Session 1: Hip
Onsdag den 22. oktober
09:00 – 10:30
Lokale: Reykjavik
Chairmen: Nanna Sillesen Hylleholt / Mogens Berg Laursen
1. Prosthetic Joint Infection (PJI): Bacterial Identification with Heat Flow Detection in Sonication Fluid of Removed Total hip or knee Arthroplasty (THA/TKA)
Christen Ravn, Michael Kemp, Per Kjærsgaard-Andersen, Søren Overgaard
Orthopaedic Research Unit, University of Southern Denmark; Department of Clinical Microbiology, Odense University Hospital; Department of Orthopaedic Surgery, Vejle Hospital; Department of Orthopaedic Surgery and Traumatology, Odense University Hospital
Background: In PJI a delay of 5-10 days after surgery
is frequent before bacterial diagnosis by
conventional culture methods.
Introduction of sonication for biofilm
dislodgement of removed implants have
increased the sensitivity of PJI-
diagnostics as compared to culture of
biopsies (Trampuz et al. NEJM, 2007).
Microcalorimetry can demonstrate
microbial growth in small fluid samples as
measured by heat flow (µW), and may
even give a more rapid diagnosis than
simple culture.
Purpose / Aim of Study: To compare microcalorimetry with culture of
sonication fluid for bacterial detection, and to
evaluate the time to detection (TTD) of
bacterial presence by microcalorimetry.
Materials and Methods: We analyzed prosthetic components
removed during joint revision for deep
infection (Dinf) or aseptic loosening (Asl) of
THA and TKA. The prostheses were
individually sonicated before aerobic and
anaerobic culture, and checked for positive
growth (>20 colonies/ml) twice daily.
Furthermore sonication fluid (SF) was
analyzed with microcalorimetry (TA
Instruments) for 48 hours. TTD (hours) was
defined as time to reach a detection limit of
10 µW.
Findings / Results: In 111 revisions of THA (70) and TKA (41)
indications were resp. Dinf (49) and Asl
(62). Sonication fluid was found culture
positive in 50 cases, whereas
microcalorimetry was positive in only 35
(sensitivity 0.70 / specificity 0.93) with a
mean TTD of 9.4 hours (range 1.5-29.4).
Bacterial findings of microcalorimetry
appears as species (no./mean TTD):
S.aureus (9/6.4), E.faecalis (7/8.2),
streptococcus sp. (4/12.3), E.coli (1/12.7),
and coagulase neg. staph. (13/14.3).
Bacteria not found incl. CNS (3), P.acnes (2)
and streptococc sp. (2).
Conclusions: Microcalorimetry of sonication fluid
demonstrated good specificity, but rather
low sensitivity. A bacterial diagnosis was
rapidly found (mean 9.4 hr) by heat flow
detection.
2. Revision risk of cementless metal-on-metal total hip arthroplasty is influenced by component brand
Claus Varnum, Alma B. Pedersen, Mäkelä Keijo, Leif Ivar Havelin, Johan Kärrholm, Søren Overgaard
Orthopaedic department, Vejle Hospital; Department of clinical epidemiology, Aarhus University Hospital; Department of Orthopaedics and Traumatology, Turku University Hospital, Finland; The Norwegian Arthroplasty Register, Department of Orthopedic Surgery, Haukeland University Hospital, Bergen, Norway; Institute of Clinical Sciences, Department of Orthopaedics, Sahlgrenska University Hospital, Gothenburg, Sweden; Department of Orthopaedic Surgery and Traumatology, Odense University Hospital
Background: There are several concerns for the use of
metal-on-metal (MoM) bearings in total hip
arthroplasty (THA) especially for certain
brands of MoM components due to
increased revision rates.
Purpose / Aim of Study: We aimed to investigate the 6-year revision
risk of cementless stemmed MoM THAs in a
population-based follow-up study from the
Nordic Arthroplasty Registry Association
(NARA).
Materials and Methods: In the NARA database, we identified 85,371
cementless stemmed primary THAs
operated from 2002 to 2010. Metal-on-
polyethylene (MoP) THA was used as
reference, and only patients operated with
MoM or MoP bearings were included. In
total, 32,678 patients were included. At 6
years follow-up, the adjusted relative risk
(aRR) for any revision with 95% confidence
intervals (CI) was assessed by the use of
regression with the pseudo-value approach
and modelled with death as competing risk.
