Eq2 - mid 1 - OCD

Question 1

OC/OCD

• Pathophysiology

Answer 1

• disturbance of cellular differentiation in the growing cartilage
• damage to vessels in cartilage canals –> improper vascular supply of the young cartilages
• Loading –> mechanical insult –> fragmentation on weak points
• Biomechanic forces: cartilage flaps, free joint mice
• result: Resporption, OR incorporation in joint capsule, OR stays in joint –> ossification, OCD fragments
• Riss in joint cartilage –> resorption –> SBC

Question 2

OC/OCD

• Aetiology

Answer 2

Genetic predisposition:

• eg. never happens in pony
• Selection if heritability, should be > 0,24
• X-rays in standardbred foals: 0.25 - 0.52
• X-ray in warmblood foals: KWPN, Holstein

Environmental influences:

• nutrition: imbalnce in feeding
• biomechnaical forces, trauma
• endocrine factors

Question 3

OC/OCD - growth rate

Answer 3

• Large, heavy foals are more likely to have OCD
• Carbohydrates in easily digestible form:
• hyperinsulineamia –> rapid removal of T3, T4 from the circulation
• T3, T4 is responsible for chondrocyte differentiation + invasion of blood vessels
• Too much carbohydrate intake also leads to decreased Cu and increased Zn.
• Cu is coenzyme for lysyl oxidase which is essential for collagen cross-links formation

Question 4

OC/OCD - healing capacity

Answer 4

• Endochondral ossification is a process in which the delicate vascularization in the horse easily leads to irregulatities based in chondronecrosis
• –> genetic susceptibility and environmental actors determine the size and severity of the irregularities
• –> once a lesion forms, a repair process will ensue immediately, facilitated by the high natural metabolic acitivy of juvenile articular cartilage
• –> the natural decline in metabolic activity makes repair progressively difficult. The momement when “the window closes” is not identical for all joints (the stifle lags behind)
• –> lesions that are not repaired may develop into clinically important articular defects

Question 5

OC/OCD - predilection sites

Answer 5

1. neck facet joints, cervical region
2. shoulder - caudal part of humerus head - cavitas glenoidalis + caudodistal ridge of scapula
3. fetlock - dorsal MCIII/MTIII crista sagitalis
4. femoropateller joint - lateral femoral throclea
5. hock - DIRT /dist tibia cran. intermed. - lateral talus trochlea distal aspect - medial malleolus

Question 6

OC/OCD - clinical forms

Answer 6

• flattening of the joint surface
• cartilage flap without rad. changes
• cartilage flaps free in joint
• cartilage with subchondral bone changes
• OCD fragments free in joint

Question 7

OC/OCD - diagnosis

Answer 7

• Age: 4months - 2 years
• joint ffusion
• lameness +/- depending on location
• synovial fluid: “normal”
• Intra articular anasthesia –> improvement
• DJD: early in shoulder, PIPJ rare in stifle and hock
• Bilateral: Stifle (50-69%), Hock (44-56%), fetlock (front and behind) –> so always take x-ray of both sides - check always the contralateral joint

Question 8

OC/OCD - treatment

Answer 8

• conservative treatment: box rest, controlled exercise, decrease carbo intake –> 37-60% success rate –> therefore not a good option
• arthroscopy: best choice

Question 9

OC/OCD - surgical treatment

Answer 9

Arthroscopy = your treatment of choice in most cases

• less soft tissue trauma
• shorter reconvalascence
• less complications
• better cosmetic result
• better function
• better view in joint
• diagnostic
• better prognosis

Question 10

Subchondral bone cysts

Answer 10

There are different ways how the cyst can develop

• juvenile form similar to OC
• tear in the weight bearing cartilage inside lining: fibrous tissue, fibrocartilage, necrotic bone

Sclerotic border around the cyst “cloaca”

• communication with the joint

Question 11

Subchondral bone cysts - diagnosis

Answer 11

• intraarticular block is not always positive
• X-rays
• Scintigraphy

Question 12

Subchondral bone cysts - predilection sites

Answer 12

• medial femoral condyle
• distal MCIII/MTIII (med or lat condylus or crista sagitalis)
• medial proximal radius epiphysis
• distal phalanx
• scapula cavum glenoidale

Question 13

Subchondral bone cysts - clinical signs

Answer 13

• lame after work
• more frequent: 6M - 2Y
• but: you will find it also in older horses
• lameness intermittent if not acute
• lameness better with rest
• recidive if starts training again
• sometimes acute lame: Medial femur condylus, Distal MCIII
• joint effusion not always present

Question 14

Subchondral bone cysts - treatment

Answer 14

Different surgical treatment regimes:

• steroid inj. into the cyst
• extra-aticular approach (drilling) and Parathormon hydrogen (PTH)
• enucleation of the cyst inside lining
• defect filled out with TGF-1 + Ca activated thrombin + fibrinogen
• position screw through the cyst
• bone morphogenic protein-2 into the debrided cyst
• autologous osteochondral transplantation (Mosaicplasty) –> donor site: med. femoral trochlea

Question 15

Subchondral bone cysts - prognosis

Answer 15

• Medial femur condylus: ca 67% with steroid inj.
• MCIII/MTIII: 12/15 - ok
• Extra-articular fetlock: in 4/5 horses: gut
• Medial proximal radius: success just with surgery
• PIPJ: in DJD: Arthrodesis