Osteochondrosis and Subchondral Bone Cyst

Question 1

What developmental process goes wrong to cause osteochondrosis dissecans in horses?

Answer 1

Endochondral Ossification (Bone formation during fetal development)

Question 2

Why is surgical removal of an OCD fragment an important consideration for horses?

Answer 2

If you do not remove the fragment it will continue to rub and cause issues like arthritis

Question 3

Where is one of the most common location of OCD?

Answer 3

In a joint

Most common joint:
Distal intermedial ridge of the tibia

Question 4

What are some Developmental Orthopedic Diseases (DOD)?

Answer 4

Osteochondrosis, Subchondral bone cyst, flexural deformities, physitis, cuboidal bone deformity, cervical compressive myelopathy

Question 5

What causes Osteochondrosis?

Answer 5

-Failure of endochondral ossification
-Chondrocytes persist in the zone of hypertrophy (no vascular invasion so it does not finish)
-Defect in the chondrocyte, extracellular matrix, vasculature, exacerbated by trauma)

Question 6

What are the stages of OC?

Answer 6

-Subchondral bone
-Osteochondrosis latens - focal cartilage necrosis
-Osteochondrosis manifesta - cartilage where bone should be, weak spot
-Osteochondrosis dissecans - trauma causing the cartilage to shear off

Question 7

What is a subchondral bone cyst (SBC)?

Answer 7

Trauma on retained cartilage on weight bearing surface
-Causes cartilage lesion
-joint fluid defect increases pressure and causes inflammation and bone resorption

Question 8

Can a subchondral bone cyst lead to OC?

Answer 8

Yes, if pressure or damage occurs to that area

Question 9

What are factors that can cause pathogenesis for ODO?

Answer 9

-Growth rate - fast growing and large
-Nutrition - Excess energy (P or Ca or Zn) excess Cu
-Heritability - stallion, multifactorial
-Trauma - normal stress on abnormal cartilage or vice versus
-exercise

Question 10

Although OCD occurs in young patients it can become aparent in…

Answer 10

aged patients

Question 11

Will you always be able to see an OCD fragment on radiographs?

Answer 11

No, if there is no cartilage in it, you will not see it

Question 12

What are clinical signs of OCD?

Answer 12

Joint effusion, lameness (worse on flexion), synovial fluid cytologic changes

Question 13

What are some diagnostics used to ID OCD?

Answer 13

Radiographs - effusion, prepurchase
Ultrasound, Contrast, CT, MRT
-Degenerative joint disease - varies by location, severity and if detached)

Question 14

What are clinical signs of Subchondral bone cysts?

Answer 14

Effusion - fetlock, rare stifle, never in elbow
Lameness - training, OA

Question 15

Where do SBC like to be?

Answer 15

In the middle of a bone
Stifle - medial trochlear ridge

Question 16

Where does OCD like to be versus a subchondral cyst?

Answer 16

OCD: Gliding Joint
Cyst: Weight Baring Joint

Question 17

How do you treat OCD and SBC?

Answer 17

Depen on joint involved and age of horse
-Young may heal with time but need to protect area
-Arthroscopy if making them lame

OCD: no OA then good prognosis, remove lose fragments, may tack cartilage

SBC: Asymptomatic, lame if communicate with joint, arthroscopic, 6-12month for final outcome

Question 18

When should you go to surgery?

Answer 18

Clinical signs, occupation (race), potential of OA, Age (foal or weanling heal without surgery- up to 18 months)

Question 19

What is the goal of medical therapy with this disease?

Answer 19

-Reduce trauma by exercise restriction
-Relieve synovitis, prevent DJD while healing (Adequan, Legend, Hyvisc, steroid)

Question 20

What are the goals of arthroscopy?

Answer 20

Full exploratory of the joint, joint lavage, remove lose and free OC fragments, debride loose and diseased cartilage, no harm to normal or attached cartilage

Question 21

What occurs post operative for OCD?

Answer 21

-Debride OCD bed heals with fibrocartilage
-Has different mechanical properties or resilience but better than loose bone
-Rehabilitation depend on severity of lesion
-Stall rest gradual return to exercise 60 days stall rest with no turn out

Question 22

What are other surgical treatments for OA and SBC?

Answer 22

OCD: dart reattach chondral flap
SBC: inject cyst with steroid, screw across it, curette the syst, fill with bone substitute

Question 23

What is SBC post op healing like?

Answer 23

Can be more painful right after - no good pain meds for bone, need longer rehabilitation

Question 24

What does post op care after surgery look like?

Answer 24

Suture removal critical - send back to surgeon in 14 days - sterile gloves, scissors, prep skin, remove all and NO loop left behind, sterile bandage 2 days
-owner must call if increased swelling or discahrge

Question 25

What is the prognosis?

Answer 25

OA decreases prognosis
Hock: DIRT = excellent
Stifle: LTR of Femur = Fair to good
Stifle: MRF Cyst = fair
Shoulder: OCD = Guarded