Biomedical Engineering Reference
In-Depth Information
Tabl e 2. 13
Market share in % for a selection of implants: evolution of the last 26 years. Data
selected from a list of 15 most common implants from the Swedish Hip Arthroplasty Register
[73, p. 7]. Values rounded to the nearest integers. The data of 1995-1999 are not listed separately
in the Register
Year
Total
a
1979-2000
2001
2002
2003
2004
2005
Cemented Cup (Stem)
Lubinus
b
17
35
36
37
40
41
34
Charnley
27
13
7
2
<1
13
c
Exeter
5
2
2
1
1
7
11
d
Numbers
191.458
12.217
12.698
12.686
13.391
13.848
256.298
Uncemented Cup (Stem)
Spotorno
8
-
-
-
-
36
12
Allofift
-
-
-
-
-
8
10
All other
7
Numbers 6.153 316 427 577 758 1,008 9.239
a
Refers to the proportion of the total number of primary THR performed during the past 10 years
b
Lubinus SPII, CLS Spotorno, Allofit (CLS Spotorno)
c
Total for a combination of 3 different types of Charnley implants
d
Total for a combination of 2 different types of Exeter implants, share of each type not listed
-
-
-
-
-
-
improved to 93.5 and 84%, respectively, a substantial windfall for patients as well
as for the national health care! Detailed analysis learned that patient- and surgery-
related reasons decreased constantly during the years 1979-2005 but periprosthetic
femoral fractures remained roughly constant. Aseptic loosening, by far the most
important reason, is reaching a plateau. Of the 69.462 cemented implants 77.6% sur-
vived after a period of 26 years. Analyzed per type, the continuous feedback from
the register is narrowing the selection, a consequence of the
good example
, though
one side of the coin only. The other side, however, could be that innovative designs
get less chance. Is it possible that the slow breakthrough of uncemented designs, at
least for Sweden, is due to this feedback? Nothing is perfect on earth. Both effects
are clearly demonstrated in Table
2.13
. Note that the total percentages are a combi-
nation for 3 types of Charnley and two of Exeter, therefore no percentages are given
for each period or year. The numbers represent the total number of implants for
the period or year and the overall total for 1979-2005. Aseptic loosening remains
the major cause for revision. Although cement is space filling and implants are not
expected to shrink in volume, the reason for loosening is mainly bone resorption. It
can be design-related (stress-shielding) or provoked by wear debris from stem and
cup, an item addressed in following chapters. Cements and cementing techniques
are not shown to cause major problems but all cement packages are registered since
the beginning of 2006 as part of the progressive refinement of the register.
Figure
2.15
should incline surgeons to choose cemented prostheses but the debate
to cement or not to cement
remains open. The evermore detailed statistic mate-
rial will hopefully learn in the near future how the choice cemented/uncemented
influences the outcome for different patient categories, and why the outcome is
occasionally different.
