Clinical News and Views
June 2010
AAOS
15
Now
Why some hips squeak
By Maureen Leahy
In recent years, incidents of
squeaking have been reported in
patients with total hip arthroplasties (THA) using hard-on-hard
(metal-on-metal or ceramic-on-
ceramic) bearings. Although the
phenomenon is not fully understood, the reasons for squeaking
include implant-, patient-, and
surgery-related factors.
“A Review of Squeaking Hips,”
in the June issue of the Journal of
the AAOS (JAAOS), explores the
factors that contribute to squeaking and the implications for patients. AAOS Now interviewed
principal author William L. Walter,
MBBS, FRACS, PhD, about the
phenomenon.
AAOS Now: What factors contribute to squeaking hips?
Dr. Walter: Squeaking occurs
in ceramic-on-ceramic (COC) and
metal-on-metal (MOM) bearings,
not usually with polyethylene
bearings. There seems to be an
increased incidence of squeaking
with some particular devices, although good quality comparative
data are not available and other
factors may confound this observation. Stems with narrow anteroposterior (AP) dimension may be more
likely to squeak due to increased
flexibility in the AP direction.
Patient factors related to squeaking in COC bearings include age,
weight, height, and range of motion. Squeaking has been found to
be more common in patients who
A
Squeaking hip
Radiologic
abnormality
Implant failure
Ceramic fracture
Gross malposition
William L. Walter, MBBS, FRACS, PhD
are younger, heavier, taller, and who
have a greater range of motion.
These factors indicate greater mechanical demands on the bearing.
Some studies have found that
acetabular component orientation
and the degree of anteversion are
associated with squeaking hips,
but this is not a consistent finding.
Other studies have found an association between a higher incidence
of squeaking and a short femoral
neck length and between squeaking
and reduced offset.
AAOS Now: In your opinion,
do squeaking hips indicate a real
problem with the implant or
technique, or are they merely an
inconvenience?
Dr. Walter: Because the causes of
squeaking hips are multifactorial,
B
Fig. 2 Illustrations demonstrating posterior edge loading, found commonly
in the bending position, which is associated with squeaking. A, Lateral view.
With the hip flexed at 90° when the patient rises from a sitting position or
climbs a high step, the load is directed approximately posterior. The direction
of the arrow represents the direction of the loading force. B, Posterior view.
At that position, the posterior edge of the liner is in contact with the superior
surface of the head. The shaded, highlighted area represents the area of edge
loading. The dark stripe indicates wear on the femoral head. The position is
retroverted with respect to a line of latitude on the head.
(Reproduced with permission from Walter WL, Insley GM, Walter WK, Tuke MA: Edge loading in thirdgeneration alumina ceramic-on-ceramic bearings: Stripe wear. J Arthroplasty 2004;19(4):402-413. http://www.
sciencedirect.com/science/journal/08835403.)
AAOS Now_June 2010.indd 15
Clinical evaluation, radiologic
assessment (radiographs, CT)
Frequent/persistent/
troublesome squeaking
Impingement/subluxation
Pain
Revision surgery:
Correct implant malposition
Correct impingement
Optimize soft-tissue tension
Change of bearing
No radiologic
abnormality
Infrequent squeaking,
not troublesome
No pain
Avoid precipitating
activities
Counseling/
reassurance
Careful follow-up
Fig. 1 Algorithm for management of squeaking ceramic-on-ceramic hip
arthroplasty.
Reprinted with permission from Walter WL, Yeung E, Esposito C: A Review of Squeaking Hips. J Am Acad
Orthop Surg 2010;18:1-8.
squeaking cannot be blamed universally on a single cause. A single
cause might be identified in specific
cases, but this is unusual. Squeaking does not indicate impending
failure of the implant and does
not necessarily mandate revision
surgery, unless the noise itself warrants revision or other troublesome
symptoms such as pain are present.
Whether squeaking is a ‘real
problem’ or just an ‘inconvenience’
depends on the noise. If the hip
makes a loud noise with every step,
it is a real problem; if the hip only
makes a subtle noise once a month
when the patient is cutting his or
her toenails, it is an inconvenience.
AAOS Now: How often do squeaking hips lead to revision surgeries?
Dr. Walter: In our experience,
squeaking very rarely leads to revision. In our series of nearly 4,000
hips with COC bearings starting in
1997, only two have been revised
for squeaking. Although 70 patients reported squeaking, most instances are benign—infrequent and
only with a specific activity. In fact,
these patients show no increased
rate of dissatisfaction with their
surgery and tend to have slightly
better function than patients with
silent hips.
AAOS Now: What should a patient
who complains about a squeaking
hip be told? How should the surgeon reassure the patient?
Dr. Walter: If the patient has a
COC hip, the surgeon should first
request a radiograph or, better
still, a computed tomography (CT)
scan, to exclude the possibility
of ceramic breakage (Fig. 1). Although it is extremely rare, ceramic
breakage can cause squeaking.
The surgeon should also advise
the patient that retrieved ceramic
squeaking hip bearings have been
shown to have 30 times more wear
than silent ceramic bearings but
that this wear is still low enough
that it should not cause a problem.
Ceramic bearings have the lowest
wear of any bearing material, and they have virtually eliminated
osteolysis, which is the most common reason for revision of hip
replacements.
If the squeak occurs with bending (Fig. 2), the patient can be
shown how to bend to avoid making the noise (knees turned
out, affected leg back). More regular follow-up is also advised. NOW
Dr. Walter reports the following
disclosures: Stryker; DePuy; Finsbury; Ceram Tec; Global Orthopaedics
A link to the JAAOS article is
available in the online version of
this article, at www.aaosnow.org
Maureen Leahy is assistant managing editor for AAOS Now. She
can be reached at [email protected]
5/26/2010 2:34:18 PM