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  Discussion on Joint Fusion to relieve subchondral bone cyst?
Author Message
New Member:
smakhoul

Posted on Saturday, Jan 17, 2009 - 1:36 pm:

My 11 yr old WB has clean hock xrays, but has consistent mild lameness behind. Blocks showed pain coming from hocks. MRI showed large, bilateral subchondral lysic lesions involving the third tarsal bone, without any other arthritic changes. Since this low motion joint could be fused I am wondering if the subchondral bone cyst pain would be relieved if the joint was fused or if pain associated with lysic lesions would persist even if joint was fused
Member:
dres

Posted on Sunday, Jan 18, 2009 - 11:00 am:

Has hock injections been suggested? Sometimes it just takes one to give the relief a horse might need..

On the first day God created horses, on the second day he painted them with spots..
New Member:
smakhoul

Posted on Sunday, Jan 18, 2009 - 4:52 pm:

Injections don't seem to touch it, and fusion was suggested, but no guarantee that the cystic lesion would not still be painful (due I think to pressure within the cyst, subchondral pain, I don't exactly understand the pathology)
Moderator:
DrO

Posted on Monday, Jan 19, 2009 - 7:26 am:

Welcome altman,
I cannot find a study on this question and don't have any personal experience with such a case so have to give you an opinion. OC lesions do have pain innervation deep to the surface and it is hard to know if they will be activated if the joint is fused. It does seem fusion should provide some protection since the joint surface will no longer be transferring force across the elastic surface overlying the lesion. Instead force will travel through rigid columns of bone that form during the arthrodesis. Success may depend on how this new bone forms. A large cystic lesion may be more likely to continue to be painful than a smaller defect. On the other hand you describe a mildly painful lesion I think that improves the prognosis.

I also think the technique will effect the outcome. If you could use surgical arthrodesis and the OC lesion could be drilled out as part of the procedure, I think the prognosis would improve considerably. If this is not possible using a chemical system that might penetrate the lesion and kill the nerves would be the second best choice. That the diagnostic anesthesia penetrated the lesion suggest this is possible.

If I understand your post correctly you will need two successful surgeries. So even if we hypothesize a "fair to good" prognosis for each leg, the prognosis for an athletic outcome, defined as two successful surgeries, would fall to "guarded to fair".
DrO
New Member:
smakhoul

Posted on Monday, Jan 19, 2009 - 1:14 pm:

Dr. O, thanks for response. I really wish there were some other case studies to compare, is this sort of lesion rare or is the location of the lesion rare? I have also been looking at the drug Tildren, which I understand builds bone. Would this "fill in" the cysts?
As I understand the lesions, they are basically an opening in the cartiledge that has created a cavity into the subchondral bone.
Is the pain coming from the defect in the cartiledge or within the cavity? Lameness is mild at first but does increase with intensity of work.
Moderator:
DrO

Posted on Wednesday, Jan 21, 2009 - 9:38 am:

I would have to say MRI diagnosed OC lesions of the hock are pretty rare. Where on the third tarsal bone did this occur? Would it be possible to post the MRI images? For a thorough explanation of how OC lesions occur see, Diseases of Horses » Lameness » Joint, Bone, Ligament Diseases » OCD and DOD in Horses. I am not sure about your question about pain and exactly where it localizes to but in general I think that the poorly perfused or necrotic tissue sets up an inflammatory response which activates the pain receptors first locally around the lesion and later throughout the whole joint. Hmmm...an orthopod may laugh at this idea.

I cannot find any studies that investigate Tildren (tiluDrOnate) as a "cure" for OCD lesions. It is important to note that Tildren and other bisphosphonates do not increase bone formation. Instead the work primarily by inhibiting bone break down. As such this treatment will have wide spread effects on the skeletal system and complications have been reported with its use in humans.
DrO
New Member:
smakhoul

Posted on Friday, Jan 23, 2009 - 8:16 am:

Dr. O, the cysts, per report, are "consistent with subchondral bone lysis/cyst formation in the distal central tarsal bone". There is active inflammation, with fluid within the cyst and also within the distal intertarsal joint.
The vet also has no prior case studies to compare to, but does feel this sort of lesion probably exists and goes undiagnosed without an MRI. I believe the course of action will be to drill/drain the cysts and fuse the joint.
Generally, what kind of recuperation experience should I expect assuming all goes well with the surgery?
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