Lecture 10: clinical correlates #3 Lameness and nerve blocks (Wronski) Flashcards
palpable structures in the thoracic limb
interosseous (suspensory) ligament flexor tendons palmar digital vein palmar digital artery palmar digital nerves
- going from dorsal to palmar on the thoracic limb just think V-A-N. the palmar vein is most dorsal, followed by the artery and finally the nerve.
in what general direction do you conduct nerve blocks
distal to proximal
palmar digital nerve block: injection site
bilateral inections midway between the fetlock and the coronet, dorsal to the flexor tendons and distal to the ligament of the ergot
palmar digital nerve block: areas desensitized
palmar portions of the hoof, digital cushion, palmar portions of the coffin and pastern joints, distal part of the deep flexor tendon navicular bursa
when nerves are desensitized by the palmar digital nerve block?
medial and lateral palmar digital nerves
when is the palmar digital nerve block most commonly done?
to identify the source of lameness exhibiting signs of caudal heel syndrome
palmar digital and dorsal branch nerve blocks: injection site
proximal to the ligament of the ergot at a point 1/3 of the distance from the fetlock to the coronet. the needle is then directed dorsally and anesthetic deposited at the extensor slip of the suspensory ligament
a more abaxial approach can also be blocked more proximally by a singl anaesthetic injection at the level of the proximal seamoid bones
areas densenstized for a palmar digital and dorsal branch nerve blocks
entire hoof, coffin joint, and palmar aspect of the pastern joint
the abaxial block will desensitize the entire pastern joint and the palmar pouch of the fetlock joint
nerves desensitized in a palmar digital and dorsal branch nerve block
dorsal branch of palmar nerve
distal metacarpal (low volar/low palmar) block: injection site
blocked in the groove between the suspensory ligament and flexor tendons at the level of the palpable button of hte small metacarpal (splint) bones.
the palmar metacarpal nerves are then blocked immediately distal tot he buttons of the splint bones.
the needle is then directed dorsally to ring block from the buttons of the splint bones to the extensor tendons
nerves desensitized in a distal metacarapal (low volar/low palmar) block
the ring block desensitizes the dorsal branch of the ulnar nerve
medial cutaneous antebrachial nerve
medial/lateral palmar nerves
palmar metacarpal nerves
areas desensitized in a distal metacarpal (low volar/low palmar block)
entire limb distal to splint bones, ring block (not always used)
proximal metacarpal (high volar/high palmar) block: injection site
1: in the groove between the suspensory ligament and the flexor tendons, slightly distal to the carpus.
2: same level axial to splint bones
3: ring block (SQ) from abaxial sides of splint bones dorsally to extensor tendons
proximal metacarpal (high volar/high palmar) block: areas desensitized
entire limb distal to the carpus
superficial/deep flexor tendons
digital tendon sheath
(carpometacarpal and midcarpal joint sacs can get anesthesized if there is greater than expected diffusion)
proximal metacarpal (high volar/high palmar) block: nerves desensitized
palmar nerves
dorsal branch of ulnar
medial cutaneous antebrachii
coffin joint: needle insertion
1 cm proximal to the coronet at the lateral border of the common digital extensor (1.5 cm lateral to dorsal midline of limb). needle needs to be directed distally, caudally and medially
fetlock joint
proximal palmar pouch between the suspensory ligament and the 3rd metacarpal bone slightly proximal to the proximal sesamoids bones.
OR
in the dorsal aspect of the fetlock joint slightly medial or lateral to the common digital extensor tendon
carpal joint - for the midcarpal and carpo-metacarpal sacs
with carpus flexed, insert into distal dimples med/lat to tendon of extensor carpii radialis
these two joints communicate so anesthetic will diffuse through both joint sacs
carpal joint - for the radiocarpal joint sac
carpus flexed - more proximal dimple (3 cm proximal to distal dimples)
navicular bursa
insert needle in the digital fossa at the palmar/plantar midline and direct needle dorsally parallel to the sole. it passes through the deep digital flexor tendon and hits the navicular bone. withdrawal slightly to enter bursa between distal sesamoid and deep digital flexor tendon.
tibiotarsal joint sac: injection site
insert slightly medial to tendons of tibialis cranialis and peroneus tertius, at level of medial malleolus of tibia
tibiotarsal joint sac: areas desensitized
between tibia and talus - swelling here is called bog spavin
medial (cunean) tendon of tibialis cranialis is sometimes rsected to relieve pressure from chronic bog spavin
tibiotarsal joint sac: what to avoid
the cranial branch of medial sphaneous vein - its very superficial
proximal intertarsal joint sac: injection site
since it communicates with the tibiotarsal joint sac there is no injection necessary (because you will have done the tibiotarsal injection first and it will diffuse into proximal intertarsal)
proximal intertarsal joint sac: area desensitized
between talus and calcaneus, proximally and central and 4th tarsal bones distally
distal intertarsal joint sac: injection site
inserted at the T-shaped junction of central, 3rd and fused 1st and 2nd tarsal bones on medial aspect of hock, dorsal to cunean tendon.
always on medial side, so you dont puncture the cranial tibial artery
distal intertarsal joint sac: area desensitized
between central tarsal, T3 and fused T1 and T2
tarsometatarsal joint sac: injection site
on lateroplantar aspect of hock between T4 and metacarpal 4 in a depression slightly proximal to head of metacarpal 4
tarsometatarsal joint sac: area desnsitized
between tarsal bones 1, 2, 3, 4 proximally and metacarpal bones distally
