Approach to Equine Regional and Synovial Anaesthesia Flashcards
Commonly performed nerve and joint blocks in equine practice?
Nerve:
- palmar digital.
- abaxial sesamoid.
- low 4 point.
Joint:
- distal inter phalangeal joint (DIP) (FL).
- tarsometatarsal joint (TMT) (HL).
Palmar digital nerve block.
Palpable from fetlock to pastern region.
Run with PD artery and vein.
Aim to block under the ungual cartilage at the most distal point.
1-2ml mepivacaine.
23-25g 5/8” needle.
Limb up or down.
Insert needle palmar to medial NVB axial to collateral cartilage, aiming distally.
Repeat on lateral aspect.
What area should the palmar digital nerve block desensitise?
Some of DIP and the laminae.
Effectively most of the hoof.
Maybe not the laminae on the dorsal aspect.
Maybe not extensor process.
Maybe not all of DIP joint.
Can test dermatome on heel to check desensitised.
Abaxial sesamoid nerve block.
1-2ml mepivacaine.
23-25G 5/8” needle (or butterfly cannula).
Palmar/plantar digital nerve block.
Limb up or down.
Palpate digital neurovascular bundle on palmarolateral and palmaromedial fetlock over annular ligament.
Insert needle palmar to medial NVB aiming distally.
Repeat on lateral aspect.
What area should an abaxial sesamoid nerve block desensitise?
Most of P1.
All of P2.
All of P3.
All of navicular bone.
All of laminae.
Some of fetlock joint.
DIP joint block.
Dorsal approach utilises the largest pouch.
Other approaches useful when dorsal area injured and need to assess joint involvement.
- if not sure, just refer.
Dorsal approach to DIP.
Full sterile prep.
Sterile gloves, needle, syringe and bottle of sterile LA.
Limb loaded.
0.5-1cm above hoof wall.
Aim vertically down or slightly caudodistal.
Approximately 2-3cm deep.
Synovial fluid usually appears rapidly.
Check viscosity of joint fluid.
Interpretation of DIP joint block.
Large volumes and long duration may also desensitise the navicular bursa palmar digital nerves, solar surface by local diffusion.
If block abolishes lameness with a low volume (5ml) and swiftly (w/in 5mins), then source of lameness likely DIP joint pain, if not consider options. Often give longer for diffusion afterwards too.
Joints of the hock.
Communications between joints in the hock.
Tibiotarsal = tarsocrural.
Proximal intertarsal = talocalcaneocentral.
Distal intertarsal = centrodistal.
Tarsometatarsal.
Comms:
- DIT-TMT = 25%.
- PIT-DIT-TMT = 10%.
- PIT-TC = all.
TMT joint block.
Horse weight bearing.
Lateral approach.
Palpate top of lateral splint (MTIV), divot just above is site for needle entry.
21G 1.5” needle.
2ml intraepicaine.
Aiming from caudolateral slightly distal to perpendicular.
Depth 1-2cm.
Synovial fluid usually spontaneously present.
- if not, try to inject, if under high pressure, you are NOT intra-articular so need to re-orientate.
0 if present, check viscosity.
Interpretation and confounding information of TMT joint block.
TMT joint block may also desensitise:
- deep branch of the lateral plantar nerve which supplies the plantar metatarsal nerves.
- (metatarsal nerves).
- many people will perform cross over blocks with deep branch of suspensory ligament to ensure interpretation is correct.
