Who Is The Best Candidate For Hr? Still <60, Active, Large Boned Male With No Cysts? How Important Are These Factors Relatively?

Dr. Schmalzried The goal in matching hip arthroplasty technology to the patient is to maximize the benefit to risk ratio for that patient. The best candidate for HR is that patient with categorically a high likelihood of success from a HR who is also at increased risk for failure of a total hip. There is data available to support some guidelines.

The demographics are a male, less than 60 years of age, of above average stature with osteoarthritis.The reported experienced of Amstutz et al. 2004 and Daniel et al. 2004 support this.

On the contrary, those with osteoporosis, such as many post-menopausal females, some males >65 years old, and some males with smaller stature, have and increased risk of resurfacing failure within the first 2 years most commonly due to femoral neck fracture. Amstutz et al. 2004 and the Australian registry support this.

Patients with a good proximal femur: 1) good bone density 2) good shape (head-neck ratio >=1.2 and neck length >=2cm) 3) no focal defects >1cm and 4) good biomechanics (neck shaft angle >= 120 and limb length difference within 1cm) have better outcomes than those with a more "compromised" femur. Patients with all 4 positive criteria are usually earlier in the disease process, have been functionally compromised for a shorter period of time so their pre-operative level of function is higher. In other words, earlier intervention of the arthritic process preserves function so the post-operative outcomes of resurfacing in those patients are better. The study of Schmalzried et al. 2005 specifically addresses this issue. The old advice to "wait as long as you can" is not appropriate given the experience with the current generation of arthroplasty techniques and devices. Jack Nicholas actually got it right when he advised in a national advertisement, "Don't wait. Go ask your doctor".

Schmalzried, T.P.; Silva, M.; de la Rosa, M.; Choi, E.S. and Fowble, V.A. : Optimizing patient selection and outcomes with total hip resurfacing. Clin. Orthop. 441:200-204, 2005

Dr. Shimmin The ideal candidate for hip resurfacing is a male < 65 years old with good proximal femoral bone quality and the absence of large femoral head cysts. In some, but not all situations, post-menopausal women may have a compromised proximal femoral bone which may indicate a total hip replacement is the preferable option.

Dr. Jacobs: Bottom line: No decisions should be made without consulting a competent surgeon. Patient selection for any medical or surgical intervention is at the heart of the practise of medicine. In this case many factors have to be considered. The patient's chonologic age, biologic age, other medical conditions, previous hip procedures, hip deformities, bone density, and patient expectations are just a few of the key factors.

There should not be a specific age cut off as many patient over sixty have more active and demanding life styles than patients who are less than 60. Each patient needs to be assessed and a phone call and inital x-ray screen are a good place to commence the process.

What Are The Most Appropriate Range Of Age And Activity
For Hip Resurfacing?

Dr. De Smet There is no range. Everything should be looked at accordingly. X-rays (meaning bone quality) and activity are factors. By looking at both, I might decide that a 60 year old would be better to get a total hip and sometimes a 80 year old would get better results with a resurfacing!!!

Dr. Vail Age is not a sole criteria for determining the appropriateness of hip resurfacing. However, age does correlate with bone density in some cases. Patients with low bone density or poor bone quality are not good candidates for hip resurfacing. Poor bone quality increases the risk of a complication such as femoral neck fracture or implant loosening.

Thus, many patients over 65 years may not fall into the category of being a "good" candidate. An advantage of hip resurfacing is that it conserves bone on the femoral side. This is an advantage if a revision to a total hip is required. Thus, younger patients or patients with high activity demands who may be at risk for later loosening or implant failure (total hip or resurfacing) are better candidates for resurfacing.

Should I have my bone density measured? If so, what is the minimum DEXA you accept to avoid neck fracture?

Dr. Shimmin Bone density test may indicate that hip resurfacing is not the ideal implant of choice. However, whatever the result of the bone density test, the final decision is made intra operatively.

