Equine Fetlock and Metacarpus/tarsus Flashcards
what is the fetlock made up of? (bones)
- distal MC/MT III
- proximal first phalanx
- proximal sesamoids
describe the synovial cavity/joint capsule of the fetlock
a single synovial space extending approx 5-7cm proximal to joint surface just below joint surface on the palmar surface
dorsally, extends from just above sagittal ridge to just below the joint surface;
dorsally, a bilobed synovial pad is located along the dorsal proximal articular border
describe the soft tissues of the fetlock
- med and lat collateral ligaments
- med and lat sesamoidean ligaments
- SDFT and DDFT
- suspensory branches: number 1 supporting structure of fetlock joint
- distal sesamoidean ligaments: continuation of suspensory = hella important
- intersesamoidean ligament
describe blood supply of fetlock and innervation
- medial and lateral palmar/plantar
- med and lat palm/plant MC/MT
same but for nerves
what are the 3 categories associated with traumatic/degenerative causes of disease to the fetlock
- acute or repetitive overload injuries
-capsulitis/synovitis
-chronic proliferative synovitis
-subchondral bone disease
-sesamoiditis
-OA
-all build on each other, start with top and if dont treat will keep moving through list - articular fragmentation: traumatic and developmental
-dorsal
-palmar/plantar fragmentation
-proximal sesamoidean fragmentation
-sagittal ridge fragmentation (OCD/developmental) - articular fractures
-condylar fractures
-proximal phalanx fractures
-proximal sesamoid fractures: unfit/unconditioned horse = soft tissues weak and bone is strong, but as train and get stronger, ST strong and bone weak
describe capsulitis/synovitis; include diagnosis and treatment
- common, esp in younger horses
- heat, effusion, positive to flexion
- subtle lameness that may subside once warmed up
- onset with increased workload
- untreated = chronic thickening, effusion, reduced ROM, and poor performance
diagnosis: based on clinical exam; palpate effusion in fetlock, rads not super helpful would just see soft tissue thickening in front and back of joint but helpful to xray anyway just to check for other injuries
-ultrasound: can see how thick joint capsule is
treatment: REST is most important! but if can’t rest or take off work, meds
1. rest and training adjustment
2. non-steroidal medication
3. topical anti-inflammatories: diclofenac sodium (surpass)
4. intra-articular therapy:
-hyaluronan
-HA + steroids
-biologics
5. oral or injectable therapy:
-glucosamines, chondroitin sulfates
-polysulfated GAGs
describe chronic proliferative synovitis; including clinical signs
- villonodular disease
- repetitive trauma to dorsal aspect of fetlock joint through hyperextension leads to inflammation and thickening of the normal synovial pad and eventually chronic fibrosis of pad
clinical signs:
1. heat, effusion, positive to distal limb flexion
2. focal thickening of dorsal aspect to joint distal to capsular attachments
describe diagnosis and treatment of chronic proliferative synovitis
diagnosis:
1. clinical exam
2 low palmar nerve block or IA anesthesia
3. radiographs:
-soft tissue thickening over dorsal joint
-bone resorption on dorsal aspect of distal MCIII proximal sagittal ridge
4. contrast arthrogram: filling defect
5. US: marked thickening of pad overlying dorsal aspect of MCIII
treatment:
1. rest and reduced training
2. NAIDs: often not as effective
3. aggressive IA therapy: HA, HA + steroids, biologics, repeat therapy
4. failed medical mgmt = arthroscopic excision of pad
5. commonly concurrent articular disease like OA
describe subchondral bone injury; include 2 common sites of injury
- palmar osteochondral disease (PODS)
- common in any horse that works hard for a living; more in front limbs than hindlimbs
- seen on front medial condyle or hind lateral condyle
- variable degrees of lameness based on stage of disease; may not see typical signs of fetlock disease
- very important to recognize and dx early before irreversible cartilage damage
common sites of injury:
1. distal palmar MCIII: possible focal overload injury at point of impact from base of prox sesamoids during maximal weight bearing
2. proximal phalanx under central articular surfaces
describe diagnosis of subchondral bone injury (7)
- clinical exam
- low palmar nerve block
- medial and lateral palmar metacarpal nerve block alone can help differentiate from other causes
- variable response to IA anesthesia; intact cartilage may prevent complete response
- radiographs: signs don’t always mean disease!
