Session 9: Hip 2
Fredag den 25. oktober
09:00 – 10:30
lokale: Reykjavik
Chairmen: Thomas Jakobsen / Søren Solgaard
83. Analysis of 484 retrieved Metal-on-Poly Total Hip Arthroplasty liners: Prevalence of Non-Concentric Loading, Concentric Loading and Impingement
Nanna H. Sillesen, Leah Elson, Shannon L. C. Rowell, Young Min Kwon, Henrik Malchau, Orhun Muratoglu
Harris Orthopaedic Laboratory, MGH + Department of Orthopedics, Hvidovre Hospital. , Massachusetts General Hospital, Boston, MA, USA. + Copenhagen University Hospital, Hvidovre, Denmark; Harris Orthopaedic Laboratory, MGH, Boston, Massachusetts General Hospital, Boston, MA, USA.
Background: Adverse loading patterns are associated
with poor outcomes and a high revision
frequency. Unfortunately, little is known on
how loading patterns affect polyethylene
liners.
Purpose / Aim of Study: To investigate loading patterns for
conventional polyethylene liners from our hip
retrieval registry and correlate the findings
with reason for revision and in vivo cup-
position data.
Materials and Methods: Liners was subjected to analysis including
(i) in-vivo orientation of the cup, (ii)
concentric or non-concentric loading, and
(iii) presence of damages including
Impingement. Head size and in-vivo service
time were also recorded. Data was
correlated with patient history and reason
for revision while x-rays were analyzed
with Martell to determine cup position.
Findings / Results: 484 liners were retrieved. 45% had
Concentric loading, 27% Non-concentric
loading and 27% Impingement. 386
patients had surgeon reported reason for
revision available with the most common
being 1) Femoral loosening, 2)
Acetabular loosening, 3) Femoral
Osteolysis, 4) Acetabular Osteolysis,
and 5) Dislocation. 263 patients had cup-
position data of which 66% were outside
the safe zone. No correlation between
loading patterns and cup-position was
identified. Independent predictors (IP) of
concentric loading were small head size
(22-28mm) (p=0.002, OR=2.8),
acetabular osteolysis (p=0.001,
OR=2.8)), reason for revision and time in
vivo (p=0.006, OR=1.05). The IP for non-
concentric loading were time in vivo
(p=0.002, OR1.06) and impingement
(p=0.001, OR=7.2). The IP of impingement
were small head size (p=0.001, OR=2.5)
and Dislocation (p=0.002, OR=3).
Conclusions: Non-concentric loading is associated with
Impingement. No correlation between
damage patterns and cup positions were
identified. This suggests that polyethylene is
a forgiving liner material when adverse
loading occurs.
84. Does reduced movement restrictions and use of assistive devices affect rehabilitation outcome after total hip replacement? A non-randomized, controlled study in 365 patients with six week follow up.
Lone Ramer Mikkelsen, Mette Krintel Petersen, Kjeld Søballe, Søren Mikkelsen, Inger Mechlenburg
Elective Surgery Centre, Silkeborg Regional Hospital ; (1)Department of Physiotherapy- and Ocupational Therapy, (2) Centre of Research in Rehabilitation (C, (1)Aarhus University Hospital, (2)Institute of Clinical Medicine, Aarhus University ; Department of Orthopedics, Aarhus University Hospital
Background: Rehabilitation after total hip replacement
(THR) has traditionally included movement
restrictions to prevent hip dislocation.
Improvements in surgical techniques and
increased femoral head size might have
changed the rationale for these restrictions.
Purpose / Aim of Study: To evaluate the influence of movement
restrictions and assistive devices on
rehabilitation after fast track THR.
Materials and Methods: 365 primary THR patients (mean age
68.7±10 years, 52% males) were
consecutively included. The 3 initial
months, patients underwent rehabilitation
with movement restrictions and received
a standard package of assistive devices
(restricted group, RG). This group was
compared to patients included into the
study the following 3 months with a less
restricted hip movement regime and use
of assistive devices according to
individual needs (unrestricted group,
UG). Questionnaires on function (primary
outcome, HOOS), anxiety (HADS),
working status and patient satisfaction
were administered before THR, 3 and 6
weeks after.