Dr. Mont Some surgeons advocate DEXA scans on patients who they might suspect have decreased bone mass. These might be patients that fall into the at-risk categories such as post-menopausal women and patients with rheumatoid arthritis. There are certainly other obvious cases where the x-ray appearance to the surgeon might denote decreased mineral mass in relationship to their other hip. Certainly, patients who have been favoring one hip over the other hip may lose mineral mass. There is no absolute standard for when to get a bone density measure.

Another problem with bone density measurements concerns their accuracy. The measurement may not reflect how much bone there is in the femoral head or proximal femur where it is necessary to perform a resurfacing.

It is my belief that the surgeon, even if they use bone density measurements, should rely on intraoperative inspection of the bone before and after it is prepared during the resurfacing procedure. There are certainly patients that would be expected to have excellent bone density and on intraoperative inspection they have very weak bone. There are other cases where one might expect a patient to have less bone (patients over 55 years of age), but in fact for various reasons (maintaining their health, athleticism, diet), they have maintained tremendous bone density and would be excellent candidates for resurfacing. In summary, this is by no means a definitive answer, but I believe that intraoperative inspection is paramount and bone density measurements should be only reserved for at-risk patients.

Can hip resurfacing be done in the case of protrusion?

Dr. Amstutz Yes, it can work very well and does not present undue difficulty. In extreme cases custom devices may be required.

Dr. Kreuzer In general yes. The concern with Protrusio Acetabuli are three fold. In severe cases, it is difficult to dislocate the hip. Patients with PA frequently have RA and therefore the bone quality may not be adequate to be a candidate for a resurfacing. Patient with a PA may have a short neck or a cyst which also disqualifies them for a HR.

Dr. Mont By protrusion, I believe we are referring to where there is loss of bone stock on the acetabulum which is found in a number of conditions including rheumatoid arthritis and osteopenia. Whereas, resurfacing can be performed in a case of this “protrusio acetabuli”, in most of the cases this might not be the appropriate procedure because in the different conditions there is associated osteopenia. In addition, the protrusio has less bone stock on the acetabulum and might need more bone grafting and screws.
These are general comments. However, in some cases patients would be excellent candidates for resurfacing and therefore, would have to be evaluated on an individual basis by analysis of patient and radiographic factors. The protrusio with no cause or “Otto pelvis” has been performed by this surgeon on a number of cases in young patients.

There Are Cysts Evident In The Xrays. Can They Be Filled? Will They Pose A Problem For Hr?

Dr. De Smet Cysts, if cleaned, if well treated, give more fixation with the prosthesis. Only concern here is that there could be more thermal necrosis because of the additional cement, but we have proven that in the technique we are doing with pulse lavage, suction canula in the lesser trochanter and early reduction, this is not an issue.

Dr. Vail Large cyst in the bone decrease the amount of healthy bone available to provide fixation of the resurfacing component. There is no good evidence that filling the cysts with bone graft results in healing. Filling cysts with large amounts of cement also has drawbacks due to the heat generated when the cement hardens at the time of implantation. In general, the larger the cyst the less favorable the prognosis for hip resurfacing. Cysts that are located in the dome of the femoral head are less likely to create a stress riser and lead to fracture than cysts closer to the lower edge of the implant.

How big can cysts be and still have HR?

Dr. Amstutz The rule of thumb is that up to 30% of the femoral head can be defective. Again, the size of the bone, the size of the defect, the quality of the bone, the patient's weight and their intended activities all play a role. While it is true that large cysts do tend to correlate with higher failure rates, the outcome largely depends on technique. With impeccable technique the failure rate remains the same. A surgeon with little hip resurfacing experience would be wise to choose patients without large cysts. However, I will accept patients with larger cysts, optimize technique and restrict impact activities.

Dr. Mont It’s a little hard to define how big the cysts have to be. Each has to be evaluated on an individual basis. It is probably more important as to the location of the cysts and that they are contained defects. This is the type of analysis that really should be done between a patient and their surgeon.

To what extent can cysts in the femoral head and/or pelvic bone be repaired and are acceptable for HR surgery?