Findings / Results: 11,567 patients (35%) had MoM and
21,111 (65%) had MoP THAs. The aRR
of any revision for MoM was 1.49 (CI:
1.30-1.71). For different brands of
acetabular cups in MoM THA, higher RR
of any revision was found for the ASR
cup (n=759; aRR 6.38, CI: 4.99-8.15),
the Conserve Plus cup (n=478; aRR
1.70, CI: 1.14-2.54), and ”other” cups
(n=351; aRR 2.38, CI: 1.45-3.92). No
difference in RR of any revision was
found for the Recap, M2a, Pinnacle,
Birmingham, and Durom cups compared
to MoP THA. After exclusion of the 759
patients having the ASR acetabular
component, the aRR of any revision was
1.12 (CI: 0.97-1.30) for MoM compared
to MoP THA.
Conclusions: The aRR of any revision at 6 years follow-
up was 49% higher for MoM compared to
MoP THA. After exclusion of the ASR cup,
the aRR of any revision was 12% higher for
MoM THA – although this was not
significant. Based on recent reports, we
may expect increasing revision rates of
MoM THAs with longer follow-up.
3. Regional differences between US and Europe in radiological osteoarthritis and self assessed quality of life in patients undergoing Total Hip Replacement (THR) surgery
Kirill Gromov, Meridith Greene, Nanna Sillesen, Peter Gebuhr, Anders Troelsen, Henrik Malchau
Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre; Harris Orthopaedic Laboratory, Massachusetts General Hospital
Background: Precise indications for THR remain unclear
and regional differences might exist in
selecting patients for surgery.
Purpose / Aim of Study: In this study we investigate radiological
grade of OA and self-reported quality of life
in patients undergoing THR in US and
Europe
Materials and Methods: There are 909 patients from 16 centers in
the USA and Europe enrolled into a
prospective 10year outcome study. All
patients were operated using an
uncemented RingLoc® or Regenerex® cup
and a Biomet® stem of surgeons’ choice.
Recorded patient demographics included
age, gender, BMI and Charnley score.
Preoperative grade of OA was recorded
using Tönnis classification as well as JSW.
Self reported survey data included pain
visual analogue scale (VAS), EQ-5D, SF36,
Harris Hip, and UCLA scores that were
recorded preoperatively and at 1 year follow
up.
Findings / Results: Patients in US were significantly younger
(61.4vs 64.2; p<0.001) and had a higher BMI
(29.9vs 27.4; p<0.001). More patients with
mild Tonnis OA grade underwent surgery in
US compared to Europe (5.3% vs 2.2%,
p=0.046). Patients in the US had significantly
higher pain VAS (6 vs 5; p=0.004) and
significantly lower SF-36 Physical Function
(29.7 vs 33.9; p=0.003), while having
significantly higher EQ VAS scores (78 vs
66; p<0.001) preoperatively.
Conclusions: Patient demographics and disease severity
according to radiological OA grade and self-
reported survey scores vary between
United States and Europe. This knowledge
can be used in the interpretation of US and
European based studies on outcome
following THR.
4. The “true” incidence of prosthetic joint infection after 32,896 primary total hip arthroplasties: A prospective cohort study
Per Hviid Gundtoft, Søren Overgaard, Henrik Carl Schønheyder, Jens Kjølseth Møller, Per Kjærsgaard-Andersen, Alma Becic Pedersen
Orthopedic, Kolding Hospital and Odense University Hospital; Orthopaedic Surgery and Traumatology, Odense University Hospital; Clinical Microbiology, Aalborg University Hospital; Clinical Epidemiology, Aarhus University Hospital
Background: The risk of prosthetic joint infection in
patients with total hip arthroplasty (THA) is
often underestimated when based on
registry data.
Purpose / Aim of Study: The purpose of this study was to estimate
the “true” incidence of prosthetic joint
infection in THA using multiple data sources.
Materials and Methods: The Danish Hip Arthroplasty Register
(DHR) was searched for primary THAs
performed between January 1, 2005 and
December 31, 2011 in the Danish
provinces Jutland and Funen. The DHR
and the Danish National Register of
Patients (NRP) were searched to identify
first revisions following a primary THA.
The revisions were classified as due to
prosthetic joint infection or to causes
other than infection using an algorithm
incorporating intraoperative cultures,
aspirations of joint fluid, plasma C-
reactive protein, prior use of antibiotics,
and clinical findings described in the
medical record. We calculated the
cumulative incidences.