-linear to crescent shaped lucency in palmar third of the condyles
-nontraditional views often beneficial: flexed horizontal beam dorsal palmar projection highlights palmar articulation; DLPMO and DMPLO highlight palmar articulation - nuclear scintigraphy: high sensitive, low specific; detects early bone activity
- MRI: high sensitive and high specific! gold standard!
-defines location and type of bone lesions
describe treatment and prognosis of subchondral bone injury
treatment:
1. REST 60-90 days (not stall rest, just not working)
2. NSAIDs
3. IA therapy in advanced cases
4. podiatry: correct an imbalance if present
prognosis: depends on the degree of structural damage and the presence of cartilage damage
describe articular fragmentation-dorsal proximal P1 fragments; include diagnosis and treatment
- common; more in frontlimb than hindlimb; medial (95%) >lateral
- see acute swelling and heat and subtle short duration lameness, positive fetlock flexion, and poor performance (right when fracture chips off)
- +/- incidental finding in yearlings and non-racehorses in prepurchase exams
diagnosis:
1. clinical exam
2. low palmar nerve block
3. IA anesthesia: once nerve block wears off, if lameness resolves with this is more common that fragment = source of/contributing to lameness and may benefit from removal!!
4. radiographs: need a good straight rad or might miss small fragment!
-best seen on straight lateral and DLPMO
-fragments can be: sharply marginated or rounded, varying sizes, single or multiple, varying amounts of displacement
treatment: as conservative as you can, not ALL fragments need to come out, likely not the source of lameness if the horse is lame; if going to spend money to remove, want to make sure good chances of having a sound horse at the end of that treatment
1. if small fragments, low level work, or economics involved, can try to manage with IA therapy BUT
2. working a horse with unstable chip fracture can lead to more rapid irreversible degenerative changes in the fetlock like extensive score lines, thin cartilage, or more advanced OA
3. surgical treatment: arthroscopy, 6-8 weeks rehab; give excellent prognosis if no other degenerative changes in the joint
describe articular fragmentation- proximal palmar/plantar P1 fragments- Type I; include diagnosis and treatment
- osteochondrosis vs trauma
-common in young, untrained animals, due to avulsion of immature bone fragments attached to short sesamoidean ligament, still classified as fragments! not OCD lesions - much more common in hindlimb than frontlimb, medial > lateral
- variable lameness, often found in sound horses; if horse lame will see effusive joints
diagnosis:
1. clinical exam
2. low palmar nerve block
3. IA anesthesia
4. radiographs:
-best seen on oblique DLPMO, DMPLO, and flexed lateral
-fragments can be: sharply marginated or rounded, varying size and shape, single or multiple, with varying amounts of displacement
treatment: conservative
1. if low level work, try to manage with NSAIDs, oral joint supplements, injectables, IA therapy (corticosteroids, corticosteroids + HA, biologics (IRAP, pro-stride)
2. arthroscopy is controversial!
-if upper level jumper or racehorse more likely to recommend to prevent possible future lameness BUT
-may lead to irreversible degenerative changes in the fetlock (score lines, cartilage thinning)
-fragments are much more challenging to take out
describe articular fragmentation- proximal palmar/plantar P1 fragments- Type II
- extra-articular, large, abaxial and extend 2-3cm
- less common than Type I
- uncommon to see lameness so removal not receommended
describe the bony structures of MC/MT
- MC/MT III
- MC/T II and IV
there is substantial articulation and weight transference through the carpus and MC II and IV, and through the tarsus and MT II, but minimal articulation between the tarsus and MC IV