Findings / Results: HOOS function score at the 3 measurement
times were (mean ± SD); UG: 46±17 - 76±9 -
83±14 compared to RG: 43±16 – 81±14 -
83±13, (difference between groups over
time, p=0.004). For return to work 6 weeks
post THR, UG compared to RG: 53% versus
32% (p=0.045). No significant differences
between groups in anxiety, hip dislocations
and patient satisfaction.
Conclusions: No clinically relevant difference between
UG and RG on patient evaluated function
was found (difference ≤5 points). Yet,
there is a beneficial or equal effect of the
unrestricted regime concerning
secondary outcomes. It seems possible
to reduce the use of assistive devices
considerably and thereby induce cost
savings. More research on safety issues
is needed to elucidate the effect of
unrestricted rehabilitation on hip
dislocation.
85. Whole blood metal ion level in two populations of metal on metal hip arthroplasty and one standard total hip arthroplasty (THA)
Martin Schou, Jeannette Penny, Jens-Erik Varmarken, Søren Overgaard
Orthopaedic Research Unit - Department of Orthopaedic Surgery and Traumatology & Department of Ortho, Odense University Hospital, Odense, Denmark & Naestved Hospital, Region Sjaelland, Denmark; Department of Orthopaedic Surgery, Naestved Hospital, Region Sjaelland, Denmark; Orthopaedic Research Unit - Department of Orthopaedic Surgery and Traumatology, Odense University Hospital, Odense, Denmark
Background: The cause of failure and poor outcome in
patients with metal-on-metal (MoM) (THA)
are debated. An association between
elevated levels of blood metal ions and
implant failure may exist.
Purpose / Aim of Study: The primary purpose of this study was to
evaluate the whole blood metal ion level of
Chromium(Cr) and Cobalt(Co) in
resurfacing hip arthroplasty (RHA), large
diameter head (LDH) MoM THA compared
to metal on polyethylene (MoPE) THA after
a minimum duration of two years post OP
(PO). A secondary purpose was to assess
whether a correlation exists between
elevated whole blood metal ion levels and
time after operation and if there was an
association with gender, age, BMI, implant
age, headsize and activity-level.
Materials and Methods: We studied a total of 170 patients
consisting of 103 with RHA in 32 females
and 71 males, 26 patients with LDH hip in
11 females and 15 males, and an age and
gender matched MoPE THA control group
consisting of 14 females and 27 males. Cr,
Co and activity-level were measured a
median of 4.6 (2 to 7) PO.
Findings / Results: Median whole blood Co levels for RHA was
3.83 (0.24 to 27.00) ppm and 5,26 (0.44 to
30.90) ppm for LDH, both significantly
higher than the 0.43 (0.05 to 1.73) ppm for
MoPE (p<0.01), similar pattern for Cr.
Females had significantly higher Cr and Co
levels, even when adjusting for headsize
(p=0.02). Cr levels decreased significantly
with increased BMI (p=0.03), Co also
displayed a tendency, although not
statisticly significant (p=0.07). Implant age
was not a factor.
Conclusions: LDH displayed higher metal ion levels than
RHA, and both were higher than MoPE.
Females gender was an isolated risk factor
for elevated metal ion concentration
together with increased BMI. Further
studies are needed to explain these
findings but renal clearance/excretion and
body tissue composition could be
candidates.
86. Incidence of pseudotumor in large diameter head metal on metal hip arthroplasty, resurfacing hip arthroplasty and standard hip arthroplasty using magnetisc resonance imaging (MRI)
Martin Schou, Jeannette Penny, Jens-Erik Varmarken, Trine Torfing, Søren Overgaard
Orthopaedic Research Unit - Department of Orthopaedic Surgery and Traumatology & Department of Ortho, Odense University Hospital, Odense, Denmark & Naestved Hospital, Region Sjaelland, Denmark; Department of Orthopaedic Surgery, Naestved Hospital, Region Sjaelland, Denmark; Department of radiology, musculoskeletal section, MRI, Odense , Odense University Hospital, Odense, Denmark; Orthopaedic Research Unit - Department of Orthopaedic Surgery and Traumatology, Odense University Hospital, Odense, Denmark
Background: Metal-on-metal (MoM) hip arthroplasty
(THA) and Resurfacing hip arthroplasty
(RHA) are associated with increased metal
ion concentration and pseudotumor(PT)
formation and increased risk of revision
surgery.