Findings / Results: A total of 32,896 primary THAs were
identified. Of these, first time revisions
were reported to the DHR and/or NRP for
1,546. The 1-year cumulative incidences
of prosthetic joint infection were 0.51 %
[CI 0.44; 0.59] and 0.48 % [0.41; 0.56] for
the DHR and NRP, respectively; while,
the 5-year cumulative incidences were
0.64 % [0.51; 0.79] and 0.57 % [0.45;
0.71], respectively. The corresponding 1-
and 5-year cumulative incidences
estimated by the algorithm were 0.86 %
[0.77; 0.97] and 1.03 % [0.87; 1.22],
respectively. Thus, the “true” incidence
of prosthetic joint infection in primary
THA was approximately 40 % higher
compared with the national registers
when using additional data.
Conclusions: The “true” incidence of prosthetic joint
infection in primary THA is significantly
higher than reported by the Danish national
registers and can be estimated using multiple
clinical and paraclinical data.
5. Comparison of outcomes and complications of hip arthroscopy for mixed hip disorders in adolescents versus adults: a prospective cohort study
Manoj Ramachandran, Pramod Achan , Martin Gottliebsen , Bjarne Møller-Madsen
Department of Paediatric Orthopaedics, Barts and The London Children’s Hospital, Whitechapel Road, Whitechapel, London, England ; Department of Children’s Orthopaedics, Aarhus University Hospital
Background: The current literature indicates that hip
arthroscopy is safe in both adolescents and
adults with good early outcomes. There are
no available studies however that directly
compare the outcomes of this procedure for
mixed indications between these two
groups.
Purpose / Aim of Study: This was a prospective cohort study of 102
consecutive supine hip arthroscopies in 96
patients (48 adolescent (<18) hips, mean
age 13.9 years and 54 adult (>18 hips),
mean age 33.8 years) at a tertiary referral
paediatric and adult university hospital
followed-up for a minimum of two years.
Materials and Methods: At two-year follow-up, the Modified
Harris Hip Score improved from a mean
of 55.3 to 87.5 (p<0.05) in the adolescent
group and from 58.7 to 86.9 (p<0.05) in
the adult group while the Non-Arthritic
Hip Score improved from 57.1 to 86.7
(p<0.05) in the adolescent group and
from 61.4 to 87.4 (p<0.05) in the adult
group. There was no statistical
significance difference in outcome
between the two groups at 2 years. With
respect to complications, there were 3
transient pudendal nerve palsies that
resolved spontaneously in the
adolescent group by 4 weeks. No cases
of proximal femoral physeal growth
disturbance or osteonecrosis were seen
at final follow-up.
Findings / Results: This study confirms that hip arthroscopy for
mixed indications leads to good early
outcomes with low complication rates in
adolescent and adult patients. The incidence
of pudendal nerve palsy in the adolescent
group is however noted and is of concern.
Advances in hip arthroscopy for adolescent
hip disorders should focus on reducing or
eliminating the side effects of traction.
Conclusions: Hip arthroscopy, although effective in
adolescents and adults in the short-term for
mixed indications, has a higher incidence of
pudendal nerve palsy in adolescents.
6. Higher UHMWPE wear rate in cementless compared with cemented cups with the Saturne® Dual-Mobility system.
Steffan Tabori Jensen, Morten Homilius, Christina Frølich, Torben Bæk Hansen, Maiken Stilling
Ortopædkirurgisk, Hospitalsenheden Vest
Background: Displaced medial femoral neck fracture (FNF) may be treated with
primary arthroplasty. Dual-mobility articulations have advantages on
stability and range of motion, however polyethylene (PE) wear on two
articulating sides might lead to excessive wear.
Purpose / Aim of Study: To investigate PE wear rate of primary DM cups in patients with acute FNF
Materials and Methods: From 2005-2011, 414 consecutive patients were operated with
Saturne DM cups, 28mm femoral metal heads, UHMWPE.
Cementless cups were coated with hydroxyapatite (HA). 239 cups
were cemented and 175 were press-fit by choice of the surgeon. In
2012, at minimum 1-year follow-up, 155 patients were dead and the
remaining 259 were invited for clinical follow-up. 80 patients were
evaluated with standard radiographs for analysis of cup placement,
2D wear and wear rate (PolyWare software 3D Pro). Mean age at
time of surgery was 80 (range 30-98) years.
Findings / Results: At a mean follow-up of 3.5 (1.4 – 7.7) years the mean 2D wear
was 0.82 (sd 0.38, 0.3-2.2) mm and 2D wear rate was 0.29 (sd
0.21, 0.1-1.2). Wear rate of 0.35 (sd 0.22) in cementless cups
were higher (p=0.045) than 0.16 (sd 0.07) in cemented cups.
