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Cemented fixation for TKA: Still the gold standard
In the literature and clinic, cemented fixation is reliable, economical and less demanding.
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Cemented fixation in total knee arthroplasty still represents the gold standard in knee fixation.
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The main goals of knee replacement are pain relief, improvement in function and durability. There is no doubt that cemented knee replacement provides very reliable pain relief, because of the outstanding initial fixation that it obtains.
The durability of cemented knee replacement is excellent. Many series in the literature show between 90% and 98% survivorship at 15-plus years.
Even in young patients, the limited number of series that we have demonstrates relatively good survivorship, although we would all admit that young patients of yesteryear may not be the same as young patients today.
When we studied 1,000 cemented, cruciate-retaining knees performed at the Mayo Clinic, the 15-year survivorship — free of revision for aseptic loosening as the end point — was 98.6%. Therefore, it is safe to say that at 15 to 20 years, loosening of cemented knee arthroplasties is not a frequent problem. In fact, the most common problems in cemented TKA leading to failure in the first 20 years are infection, wear and periprosthetic fracture, which are mostly independent of fixation method. Cementing is technically straightforward to perform, and the bone cuts aren’t as demanding as in uncemented fixation.
Uncemented fixation does have advantages: It provides a faster procedure because there is no cement to deal with, and it facilitates using a smaller incision.
Also, once an uncemented prosthesis is fixed biologically, the fixation is likely to be durable.
However, there are some important drawbacks of uncemented fixation. There’s the risk of initial failure of fixation, leading to pain and unhappy patients.
A secondary problem impacts the patient who has an unsatisfactory result: It is ultimately much harder to evaluate the fixation interface of an uncemented knee to find the etiology of that discomfort, compared to a cemented knee arthroplasty. Finally, uncemented implants are more expensive.
Comparing approaches
Direct comparison of the two fixation types are difficult due to the selection criteria involved in different studies.
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Terry Gioe, MD, has shown that in over 5,000 knee arthroplasties recorded in a community joint registry, the group with the lowest reported survival rate included patients who had uncemented implants. The best were those with the cemented implants.
James Rand, MD, and Robert Trousdale, MD, at the Mayo Clinic looked at more than 11,000 knees, and at 10 years, the cemented knee arthroplasties performed markedly better than the uncemented.
In a separate investigation, Robert Barrack, MD, studied 158 rotating platform knees.
The revision rate in the cemented group was 0%, but it was 8% in the uncemented group, predominately due to problems with tibial fixation.
In summary, aggregate studies of uncemented implants have not demonstrated better long-term fixation rates than cement.
Is cement perfect? No. Is it better than uncemented fixation for TKA today? Yes.
Uncemented fixation needs better reliability of bone ingrowth and a simpler, more reproducible surgical technique to successfully compete with cement. This may happen in the future, but it has not happened yet.
For more information:
- Daniel J. Berry, MD, can be reached at the Department of Orthopedic Surgery, Mayo Clinic, 200 First St. S.W., Rochester, MN 55905; (507) 284-4204; e-mail: mundt.norma@mayo.edu. He indicated he receives royalties on some knee replacement products from DePuy.