Purpose / Aim of Study: Our primary aim was to evaluate the
incidence of PT in Large diameter
head(LDH) MoM THA, RHA and standard
metal on polyethylene(MoPE) THA
population after a minimum of two years
follow-up, and secondary to assess
whether a correlation exists between
elevated whole blood metal ion level,
gender, patient age, implant age, BMI and
headsize on PT formation
Materials and Methods: We studied a total of 205 THA hips in 170
patients consisting of; 121 ASR RHAs in 41
females and 80 males, 34 MoM LDH in 13
females and 21 males, and a matched
control group of 50 MoPE THA hips in 15
females and 35 males. The PTs were
classified using modified Oxford type I-III.
MRI was evaluated by the same senior
musculoskeletal specialist
Findings / Results: PT were seen in a 50 (24%) hips. ASR
resurfacing had 31 cases (25.6%)
distributed on 15 type I (12.4%), 14 II
(11.6%) and 2 III (1.6%). LDH had 9 PT
(26,5%) distributed on 7 type I (20.7%), 1 II
(2,9%) and 1 III (2,9%). MoPE THA had 10
PT (20%) distributed on 6 type I (12%), 4 II
(8%) and no type III. There was no
significant difference between the incidence
of PT in the three implant types and no
association with gender or metal ion levels.
If PT is diagnosed, the risk of presenting
with a more severe type increases over
time (p <0.05), but the risk of diagnosing
new PT decreased over time (p<0.05)
Conclusions: The incidence of PT was not different
between RHA, LDH or MoPE, but type III
was only shown in MoM hip. No
association to age, gender or metal ion
concentrations were demonstrated. If a
pseudotumor of any type is detected, there
is an increased risk of more severe type
PT with implant age
87. Risk for revision of cementless stemmed metal-on-metal (MoM) total hip arthroplasty (THA)
Claus Varnum, Alma B. Pedersen, Mäkelä Keijo, Johan Kärrholm, Leif I. Havelin, Søren Overgaard
Department of orthopaedic surgery, Vejle Hospital; Department of clinical epidemiology, Aarhus University Hospital; Department of Orthopaedics and Traumatology, Turku University Central Hospital, Tampere, Finland; Department of Orthopaedics , Sahlgrenska University Hospital, Gothenburg, Sweden; Department of Orthopedic Surgery, Haukeland University Hospital, Bergen, Norway; Department of orthopaedic surgery and traumatology, Odense University Hospital
Background: The use of MoM bearings on stemmed
THAs during the last decade has been
motivated by a hope for reduced revision
risk.
Purpose / Aim of Study: We aimed to investigate the 10-year revision
risk of MoM compared to metal-on-
polyethylene (MoP) bearings in stemmed
THAs in a population-based follow-up study.
Materials and Methods: From the NARA (Nordic Arthroplasty
Registry Association) database (DK, S,
N, SF), all cementless MoM and MoP
THAs operated between the 1st of
January 2002 and the 31st of December
2010 were identified. Only the first THA
was included in patients with bilateral
procedures. In total, 19,588 THAs were
included with complete information on
sex, age, diagnosis, year of surgery,
femoral head size, and nation. Patients
were followed until death, emigration,
revision, or end of study period (31st of
December 2011). The Cox multiple
regression with adjustments was
modelled with death as competing risk.
The Wilcoxon rank-sum test was used to
compare follow-up times.
Findings / Results: 11,574 patients (59.1%) had MoM and
8,014 (40.9%) had MoP THAs. The
median follow-up was 3.6 years
(interquartile range (IQR), 2.4-4.8) for
MoM and 6.0 years (IQR, 4.1-7.7) for
MoP bearings (p<0.001). Revision rates
were 4.1% for MoM and 4.6% for MoP
bearings, and the adjusted RR of any
revision for MoM was 0.98 (95%
confidence intervals (CI), 0.60-1.61)
during complete follow-up. The RR of any
revision was similar in the two bearing
groups for women, men, patients
younger or older than 60 years, patients
diagnosed with osteoarthrosis of the hip,
and femoral head size smaller (adjusted
RR 0.68, 95% CI 0.41-1.13) or larger
than 36 mm (adjusted RR 1.49, 95% CI
0.87-2.54).