Dr. Amstutz Unfortunately there are no clear guidelines on this. The size of the bone, the size of the defect, the quality of the bone, the patient's weight and their intended activities all play a role. While it is true that large cysts do tend to correlate with higher failure rates, the outcome largely depends on technique. With impeccable technique the failure rate remains the same as with patients with no cysts.

Dr. Mont Almost every femoral head or pelvis has some degree of cysts. This is the nature of almost every arthritic condition. Most of the cysts are either small or not structural and would have no effect on the surgical procedure. The cysts can be filled up with cement or bone grafts and would not affect a standard hip replacement or a resurfacing hip replacement. There are many studies that have delineated this with both procedures.

In some cases, the cysts can be in an area which could structurally compromise a resurfacing. On the femoral side, if the cysts happened to be right at the neck where the resurfacing point would be placed, especially on the lateral side, it could very easily lead to a femoral neck fracture. Initially, some of the surgeons in a multi-center study filled these cysts up with either bone graft or cement or combinations and yet there still was a high fracture rate. Fortunately, these type of cysts that would have structural consequences are quite rare with initial arthritis and in some cases this is an argument for performing a resurfacing earlier rather than waiting too long for cysts to expand and become structurally compromising. Cysts that involve the acetabulum or the pelvis would have the same argument. Smaller cysts pose no problems for doing a resurfacing, however, large cysts would have to be filled with bone grafts and occasionally would obviate against a resurfacing. This is also primarily due to the fact that many resurfacing systems do not have ancillary screws for fixation or have minimal screws for fixation and could prevent patients from getting a resurfacing.

In summary, each of these cysts have to be evaluated both on preoperative x-rays which are only 2-dimensional representations of 3-dimensional objects, but obviously permanently evaluated in the operating room theater.

For What Severity/Extent Of Avn Is Hip Resurfacing Appropriate?

Dr. De Smet  Sometimes I still would do a resurfacing if there is bad necrosis. Everything has to do with the age and condition of the patient. There must be enough healthy bone to create a circumferential seal and to get a good fixation with the cemented head. This must be decided individually - each patient is different.

Dr. Vail This is a question for which there is not a proven quantitative answer. I generally prefer to resurface only those hips wherein the involvement is limited to less than 20% of the head volume and does not extend below the femoral head growth plate. Patients with femoral heads which are structurally damaged or fragmented by osteonecrosis are not good candidates.

What Conditions Are Definite Contra-indications For Hip Resurfacing?

Dr. De Smet This should be looked at for every patient individually. Sometimes a big cyst with good bone quality and young age is still possible. If we don't have good bone stock, especially in the pelvis, then resurfacing become a contra-indication.

Dr. Vail   There are strict contraindications for any implant: active infection or pregnancy being two. Durable hip resurfacing requires that the femoral head bone be healthy and strong. Thus, patients with femoral head bone loss, large cysts, severe osteopenia (osteoporosis) are not candidates.
Likewise, a patient that has a known allergy to metal (especially Fe, Co, Cr, Ni, or Mb) or bone cement (polymethylmethacrylate) is not a candidate.

Patients with abnormal kidney function are also excluded from consideration because the metal ions generated by the resurfacing implant are cleared by the kidney.

Do you have any knowledge of cases of successfully
resurfaced Protrusio Acetabuli?

Dr. Amstutz Yes, there are plenty. It can work very well and does not present undue difficulty.

Dr. Mont By protrusion, I believe we are referring to where there is loss of bone stock on the acetabulum which is found in a number of conditions including rheumatoid arthritis and osteopenia. Whereas, resurfacing can be performed in a case of this “protrusio acetabuli”, in most of the cases this might not be the appropriate procedure because in the different conditions there is associated osteopenia. In addition, the protrusio has less bone stock on the acetabulum and might need more bone grafting and screws.

These are general comments. However, in some cases patients would be excellent candidates for resurfacing and therefore, would have to be evaluated on an individual basis by analysis of patient and radiographic factors. The protrusio with no cause or “Otto pelvis” has been performed by this surgeon on a number of cases in young patients.