Dual Poly Liner Mobility Optimizes Wear and Stability in THA - Healio

■ Emergent Hip Technologies?
Dual Poly Liner Mobility Optimizes Wear
and Stability in THA: Affirms
S. DAVID STULBERG, MD
abstract
Full article available online at OrthoSuperSite.com. Search: 20110714-23
A dual-mobility acetabular component consists of a large, fixed, porous-coated acetabular
component and a bipolar femoral component. These components are often
called tripolar components. This configuration provides a stable, well-fixed implant
platform against bone and 2 articular interfaces, a large polyethylene surface directly
apposed to a highly polished metal implant, and a standard-sized (28- or 32-mm)
femoral head captured within polyethylene.
The dual-mobility cup appears to offer a safe, effective, durable solution to hip instability.
The concept has extensive laboratory and clinical support. Although the long-term
durability of these implants is unknown, the tested wear rates of a dual-mobility design
with the current generation of highly cross-linked polyethylene are significantly lower
than any previously reported wear rates. The recently introduced modular dual-mobility
shell offers surgeons substantial flexibility in addressing the issue of hip instability
with a cost-efficient, familiar option.
Figure: The 3 components of a dual mobility cup:
fi xed porous shell, polyethylene bipolar component,
and femoral head.
Dr Stulberg is from Northwestern University, Chicago, Illinois.
Dr Stulberg has fi nancial interests in Stryker, Zimmer, Aesculap, and Innomed.
Presented at Current Concepts in Joint Replacement 2010 Winter Meeting; December 8-11, 2010;
Orlando, Florida.
Correspondence should be addressed to: S. David Stulberg, MD, Northwestern University, 680 N
Lake Shore Dr, Ste 1028, Chicago, IL 60611 (jointsurg@northwestern.edu).
doi: 10.3928/01477447-20110714-23
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■ Emergent Hip Technologies?
A
dual-mobility acetabular component
consists of a large, fixed,
porous-coated acetabular component
and a bipolar femoral component
(Figure 1). These components are often
called tripolar components. This configuration
provides a stable, well-fixed
implant platform against bone and 2 articular
interfaces, a large polyethylene surface
directly apposed to a highly polished
metal implant, and a standard-sized (28-
or 32-mm) femoral head captured within
polyethylene (Figure 2). This concept
was conceived, developed, and described
by the French orthopedic surgeon, Gilles
Bousquet, in 1976. 1
The dual-mobility implant was developed
to reduce the incidence of dislocation
in patients at risk of instability who required
total hip arthroplasty (THA). Patients at increased
at risk may include those: (1) older
than 75 years; (2) who have had prior hip
surgery; (3) with neuromuscular diseases;
(4) with cognitive dysfunction; and (5) with
American Society of Anesthesiologists
scores 3. Hip instability remains one of
the most common causes of THA failure,
especially following revision THA.
The dual-mobility acetabular component
potentially provides substantially
greater range of motion than conventional
articulations with large femoral heads
(Figure 3). This theoretical protection in
stability has been confirmed in a number
of studies (Table 1). 1 The dual-mobility
cup has also been used successfully in revision
THA, where the dislocation rate using
conventional, nonconstrained implants
may be 10% to 20% (Table 2). This high
rate of stability achieved with the dualmobility
cup in patients at increased risk
of dislocation has been accompanied by a
survival rate that compares favorably with
THA using conventional, unconstrained
articular surfaces (Table 3). 2
Recent modifications of the original
dual-mobility implant have sought to increase
the durability of the device, reduce
the potential for soft tissue impingement
that might be associated with the original
prosthesis, and increase the flexibility of
the acetabular shell.
The dual-mobility design using firstgeneration
cross-linked polyethylene has
been shown to reduce polyethylene wear
to rates below those reported for conventional
articulations using conventional
polyethylene. Moreover, when the dualmobility
concept is paired with the current
generation of highly cross-linked polyethylene,
the wear rates are 97% lower than
those obtained with the first-generation
cross-linked polyethylene in dual-mobility
cups (Figure 4).
The original dual-mobility acetabular
shell was hemispherical. This design, especially
in larger sizes, had the potential to
be associated with iliopsoas impingement.
An anatomic shell has been developed that
seeks to avoid this complication. A surgical
technique with dedicated instrumentation
has been developed to optimize the
insertion of this shell.
A major drawback of the original
monoblock dual-mobility and monoblock
anatomic variation of the acetabular
shell has been the inability to augment the
press-fit fixation with cancellous screws.