Conclusions: This study did not demonstrate any
difference in RR for any revision of MoM
THA after a median follow-up of 3.6 years.
Longer follow-up is needed to draw firm
conclusions.
88. A novel program for manual measurement of acetabular angles with improved intra- and inter-rater reliability
Sepp de Raedt, Marleen de Bruijne, Inger Mechlenburg, Maik Stilling, Lone Rømer, Kjeld Søballe
Orthopaedic Research Unit, Aarhus University Hospital; BIGR/DIKU, Erasmus MC Rotterdam/University of Copenhagen; Department of Radiology, Aarhus University Hospital
Background: In the diagnosis of hip dysplasia (HD)
manual measurements of acetabular
angles are considered the gold standard.
These measurements often play an
important role in the diagnosis and pre-
operative planning. However, previous
work has shown large intra- and inter-rater
variability for manual measurements.
Purpose / Aim of Study: To develop a systematic and intuitive
program to accurately measure angles for
the diagnosis of HD and to evaluate the
intra- and inter-rater reliability.
Materials and Methods: Measurements were performed on 18
patients (36 hips) by 1) a senior radiologist,
2) a specialist in training, and 3) a
biomedical engineer using a custom
software application on a dataset of
preoperative CTs of HD patients. A
systematic approach was used to
determine the center point of the femoral
head and the landmark points needed for
determining the CE, AI, PASA, AASA, AcAV
angles. The angle measurements were
automatically derived from the indicated
points. We report the mean difference and
1.96*SD. The concordance correlation
coefficient (CCC) is reported for angle
measurements.
Findings / Results: For brevity we report only the CE and AI
angle results. Differences were calculated
with respect to the senior radiologist. CE:
Rater2: Diff: -0.6±5.0°, CCC: 0.93; Rater3:
Diff: 0.0±6.3°, CCC: 0.89. AI: Rater2: Diff:
0.1±5.9°, CCC: 0.83; Rater3: Diff: 0.5±3.8°,
CCC: 0.93. Distance: Rater2: Diff:
1.62±0.89mm; Rater3: Diff: 1.36±0.51mm.
Intra Rater3: CE: Diff: -0.1±4.8°, CCC:
0.93; AI: Diff: 0.2±3.4°, CCC: 0.94.
Distance: Diff: 1.09±0.38mm.
Conclusions: We presented a novel software program
for performing manual measurements
including the analysis of point placement.
We found an improved inter- and intra-rater
reliability. The program is easy and fast to
use and may be extended for use in the
diagnosis of for example femoral
acetabular impingement.
89. MoM ion analyses; a comparison of full blood versus serum and two different laboratories
Morten Bøgehøj, Ole Ovesen, Søren Overgaard
Ortopaedic department, Odense University Hospital
Background: Metal on metal hip arthroplasty have been
known to produce elevated levels of
Chromium- and Cobolt ions in the blood.
As a tool in monitoring these patients
bloodsamples are tested for Chromium and
Cobolt.
The threshold value for clinical concern is
expected to be more than 7 μg/L (EFORT
consensus on MoM).
Purpose / Aim of Study: To compare fullblood and plasma
measurements of Cr and Co from the same
laboratory, and to compare two different
laboratories making the analyses on serum.
Materials and Methods: Blood samples drawn from the same
patient at the same time point were
analyzed by the ALS Enviromental
(Humlebæk, DK) laboratories for Chrome
(Cr) and Cobalt (Co) in both serum and
full blood, and at the laboratorium at Vejle
Hospital for Cr and Co in serum.
The levels in full blood were compared
with the levels in serum (n=54) and the
results in serum from the two different
laboratories (n=51) were compared by
Scatter plots and Bland Altman limits of
agreement.
Findings / Results: Blood vs serum: The mean Delta value for Cr
and Co Blood vs serum was -3,50 ppb (SD
6,81) and -1,43 (SD 6,06), respectively
meaning that the value in serum is
significantly higher than in full blood. The
limits of agreement is -13,3 – 10,4.
ALS laboratories compared to Vejle Hospital.
The mean delta value for Cr was 0,09 ppb
(SD 5,50), the limits of agreement was -10,7
– 10,9. The mean delta value for Co was
-0,65 ppb (SD 4,97), the limits of agreement
was -10,4 – 9,1.
