HIP RESURFACING: TO CEMENT OR NOT TO CEMENT
We have received a number of inquiries in our office regarding the merits of cemented versus non-cemented femoral head components in hip resurfacing arthroplasty.
Bear in mind that my experience with hip resurfacing to date has essentially been associated with the Smith and Nephew Birmingham hip resurfacing system as designed by Drs. McMinn and Treacy.
The system utilizes a line to line fit on the femoral head component with a very thin thickness of cement. A small amount of liquid cement is poured into the hollow inverted femoral head component and then extruded (and cleaned off as necessary) as it is gently impacted onto the milled head/neck.
This contrasts with the technique for a non-cemented femoral component where the femoral head is reamed to a raw cancellous surface which then abuts the porous coated inner surface of the femoral head component and grows into the porous coating, similar to what occurs on the acetabular socket component.
Why do I prefer the cemented technique as developed by Dr. McMinn?
- The BHR has the longest experience and most successful results globally of any of the presently used hip resurfacings and utilizes the cemented technique.
- None of the currently available porous coated femoral component prostheses are FDA approved.
- Many of the most severely involved arthritic hips have very oblong and sclerotic (rock hard) bone on the top of the femoral head that even when reamed has poor ingrowth potential and may be more susceptible to stress shielding and/or loosening. In order to compensate for this sclerosis and lack of sphericity, there is a tendency to ream the head to a greater depth, resulting in shortening and/ or injury to femoral circulation and possible avascular necrosis. Cement utilization decreases the above risks.
- A thin cement mantle can compensate for asymmetric sclerotic heads and allows one to place fixation holes or use small cysts in the femoral head for the cement to lock into.
- The most common femoral porous coated system on the market has a round on round bone/metal interface which is less resistant to rotational forces biomechanically.
- Porous coating on the available non-cemented systems is applied to the femoral component with heat treatment which affects the metal carbide size and ultimate wear characteristics.
- Porous coating on the femoral side appears to be "fixing" a problem that doesn't exist-we have not experienced femoral component loosening in our series or those previously referred to Europe.
- If loosening did occur, there would be no difference in ease of revision between cemented vs. non-cemented prostheses.
In summary, there are numerous factors, as noted above, that convince me that the BHR (with a cemented femoral head component and a non-cemented porous ingrowth "as cast" acetabular component) is the most successful hip resurfacing option with the longest track record on the market today.