Patients with cementless cups were younger (78 vs. 81 years,
p=0.005). Mean cup inclination was 44 (26-65) degrees and
mean cup anteversion 17 (-12-47). There was no correlation
between cup inclination and wear (p>0.34) and no difference in
wear between gender (p>0.33). There was no correlation
between age at time of surgery and wear (p>0.06). Cup
inclination was similar (p=0.13) for cemented and cementless
cups.
Conclusions: At short term follow-up, we found a higher wear rate in cementless
HA coated cups compared with cemented cups. In general mean
2D wear and wear rate in these old and low demand patients was
high and above the osteolysis threshold (0.1mm).
7. Early morbidity after aseptic revision hip arthroplasty in Denmark. A 2 year nationwide study.
Martin Lindberg-Larsen, Christoffer Calov Jørgensen , Torben Bæk Hansen, Søren Solgaard, Henrik Kehlet
Section of Surgical Pathophysiology and The Lundbeck Centre for Fast-track Hip and Knee Arthroplasty, Rigshospitalet, Copenhagen University, Denmark; Department of Orthopaedic Surgery and The Lundbeck Centre for Fast-track Hip and Knee Arthroplasty, Holstebro Regional Hospital, Holstebro, Denmark
Background: Limited data exist on early morbidity after
revision total hip arthroplasty (RTHA).
Purpose / Aim of Study: To describe early morbidity after aseptic
RTHA and relate the morbidity to the extent
of the revision procedure.
Materials and Methods: All aseptic RTHA procedures from 2009 to
2011 were analysed using the Danish
National Patient Registry with additional
information from the Danish Hip
Arthroplasty Registry. The procedures
were divided into total revisions, acetabular
cup revisions, femoral stem revisions and
partial revisions. All readmissions and in-
hospital complications were analyzed
based upon detailed evaluation of patient
records and causes were divided
into “surgical” and “medical” complications.
Findings / Results: 1553 procedures were performed in 40
centres. The mean age was 70.4 years
(range: 25-98) and median length of
hospital stay (LOS) 5 days (interquartile
range, IQR: 3-7). Within 90 days
postoperatively the readmission rate was
18.3% and mortality rate 1.4%. The 90-day
reoperation rate was 6.1%, dislocation rate
7.0% and infection rate 3.0%. Of all
readmissions, 63.9% were due
to “surgical” complications vs.
36.1% “medical” complications. The
duration of surgery, bone loss,
intraoperative complications and LOS
indicated that the total revisions and
femoral stem revisions represented the
most complex surgery, but there were no
differences in early morbidity across the
surgical subgroups.
Conclusions: Aseptic RTHA was performed with LOS of
5 days and without differences in early
morbidity across revision subgroups
despite major differences surgical extent.
All types of RTHA were associated with
increased early morbidity compared to
primary hip arthroplasty. The results from
this study suggest that future focus should
be held on the surgical technique as well
as the perioperative set-up according to
the “fast-track” methodology.
8. Promising migration Pattern at 1 year follow-up of the short Primoris Femoral Stem
Mogens Berg Laursen, Janus Duus Christiansen, Gordon Blunn, Poul Torben Nielsen
Northern Ortopaedic Division, Aalborg University Hospital; University College London, RNOHT, Stanmore, United Kingdom
Background: In order to save proximal bone stock in
primary total hip arthroplasty (THA), short
femoral stems are introduced.
Purpose / Aim of Study: Designed for perfect fit within the femoral
neck, the Primoris® femoral stem has been
released for clinical studies in coherence
with the stepwise introduction of new
implants. This is the preliminary report of the
Radio Stereometric Analysis (RSA) results
after 1 year follow-up (FU).
Materials and Methods: We carried out a prospective cohort study of
52 patients scheduled for surgery with the
femoral neck-preserving Primoris® stem.
Migration was analyzed by RSA, and the
Harris hip score, UCLA activity score,
WOMAC, EQ5D health questionnaire and
Oxford Hip scores were recorded.
Findings / Results: 2 patients were excluded intra-operatively
and 1 patient was revised due to aseptic
loosening after 3 months, leaving 47 patients
for analysis. Further 2 patients were
excluded from the RSA analysis due to
technical problems. RSA showed minor
micromotion of the stem: Mean subsidence
was 0.35 mm (precision: 0.10 ) and mean
rotation around the longitudinal axis was
0.10º (precision: 0.64) after 1 year.