Conclusions: The wide limits of agreement on both the
comparison of blood vs serum and the two
laboratories and that the serum values
especially for Cr are higher than in full blood
suggests that the serum and blood values
are very uncertain tools in the surveillance
of MoM hips.
90. Acetabular & Femoral BMD around a Large Diameter Head, Standard and Resurfacing THA. 2 Year Results
Jeannette Penny, Ole Ovesen, Jens-Erik Varmarken, Søren Overgaard
Dept. of orthopaedics, OUH/Næstved
Background: Resurfacing Hip Arthroplasty (RHA) is
known to transfer load to the proximal
femur different from the total hip
arthroplasty (THA) resulting in different
patters of bone mineral density (BMD)
loss. Less is known about BMD around
large diameter head MoM THA’s (LDH-
THA).
Purpose / Aim of Study: We aimed to measure the BMD of the
proximal femur and the acetabulum
around LDH-THA and compare it to RHA
and THA
Materials and Methods: 54 patients with primary OA were
randomized in two locations to LDH-THA
(n=16), or RHA (n=19)/THA (n=19). DXA
scans were performed within 3 days of
surgery, 8 weeks, and at 1 and 2 years.
The images were analyzed for BMD in 4
acetabular Wilkinson zones (W1-4) and
7 Gruen zones in the proximal femur (G1-
7).
Baseline to two years were analysed by
t test (matched pairs).Between group
data compared by ANCOVA
Findings / Results: Around the acetabulum the LDH-THA
increased 10% in BMD in Wilkinson’s
zone 1 at one year compared to the
other components (p<0.01). After 2
years the 7% difference was only
borderline significant (p=0.05) but the
LDH-THA maintained BMD where the
other components lost it. No difference
was found in W2-4.
On the femoral side the LDH-THA
maintained BMD at two years in all
Gruen zones except zone 7 where it
lost 20% (p<0.001). Both stemmed
THA’s had less BMD at zone 6 and 7
than RHA (p<0.01), and the loss was
more pronounced for LDH-THA. In zone
1 LDH-THA and RHA maintained BMD
where THA gained 9% (p=0.04).
Conclusions: In this study, LDH-THA displays a small
advantage in BMD preservation over
RHA and THA on the acetabular side,
but the difference is small and narrows
in after two years. On the femoral side
the LDH-THA transfer the load similar to
a THA apart from a lacking BMD
increase in the trochanter tip. Both
stemmed THA’s display marked bone
loss in the calcar area, where the BMD
is preserved by RHA
91. Patient matched implant (PMI) in reconstruction of severe acetabular bone loss and pelvic discontinuity after total hip arthroplasty.
Anne Mette Stausholm, Jens Stürup , Poul Torben Nielsen
Department of Ortopedic Surgery, Aalborg University Hospital
Background: Revision of a failed total hip arthroplasty
(THA) with massive acetabular bone
loss and pelvic discontinuity is a
challenge. Several methods are available
but a relatively new treatment option for
these complex cases is use of a patient
matched implant (PMI).
Purpose / Aim of Study: To describe our experience and early
clinical results of revision hip
arthroplasty with use of PMI in a
patientgroup who had massive
acetabular bone loss and pelvic
discontinuity
Materials and Methods: 4 cases of revision THA using PMI
(Biomet) were reviewed (verbal pain
score and plain radiographs) at an
average follow-up period at 12 months
(range, six to 22 months). The
prosthesis was custom-manufactured
on the basis of three-dimensional model
of the hemipelvis created with computed
tomography.
Findings / Results: Preoperatively all patients had severe
pain, three had impaired walking and one
were unable to walk. At follow-up three
patients had no pain at all but all used
one or two crutches and all had positive
Trendelenburg. All declared to be
satisfied with the operation. There were
no major complications. At the time of
follow-up all implants were in-situ and
without detectable migration on plain
radiographs.
Conclusions: After acetabular reconstruction with
patient matched implants pain relief was
achieved and patients were able to
walk. Early clinical results are good and
patient satisfaction is high. Patient
matched implant to treat massive
acetabular bone loss and pelvis
discontinuity is an option that should be
considered in such cases.
