Lecture 13: Osteochondrosis and Subchondral Cystic Lesions Flashcards by Jen McGann

what lesions can be considered Developmental Orthopedic Disease (DOD)

OCD, angular limb deformities, SCB cysts, physitis, flexural deformities, cuboidal bone deformity, vertebral malformation

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What is Osteochondrosis

Failure of endochondral ossification in articular-epiphyseal complex (growth plate)

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What is Osteochondritis dissecans (OCD)

Clinical condition of synovitis due to disrupted joint surface due to DOD

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What are Subchondral bone cysts (SCB)

Invaginations into the bone just below the articular cartilage filled with debris and lined with fibrous tissue

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What is juvenile osteochodnral conditions

Specific to disturbance of chondral ossification of the AE complex

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Describe endochondral ossification

Starts as cartilage and as cartilage expands it ossifies from center to outward

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Where are the locations for endochondral ossification

Epiphysis, joint surface, metaphysical growth plate
Secondary ossification center s- carpal and tarsal bones, apophyses

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Failure of endochondral ossification results in __which in legs causes ___ and in neck causes ___

Osteochondrosis
Leg- lameness
Neck- neurological signs (wobblers)

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What is the zone of hypertrophy

Chondrocytes are fatter and expanding as cartilage and then ossify behind

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What is the blue arrow pointing at

zone of hypertrophy

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Lesions of Osteochondrosis are a result of persisting ___

Chondrocytes in the zone of hypertrophy— cartilage becomes thicker but doesn’t ossify

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What can cause chondrocytes to persist in zone of hypertrophy

Failure of vascular invasion
Failure of ossification

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what does this show

Failure of Osteochondrosis, cartilage becomes thicker, not strong

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What does this show

left: Osteochondrosis (not dissecans because hasn’t broken off yet)
Right: healing but still cartilage, bone has just formed around

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What does this show

OCD on trochlear ridge

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What does this show

Subchondral bone cyst

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What happens in the formation of Subchondral bone cyst

Articular defect allows synovial fluid pressure into Subchondral bone causing bone resorption

Enlarges until pressure equilibrates

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OCD vs SBC, which forms from weight bearing

SBC

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OCD vs SBC: which occurs from shear forces on gliding surfaces

OCD

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OCD vs SCB: which forms from compressive forces on loaded areas

SCB

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What is wrong here

Subchondral post cyst

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What are some possible factors of OC

Growth rate
Diet
Heritability
Trauma (normal trauma on defective cartilage and excessive trauma on healthy cartilage)
Exercise

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Excess ___in diet is strongly implicated in OC

Energy- excess phosphorous and calcium

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Deficiency in what trace mineral is linked to OC

Copper

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Excess of what mineral leads to OC

Zinc

What does a deficiency in cooper cause to result in OC

Failure of hydroxylysine cross link in collagen (loss -of “grass in adobe”) Lysyl oxidase requires Copper

What is the heritable cause for OC

Propensity for rapid growth (not a particular gene)

What are some clinical signs of OC

1. Joint effusion 2. Lameness 3. DJD

OC can be asymptomatic if fragment is stable, you may need to ___if for sale

Treat the radiographs

What is the synovial fluid analysis like for OC

Normal

__% bilateral for OC

50%

What is wrong here

OCD at distal intermediate ridge of tibia

What does the treatment of OCD depend on

1. Joint involved- accessibility, expected success 2. Age of horse- give time for <1

What is the surgical treatment for OCD

Arthroscopy- remove fragment and loose cartilage, debridement parent bone to healthy bone with firm margins so fibrocartilage can fill in

How do you medically manage OC

1. Relieve synovitis, prevent DJD- give Adequan IM and hyaluronic Acid IA 2. Steroids (avoid in foals)

What is wrong here

SBC on medial femoral condyle

What are some signs for SBC

1. Joint inflammation 2. Effusion (likely fetlock only) 3. Lameness

What is the conservation approach to OC for young horses

1. Confine 2. Minimize synovitis with IA hyalartin, adequan, cosequin 3. Balance diet 4. Minimize weight gain

What is the medical therapy for SBC

1. Triamcinolone injection of cyst/lining

What are some surgical treatments for SBC

1. Enucleate the cavity- remove fibrous lining and sclerotic bony margin 2. Transcondylar bone screw 3. Debridement and grafting

What does this show

Transconylar bone screw treating SBC

What is chondrocytes grafting

Put chondrocytes into joint with fibrin glue

Coffin joint primarily gets OCD or SBC

SBC

What does the lameness exam look like for SBC

1. No swelling or effusion 2. Digital flexion positive

What is wrong

SBC in coffin bone/ p3

What is the only site in the coffin joint where you can operate for OCD arthroscopically

Extensor process

What wrong

OCD of extensor process

How does the lameness exam look for SBC in pastern joint

Positive flexion IA block test- abaxial with ring

What is wrong here

SBC at pastern joint

What does lameness exam look like for fetlock with OCD

1. Lameness variable because multiple joints 2. Fetlock effusion 3. IA block

What is the most common fetlock OCD site- name and number

Sagittal- #1

What is wrong here

Sagittal ridge OCD- fetlock

what wrong here

SBC in fetlock

What is wrong here

SBC in radial carpal bone

Where are SBC common in elbow joint

Medial proximal radial condyle

T or F: elbow joint SCB are arthroscopically accessible

False, subarticular approach

What is wrong here

SBC in elbow/ humerus

Where is OCD generally in elbow

Distal numeral condyle

Is shoulder joint/ numeral OCD common

Yes

How do you dx shoulder joint/ numeral OCD

1. IA blocks 2. Scintigraphy 3. Quality rads may require Anesthesia

What is wrong here

Shoulder/humeral OCD

Which is more common OCD or SBC on tibiotarsal joint

OCD

What does lameness show in tibiotarsal joint OCD

1. Effusion- obvious bog spavin 2. Minimal lameness- may require flexion

What is wrong here and likely cause

Tibiotarsal joint effusion/ bog spavin- OCD

What are the tarsal sites of predilection of OCD

1. Distal intermediate ridge of tibia 2. Medial malleolus of tibia 3. Distal lateral trochlear ridge of tibial tarsal bone

What wrong here

OCD of distal intermediate ridge of tibia

What is wrong here

Lateral trochlear ridge OCD

What wrong here

Medial malleolar OCD

SBC or OCD more common in femorotibial joints

SBC (very common)

Where is SBC usually located in femorotibial joints

Medial femorotibial joint

What is wrong here

Medial femoral joint SBC

OCD or SBC: more common in femoropatellar joints

OCD

What is wrong here and likely cause

Femoropatellar joint effusion- OCD

What is wrong here

lateral trochlear ridge OCD

What wrong here

lateral trochlear ridge OCD

What does a lameness exam look like for coxofemoral joint for SBC

Positive flexion IA anesthesia

Where are coxofemoral joint SBC located

Femoral head