PRAGUE — Swiss investigators have found high early loosening rates
in a double-blinded randomized prospective trial of AL203-free surface
Zweymueller femoral stems, according to a presentation at the SICOT XXV
Triennial World Congress 2011, here.
“The Zweymueller principle works … [The] stem with an altered
surface just doesn’t work,” Lukas Dominik Burger, MD, a resident and
research fellow at Kantonsspital Bruderholz, in Bruderholz, near Basel,
Burger and colleagues theorized that since some AL203 inevitably remains
on the surface of these grit-blasted stems after grit-blasting is completed,
which has been associated with some reports of loosening, those stems that
undergo a special chemical and mechanical treatment to remove the AL203 may
show improved fixation and osteointegration. Therefore, a single-center
prospective randomized study was performed to compare results in 24 patients
with AL203-free surface stems (trial group) to 25 patients with regular
grit-blasted stems that did not undergo the AL203-removal process (standard
Based on follow-up bone mineral density (BMD) tests results from
dual-energy X-ray absorptiometry testing, the trial group had higher overall
BMD at 12 months postoperatively in Gruen zones 6 and 7 and at 24 months in
zones 6 and 7, as well as zone 2.
“Zones 3, 4 and 5, which are considered most important for
anchorage of the Zweymueller stem (SL Plus; Smith & Nephew), showed
considerably higher BMD in the AL203 group [standard]. Now we interpret this as
a sign of trouble with the stem, which showed that the primary replacement
doesn’t really work in this modified stem as opposed to the standard
stem,” Burger said.
“Nine of 24 patients were revised for loosening of the AL203-free
surface stem,” he said. “We have more patients in the pipeline which
are already now presenting with typical loosening.”
Two of 25 patients in the standard group were revised. It will take more
research to determine whether the process of AL203 grit blasting or rendering
the implant AL203-free after production is the real problem, Burger said.
- Burger LD, Hirschmann MT, Afifi FK, et al. Do not implant!
Unexpected high loosening rate of AL203-FREE non-cemented titanium
trial-hip-stems. A randomized, prospective study of a new surface technology in
THR. Paper #29109. Presented at the SICOT XXV Triennial World Congress 2011.
Sept. 6-9. Prague.
- Disclosure: The study was supported by a research grant from
Plus-Surgical/Smith & Nephew.
Congratulations on presenting those data; it took courage to do it. Make
sure you get your data published. I hope you will also ask the manufacturer to
inform everyone of what they did [with the surface finish and treatment]. They
won't do it again, but somebody else might.
— Daniel J. Berry, MD
Academy of Orthopaedic Surgeons
Chair in the Department of Orthopaedic
Disclosure: Berry receives royalties from DePuy on certain hip
and knee implants. His department receives research support from Biomet, DePuy,
Smith-Nephew, Stryker and Zimmer.
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