92. 15-years in risk of cardiovascular events and bleeding in total hip and knee replacement patients receiving thromboprophylaxis in routine clinical practice: a nationwide Danish cohort study of 83,756 osteoarthritis patients
B. Pedersen Alma, Mehnert Frank , Sorensen Henrik Toft, Emmeluth Claus, Overgaard Soren, Johnsen Soren Paaske
Department of Clinical Epidemiology, Aarhus University Hospital ; Department of Orthopaedic Surgery, Odense University Hospital
Background: A little is known about cardiovascular and
bleeding time-trend risk in patients
undergoing total hip and knee replacement
(THR and TKR) in routine clinical practice.
Purpose / Aim of Study: We examined the risk and predictors of
cardiovascular events and major bleeding
among thromboprophylaxis-treated THR and
TKR patients.
Materials and Methods: Nationwide, population-based follow-up
cohort of 83,756 primary THR and TKR
performed in Denmark 1997- 2011 due to
primary osteoarthritis was identified
using medical registries.
The outcomes included were arterial
(myocardial infarction and ischemic
stroke) and venous thromboembolism,
and major bleeding (intracranial
hemorrhage, gastrointestinal bleeding
and urinary/ lung bleeding) requiring
hospitalization within 90 days of surgery.
Findings / Results: Of 51,002 and 32,754 THR and TKR
patients, 1.923 (2.3%) and 483 (0.6%)
experienced cardiovascular events and
major bleeding, respectively within 90
days of surgery. The risks of myocardial
infarction, ischemic stroke and venous
thromboembolism were 0.5%, 0.5% and
1.3%, respectively. The risks of
intracranial hemorrhage, gastrointestinal
and urinary/lung bleeding were 0.04%,
0.3% and 0.1% respectively. The annual
cardiovascular risk varied between 2.0%
and 2.9% in 1997-2011, whereas the risk
of bleeding varied between 0.4% and
0.8%, corresponding to a 2- to 6-fold
excess risk of cardiovascular events.
Predictors of increased cardiovascular
risk and bleeding were male gender,
increasing age, and high level of
comorbidity, with no difference between
THR and TKR.
Conclusions: In this routine clinical practice cohort of THR
and TKR patients 3% experienced
cardiovascular or bleeding events. The
cardiovascular risk consistently exceeded
the bleeding risk. No major changes were
observed in the cardiovascular and bleeding
risk during 15 years long study period.
93. Total Hip Artroplasty (THA) following Open Reduction and Internal Fixation (ORIF) of acetabular fractures. A case-kontrol study
Jesper Høeg Vinther, Søren Overgaard, Ole Ovesen
Department of orthopaedic surgery and traumatology, Odense University Hospital
Background: The most frequent complication following an
acetabular facture is posttraumatic
osteoarthrosis (OA). This may necessitate
a THA. It is the general impression that the
clinical outcome of THA after an acetabular
fracture is worse compared to primary THA
in nontraumatic OA, but knowledge about
patients experience after surgery is limited.
Purpose / Aim of Study: The aim of this study was to analyze the
long-term results of cementless THA
inserted in patients who previously had
ORIF of an acetabular fracture and
compare these results to patients having a
THA after primary OA.
Materials and Methods: In a case control study we included 96
patients who all underwent THA between
1998-2010. Thirty-two patients had
previously ORIF of an acetabular fracture.
The remaining 64 patients were matched by
sex, age, time and site of THA, and served
as controls. They were all registered in the
Danish Hip Registry. Outcome was
evaluated by using 3 questionnaires: EQ5D,
Oxford Hip score (OHS) and UCLA.
Findings / Results: The median EQ5D index was 0.72 (Inter
Quartile Range (IQR): 0.66-0.82) for cases
and 1 (IQR: 0.82-1) for controls. EQ5D
index was significant lower in cases
(p<0.0001). The median OHS was 24.5
(IQR: 17-31) for cases and 14 (12-20) for
controls. OHS was significant higher in
cases (p<0.0001). The median UCLA score
was 4.5 (IQR: 3-7) for cases, and 8(IQR: 6-
9) for controls. The UCLA score was
significant lower in cases (p<0.0001).
Conclusions: We found that THA after ORIF of an
acetabular fracture is performing
significantly worse regarding quality of life,
pain and activity level compared to age and
sex matched patients undergoing THA
following primary OA. Our results confirm
the general impression, but whether it is due
to ORIF of the fracture or the fact that THA
is a new surgery in already affected bone
and soft tissue is unknown.