Does using stems for all revision TKAs lead to better overall results?

One surgeon uses mostly CCK devices without stems. Another claims stem advantages outweigh the risks of difficult future revisions.

ORLANDO, Fla. — Some orthopedic surgeons use stems in every revision total knee arthroplasty they perform. Others reserve stem use in such cases mostly for patients with poor femoral bone stock. Proponents for each approach made their case at a recent medical meeting, backing it up with some statistical evidence.

Thomas P. Sculco, MD, of the Hospital for Special Surgery in New York, said he only uses stems in cases with poor femoral bone preservation because stems are more expensive, adding $300 to $500 to the implant expense. And, more importantly, they can complicate future revisions and require femoral or tibial osteotomy.

“[Stems] violate the intramedullary bone, so if you put a stem on the femoral component you’re potentially violating that bone, should infection occur or other potential mechanical problems,” Sculco said at the 22nd Annual Current Concepts in Joint Replacement Winter 2005 Meeting.

But Daniel J. Berry, MD, of the Mayo Clinic in Rochester, Minn., said selective stem use in revision total knee arthroplasty (TKA) can backfire and cause more complications in the long run.

“It’s hard to be sure when you can get away without a stem,” he said. “And failure rates are lower if you use stems routinely.”

Stem benefits

Although conceding that future revision surgery is more difficult in some stem cases, Berry said he would “accept that minor drawback for the benefit of a higher success rate.”

If used correctly, stems offload stress from weaker, damaged bone, guarantee alignment, protect fixation surfaces and, when used with cement, increase fixation surfaces, he said. Plus, they are compatible with intramedullary instrumentation, he added.

“Stems help solve the problem definitively and ... if you use stems, you can avoid repetitive revisions, which potentially can lead to infection, progressive bone loss, soft tissue problems and prolonged knee dysfunction,” Berry said.

Results from a study at the Hospital for Special Surgery found a low aseptic loosening rate of 3% in 76 knees treated with stems at 3.5-year follow-up. In a study at the Mayo Clinic, researchers found a 2% aseptic loosening rate in 119 knees at 10-year follow-up. “So both series [are] consistent with the fact that if you use a stemmed implant, the aseptic loosening rate in revision knee arthroplasty is low,” Berry said.

Selective stem use

Unlike Sculco, Berry believes that surgeons should not be selective when it comes to using stems in revision TKA.

In a study led by Gerald Engh, MD, researchers followed 139 knee revisions for five to nine years, treating some patients with unstemmed implants and others with stemmed implants.

“The unstemmed implants were, in general, used in patients with milder bone loss, Type I and Type II bone loss,” Berry said. “Whereas the stemmed implants, in general, were used in the tougher cases — those with more severe bone loss, predominantly Type II and Type III bone loss.”

In contrast to the assumption that patients with the least amount of bone loss would have the least amount of aseptic loosenings, results instead showed that all tibial and femoral aseptic loosening cases were patients treated with unstemmed implants — at a 12% failure rate. The group treated with stems experienced no tibial or femoral loosening.

Effectiveness of CCK devices

Sculco prefers to use constrained condylar knee (CCK) devices without stems in those primary and revision TKA cases with good femoral bone quality, such as unicompartmental revision, posterior-cruciate retaining revisions and in some posterior-stabilized revisions.

In a patient with valgus knee deformity and a lax medial ligament, Sculco performed a primary TKA using a cementless CCK. At five-year follow-up, he found good alignment, no evidence of loosening and no recurrent deformity.

Sculco presented data on 196 TKAs with CCKs in 149 patients at the Hospital for Special Surgery. The majority of the cases — 150 of 196 — were primary TKAs with a bad valgus deformity, and 40 were revisions. “These are badly disabled patients,” Sculco said. “These are not your usual straightforward knees.”

At seven-year follow-up, researchers found a 3.5% failure rate — “higher than most garden-variety results, but for a revision or complex series like this, I think it’s absolutely adequate,” Sculco said. They found three loosenings, two infections, one supracondylar fracture, one tibial post fracture and five patella clunks.

“There is a place for the concept of using the CCK device without stems on these complex primary knees and they could also maybe be useful in the revision when you don't have extensive bone loss,” Sculco said. “It’s an easy conversion, less expensive and I think these results are certainly encouraging to date.”

For more information:
Berry D. Stems are necessary in revision TKA — Affirms. #100.
Sculco T. Stems are necessary in revision TKA — Opposes. #101. Presented at 22nd Annual Current Concepts in Joint Replacement Winter 2005 Meeting. Dec. 14-17, 2005. Orlando, Fla.
Bugbee WD, Ammeen DJ, Engh GA. Does implant selection affect outcome of revision knee arthroplasty? J Arthroplasty. 2001;16(5):581-585.