Non-Cemented Fixation
Another method of fixation is the use of a porous in growth component. Normally, this is a metallic stem which has a surface covered with beads that rigidly adhere to the base stem. The bone is then allowed to grow into this three dimensional architecture to maintain both short and long term fixation.
The benefit of non-cemented fixation is that once the bone grows in it will remain ingrown for quite a long period of time. The 15-year results with non-cemented femoral fixation have yielded a revision rate of less than 10%. The down side of non-cemented femoral fixation is a phenomenon known as thigh pain. This is a mechanical pain or ache along the front of the thigh, occasionally radiating to the knee. This pain is worsened with activities. Usually this pain will begin between three to six months postoperative. It may remain for as long as two years. In a very few patients, less than 1-2%, will it remain beyond two years. Rarely this pain can become severe enough to require additional surgery to treat the thigh pain.
Bone Cement
Bone cement has the longest history in total hip arthroplasty. As outlined above, the minimum 25-year follow up on patients having cement total hip arthroplasties has yielded excellent long term survival. This has been particularly true of the femoral stem. In 1993, there was a consensus panel formed at the National Institutes of Health. Their recommendation for fixation of the femoral stem was to use bone cement in the vast majority of patients. The bone cement is made of polymethylmethacrylate. This is a material that when prepared in the operating room initially resembles the consistency of toothpaste. It is inserted into the canal and then pressurized to get fixation onto the bone. The bone cement serves as a grout rather than glue. Therefore, in order to maintain fixation, the bone cement must be interdigitated well into the porous surface of the inside of the bone. The advantage of using cement is that these components are essentially pain free from the time of surgery throughout their longevity.
One of the concerns, however, has been loosening of femoral stems. While this does occur at a very low rate, when a stem does become loose revision or re-operation on the hip is required.
The method of femoral fixation is usually based upon a
patient's age and generalized activity status. For the majority of
patients, non-cemented femoral porous in growth fixation will be the optimal
choice. This decision will be made in conjunction with your surgeon.
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Joint Reconstruction Center Department of Orthopaedics |
