Joint Space Narrowing & Hip Resurfacing By Dr. Vijay Bose
Dr. Vijay Bose
Thanks. Arthritis in any joint starts off with inflammation of the cartilage covering of the articulating surfaces. This can usually be managed with drugs. Then there is cartilage loss which is seen in x-rays as joint space narrowing. This loss of cartilage triggers off a series of changes in the joint by which bone spurs form and usually the bone ends become larger leading finally to end stage arthritis. (primary or secondary osteoarthitis). When any tissue in the body becomes bigger (hypertrophy), it has to be associated with increased blood supply. Even if a tumour grows big rapidly, it implies that it is highly vascular.
Similarly these arthritic changes trigger changes in the blood supply which is not only increased but also becomes intra-osseus or through bone instead of being outside bone (extraosseus). This has to occur because the soft tissues outside the bone are stripped by the bone spurs (osteophytes). This situation obviously becomes very conducive to resurfacing. The damage to the blood supply etc is not very significant by the approach etc., in resurfacing as the blood supply increasingly comes more from inside bone rather than outside.
I am skeptical to do resurfacing in a joint which does not show these changes because the blood supply is outside bone which could be damaged during the resurfacing and the increased blood supply situation has not yet occurred. There could also be a phase in early arthritis where the blood supply could be less to trigger these changes which eventually becomes favorable for resurfacing.
The other reason is that of course when the joint space is still maintained one has to think whether other the pain is originating from somewhere else and not the hip per se.
I hope I have made this non-technical for everyone to understand.
With best regards,
Dr. Edwin Su
April 2, 2009
This is an interesting point that I think applies more to osteonecrosis, but is certainly still of concern with osteoarthritis. Generally, I would guess that by the time an arthritic hip causes the kind of pain that would lead us to suggest surgery, that these changes that Dr. Bose has so nicely described, have
already taken place.
To require someone to demonstrate x-rays changes with full joint space narrowing, I believe, would subject a lot of people to unnecessary pain. There are now more sensitive imaging modalities such as MRI that can detect the full thickness loss of cartilage. Of course, Vijay is right that if the xrays don't correlate well with the amount of pain that someone is in, that one must have a suspicion for pain arising elsewhere.
In these cases in which the arthritic changes may not be as obvious, I think that the application of the neck-capsule preserving technique is critical to preserve the blood supply around the neck.