Conclusions: The stems showed very small migration—as
it is characteristic for stable uncemented
implants. If they stay stable until the 2 year
FU, we will go on with a multi center study.
9. Fast-track pathway for reduction of dislocated Hip Arthroplasty reduces surgical delay and length of stay
Kirill Gromov, Fatin Willendrup , Henrik Palm, Anders Troelsen, Henrik Husted
Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre
Background: Dislocation is one of the most common
complications following hip arthroplasty.
Delay until reduction leads to pain and
discomfort for the patient and can potentially
increase risk for complications.
Purpose / Aim of Study: In this study we investigated the safety
aspect of a fast-track pathway for dislocated
hip arthroplasties and evaluated its effect on
surgical delay and Length of Stay (LOS)
Materials and Methods: 402 consecutive and unselected
dislocations (253 patients) were admitted at
our institution between 05-10-2010 and 09-
31-2013. Fast track pathway for early
reduction was introduced on 01.01.2012.
Fast track patients with clinically suspected
dislocation (no radiographic verification)
were moved directly to post anesthesia care
unit (PACU) and then straight to the OR
(operating room). Dislocation was confirmed
under fluoroscopy and reduced under
general anesthesia. Surgical delay (hours),
LOS (hours), perioperative complications
and complications during hospital stay were
recorded. Dislocation status for fast-track
patients (confirmed vs unconfirmed by
fluoroscopy) was recorded as well
Findings / Results: Both surgical delay (2.5 vs 4.1; p<0.001)
and LOS (26.0 vs 30.5; p<0.05) were
significantly reduced in patients admitted
through fast-track pathway compared to
regular pathway. Perioperative
complications (1.6% vs 3.7%) and
complications during stay (11.2% vs 15.4%)
were also reduced, however insignificantly.
Only 1 case admitted through fast-track
pathway had a fracture instead of a
dislocation; no fast-track patients with
suspected dislocation had no dislocations
Conclusions: Fast-track pathway for reduction of
dislocated hip arthroplasty results in
decreased surgical delay as well as LOS,
without increasing perioperative
complications or complications during
hospital stay
10. Re-revision rates following revision of cemented and cementless primary hip arthroplasty
Kirill Gromov, Alma Pedersen, Søren Overgaard, Peter Gebuhr, Henrik Malchau, Anders Troelsen
Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre; Department of Clinical Epidemiology, Aarhus University Hospital; 3Department of Orthopaedic Surgery, Traumatology and Clinical Institute, Odense University Hospital; Orthopaedic Department, Massachusetts General Hospital
Background: Increased use of cementless technique for
primary THA in most parts of the world can
lead to changes in reoperation patterns, ie
indications for revision, and potentially
influence the survival of revision
arthroplasty.
Purpose / Aim of Study: In this registry-based study we wanted to
investigate the role, primary femoral fixation
plays in survival of revision arthroplasty.
Materials and Methods: Primary THA’s with cemented (n=1889) and
uncemented (n=805) femoral component
that subsequently sustained 1st revision of
femoral component were identified from the
Danish Hip Registry. Survival of 1st revision
THA, with 2nd revision of the femur as
outcome, was evaluated using cox
regression analyses to calculate adjusted
hazard ratios (HR). Patient demographics,
time until revision, indications for revision
and femoral bone defects at the time of 1st
revision were also recorded.
Findings / Results: Adjusted HR for 2nd revision due to any
reason of cementless compared with
cemented primary THA with 1st revision
was 1.36; 95%CI (1.02 -1.83). 71.6% of
cemented primary THAs were revised due
to aseptic loosening; while 46.1% of
cementless primary THAs were revised due
to femoral fracture. 3.6% of revisions on
cemented primary THAs were performed <1
year after index surgery, compared to
37.1% of revisions on cementless THA’s
when only looking at revisions performed
due to aseptic loosening.
Conclusions: We found significantly increased risk of 2nd
revision after 1st revision performed on
primary cementless THA compared to
cemented THA considering all causes for
revision. Different indications for 1st revision
could potentially explain inferior survival of
revision performed on cementless THA. Our
data suggest that increased use of
cementless fixation in primary THA might
lead to inferior survivorship of 1st revision
THA.
11. Can hip surgeons code periprosthetic joint infection? A cross-sectional study of data validity in the Danish National Patient Registry.
