Dr. Bose – I have bone cysts, can I have a hip resurfacing?
The presence of a cysts by itself is not a contraindication for resurfacing. It does not preclude resurfacing automatically. One must keep in mind that cyst formation is a natural occurrence in osteoarthritis and is very common though the extent, quantity & location may vary.
Cysts are of course much more common and invariably present in AVN. The assessment of certain technical factors would the real issue. This is based on the amount of residual bone after head preparation. Some resurfacing prosthesis are thicker at the top and tend to replace more bone in the head of the femur than other prosthesis. This is a great advantage in managing cysts as at the end of head preparation one is left with nearly 100% head support in a majority of cases. The cysts get reamed away in bone that would have been removed anyway. The BHR is a good example of a prosthesis of this type.
The technical criteria which we we have been using in our centre ( ARCH) for the last 7 yrs without any problems has been termed as ‘mid – path recommendations’ because we chose 50% as an arbitrary value when we started.
1.The criteria are an intact – head neck junction across the entire circumference to a height of 50% of profile cut (the actual height would vary depending on the size used)
2. Residual bone above the intack head neck junction must be at least 50%
Dr . Sugano from Japan has done an experiment where he removed 50% of head of fresh cadaveric bones and implanted a cemented resurfacing on them . He also implanted a cemented resurfacing on an equal amt of fresh cadaveric bones with an intact head. He compared the mechanical strength of both in the lab and found the mech. strength to be equal in both groups.
The surgeon has to see the x-rays and CT scan before he can comment on a particular case. I have tackled successfully some hips with significant cyst formation.
Bone spurs on femoral neck are not a contraindication for resurfacing–but obviously each x-ray would have to be looked at individually–almost all arthritis is associated with spurs on neck by the way.
Among the criteria Dr. Vail considers (for hip resurfacing) are age (under 60 is ideal), bone density and the shape of a person’s hip. He also looks for cysts in the ball of the hip, which signal the bone might be too weak for capping.
Its use (BHR) is also contraindicated in patients who are severely overweight and those whose bones are not strong/healthy enough due to osteoporosis or a family history of severe bone loss; bone loss affecting more than half of the femoral head; or multiple cysts larger than 1 cm in the femoral head. A test such as a DEXA scan
may be required to determine the level of bone loss.
Cysts are very common in arthritic hips and can usually be seen on x-rays. Most of the time they are not a problem with resurfacing because they are small and in the part of the bone removed in milling the femoral head for a resurf. Most larger ones can be filled with a cement of bone chips and still do a good resurf. The only cysts that are problematic are those that erode the superior femoral neck weakening the bone at a critical place. This can lead to fracture with a resurf and that is an indication for a THR instead. They can usually be seen on a pre op x-ray so I can tell the patient that a resurf may not be possible and a decision can be made at surgery. In the one case I was surprised on the cyst was under a large osteophyte and was obscured on the x-ray. The patient got a big head metal-metal THR and is doing fine.
Alan Ray – A Patient’s answer
The size of a cyst isn’t always the issue. Successful resurfacing also depends upon the location of the cyst. If a cyst occurs in the wrong place on the femur it can change the way the prosthesis would or could be placed.
If the location of the cyst would compromise the loading angle, or if it simply occurred along the line where the femoral cap would be inserted, the load integrity of the resurfacing would be poor.