Moreover, the monoblock versions require
surgeons to use a unique implant
that is not routinely a part of an operating
room acetabular cell inventory. In the past
6 months, a modular dual-mobility shell
has become available (Figure 5). Standard
hemispherical shells can be converted to
a dual-mobility implant with the insertion
of a highly polished, thin metal insert that
articulates with the bipolar polyethylene
femoral head. Thus, a standard acetabular
design that is routinely stocked by
hospitals, is familiar to orthopedic surgeons,
and is inserted using conventional
instrumentation can be converted intraoperatively
to a dual-mobility cup if additional
stability is needed. This modular
1
2
3
Figure 1: Fixed porous shell and bipolar femoral component. Figure 2: The 3 components of a dual mobility cup: fi xed porous shell, polyethylene bipolar component,
and femoral head. Figure 3: Potential range of motion of a dual-mobility cup (ADM) vs conventional articulations with large femoral heads.
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■ Emergent Hip Technologies?
Table 1
Dislocations in Primary
THA Using the Dualmobility
Cup 2
Study
No. of
Cases
No. of
Dislocations a
Philippot, 2004 106 0
Aubriot, 1993 110 1
Vanel, 2003 127 1
Béjui-Hughes, 167 0
2006
Philippot, 2006 70 0
Abbreviation: THA, total hip arthroplasty.
a
Overall dislocation rate is 0.4%.
Table 2
Dislocation Rate in
Revision THA Using the
Dual-mobility Cup 2
No. of
Study
Revision
THAs
No. of
Dislocations a
Aubriot, 1995 13 0
Beguin, 2002 42 0
SFHG, 2006 403 8
Guyen, 2009 54 3
Abbreviation: THA, total hip
arthroplasty.
a
Overall dislocation rate is 2.1%.
Table 3
Dual-mobility
Survival Rates 2
Study
No. of
Hips Survivorship
Aubriot, 1993 100 97% at 5 y
Farizon, 1998 135 95.4% at 10 y
Leclerc, 1999 153 96% at 10 y,
94% at 15 y
Philippot, 106 94.6% at 10 y
2004
Philippot,
2006
100 95% at 10 y
6A
6B
Figure 6: Radiographs of a dysplastic hip with severe
degenerative arthritis (A) treated with a modular
dual-mobility cup (B).
Figure 4: The impact of dual-mobility design on polyethylene wear (Trident and ADM; Stryker, Mahwah,
New Jersey).
5
Figure 5: The modular dual-mobility cup consists of a conventional press-fi t shell, a polished modular
metal or standard X3 poly inserts (Stryker, Mahwah, New Jersey), a large X3 poly head (Stryker), and a 22-
or 28-mm cobalt chrome or ceramic head. Abbreviations: CoCr, cobalt chrome; MOM, metal-on-metal.
4
design has been used at our institution in
various situations, including: (1) dysplasia
(Figure 6); (2) osteoarthritis with a large
horizontal offset; (3) avascular necrosis
in patients requiring small cups; (4) failed
metal-on-metal implants; (5) failed bipolar
implants; (6) infected bipolar implants;
(7) acute dislocations after revision THA;
and (8) recurrent early and late dislocations
after primary THA.
The dual-mobility cup appears to offer
a safe, effective, durable solution to hip
instability. The concept has extensive laboratory
and clinical support. Although the
long-term durability of these implants is
unknown, the tested wear rates of a dual-
SEPTEMBER 2011 | Volume 34 • Number 9
e447

■ Emergent Hip Technologies?
mobility design with the current generation
of highly cross-linked polyethylene
are significantly lower than any previously
reported wear rates. The recently introduced
modular dual-mobility shell offers
surgeons substantial flexibility in addressing
the issue of hip instability with a costefficient,
familiar option.
REFERENCES
1. Guyen O, Pibarot V, Vaz G, Chevillotte C, Carret
JP, Béjui-Hugues J. Unconstrained tripolar
implants for primary total hip arthroplasty in
patients at risk for dislocation [published online
ahead of print July 25, 2007]. J Arthroplasty.
2007; 22(6):849-858.
2. Guyen O, Pibarot V, Vaz G, Chevillotte C, Béjui-
Hugues J. Use of a dual mobility socket to manage
total hip arthroplasty instability [published
online ahead of print September 9, 2008]. Clin
Orthop Relat Res. 2009; 467(2):465-472.
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