad)
  E.g. in Holland, Dutch warmblood stallions and mares with grade 4 navicular (evaluate on x rays) cant be used for breeding
  Reduction in grade 3 and 4 bones over a 10 year period