Jeppe Lange, Alma B. Pedersen, Anders Troelsen, Kjeld Søballe
Lundbeckfoundation Centre for Fast-track Hip and Knee Surgery, Tage-Hansens Gade 2, 8000 Aarhus, Den, Department of Orthopaedic Surgery, Aarhus University Hospital, Tage-Hansens Gade 2, 8000 Aarhus, Den; Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, 8200 Aarhus, Denmark; Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Kettegaard Allé 30, 2650 Hvidovre Denmark
Background: The Danish National Patient Registry (DNPR)
collects data for all patients in Denmark. The
DNPR is a potential high quality research
database, however, validity of data on
prosthetic joint infection (PJI) is unknown.
Purpose / Aim of Study: To evaluate the positive predictive value
(PPV) of diagnosis and procedure codes
associated with hip PJI.
Materials and Methods: We identified patients in the DNPR from
2003-2008 in Aarhus, Aalborg, Silkeborg,
Viborg, Hvidovre, Vejle, Gentofte, Hørsholm,
Hillerød, Helsingør, and Frederikssund with a
primary and secondary ICD10 discharge
diagnosis of T84.5. As we aim to validate
only hip joint affections, we combined T84.5
with a hip joint noninfectious-specific (NIS)
or infectious-specific (IS) procedure code.
Medical records of all identified patients (n=
236) were reviewed by one of the authors.
Findings / Results: 190 of the 236 patients were confirmed as
having a hip PJI according to a priori defined
criteria, corresponding to an overall PPV of
81%. This means that the T84.5 diagnosis
code truly correlates with hip PJI in 81% of
the patients coded with the investigated
combination in the DNRP. The PPV of the
T84.5 diagnosis code in combination alone
with a hip NIS procedure code was 69%,
while T84.5 in combination alone with a hip
IS procedure codes was 87%.
Conclusions: T84.5 is the sole discharge diagnosis
regarding PJI. The PPV of T84.5 in the
DNRP is currently not satisfactory. Data
on PJI obtained from administrative
registries are a valuable source of
information, but should be used with
caution in medical research. We urge hip
surgeons to be meticulous in their
onward coding practice, to increase the
PPV of the T84.5 code to enable valid
research in a field where absolute
number of PJI is low, making clinical
epidemiologic research on register data a
valuable source of future knowledge.
12. No association between pseudotumors, high serum metal-ion levels and metal hypersensitivity in large-head metal-on-metal total hip arthroplasty at 5-7-year follow-up
Mette Holm Hjorth, Maiken Stilling, Kjeld Søballe, Lars Hans Bolvig, Inger Mechlenburg, Stig Storgaard Jakobsen
Department of Orthopaedics, Aarhus University Hospital; Department of Radiology , Aarhus University Hospital
Background: The relationship between metal wear debris,
pseudotumor formation and metal
hypersensitivity is complex and not
completely understood.
Purpose / Aim of Study: The purpose of this study was to assess the
prevalence of pseudotumor formation in a
consecutive series of metal-on-metal (MoM)
total hip arthroplasty (THA) and to investigate
its relationship to serum metal-ion levels and
hypersensitivity to metal.
Materials and Methods: Forty-one patients (31 males), mean age 52
(28-68) years, with a total of 49 large-head
MoM THA participated in a 5-7-year follow-up
study. Patients underwent ultrasonography
(US), serum metal-ion concentrations were
measured, metal allergy (patch test) and
atopic dermatitis were evaluated, and the
patients completed the questionnaires of the
Oxford Hip Score (OHS), Harris Hip Score
(HHS) and the Short-Form Health Survey (SF-
36).
Findings / Results: Pseudotumors were found in eight
patients, but they were asymptomatic
and their serum metal-ion levels were
similar to those observed in patients with
no pseudotumors (p>0.36). The capsule-
stem distance of mean 8.6 mm (SD 3.82,
95% CI: 5.40-11.79) was wider (p=0.02)
in patients with pseudotumours than in
patients without pseudotumors of mean
5.6 mm (SD 2.89, 95% CI: 4.68-6.58).
Positive patch test reactions were seen
in three patients (two to nickel and one to
iron). Higher serum metal-ion levels of
chromium and cobalt were significantly
correlated with steeper cup inclination
and smaller femoral head sizes, and
were associated with female gender
(p<0.04).
Conclusions: We found no association between
pseudotumor formation, serum metal-ion
levels, metal patch test reactivity, and atopic
dermatitis. However, clinicians should be
aware of asymptomatic pseudotumors, and
we advise further exploration into the
mechanisms involved in the pathogenesis of
pseudotumors.