Investigation of Lameness in the Horse (Week 3, Mod 7)

Is forelimb lameness or hindlimb lameness more common?

Forelimb lameness is more common

What are 3 other patterns for horse lameness that you should be aware of?

Patterns – may be helpful but be wary of exceptions

• Distal limb lameness more common than proximal limb lameness

• Front foot pain most common cause of lameness

• Bilateral lameness due to same condition affecting both limbs of a pair is common

What is the order of operations to follow when investigating possible lameness?  Think of 5 steps 

1) Patient data, focused medical history

2) Focused physical examination

3) Gait evaluation

4) Use information to inform further investigation

• Not required if can already make diagnosis

• Often diagnostic local anaesthesia then diagnostic imaging

5) Diagnosis

• Develop list of differential diagnoses at early stage, re-visit to refine as more information becomes available 

What are certain pieces of patient data to consider when investigating lameness?  Think of 4

1) Breed variations, age variations 

2) Use; are they a working breed?

3) Duration of ownership, was a prior to purchase examination performed?

• Implications regarding medical history

4) Management

• Exercise, shoeing, feeding

What are 5 things to consider when taking a medical history of the patient?  Remember, focus on the lameness 

1) Owner’s description of lameness

• Severity, nature of onset and progression

• Duration

2) External trauma

3) Localising signs

4) Response to DIY therapy

5) Previous lameness – owner & patient record

What are 4 things you can assess “hands off” when beginning your physical exam?

1) Posture – Is the horse weight bearing normally at rest?

2) Asymmetry

• Swellings, localised muscle atrophy, altered bony landmarks

3) Body condition (obesity), poor condition vs generalised muscle atrophy

4) Conformation

• Foot & limb

What are 4 things to do in the “hands on” portion of your exam?

“Hands on” is for a DETAILED examination

1) Palpation - 

• Heat, pain, and swelling

• Digital pulse strength 

2) Manipulation -

• Reduced range of joint movement; pain

3) COMPARE LEFT WITH RIGHT

4) Foot examination -

• Hoof testers (and percussion) → pain

• Examine the solar area of the hoof for 

  • Obvious punctures 

  • Discoloration 

  • Abnormalities in the frog (discharge, abnormal horn)

• Remove superficial solar horn with hoof knife in painful areas for better inspection 

When would you NOT do a gait evaluation in your exam?  How would you perform an effective gait evaluation?

NOT IF A FRACTION IS SUSPECTED

Gait evaluation:

Straight line at walk & trot (in-hand)

Lunge (circle) at trot +/- canter in both directions

• Useful in identifying bilateral lameness

• Direction may affect severity

  • Loading: inside limb > outside limb

  • Usually more severe when lame limb inside

• Surface may affect severity

  • Hard: impact pain, e.g. laminitis, bruised sole

  • Soft: pain on maximum weight bearing, e.g. suspensory ligament injury

What is the purpose of doing a “flexion test”?

• To exacerbate mild lameness/provoke lameness, likely to be joint-related

• To localise the lesion causing the lameness

  • but can joints be flexed individually? (think of  reciprocal apparatus in hindlimb)

    • Possible difficulty; leads to non-specific diagnosis

Less lame limb first

What is the purpose of diagnostic local anesthesia?  When should you perform it, and when should you not?  

Is the localization of the source of pain by “numbing” specific regions of the limb

• Done either perineurally or intrasynovially (joint, tendon sheath, bursa)

Horse must be adequately and consistently lame

Do not perform if horse is acutely, severely lame, i.e. if there is a possibility of exacerbating the injury when limb is rendered pain free

Assessment:

• •5-10’; longer larger nerves & joints; ensure –ve before next block

• •Skin sensation perineural; improvement in lameness both

• •May not be 100% improvement; better for perineural vs intra-synovial? NB Consider multiple sources of pain

What are the 2 nerve blocks to target in the fetlock? Where can they be found? What is the general strategy when performing diagnostic local anesthesia?

1) Palmar digital nerve block - Found on the palmar aspect of the phalanges 

2) Abaxial sesamoid nerve block - Found on the palmar aspect of the metacarpo-interphalangeal joint, by the proximal sesamoids 

Strategy:

• Apply anesthetic in a DISTAL to PROXIMAL sequence

  • If you numb the palmar digital nerve block first and the horse is seeing no improvement, but it DOES improve when numbing the abaxial sesamoid nerve block, then you know the damage must be localized to the fetlock area